Recent advances of nanotechnology in COVID 19: A critical review and future perspective

Abstract

The global anxiety and economic crisis causes the deadly pandemic coronavirus disease of 2019 (COVID 19) affect millions of people right now. Subsequently, this life threatened viral disease is caused due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, morbidity and mortality of infected patients are due to cytokines storm syndrome associated with lung injury and multiorgan failure caused by COVID 19. Thereafter, several methodological advances have been approved by WHO and US-FDA for the detection, diagnosis and control of this wide spreadable communicable disease but still facing multi-challenges to control. Herein, we majorly emphasize the current trends and future perspectives of nano-medicinal based approaches for the delivery of anti-COVID 19 therapeutic moieties. Interestingly, Nanoparticles (NPs) loaded with drug molecules or vaccines resemble morphological features of SARS-CoV-2 in their size (60–140 nm) and shape (circular or spherical) that particularly mimics the virus facilitating strong interaction between them. Indeed, the delivery of anti-COVID 19 cargos via a nanoparticle such as Lipidic nanoparticles, Polymeric nanoparticles, Metallic nanoparticles, and Multi-functionalized nanoparticles to overcome the drawbacks of conventional approaches, specifying the site-specific targeting with reduced drug loading and toxicities, exhibit their immense potential. Additionally, nano-technological based drug delivery with their peculiar characteristics of having low immunogenicity, tunable drug release, multidrug delivery, higher selectivity and specificity, higher efficacy and tolerability switch on the novel pathway for the prevention and treatment of COVID 19.

1. Introduction

1.1. Epidemiology

The health condition of the entire globe is in danger right now due to the outbreak of coronavirus disease 2019 (COVID 19) which has already been declared as the Public Health Emergency of International Concern (PHEIC) by the world health organization (WHO) in 30th January 2020 [1,2]. As the 2019-nCoV has been renamed as pandemic coronavirus disease (COVID 19) by WHO on 11th February 2020, which further been renamed as a severe acute respiratory syndrome (SARS-CoV-2) by the international committee on taxonomy of virus (ICTV) [3]. However, the transmission rate of COVID 19 is severe with respect to severe acute respiratory syndrome (SARS-CoV) and middle east respiratory syndrome (MERS-CoV) coronavirus as per many recent studies published in August 2020 [4,5]. The origin place and outbreak year for SARS-CoV was Guangdong province of China in 2002, for MERS-CoV was Arabian Peninsula in 2012 and for COVID 19 was Wuhan city of China in 2019 [6,7] as illustrated in Fig. 1 . Unfortunately, patients with COVID 19 are increasing unexpectedly day by day causing an unbearable threat to public health. According to the world health organization (WHO), until March 30th^, 2020, 82,447 people were infected with the loss of 3310 patients' lives in China with an estimated mortality rate of 4%. Additionally, WHO confirmed that till 10th June 2022, total confirmed case of COVID 19 was estimated as 532,201,219 with 6305,358 deaths, where Europe (222,417,177) become the leading continent in case of confirmed cases followed by America (158,983,746) western pacific (61,735,224), south east Asia (58,217,287), eastern Mediterranean (21,807,376) and Africa (9039,645) respectively [8] as shown in Fig. 2 . Furthermore, as per the WHO report by 11th June 2022, among the top 8 countries or territories, the United States of America (87,246,309) become the prime area for infection followed by India (43,213,435), Brazil (31,417,341), France (29,753,370), Germany (26,802,782), United Kingdom (22,382,352), Russia (18,369,557) and South Korea (18,218,078) as ascribed in Fig. 2. As per the report, 216 countries were infected till 21st September 2020, in addition to this 230 countries of the entire globe have been infected with pandemic COVID 19 till 11th June 2022 [9,10]. The new variant of the corona virus i.e., omicron was first spotted in South Africa and then spread vigorously over other countries like Europe, America, India and 120 other countries till January 2022, respectively [11]. It was reported that this variant consisted of more than 50 mutations when compared to SARS-CoV-2. Among them 30 mutation are responsible for the change in the amino acid spike protein with which it attach and fuse with the cells (ACE 2 receptors). It was also reported that the previous version of the virus have only such 10 mutations with which it can change in the amino acid spikes. From the genomic point of view it has three distinct sub-lineages known as BA.1, BA.2 and BA.3. Although Europe, America and India were severely affected with BA.4, BA.5 and BA2.75 sub variants, respectively [12,13].

Fig. 1.

Three different types of corona virus, showing its origin place including primary and secondary host, outbreak year, affected countries, infected people with total death cases, and fatality rate [6,7].

Fig. 2.

(a) Global COVID 19 cases showing as continent wise. Europe is the leading continent of infection followed by America, the Western Pacific, South East Asia, Eastern Mediterranean and Africa.s, (b) COVID 19 infected eight highly burdened countries. The United States of America is the leading country subsequently followed by India, Brazil, France, Germany, the United Kingdom, Russia and South Korea.

1.2. Mode of transmission and clinical manifestation

The highly contagious and exponentially spreadable COVID 19 with zoonotic origin has single-stranded RNA and has the potential to transmit from one person to another. Many studies suggested that birds or mammals are regarded to be reservoirs of COV, with an identity of exhibiting 88% birds-derived SARS-like CoV as a genomic sequence of COVID 19 [14,15]. Sneezing or coughing via a human from which suspended respiratory droplets are generated is regarded as the primary well-established mode of COVID 19 transmission. Droplet nuclei with diameters of < 5–10 µm are more effectively transmitted in which virus can persist for 2 h to a few days [16,17]. Besides this, direct (hand-to-hand shake) or indirect (through medical accessories, personal utensils) contact of virally infected hands into the mouth or nose or even eyes further lead to infection. Moreover, oral-fecal contamination of infected patients further leads to its transmission. Henceforth, isolation of an infected individual from the population, personal hygienic behavior, applying well safety measures, wearing masks and gloves, keep quarantine of infected persons are some preventive measures that ultimately lead to control [18,19].

Once the person gets infected with COVID 19, most of the cases showed manifestation within 2–14 days while some cases prevail after 27 days. Although, approximately 5.6 days of incubation period has been identified by a group of many researchers [20,21]. Various research groups revealed that older people (especially males) age of above 60 and children are more susceptible to SARS-CoV-2 [22,23]. As per the basis of observing symptoms in the infected patient, the most common symptoms like fever, dry cough and fatigue, sputum production, and shortness of breath are predominant over another type of manifestation. Similarly, less common symptoms like prevail the aches and pains, conjunctivitis, sore throat, diarrhea, headache, loss of taste or smell and rashes on the skin. However, long lasting serious manifestations like respiratory failure, multiorgan failure, cardiac failure, and renal failure are identified as the primary cause of mortality and morbidity [24], [25], [26], [27], [28], [29]. More importantly, increased levels of pro-inflammatory cytokines and chemokines including granulocyte-colony stimulating factor, monocyte chemoattractant protein-1, and chemokine ligand-3 are observed in COVID 19 patients promoting viral survivability and hence exacerbating viral disease [30], [31], [32], [33].

1.3. Virology and pathogenesis of SARS-CoV-2

Coronaviruses are crown-shaped single-strand RNA virus with a size range of 80–160 nm that falls under the order-nidovirus, family-coronaviridae and subfamily-coronavineae. Moreover, they are classified as α, β, γ and δ genus, among which α genus (that contains HCoV-22E and NL63) and β genus (that contains HKU1, 229E, OC43, MERS-CoV, SARS-CoV and the latest outbreak SARS-CoV-2) majorly affects to mankind [34], [35], [36], [37]. Viral components like single-strand RNA, envelop protein, nucleocapsid protein, spike glycoprotein and membrane protein gives the characteristics of shape, function, rigidity and survivability to coronavirus. Spike (S) glycoprotein forms the crown-like structure at the outer surface of the virus that consists of two subunits, S1 which facilitates the binding of human angiotensin-converting enzyme-2 (hACE2) receptors and S2 which facilitates fusion between the host and the viral cell membrane. Interestingly, mutational behavior of receptor-binding domain (RBD) of S protein and the presence of polybasic furin cleavage sites (that facilitates the strong binding of S-glycoprotein to hACE2) and O-linked glycans are genomic features of SARS-CoV-2 that play an important role for binding efficacy to the host [38], [39], [40], [41], [42].

In addition, entry of SARS-CoV-2 virus into human lungs where ACE 2 receptors exist, gets bind with viral RBD of S1 subunit of S-glycoprotein that ultimately leads to downregulation of ACE2 receptors. This subsequent down regulation of ACE2 receptors further leads to increased production of angiotensin-2 (AT2) induces pulmonary vascular permeability and causes lung injury [43,44]. Further, the interaction between antigen presenting cells (APC) of SARS-CoV-2 and the dendritic cell of the host causes Macrophagic stimulation that subsequently leads to severe immunological reaction. After all, these immunogenic reactions further cause the production of excess pro- inflammatory cytokines (IFN-α, IFN-γ, IL-1β, IL-6, IL-12, IL-18, IL-33, TNF-α,) and chemokines (CCL2, CCL3, CCL5, CCL8, CCL9, CCL10, etc.) called cytokines storm which results for epithelial cell lining damage than enters into the bloodstream and finally exerts multiorgan damage as shown in Fig. 3 [45], [46], [47], [48].

Fig. 3.

Pathogenesis and mechanism of SASR-CoV 2 infection exhibiting six different steps; (1). Entry of Corona virus and infects lung cells, (2). Production of cytokines after identification of virus via immune cells including macrophages (3). Production of cytokine storm due attraction of more immune cells like white blood cells and causes inflammation. (4). Formation of fibrin, causing lung cell damage, (5) Entry of fluid into lungs cavities through weakened blood vessels causing respiratory failure, (6). Circulation of a virus into various parts of the body through systemic circulation causes multiorgan damage.

1.4. Conventional diagnostic approach for covid 19

Early diagnosis of COVID 19 is equally important to save the patient's life. Luckily, various diagnostic approaches have been started to adopt which protect the patient's life from worsening. Screening of this pandemic COVID 19 can be done by below mentioned recommended diagnostic tools.

1.4.1. Infrared scanner and thermal camera

An infrared scanner is used to scan individuals, while thermal cameras are used to detect incremental body temperature by which COVID 19 affected population can be isolated from a large population. These scanners and cameras are mainly used in crowded areas like hospitals, airports, academic institutions, railway stations and research centres through which visual images can be observed by converting and detecting infrared energy in terms of heat [49], [50], [51].

1.4.2. Nucleic acid amplification test (NAAT)

NAAT is WHO established based diagnostic approach in which a nasal swab or blood sample can be used to confirm COVID 19 via real-time fluorescence polymerase chain reaction (RT-PCR). Likewise, several diagnostic kits have been launched by the US-FDA and other various regulatory bodies as an emergency kit for the detection of COVID 19 that works based on RT-PCR technology. The first commercial diagnostic kit was Cobas^R SARS-CoV-2, which was been launched under the clinical laboratory improvement amendments of 1988 (CLIA) specifying the fulfillment of required medical emergency needs [52], [53], [54], [55], [56]. However, numerous complications have been identified associated with false identification, complex sample preparations, less sensitivity and selectivity for low viral load cases, and stability issues along with its time-consuming procedure that limits its use [57].

1.4.3. Computerized tomography (CT) scan

Due to several drawbacks of NAAT associated with false reading and detection for COVID 19, Chinese researchers recommended computerized tomography imaging as a primary diagnostic approach. Huang et al., reported that after examination of the suspected patient's chest CT imaging showed multiple peripheral ground glass opacities in both lungs leading to hospitalization after three days which initially was observed with negative results via RT-PCR. Thereafter, this technique is being highly applied for the detection of COVID 19-associated viral pneumonia [58], [59], [60].

1.4.4. Immunoassay-based diagnostic approach

IgM-IgG combined antibodies detection-based approach against SARS-CoV-2 in COVID 19 infected patients was reported by Li et al. Hopefully, the group has developed an immunoassay-based diagnostic test kit with rapid screening (within 15 mins) and a simple point of view [61], [62], [63].

1.4.5. BioFire COVID 19 test 2

This approach has been adopted by FDA under Emergency Use Authorization (EUA) since March 2020, which is based on a molecular diagnostic test. A swab sample taken from the nasopharyngeal region is being detected to confirm the presence of SARS-CoV-2 [64,65].

2. Current inline treatment

After the emergence of the deadly pandemic COVID 19, today's whole world's health organizations, medicinal industries, health institutes and scientists are eagerly searching for potent anti-COVID medicines or vaccines. Numerous preclinical and clinical trials are on-going for both newly developed and existing drug molecules. Most antiviral drugs including other disease-specified drugs are continuously been tested for their anti-COVID activity. Solidarity clinical trials launched by WHO and partners have specified wide varieties of on-going clinically trial therapeutic candidates to determine the efficacy against coronavirus along with its safety for human use [66,67]. Additionally, US-FDA and other various regulatory bodies have equally engaged in research work on anti-COVID moieties and medical countermeasures (MCMs). Numerous anti-COVID 19 drug molecules have been approved by FDA under Emergency Use Authorization (EUA) and recommended by WHO for both hospitalized (inpatients) as well as non-hospitalized patients (outpatients) [68,69]. Hopefully, the number of therapeutic moieties is aggressively being investigated to determine their effectiveness against COVID 19. Preclinical and Clinical trials are progressively being conducted by many regulatory bodies including health institutions, government health agencies and other various researchers of antivirals, monoclonal antibodies, corticosteroids, steroids, anti-inflammatory and other molecules against coronavirus. Interestingly, the solidarity trial committee has been organized by WHO and partners to expedite potential treatment for COVID 19 by conducting clinical trials. Although, the Solidarity trial committee has withdrawn hydroxychloroquine and lopinavir/ritonavir from their trial phase on 4th July 2020 due to their greater adverse effects (like arrhythmia) [66,[70], [71], [72]]. According to a report published by the U.S Department of Human Health Services (HHS) on 24th January 2022, REGEN—COV (Bamlanivimab and etesevimab, casirivimab and imdevimab combinations) was not been found as an effective drug against Omicron variant of COVID 19. Similarly, as per a CDC report published in December 2021, Janssen/ Johnson & Johnson vaccine was less likely to be preferred over Pfizer and Moderna vaccines due to a greater risk of developing severe (but rare) blood clot called thrombosis with thrombocytopenia syndrome (TTS) [73,74]. However, adverse effect of both Pfizer and Moderna's vaccines with the rare occurrence of myocarditis has also been established as per the report suggested by CDC but remains preferable over other due to its higher benefits that outweigh their risks [75,76].

Thereafter, focusing on all these serious toxicities along with intolerable adverse effects of recommended drugs and vaccines for COVID 19, full attention has been gained towards the development of novel Nano-technological based delivery. Nanotechnologies with a great significance specifying the characteristics of rapid and accurate diagnosis, target-specific delivery with reduced dosing frequency and hence toxicities, combinatorial therapy, tunable drug release, biocompatibility, low immunogenicity, multidrug delivery with high selectivity and specificity make the nano therapeutic strategy more significant over conventional delivery as shown in Fig. 4 [77], [78], [79]. In this review, we broadly investigated the current approach and future possibilities of a nano-technological based approach for diagnosis, delivery of potential Anti-COVID 19 therapeutic moieties and vaccine delivery as well.

Fig. 4.

Nano-technological based strategy for the Diagnose, treatment and prevention of pandemic SARS-CoV-2 infections.

3. Nanoparticle-based diagnostic approach against COVID 19

Early detection of coronavirus in an infected patient emphasis more important rather to treated them later. To obtain accurate and positive diagnostic results from every patient via a conventional approach is somewhat critical that ultimately limit its use. Besides this, other limitations like the time-consuming process and low efficiency for viral detection through the most popular and widely used RT-PCR method greatly hinder its worldwide acceptance [80,81]. Thereafter multipronged scientific strategy with nanoparticle-based technique seems to be highlighted and needs to be addressed for effective and accurate diagnostic examination. In addition to this, the use of nanoparticles (like metal NP, magnetic NP, quantum dots, etc.) in RT-PCR further creates the track for use in other viral detection methods as well like Enzyme-Linked Immunosorbent Assay (ELISA), Reverse Transcription Loop-mediated isothermal Amplification (RT-LAMP) with a hope to brings the array of greater accuracy, sensitivity and efficiency due their peculiar features of high surface area and ultra-small size. Moreover, unique optical and electrochemical properties including its biocompatible and stable feature enforce the nano-technological field to be investigated in depth for biological application [82], [83], [84], [85], [86]. Various researchers have attempted the use of nano-technological tools to diagnose the COVID 19 infected patients as ascribed in Table 1 .

Table 1.

Metallic nanoparticles to diagnose COVID-19.

Studied by	Diagnostic agent	Method	Purpose of study	Finding/outcomes	Refs.
Li H and Rotherber et al.,	Citrate ion fabricated AuNPs	Colorimetric method	To measure the efficiency of interaction for AuNPs with viral nucleic acid	Change in color of colloidal solution for dsDNA but not for ssDNA/ssRNA.	[87]
Moitra et al.,	Thiol modified Antisense oligonucleotide impregnated AuNPs (TASO-AuNPs	Colorimetric assay	To determine the propensity of interaction between TASO-AuNPs with viral RNA sequence	Change in color of colloidal solution due aggregation of AuNPs.	[88]
Aithal et al.,	Aptamer functionalized AuNPs (Nanoprobe	ELISA method	To find out the degree of aptamer binding with S-protein of SARS-CoV 2	Unconjugated nanoprobes agglomerate with colloidal solution's color change and vice versa.	[89]
Kim et al.,	Thiolated ssDNA functionalized AuNPs (t-ssDNA-AuNPs	Colorimetric assay	Aggregatory capability of t-ssDNA-AuNPs with target DNA	Formed dsDNA-AuNPs networks cause agglomeration with colloidal solution's color changes.	[90]
Fu et al.,	Polyclonal antibody functionalized Au@Pt NPs	Colorimetric assay	Exploration of viral enzyme catalytic pathway due to interaction between S1-protein and Au@Pt NPs	Enhancement of sensitivity and selectivity for S1 viral protein due to increment of porous core shell nanostructures on the surface of AuNPs.	[91]
Karakus et al.,	Recombinant SARS-CoV 2 spike antibody fabricated AuNPs (AuNPs-mAb)	Dual colorimetric and electrochemical method	To estimate the SARS-CoV 2 spike Antigens	Colloidal solution's color changes due aggregation of AuNPs. Both techniques were highly sensitive against SARS-CoV 2 Antigen compared to H1N1 and MERS-CoV.	[92]
Teengam et al.,	Pyrrolidinyl peptide nucleic acid incorporated AgNPs (acpcPNA-AgNPs	Colorimetric assay	Agglomeration efficiency of AgNPs with acpcPNA	DNA-acpcPNA-AgNPs aggregates cause change in color of colloidal solution leading to ease detection of target Oligonucleotide.	[93]
Zhang Z et al.,	Bromine ions and acetonitrile fabricated AgNPs	Surface Enhanced Raman Spectroscopy (SERS technique	To measures the detectable and quantifiable capability of modified AgNPs for SARS-CoV 2	Modified AgNPs showed improved quantifiable efficiency for SARS-CoV 2 with lower detection limit of 100 copies/test within 1–2 mins.	[94]
Gong et al.,	Silica coated superparamagnetic NPs (si@SPMNPs	Si@PMNPs-PCR assay	To explore the effectiveness of developed si@SPMNPs against viral target cDNA of SARS-CoV	Observed to be excellent selectivity and sensitivity for cDNA with detection limit of 2.0 × 103 copies within 6 hrs.	[95]
Zhoe et al.,	Polycarboxyl fabricated Magnetic NPs (pcMNPs	Colorimetric assay	For viral RNA extraction potentiality of SARS-CoV 2	pcMNPs showed rapid (within 30 mins) and improved RNA extraction capability (10-copies sensitivity with 5-log enhanced linearity).	[96]
Somvanshi et al.,	Multifunctionalized magnetic NPs (MNPs	Colorimetric assay	Viral RNA extraction efficiency of Multifunctionalized MNPs	Shortens the time period and necessities for viral detection compared to conventional diagnostic tool.	[97]
Roh et al.,	RNA aptamer conjugated Quantum Dots (apt-QD	Confocal laser scanning microscopic (CLSM)- Biosensor	For the detection of N-protein of SARS-CoV	Detection limit for SARS-CoV with 0.1 pg/ml paves the effective pathway for diagnosis of SARS-CoV 2 as well.	[98]

3.1. Metallic nanoparticle-based diagnostic approach

More specifically, localized surface plasmon resonance (LSPR), an optical property developed by gold (Au), silver (Ag) and copper (Cu) NP that represents a color with maximal absorbance wavelength is particularly associated with bio sensing application [99]. In particular, the degree of NP aggregation causes a change in tunable light absorption and scattering of wavelength in the visible region with a change in LSPR extinction maxima of metal NP that results in an obvious change of colloidal solution color as detected by the necked eye [100]. In the current situation, both the gold nanoparticle and silver nanoparticles are vigorously been investigated for their biomedical application. However, several studies suggested that the optical properties of AgNPs were found to be improved due to their higher extinction coefficient compared to AuNPs. In addition, the shape and size of different metallic NPs further determine their optical and electrochemical propensities [85]. The colorimetric assay can be performed for target viral DNA or RNA detection for clinical diagnosis and can be accomplished by the aggregation of AgNPs with subsequent color changes of colloidal solution [101,102].

3.1.1. Gold nanoparticles

In this regard, Li H and Rothber L, suggested efficiency and degree of aggregation for gold NP (AuNPs) after interaction with viral single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) are completely different due to variations in both viral electrostatic propensities. The study was performed to determine SARS-CoV via a colorimetric hybridization assay with found a lack of AuNPs aggregation after treatment with ssDNA or ssRNA even after the addition of salt. This is happened due interaction of ssDNA or ssRNA with citrate ions fabricated AuNPs that results in the stabilization of NP and hence prevents change in the color of colloidal solution. However, a change in color of colloidal solution was observed with dsDNA, indicating aggregation of NPs. The phenomenon for detection was simple and less time-consuming (within 10 mins) which is a more suitable diagnostic approach against existing and upcoming variants of COVID 19 [87].

In a similar study, Moitra et al., developed thiol modified Antisense Oligonucleotide (T-ASO) fabricated gold NPs (T-ASO-AuNPs). The technique was based on the assessment of the N-gene (nucleocapsid phosphoprotein) of SARS-CoV-2 via a colorimetric assay in which the target viral RNA sequence was treated with T-ASO-AuNPs that resulting in the agglomeration of treated gold NP due to change in LSPR. In particular, this agglomeration cause change in the color of the colloidal solution and the precipitate of these agglomerates can be visually seen by necked eyes after the addition of ribonuclease H (RNase H). Henceforth, this short time-consuming technique (within 10 min after the RNA isolation process) with a detection limit value of 0.18 ng/µl may create a novel pathway for an accurate, selective, sensitive and more reproducible diagnostic approach [88].

Recently, another study was performed by Aithal et al., based on aptamer functionalized AuNPs (nanoprobes) for the detection of SARS-CoV-2. Herein, the degree of aptamer binding potency with spike (S) protein of SARS-CoV-2 was estimated by the ELISA technique. Interestingly, nano probes without conjugated with S-protein agglomerates while conjugated nano probes do not due to the stabilization of nano probes after the addition of coagulants (MgCl₂ salt solution). These agglomerated nano probes result in a change in the colloidal solution's color with a change in plasmon resonance. Collectively, this short time-consuming diagnostic method with a detection capability of nano-sensors was observed to be 3540 genome copies/µl and higher concentrations of inactivated SARS-CoV-2 at the absorbance of 540 nm, indicating fruitful viral screening and detectable tool for upcoming days [89].

In the same manner, Kim et al., previously proposed a colorimetric assay for the detection of MERS-CoV via hybridization of thiolated ssDNA functionalized gold NP(t-ssDNA-AuNPs) with target DNA (that act as a linker between two ssDNA functionalized AuNPs). In the study, formed dsDNA-AuNPs networks causing aggregation of AuNPs resulted in a dramatic color change of colloidal solution indicating that the use of gold nanoparticles could be effective for analysis of SARS-CoV-2 as well, without using any complicated and sophisticated instruments [90].

The next study performed by Fu et al., demonstrated the colorimetric detection of target viral S1 protein of SARS-CoV-2 by the introduction of polyclonal antibody functionalized Au@Pt NPs based on peroxidase catalysis activity. More deeply, the initial fabrication of reduced Pt⁴⁺ions onto the surface of AuNP further creates porous core-shell nanostructures and leads to a remarkable change in enzyme catalysis pathway i.e., from ROS generation to fast electron transfer (FET) process which enables sensitive and more selective identification of viral S1 protein. Notably, the linear detection range for viral spike protein was ascribed to 10–100 ng ml⁻¹ with a limit of detection (LOD) of 11 ng ml⁻¹ within 15 min. After all, the study is straightforward towards the development of a metallic NP fabricated colorimetric biosensor based on nano-enzyme catalysis for practical applications [91].

Similarly, Karakus et al., developed a monoclonal antibody (recombinant SARS-CoV-2 spike antibody) fabricated gold NPs (AuNPs-mAb) for the estimation of SARS-CoV-2 spike antigen via dual colorimetric and electrochemical analytical technique. Moreover, the study anticipated that after optical visualization, changes in the color of the colloidal solution from red to purple were due to irreversible aggregation of AuNPs in the presence of SARS-CoV-2 antigens. Interestingly, the author developed an electrochemical method for the first time in such a way that SARS-CoV-2 spike antigen can be detected without the requirement of sensor preparation and its modification that subsequently reduces the time-consuming process (within 10 min). Additionally, both methods were found to be highly sensitive against SARS-CoV-2 antigen irrespective of another infectious viral antigen like H1NI, MERS-CoV, and Streptococcus pneumonia with a detection limit of 48 ng/ml and 1pg/ml for colorimetric and electrochemical method respectively [92].

In addition to this, Yano et al., invented large AuNPs-enhanced surface plasmon resonance (AuNPs-SPR) for ultra-sensitive detection of SARS-CoV-2 associated N-protein. Herein, SPR sensitivity of two different sizes of AuNPs of 150 nm and 40 nm were monitored. The study revealed that AuNPs with large size of 150 nm displayed significantly greater sensitivity against viral N-protein with a detection limit 4pg/ml compared to small size particle of 40 nm as well as with typical RT-PCR (detection limit of 4.5pg/ml). In this regard, novel SPR-based nanoparticles could have a remarkable capability to diagnose pandemic viruses [93]. Additionally, Silva et al., explored the efficiency of bio-conjugation of Antibody functionalized AuNPs (pAbS1N@AuNPs) with SARS-CoV-2 spike glycoprotein. However, successful development and bio-conjugation of spike glycoprotein with pAbS1N@AuNPs were confirmed through physicochemical characterizations (like FTIR, TEM, UV–VIS spectroscopy and SERS). Most interestingly, a study demonstrated that interaction of pAbS1N@AuNPs with influenza viruses showed no increment in the size of bio-conjugates while with SARS-CoV-2 spike glycoprotein exhibited size enhancement after dynamic light scattering (DLS) measurement, indicating better selectivity for SARS-CoV-2 [103].

In the next investigation, Diaz et al., developed colorimetric sensor-based AuNPs for the detection of SARS-CoV-2 coding sequences (RdRp, E and S protein). More specifically, developing colorimetric sensor-based AuNPs took only 2.5 h for complete amplification and detection with a viral load of ≥10³–10⁴ viral RNA copies/µl in the patient sample. Forwards, rapid visual detection of SARS-CoV-2 sequences (within 15 min) through colorimetric sensor-based AuNPs with better stability up to several months and its simplified version further restrict its use for diagnostic purposes against COVID 19 [104].

3.1.2. Silver nanoparticles

Recently, Teengam et al., synthesized the multiplex paper-based colorimetric DNA sensor using pyrrolidinyl peptide Nucleic acid (acpcPNA) conjugated AgNPs (acpcPNA-AgNPs) for the quantitative detection of MERS-CoV along with MTB and HPV oligonucleotides. Herein, aggregation of citrate ion stabilized AgNPs was observed as a result of acpcPNA probe in the absence of complementary DNA. Moreover, DNA-acpcPNA duplex mediated AgNPs dispersion due to electrostatic repulsion in the presence of target DNA causes a significant color change through which target oligonucleotide can be detected easily. Overall, the study with finding a detection limit of 1.53 for MERS-CoV along with improved hybridization efficiency, rapid intense color change, simplified assay estimation and superior sensitivity and selectivity of target DNA detection showing a remarkable and efficient approach for diagnosis of SARS-CoV-2 as well [105].

Going forwards, Zhang et al., engineered bromine ions and acetonitrile fabricated AgNPs based on surface-enhanced Raman spectroscopy for the rapid detection and quantification of SARS-CoV-2 including Human Adenovirus 3 and H1N1 virus. Herein, an author suggested that the viral quantification capability of such modified AgNPs was significantly improved with a lower detection limit of 100 copies /test, with a principal component analytical duration of 1–2 min for those three viruses. Interestingly, the impregnation of acetonitrile on the surface of AgNPs greatly intensified and amplified the SERS peak signals of those viruses. Additionally, stability and fingerprint for those developed nanoparticles further showed an improved version with preferable cost effectivity as compared to other detection methods, enabling the tractable solution for accurate and immense diagnosis of COVID 19 [106].

3.1.3. Magnetic nanoparticle

Beyond the use of metallic nanoparticles, the potential use of magnetic nanoparticles for selective and sensitive diagnosis of the SARS-CoV-2 virus has further drawn attention in the biopharmaceutical field. Iron oxide nanoparticles among various MNP are immensely investigated for their use in diagnostic purposes against deadly infectious viral diseases due to their higher magnetic efficiency with simple synthesis approaches [94,95]. Various studies ascribed that the use of iron oxide NPs for extraction of target DNA and RNA showed an efficient strategy for diagnostic purposes. Lee et al., in 2018 anticipated the zika viral RNA extraction using iron oxide silica NPs [96]. Additionally, Wang et al., further performed the study by using silica-coated MNP for the simultaneous extraction of DNA and RNA from hepatocellular carcinoma cells [97].

Previously, Gong et al., demonstrated the study for the detection of SARS-CoV using silica coated-superparamagnetic NPs (si@SMNPs) fabricated PCR-based assay. Herein, magnetic-conjugated dsDNA complex was developed by the introduction of an oligonucleotide probe fabricated silica-coated SMNPs with viral target cDNA, which then subsequently allowed to form enriched cDNA through simple magnetic separation phenomenon followed by amplification of that enriched cDNA through PCR using another magnetic separation step. After all, by the application of silica-coated florescent NPs (SFNPs), amplified viral target cDNA was been detected through sandwich hybridization assay. At last, the study revealed that selectivity and sensitivity for viral target cDNA of SARS-CoV were observed to be excellent with a detection limit of 2.0 × 10³ copies within 6 h establishing a suitable track for clinically diagnostic track [107].

In an investigation, Zhao et al., synthesized poly-carboxyl fabricated magnetic nanoparticles (pcMNPs) for the effective and sensitive extraction of viral RNA using SARS-CoV-2 pseudo-virus as a model. However, the developed pcMNPs dramatically simplified RNA extraction phenomenon over conventional MNPs and normal RT-PCR by combining lysis and binding steps into one with subsequent introduction of pcMNPs-RNA complex into RT-PCR reactions that ultimately reduce time-consuming as well (completed within 30 min). Importantly, applied external magnetic force subsequently causes rapid and easier extraction of pcMNPs-RNA complex from the solution as pcMNPs to possess magnetic property. Moreover, the pcMNPs-based approach showed 10-copy sensitivity with immense improved linearity over 5 logs of gradients, indicating superior viral RNA binding performance [108].

Furthermore, Somvanshi et al., highlighted the applicability of multifunctional nano-magnetic particles (MNPs) for the detection of COVID 19 via assessing the viral RNA extraction potentiality. Herewith, silica-coated zinc ferrite magnetic nanoparticles (ZiF@Si@ MNPs) developed by sol-gel auto combustion technique were simultaneously fabricated with carboxyl modified polyvinyl alcohol followed by accumulation of magnet (ZiF@Si@NH2@Cpoly MNPs). The successful synthesis of surface-functionalized MNPs was confirmed after physicochemical characterization. The developed MNPs impressively shorten the operation period and necessities as compared to normal diagnostic tools for the detection of COVID 19 [98].

3.1.4. Quantum dots

Currently, the use of QDs for the detection of verities of pathogenic bacteria and viruses in humans become a keen subject for many researchers. Some unique features for optical and electrical properties including extraordinary plasmonic properties of QDs have attracted attention for their use in biomedical fields. As per several studies, effective diagnosis, detection and control of the deadliest viral infections including pandemic SARS-CoV-2 can be accomplished by the use of QDs as screening agents [109,110].

In one study, Roh et al., developed a QDs-conjugated RNA aptamer for the detection of nucleocapsid (N) protein of SARS-COV on an immobilized protein chip based on the optical signal variation. The study with finding a detection limit of 0.1 pg/ml by detecting fluorescent emission intensity through confocal laser scanning microscopy concluded that this developed biosensor was very sensitive, highly selective and easy to use against SARS-COV protein which further directs the study one step forward for effective clinical diagnosis of novel SARS-CoV-2 antigen as well [111].

3.2. Carbon-based nano-materials for diagnostic approach

Similar to the applicability of metallic NPs, carbon-based nanomaterials (CBNMs) such as graphene, carbon nanotubes (CNTs), and their derivatives are equally being investigated for the diagnostic and drug or vaccine delivery purposes, against broad spectrum single envelop RNA viruses including SARS-CoV-2 as depicted in Fig. 5 . Importantly, CBNMs constitute promising alternatives due to exhibiting their peculiar characteristics of biodegradability, biocompatibility, low to no toxicity and tissue regeneration inducement capability [112,113]. Besides, CBNMs with excellent thermoelectrical and mechanical conductivity, higher surface area, and better functionalization potentiality with targeted molecules, are equally enforced for their potential use in bio-medicinal fields [114].

Fig. 5.

Carbon Based Nano material for diagnosis, drug and vaccine delivery, treatment and prevention of COVID 19.

3.2.1. Graphene-based materials

Graphenes are two-dimensional hexagonally bonded CBNMs, exhibiting outstanding characteristics of large specific surface area, greater electromechanical and thermal conductivity with improved optical and catalytic properties [115]. Moreover, graphene and its derivatives have immense applicability in the biomedical and biotechnological fields for bio-sensing and bio-imaging, early diagnosis, drug screening and conventional textile utilities [116].

Recently, Seo et al., demonstrated the spike protein antibody fabricated graphene-based field effect transistors (FET) biosensor for the efficient detection of COVID 19. Herein, sensitivity and selectivity for detection of SARS-CoV-2 spike protein were found to be superior in COVID 19 patients with a limit of detection (LOD) of 1fg ml⁻¹, irrespective to control subjects [117]. Similarly, the next study performed by Li et al., further identified the viral detection potentiality against influenza and SARS-CoV-2 viruses through a developed MXene- graphene FET sensor. Interestingly, the study suggested that the developed sensor showed ultra-sensitivity and a short time-consuming phenomenon (~50 ms), towards the determination of viruses with LOD of 125 copies ml⁻¹ and of 1fg ml⁻¹, for influenza virus and recombinant 2019-nCoV spike protein respectively [118]. Additionally, El-Said et al., synthesized AuNPs incorporated reduced porous graphene oxide (rGO) to enhance the biosensing efficiency of ITO electrode, against COVID 19 S- protein. However, the experiment suggested that the developed Spectro-electrochemical biosensor exhibited potential selectivity and sensitivity against viral protein with LOD of 39.5 f mol⁻¹, indicating an efficient alternative for early diagnosis of COVID 19 [119].

Similarly, Shahdeo et al., experimented with the ultrasensitive immuno-sensing of spike S1 antigen (S1-Ag) of SARS-CoV-2 through a developed graphene-based FET sensor (G-FET). Notably, immobilization of SARS-CoV-2 spike S1 antibody (S1-Ab) as a sensing element onto the surface of the G-FET sensor has superior S1-Ag binding potentiality. Furthermore, sensitivity and selectivity of the G-FET sensor against SARS-CoV 2 S1-Ag were found to be superior with LOD of 10 fM [120].

In the next study, Payandehpeyman et al., developed SARS-CoV 2 spike S1 antibody (S1-Ab) fabricated graphene-based nanoresonator sensor for rapid and effective detection of viral S1-Ag. Importantly, the study suggested that immobilized S1-Ab over a single-layer graphene sheet (SLGS) surface showed strong viral S1-Ag capturing capability. However, the sensitivity and detection ability of such SLGS modified G-FET sensor further depends upon the geometry of SLGS. The author showed that the detection capacity of the developed sensor against SARS-CoV 2 was ranging from 10 to 1000 viruses per test, with an LOD of 10 viruses per test [121].

In addition to this, the next study performed by Ang et al., developed Graphene Oxide Nanocolloids (GONC) for the detection of 2019 nCoV targeted sequences. In the study, an author demonstrates the quantitative correlation between the inherent electro-activity of GONC immobilization platform and 2019 nCoV concentrations, showing analyte detection capability of 10⁻¹⁰ to 10⁻⁵ M. Moreover, the developed geno-sensor showed the potentiality of rapid and effective viral genome sensing affinity and could be integrated into a DNA amplifier for early SARS-CoV 2 diagnosis [122].

In another investigation, Li et al., synthesized AuNPs decorated G-FET sensor (AuNPs@G-FET) for the detection of SARS-CoV-2 RNA in human throat swab sample. Importantly, the surface of AuNPs@G-FET sensor was initially immobilized with phosphorodiamidate morpholino oligos (PMO) probes. The PMO modified-AuNPs@G-FET sensor showed higher sensitivity and selectivity against SARS-CoV-2 RdRp, with LOD of 2.29 fM in the throat swab sample. More importantly, the developed sensor has amplification-free direct SARS-CoV-2 RdRp detection capability within a very short time (2 min), with ultrasensitive potential to distinguish among another SARS-CoV RdRp sequence [123].

In the next research, Zhao et al., synthesized a calixarene functionalized ultrasensitive super sandwich-type electrochemical sensor to detect the RNA of SARS-CoV-2. Interestingly, an ongoing study revealed that the developed sensor was highly sensitive and specific towards the detection of viral RNA, specifying an LOD of 200 copies/ ml for a clinical specimen. Moreover, the viral RNA detectable ratio of that developed sensor was observed to be higher (85.5% and 46.2%) as compared to RT-qPCR (56.5% and 7.7%), signifying the novel rapid, accurate, and ultrasensitive approach to detecting pandemic SARS-CoV-2 [124].

3.2.2. Carbon nanotube-based materials

Carbon nanotubes (CNTs) are other promising carbonaceous materials with immense utility in the biochemical field. Various peculiar properties such as biocompatible, non-cytotoxic, greater surface area, ROS-producing capability, and mechanochemical resistance, enhance the significant attribution in Nano-technological aspects [125,126].

Recently, Thanihaichelvan et al., proposed CNT- FET biosensor by immobilizing the RNA-dependent RNA polymerase gene of SARS-CoV-2 onto the CNT channel. The synthesized CNT- FET biosensor showed the LOD of 10 fM with selective sensing response, against a positive target viral sequence, indicating a reliable, fast and easy approach for diagnosis of SARS-CoV-2 [127].

Similarly, the next study carried out by Zamzami et al., further demonstrate the CNT-FET electrochemical sensor to detect the S1 antigen of SARS-CoV-2, via immobilization of SARS-CoV-2 S1 antibody onto the surface of CNT channels, using 1-pyrenebutanoic acid succinimidyl ester (PBASE) as a linker. Interestingly, CNT-FET electrochemical sensor exhibited strong selectivity, sensitivity and accuracy against SARS-CoV-2 S1 antigen with LOD of 4.12 fg/ml, while, no response was observed against SARS-CoV-1 S1 and MERS-CoV S1 antigen [128].

Likewise, Pinals et al., highlighted the rapid and sensitive detection capability for SARS-CoV-2 spike protein through developed ACE-2 functionalized single-walled CNTs (ACE2-SWCNTs) optical nanosensor. Interestingly, ACE2-SWCNTs nanosensor showed 2-fold enhancement of fluorescence within 90 min, after exposing SARS-CoV-2 spike protein. Moreover, ACE2-SWCNTs nanosensor further exhibited good colloidal stability with improved retained sensing capacity, showing 73% fluorescence for 35 mg/L SARS-CoV-2 virus-like particles, within 5 s, indicating an effective novel toolkit to combat COVID-19 [129].

Concurrently, Kim et al., performed optimization of carbon nanotube Thin-Film Immunosensor (CNT-TFI) by a computational method for rapid and effective diagnosis of SARS-CoV-2 virus. Herein, the optimized immunosensor was found to be higher sensitive against SARS-CoV-2, with LOD of 0.024 [fg/ ml]⁻¹ in buffer solution and 0.048 [copies/ ml]⁻¹ in the lysed virus. Thus, an author concludes that this CNT-TFI strategy could be a very effective, accurate, and sensitive technique for SARS-CoV-2 diagnosis, without the need for molecular amplification [130].

In next similar study, Shao et al., revealed antigen detection efficiency of SARS-CoV-2 (both S-antigen and N-antigen) in clinical nasopharyngeal samples through developed high purity semiconducting SWCNTs-FET sensor. Specifically, the developed SWCNTs-FET sensor was well decorated with anti-SARS-CoV-2 spike protein antibody (SAb) and anti- nucleocapsid antibody. Importantly, antibody functionalized SWCNTs-FET sensor showed greater sensitivity against both S-antigen and N-antigen with LOD of 0.55 fg/ ml and 0.016 fg/ ml, respectively. Besides, the sensing capability of SAb- functionalized SWCNTs-FET sensor against both positive and negative clinical samples was also found to be effective, indicating an effective novel diagnostic tool against COVID-19 [131].

In similar next research, Jeong et al., prepared ‘capture’ ssDNA functionalized SWCNTs (ssDNA-SWCNTs) to determine the SARS-CoV-2 viral RNA detection efficiency and sensitivity. The study revealed that viral extraction potentiality of developed ssDNA-SWCNTs from phosphate buffered saline was found to be 100% efficient as compared to the commercial silica-column kit, whose extraction efficiency was observed to be ~20%. Furthermore, viral nucleic acid extraction propensity of ssDNA-SWCNTs was almost 50% from human saliva, which was similar to commercial DNA/RNA extraction kits. Therefore, this CNTs-based viral nucleic acid extraction strategy could be a highly sensitive and high-yield identification technique for future perspective [132].

3.3. Miscellaneous

In the next exploration, Rajil et al., developed streptavidin-coated up conversion NPs conjugated with SARS-CoV-2 RBD as phantom virion (SUPPV NPs) to determine the strength of viral detection potentiality through neutralizing antibodies. In the study, neutralizing antibodies (IgG) containing sample showed no attachment of nanoparticles with ACE2 coated substrate while nanoparticles exhibited a strong affinity for binding with ACE2 coated substrates which lacks neutralizing antibodies. More importantly, developed SUPPV NPs possessed the highest sensitivity against SARS-CoV-2 with a detection limit of 4 ng/ml which was comparatively lower than the commercially available diagnostic kit with a detection limit of 19 ng/ml [133].

4. Nanoparticles for therapeutic drug delivery

The emergence and outbreak of this novel SARS-CoV-2 viral infection create dramatic health and economic crisis throughout the world the current situation is due to which the whole world's medical and pharmaceutical researchers became engaged in the development of effective and potential anti-COVID 19 therapeutic candidates. Although selective countable drugs have been approved by regulatory bodies like FDA under EUA and WHO for their treatment but still face challenges due to their high dose regimen therapy and hence toxicities, non-specific site delivery, low therapeutic potentiality, low dose availability at a target site, poor biopharmaceutical attributes and mutational behavior of viral gene [134,135]. Thereafter, keeping into consideration all aforementioned problems associated with conventional therapy, the nano-medicinal based approach has been identified for effective and selective therapeutic drug delivery, particularly specifying the site-specific and viral targeted drug delivery accompanying reduced dosing frequency and hence toxicities [136,137]. In this section, we majorly investigated the various attempts and possible future perspectives of Nano-medicinal based drug delivery system that helps to improve the pharmacological profile of the ingested drug and could be represented as novel valid pharmacotherapeutic options to treat COVID 19 as depicted in Table 2 .

Table 2.

Nanoparticles for the delivery of therapeutical moieties against COVID 19.

Studied by	Delivery system /therapeutic agents	Purpose of study	Outcomes	Refs.
Pooladanda et al.,	iRGD peptide fabricated Nimbolide liposome (iRGD-NIMLIP	To determine the anti-inflammatory activity of iRGD-NIMLIP	iRGD-NIMLIP possess superior anti-inflammatory property compared to free Nimbolide, NIMLIP and Dexamethasone enabling effective approach against SARS-CoV 2 associated ARDS as well.	[138]
Lima et al.,	chloroquine encapsulated Polylactic Acid NPs (CH-PLA NPs	To explore the affinity of CH-PLA NPs to inhibit the entry of virus into host	Developed NPs significantly blocks the SARS-CoV 2 entry into human host due to morphologically resemble.	[139]
Abouaitah et al.,	Ellagic acid impregnated ZnONPs functionalized with triptycene organic molecule (TRP-ELG-ZnONPs	Antiviral activity of TRP-ELG-ZnONPs	TRP-ELG-ZnONPs with virucidal efficiency of >60% was comparatively less cytotoxic with respect to free ELG and ZnONPs.	[140]
Molinaro et al.,	Dexamethasone incorporated NPs (Dex-NPs	to estimate anti-inflammatory activity of Dex-NPs	Dex-NPs cause inducement of immune response against pro-inflammatory cytokines in LPS- injected murine model enabling their survivability rate.	[141]
He et al.,	Surface modified AgNPs	To determine virucidal activity modified AgNPs	Branched polyethyleneimine (BPEI AgNPs showed minimal cytotoxic effect against vero-E6 cells with superior virucidal potentiality against SARS-CoV 2 as compared to citrate and PVP modified AgNPs and free AgNPs.	[142]
Almanza et al.,	AgNO3 solution	Therapeutic exploration of AgNO3 solution against SARS-CoV 2 infection	Participants allowed to do mouthwash and nose rinse with AgNO3 solution showed minimal (only 1.8% incidence of infection compared to control group (showed 28.2%). In-vitro study performed in culture cells further revealed greater inhibitory activity.	[143]
Jin et al.,	Hesperidin conjugated chitosan NPs (HPD-CHNPs	Anti-inflammatory activity against acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) associated cytokine storm syndrome (CSS).	Exhibited significant reduction of ALI and ARDS induced inflammatory cytokines along with improved cellular uptake in inflammatory microenvironment irrespective to free HPD.	[144]
Ozturk et al.,	Cefaclor loaded Eudragit 100 NPs (CFC-ENPs, Cefaclor loaded Eudragit 100+PLGA NPs (CFC-EPNPs) and Cefaclor loaded PLGA NPs (CFC-PNPs)	Antimycobacterial property and therapeutic efficacy against SARS-CoV 2 accompanied coinfections and abdominal discomfort	Antimycobacterial activity for CFC-ENPs and CFC-EPNPs was observed to be 16-folds and for CFC-PNPs was 2-folds superior against S. aureus and E. coli, compared to free CFC.	[145]
Mehranfar et al.,	Functionalized AuNPs (AuNPs-pep	To determine the binding affinity of AuNPs-pep for RBD of SARS-CoV 2	AuNPs-pep exhibited greater interaction with RBD forming stable complex with it and hence inhibit viral infection.	[146]
Dormont et al.,	Squalene based multidrug NPs (SQ-Ad\Vit.E NPs	Anti-inflammatory activity against covid 19 infection	SQ-Ad\Vit.E NPs at concentration of 10 µg/ml showed enhanced inhibitory potentiality of pro-inflammatory cytokines and reactive nitrogen species in LPS induced in-vitro model of RAW 264.7 macrophage. In-vivo endotoxemia mouse model showed significant reduction of TNF-α, MLP-1, IL-6 with improved survivability rate.	[147]
Hanafy et al.,	Dual silymarin/curcumin loaded chitosan coated BSA NPs (CH—Curc/Sily BSA NPs	Determination of anti-inflammatory and anti-viral activity against covid 19	showed potential anti-viral activity against covid 19 at conc. of 25 µg/ml. Additionally, developed NPs exhibited strong anti-inflammatory activity against oleic acid model at minimal concentration.	[148]
Ding et al.,	RBC incorporated methylprednisolone sodium succinate loaded chitosan NPs (RBC-MPSS-CH NPs	To find out the potentiality and effectivity of developed NPs for lung targeting where SARS-CoV 2 primarily exist.	RBC-MPSS-CH NPs showed improved pharmacokinetic profile with greater drug accumulation throughout lungs. RBC-MPSS-CH NPs further displayed superior anti-inflammatory activity against LPS induced mouse model.	[149]
Khater et al.,	Fluoxetine HCL loaded lipid polymer hybrid NPs (FH-LPH NPs	To investigate therapeutic efficacy against SARS-CoV 2	Showed highest possible interaction with viral protease. Displayed enhanced cellular internalization with good biocompatibility.	[150]
Idris et al.,	siRNA incorporated stealth lipid NPs (siRNA-SLNPs	Examined the pharmacotherapeutic activity against SARS-CoV 2.	In-vivo study demonstrated the enhanced viral suppressive efficiency with improved survival rate in mice model.	[151]
Martins et al.,	Meso 2,3-dimercaptosuccinic acid fabricated iron oxide NPs (DMSA-Fe3O4 NPs	To investigate the possibility for drug delivery and treatment of SARS-CoV 2.	Successfully developed and physiochemically characterized NPs showed good biocompatibility against normal cell lines.	[152]
Hamouda et al.,	AgNPs fabricated wearing mask	Antiviral activity and breathability performance	AgNPs exhibited less toxicity with immense viral inhibitory potentiality. AgNPs fabricated cotton mask showed better air permeability and breathability compared to surgical mask.	[153]
Archana et al.,	Flower extract incorporated copper iodide NPs (FE-CuI NPs)	Antimicrobial activity against SARS-CoV 2	In-vitro study suggested less toxic against normal cells. Showed highest possible interaction with vial protease after molecular docking. FE-CuI NPs engineered cotton mask provides better viral entry inhibition capacity.	[154]
Deng et al.,	mRNA incorporated lipid NPs (mRNA- HB27-LNPs	Antiviral efficacy against corona virus	In- vivo study speculated the improved circulating half-life with greater protection against virus after i.v administration of mRNA-HB27-LNPs into mice model.	[155]
Sanna et al.,	Remdesivir loaded targeted NPs (RDV-TNP-1	Antiviral activity against COVID 19	RDV-TNP-1 showed highest binding propensity to ACE2 receptor with enhanced antiviral efficacy and better biocompatibility.	[156]
Zheng et al.,	RBC hitchhiked ivermectin loaded PLGA NPs (RBC-IVM-PNPs and chitosan coated PLGA NPs (RBC-IVM-CSPNPs)	Anti-inflammatory activity of ivermectin associated with SARS-CoV 2 virus.	RBC-IVM-CSPNPs exhibited prolonged circulating time profile with superior anti-inflammatory activity as compared to RBC-IVM-PNPs.	[157]

In this context, Pooladanda et al., developed an iRGD peptide fabricated Nimbolide liposome (iRGD - NIM_LIP) to determine its anti-inflammatory activity. Interestingly, the study showed that iRGD - NIM_LIP possessed superior potentiality to inhibit STAT3-DNMT-induced oxidative stress and cytokine storm as compared to free NIM, NIM_LIP and dexamethasone_. Additionally, iRGD - NIM_LIP further demonstrated the downregulation of bacterial endotoxin lipopolysaccharide (LPS) induced lipid peroxidation, pro-inflammatory cytokines, TNF-α mediated P65NF-κB signaling with additional antioxidant property in-vitro and in-vivo mouse model. Therefore, an author concluded that iRGD peptide fabricated Nimbolide liposome could be an effective approach for the treatment of SARS-CoV-2 induced acute respiratory distress syndrome (ARDS), a prime cause of mortality [138].

In one study, Lima et al., accessed the improved efficiency of poly lactic acid (PLA) encapsulated chloroquine to inhibit endocytosis of NPs. The study suggested that targeted delivery of nanoparticle fabricated chloroquine that morphologically resembles with SARS-CoV-2 virus may greatly block the host's cellular entry and hence could be one strong Nano-therapeutic approach for COVID 19 treatment as well [139].

In another investigation, Abouaitah et al., demonstrated the antiviral activity of ellagic acid (ELG) impregnated zinc oxide NP (ZnONPs) functionalized with triptycene organic molecule (TRP), a hybrid Nano formulation. In the study, the cytotoxic activity of free ELG against host cells was observed to be significantly higher compared to both ZnONPs and hybrid Nano formulations. Moreover, the antiviral potentiality of the developed Nano formulation was found to be superior irrespective of ZnONPs and ELG alone, with a therapeutic index of 77.3 for H1N1, 75.7 for HCoV-229E (RNA virus), 57.5 for HSV-2 and 51.7 for Ad-7 (DNA virus). Hence, a hybrid Nano formulation exhibiting direct viricidal efficiency of > 60% could be a new alternative therapeutic strategy to treat COVID 19 [140].

Similar to another study, Molinaro et al., assessed the anti-inflammatory property of dexamethasone using leukocyte-derived nano-vesicles called leukosomes. The study revealed that dexamethasone fabricated biomimetic nanoparticles could significantly reduce pro-inflammatory cytokines in lipopolysaccharide (LPS) injected murine model by enhancing their immune response and hence survivability rate as compared to free drug. Eventually, an author speculated that cytokine storm syndrome associated with COVID 19 can be mitigated and treated well through nanoparticle-incorporated corticosteroids including other anti-COVID 19 pharmacotherapeutic moieties [141].

In addition to this study, He et al., emphasized the virucidal potentiality of three different surfaces impregnated AgNPs (citrate modified, polyvinyl pyrrolidone modified-PVP and branched polyethyleneimine modified-BPEI) against SARS-CoV-2. In the observation, all three developed surfaces modified AgNPs were found to be less toxic against Vero E6 cells exhibiting significant cell viability concerning AgNO3. Moreover, BPEI-modified AgNPs with 50 nm particle size showed greater antiviral activity than citrate-modified and PVP-modified AgNPs providing sophisticated insight for the development of such battle-winner tools against COVID 19 [142].

On other hand, Almanza et al., presented the potential therapeutic efficiency of AgNO3 solution against SARS-CoV-2 in healthcare personnel. In the investigation, in vitro study performed in cultured cells showed higher inhibitory activity. Moreover, a clinical study conducted on 231 participants over 9 weeks further demonstrated that the experimental group who were instructed to do mouthwash and nose rinse through AgNO3 solution showed a significantly lower incidence of infection (only 2 out of 114, i.e., 1.8%) compared to control group (got an infection in 33 out of 117, i.e., 28.2%) who were instructed to use in a conventional way indicating that nanoparticle-based treatment could be worth noting [143].

Additionally, to get insight into the treatment of COVID 19, Jin et al., investigated the anti-inflammatory activity of hesperidin conjugated chitosan NPs (HPD-CHNPs) against acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) associated cytokine storm syndrome (CSS) through nasal delivery in a mouse model. However, in vivo study suggested that compared to free HPD, HPD-CHNPs exhibited a significant reduction of inflammatory cytokines and vasculature permeability that ultimately results in marked inhibition of ALI and ARDS, in addition to higher cellular uptake of drug in an inflammatory microenvironment. Overall, nanoparticle-based drug delivery could be relevant to attenuating CSS and ARDS specified for COVID 19 patients [144].

In another context of an investigation, Ozturk et al., performed the study of Cefaclor monohydrate (CFC) for its antimycobacterial activity and therapeutic efficacy against COVID 19 accompanied coinfections and intestinal symptoms through the delivery of either CFC-loaded Eudragit S100 NPs (CFC-ENPs) or CFC loaded Eudragit S100+PLGA NPs (CFC-EPNPs) or through CFC loaded PLGA NPs (CFC-PNPs). As per the study, the antibacterial activity for all three different nanoparticle-based formulations exhibiting the size range of 171.4–198.8 nm and encapsulation efficiency of 58.4%- 81.2% were found to be superior by 16-folds for both CFC-ENPs and CFC-EPNPs and by 2-folds for CFC-PNPs as compared to free CFS against S. aureus and E. coli. Additionally, Eudragit fabricated both nano formulations were found to be pH -sensitive, a colon targetable while CFC-PNPs showed prolonged release profile after in vitro dissolution study [145].

Likewise, Mehranfar et al., synthesized the functionalized AuNPs to determine their ability to bind RBD of SARS-CoV-2 via the molecular (MD) dynamic simulation method. Interestingly, AuNPs-pep exhibited minimum distance with RBD indicating greater interaction between them compared to other functionalized nanoparticles. Additionally, AuNPs-pep further causes a significant reduction of average solvent accessible surface area value (SASA) of RBD with 8970 A², which results in coverage of the whole binding surface of RBD with forming most stable complex as similar to ACE2 whose SASA value of RBD was 8941 A², providing new insight for subsequent inhibition of COVID 19 [146].

In the search, Dormont et al., devised squalene-based multidrug NPs to determine their potentiality against COVID 19 induced hyper inflammation. Indeed, successful delivery of adenosine (endogenous immunomodulator as anti-inflammatory) and α-tocopherol (Vit. E as an antioxidant) by conjugating with squalene (endogenous lipid) NPs (SQ-Ad\Vit.E NPs) was presented. Importantly, SQ-Ad\Vit.E NPs exhibited an efficient inhibitory profile for pro-inflammatory cytokines and reactive nitrogen species (NOx) at a concentration of 10 µg/ml in LPS induced in vitro model of RAW 264.7 macrophage while in vivo endotoxemia mouse model showed a significant reduction of TNF-α, MLP-1, IL-6 with increased IL-10 along with the improved pharmacological response (bioavailability) compared to free drug. Accordingly, SQ-Ad\Vit.E NPs further demonstrated for its side effect study where they showed no significant reduction of BP with a protective effect of liver injury and hence improved survival rate in lethal LPS treated mouse model [147].

Recently, Hanafy et al., synthesized chitosan-coated bovine serum albumin NPs encapsulated with silymarin/curcumin (CH—Curc/Sily-BSA NPs) to determine its anti-inflammatory and anti-COVID19 activity. However, thus developed CH—Curc/Sily-BSA NPs were found to be optimally efficient for muco-inhalable delivery with higher dispersibility and improved lung deposition capability. Importantly, the developed CH—Curc/Sily-BSA NPs displayed a significant reduction of IL-6 at 64 ± 0.8 Pg/µL and superior inhibition of CRP at 6 ± 0.5 µg/µL in the oleic acid model. Further, dual curcumin and silymarin-loaded NPs at a concentration of 25 µg/ml showed potential antiviral activity against COVID 19 (44.4% viral inhibition) with improved histopathological evidence, contributing to its strong pharmacotherapeutic potentiality [148].

Besides that, Ding et al., formulated RBC incorporated methylprednisolone sodium succinate (MPSS) loaded chitosan NPs (RBC-MPSS-CH NPs) for effective delivery targeting the lung where COVID 19 primarily exists with a motive for reduced dosing frequency and hence toxicities. An ongoing study further identified the significant reduction of drug plasma concentration with improved circulation time through RBC Hitchhiking after in vivo pharmacokinetic study. Additionally, irrespective of MPSS-CH NPs and free MPSS, RBC- MPSS-CH NPs showed higher mean residence time (MRT) and area under curve (AUC) profile. On the other side, hepatocellular uptake of delivered drug through RBC- MPSS-CH NPs was superior with greater drug accumulation throughout the lungs as identified via in vivo fluorescent study in a mouse model. Equally important, RBC- MPSS-CH NPs exhibited a significant reduction of TNF-α and IL-6 in LPS induced lung injury rat model as compared to MPSS-CH NPs and free MPSS [149].

Another investigation conducted by Khater et al., introduced Fluoxetine HCL (FH) loaded lipid polymer hybrid NPs (FH-LPH NPs) to identify the potentiality and its efficacy against SARS-CoV-2 infection. The experiment initiated by determining the possible interaction between selective serotonin reuptake inhibitors (SSRIs) and SARS-CoV-2 main protease through molecular docking (MD) confirmed the highest possible interaction of FH through hydrogen bonding formation with a minimum required energy among other SSRIs. Most importantly, a cytotoxicity study performed for developed NPs in CCD-19 L4 cells (human lung fibroblast) exerted biocompatible to human cells. In addition, a cellular uptake study performed through Flow cytometry using Dil Labeled FH-LPH NPs of 50 nm size in CCD-19 L4 cells showed satisfactory cellular internalization. Contrarily, in vitro release study of FH-LPH NPs carried out in phosphate buffer saline (PBS) and 10% v/v fetal bovine serum (FBS) showed 86% and 92% release profiles respectively after 24 h, indicating the controlled release behavior [150].

On the contrary, Idris et al., aimed to synthesize different types of siRNA-incorporated stealth lipid nanoparticles (SLNPs) to investigate the pharmacotherapeutic efficacy against SARS-CoV-2. As the study demonstrated that the suppressive potentiality of siRNAs-SLNPs against COVID 19 was satisfactory after in vivo study in an infected mice model. In addition to this, siUC7-SLNPs and siHeL2-SLNPs after intravenous administration in mice model greatly enhance the survival rate by causing lower weight loss as compared to viral infected and control-treated mice. Notably, an author identified that the siRNAs-SLNPs delivery system has the immense potential to block viral expression and replication in humans as well [151].

On other hand, Martins et al., further displayed the potential use of meso 2,3-dimercaptosuccinic acid (DMSA) fabricated iron oxide NPs (DMSA-Fe₃O₄ NPs) against COVID 19 disease. Thus developed DMSA-Fe₃O₄ NPs with a size range of 12 nm were physiochemically and magnetically characterized using different techniques owing to optimally synthesized for delivery. Moreover, a biocompatibility study of DMSA-Fe₃O₄ NPs further demonstrated the lack of toxicity to a normal cell, providing new insight for use of Nano-medicinal based delivery to mitigate the deadliest COVID 19 [152].

Besides the delivery of antiviral candidates site-specific through a nanoparticles-based approach, Hamouda et al., addressed the use of AgNPs in wearing a mask for its antiviral activity against COVID 19 and also measures the breathability performance of AgNPs treated masks. The cytotoxicity study and viral inhibitory study of AgNPs were performed in VERO-E6 cells which displayed cytotoxic concentration (CC₅₀) 142.5 µl/ml indicating less toxic to host and inhibitory concentration (IC₅₀) 25 µl/ml for 21.49% viral inhibition and displayed potent antiviral activity. On other hand, air permeability and breathability of 100% cotton mask performed on volunteers showed no significant alteration in blood oxygen saturation (SpO2%) and heart rate even at working and waking time compared to surgical mask. Noteworthy, the author concluded that AgNPs fabricated cloth masks could be a promising strategy to control COVID 19 [153].

Similarly, Archana et al., also examined the antimicrobial activity of flower extract (Hibiscus rosa Sinensis) incorporated copper iodide NPs (FE-CuI NPs) against COVID 19. The developed prismatic-shaped FE-CuI NPs with a size range of 552.45 nm were further fabricated into cotton fabric protective face masks to knock down the entry of COVID 19 into a human host. Additionally, in vitro cytotoxicity study of developed NPs was analyzed against cancer and spleen cell lines and was observed to be dose-dependent manner with IC₅₀ value of 233.93 µg/ml indicating biocompatible. Noteworthy, a molecular docking study confirmed the strong interaction between FE-CuI NPs and COVID 19 main protease that reinforces the approach for efficient and effective mitigation of existing COVID 19 [154].

In addition, Deng et al., explored the therapeutic efficacy of mRNA Antibody encapsulated lipid NPs (mRNA-LNPs) against SARS-CoV-2 infections. Importantly, in vivo study suggested that intravenous administration of mRNA-HB₂₇- LNPs in mice model showed improved circulating half-life with longer protection for 1,7 and even 63 days against SARS-CoV-2, irrespective to free HB₂₇ antibody. Additionally, study further revealed that the antiviral efficacy of mRNA-HB₂₇- LNPs in the hamster model was observed to be dose-dependent manner after prophylactic administration [155].

In the next investigation, Sanna et al., demonstrated the antiviral activity of remdesivir-loaded targeted NPs (RDV-TNP-1) against SARS-CoV-2 infected Vero E6 cells. Afterward, the antiviral potentiality of RDV-TNP-1was observed to be significantly improved along with the highest ACE2 binding capability as compared to free RDV or non-targeted ones. Most interestingly, empty TNP-1E further exhibited antiviral efficacy which might be due to its direct competitive mechanism with viral particles for ACE2 receptors. Moreover, RDV-TNP1 further exposed its better biocompatible properties against normal cell lines irrespective to free RDV. Accordingly, an author concluded that TNP-based inhalable antiviral drug delivery for pulmonary targeting could be extremely favorable [156].

In addition to this, Zheng et al., highlighted the antiviral activity of Ivermectin (IVM) against SARS-CoV-2 via enhancing its pharmacokinetic attributes through the delivery of RBC- Hitchhiked IVM loaded PLGA NPs (RBC-IVM-PNPs) and chitosan-coated PLGA NPs (RBC-IVM-CSPNPs). Very importantly, both developed RBC—Hitchhiked NPs showed efficient pulmonary delivery with improved drug accumulation to the lung tissues which ultimately leads to potential suppression of inflammatory response and progression of acute lung injury. Although, cationic RBC-IVM-CSPNPs displayed superior anti-inflammatory activity due to their longer circulation times and minimal elimination rate irrespective of RBC-IVM-PNPs [157].

5. Nanoparticles based vaccines delivery against COVID 19

The current situation facing mutational behaviours of corona virus frequently leads the global health and economy towards massive disruptions. Such multiple mutation and novel viral strain of COVID 19 primarily persists as a great wall barrier for the delivery of traditional vaccines like inactivated vaccines live attenuated vaccines, recombinant vaccines, DNA and viral vector-based vaccines that ultimately results in unexpected poor efficacy and effectiveness. Going towards, the development and deployment of future-proofing nanoparticles-based vaccine delivery against COVID 19 straightforward the emerging promise and become a selective track. Vaccine antigens either encapsulating at the core of nanoparticles (antigen encapsulated NPs) or trapped at the surface of nanoparticle (antigen-presenting NPs) offers feasible and tunable particulate structures that mimic the structural features of natural viruses [158], [159], [160].

In the present study, Walsh et al., developed lipidic nanoparticles for the delivery of two candidates (BNT162b1 and BNT162b2) based on nucleoside-modified RNA vaccines. They took trial on 195 candidates, in which 15 candidates are assembled in each of 13 batches. However, in adults, especially, BNT162b1 (secretes trimerized COVID-19 receptor binding sector) is accessorized with mild systemic reactions as compared to BNT162b2 (membrane-affixed COVID-19). Importantly, BNT162b2-based lipidic delivery showed superior safety and immunogenicity in younger and elder as compared to the BNT162b1 lipidic-based delivery system which further enforces to conduct of phase 2–3 clinical trials to investigate its safety and efficacy as well [161].

In another study, small interfering RNA (siRNA) incorporated three different lipidic nanoparticles (LNPs) were prepared by Idris et al., to target SARS-CoV-2. The study demonstrated that 90% of therapeutic effect was screened among all 3 developed LNPs when administered either singly or in combination form. In the meantime, siRNA-loaded two novel LNPs further possessed higher efficacy against SARS-CoV-2 infection with improved survivability rate after i.v administration into mice model. Noticeably, prepared LNPs can be scaled up to demonstrate in humans to treat the first arrival of viral symptoms [151].

Simultaneously, Elia et al., engineered mRNA vaccines based on LNPs conjugated SARS-CoV-2 human Fc-incorporated receptor binding domain (LNPs-RBD-hFc mRNA). Herein, in-vivo study demonstrated in BALB/c mice model showed improved Th-1 biased cellular response and robust humoral response, in addition to increased neutralizing antibodies [162].

Similarly, the next study performed by Rao et al., has further demonstrated the significance of genetically engineered derived decoy nanoparticles (nano-decoys) against SARS-CoV-2 infection. Most importantly, nano-decoys engineered by fusing cellular membrane nano-vesicles of ACE-2 receptors and human monocytes showed the potential to adsorb viral and inflammatory cytokines (interleukin-6 and granulocyte-macrophage colony-stimulating factor) in a mouse model, providing efficient protection against SARS-CoV-2 associated immune disorder and lung injury by competing with host cells [163].

In another investigation, Smith and co-workers et al., prepared a synthetic DNA vaccine to target the S protein of Covid-19. In in-vitro experiment, they found the robust nature of INO-4800. Furthermore, immunization with INO-4800 in mice and guinea model were tested for T-cell response which is antigen specified. Also, neutralized by functional antibodies and occlude the ACE-2 receptor from protein binding along with bio-distribution to the pulmonary region. Finally, we can conclude as the INO4800 vaccine stands as a possible applicant for translational analysis [164].

In addition, Gu et al., speculated the efficacy and safety profile of REVX-128 loaded trimeric spike protein impregnated NPs based vaccine delivery against SARS-CoV-2. Interestingly, the study exposed that even a single shot of NPs based vaccine immunization in mice model provides significantly higher serum antibody naturalizing potentiality as compared to NPs deficient vaccine immunization. Moreover, NPs based immunization in the Syrian golden hamster model further revealed superior antiviral activity and a greater safety profile irrespective of unprotected animals. Subsequently, NPs based REVX-128 vaccine also provides better thermostability up to 37 °C for at least 4 weeks, enabling its propensity towards considerable progress on mitigation of COVID 19 [165].

In another experiment, Yang et al., formulated SW0123 incorporated SARS-CoV-2 spike protein packaged core-shell structured lipo-polyplex NPs (SW0123-LPP NPs) to fight against pandemic COVID 19. They reported that SW0123-LPP NPs-based vaccine immunization by intramuscular route to mice and non-human primates showed better uptake and prudent bio-distribution pattern with reduced liver targeting effect. In addition, inducement capability for Th-1 polarized T cells response and antibody neutralizing capacity of SW0123-LPP NPs based vaccine delivery associated with SARS-CoV-2 as well as D614G and N501Y variants was found to be significantly higher, depicting its potent immunogenicity [166].

In another similar study, Shinde et al., formulated an NVX-CoV2373 nanoparticle vaccine to determine its efficacy against the B.1.351 variant of COVID 19. The ongoing study demonstrated that NVX-CoV2373 nanoparticle vaccine exhibited superior efficacy of 60.1% (95% CI,19.9 to 80.1) among HIV negative with seronegative at the base line while vaccine efficacy in seropositive at baseline was 52.2% (95% CI, −24,8 to 81.7%). Notably, prototype sequenced NVX-CoV2373 nanoparticle-based vaccine immunization showed strong antibody neutralizing efficacy and improved antigen-specific poly-functional CD4 + T-cells response which may prevent cross-transmission of serological variants of SARS-CoV-2 [167].

Very hopefully, Zhang YN et al., investigated the mechanism of vaccine-induced immunity and antibody neutralizing potentiality of self-assembling protein NPs (SApNPs) against various variants of SARS-CoV-2. Afterward, the study revealed that S2GΔHR2 spikes (of ancestral Wuhan-Hu-1 strain) incorporated SApNPs exhibited a superior tendency to neutralize all B.1.1.7, B.1.351, P.1, and B.1.617 variants with comparable potency. Most importantly, 13–01v9-SApNPs possessed longer retentibility by 6-folds with 4-fold higher follicular dendritic cellular presentation and 5-folds greater germinal center reactibility in lymph node follicles of the mouse model as compared to soluble spikes [168].

Similarly, Thomas et al., designed BNT162b2-lipid NPs based mRNA vaccine to examine its efficacy and safety against COVID 19. In the study, BNT162b2-lipid NPs exhibited acceptable adverse event profiles with vaccine efficacy estimated as 96.7% (95% CI, 80.3 to 99.9) in severe disease cases while 91.3% (95% CI, 89.0 to 93.2) among participants without evidence of previous SARS-CoV-2 infections after 6 months follow up. Interestingly, almost 100% vaccine efficacy was observed against B.1.351 variants of SARS-CoV-2 in the south African region [169].

In one study, Kremsner et al., developed mRNA-based lipid nanoparticles-based viral S protein incorporated vaccine (CVnCoV-SLNPs) to determine its safety and efficacy profile in human volunteers. In the study, an experiment was performed with limited participants with different controlled groups at variable concentrations ranging from 2 to 12 μg for 28 days, where safety, efficacy and immunogenicity were observed to be concentration dependent and hence regarded to be safe for human use [170].

In this regard, the same experimental group further investigated the antibody neutralizing efficacy of CVnCoV-SLNPs against SARS-CoV-2 in a large participant group. Herein, after immunization of the 2nd dose of 12 μg CVnCoV-SLNPs, antibody neutralizing capacity was found to be 83% against seroconverted SARS-CoV-2 neutralizing titer (MN50) and 100% against SARS-CoV-2 S protein or RBD. After all, an author and group concluded that a concentration of CVnCoV-SLNPs with 12 μg exhibiting strong efficacy and immunogenicity with acceptable side effects, could be an effective approach for COVID 19 prevention [171].

In addition, McKay et al., also formulated a self-amplifying RNA encoded viral S protein incorporated LNPs (saRNA-SLNPs) to find out its antibody neutralizing capacity and humoral response between injected murine and COVID 19 recovered patients. Here, saRNA-SLNPs injected mice model showed dose-dependent viral neutralization efficiency of IC50 of 5 × 10³ to 10⁵ and higher antibody titer compared to a naturally infectious human with IC50 of 10³. Furthermore, saRNA-SLNPs injection into mice model also exhibited dose-dependent immunogenicity which was particularly higher than in COVID 19 recovered patients, enabling rapid translation for clinical use as well [172].

Sequentially, another research conducted by the same research group, prepared the same formulation of self-amplifying-RNA encoded lipidic nano-formulated vaccine (saRNA-SLNPs). In this investigation, saRNA-SLNPs exhibited robust neutralization against both pseudo virus and wild-type virus along with remarkable superior and dose-dependent SARS-CoV-2 specific antibody titers in mouse sera. Equally important, developed saRNA-SLNPs further showed enhanced cellular response with improved immunogenicity in the mice model [173].

6. Nano-technological strategy in personal protection equipment (PPE)

However, nanotechnology plays a crucial role in multi sectors such as in a diagnostic field, drug and vaccine delivery, against COVID-19 [174]. Besides, the applicability of nanotechnology in personal protection equipment (PPE) in the current scenario becomes equally fruitful for the prevention of SARS-CoV-2. Although, the world is currently consuming enormous PPE such as masks, face shields, respirators, etc. just to be protected from entry of the SARS-CoV-2 virus, but 100% effectiveness was not achieved through the use of such conventional PPE. Globally, consumers are limited to the use of conventional PPE right now, due to which they are still facing challenges with COVID-19. Therefore, the use of Nano-technological strategy in various PPE could easily surpass the theatrical situation of COVID-19 [175,176].

Recently, Zhong et al., synthesized a graphene-coated temperature-sensitive surgical mask by dual-mode laser fabrication method. Importantly, this reusable and recycled graphene-coated mask showed an efficient viral sterilization activity under solar illumination, due to high surface temperature (quickly increase to over 80 °C) and provides better protection from incoming viral droplets due to its super-hydrophobic surface. Additionally, pertaining to its outstanding salt-rejection performance, a photothermal graphene-coated mask could be directly used in solar-driven desalination for long-term use as well [177].

In addition to this, Huang et al., demonstrated that the bacterial inhibition rate of developed laser-induced graphene modified mask showed 80%, with additional 99.99% bacterial killing efficiency within 10 min, was observed after combination with graphene layer's photothermal effect. Thereby, the study further suggested the importance and applicability of nano-technological based PPE for effective prevention of COVID-19 [178]. In next study, Chen et al., further discussed the antiviral activity of graphene oxide (GO) fabricated with AgNPs (GO-AgNPs) against both enveloped and non-enveloped viruses, indicating an effective approach for the development of viral-resistant PPE [179]. Moreover, Nakamura et al. also demonstrated the antibacterial and antiviral activity of devised AgNPs chitin nano fiber sheet (CNFS) against E. coli and H1N1 virus respectively. The study showed that AgNPs-CNFS possessed potential antiviral activity against the influenza virus, indicating that such NPs could be equally efficacious against SARS-CoV-2 when applied to protective cloths, masks and gloves [180]. Similarly, the study conducted by Borkow et al., suggested that impregnation of CuONPs into N95 respiratory mask exhibited improved biocidal and antiviral activity against influenza viruses without alteration in filtration efficiency of a mask [181]. On the other hand, Ungur et al., devised polyurethane fabricated CuO nano fiber to determine the air filtration efficiency. Such developed nano fibers showed improved air filtration efficiency and could be a better platform for its use in various surgical masks to be protected from virally contaminated air droplets [182].

7. Nanotechnology in surface decontamination and sanitization

Many studies suggested that SARS-CoV-2 viral contaminated micro-droplets released during sneezing and coughing may persist for 3 h to up to 9 days at 30 °C or even more, in an aerosolized form. These droplets can be transmitted from one person to another, if someone touches a contaminated surface and thereafter gets infected. To be free from such contamination, numerous conventional disinfectants and sanitizers such as alcohols, soap, sodium hypochlorite, hydrogen peroxide, etc. are available but still facing challenges to control COVID-19 [183,184]. Therefore, nano-technological based approach such as metallic NPs which are well known for their antibacterial, antifungal and antiviral activities, provides enormous strength and opens a new avenue for developing highly efficient and very effective disinfectants [185]. Additionally, activation of nano-technological devices upon electrothermal, photocatalytic and photothermal stimuli causes a release of active substance more efficiently, accompanying clear and upto 100% disinfection potentiality [186].

In this regard, the antiviral activity of AgNPs has been studied by various researchers and group against the different virus. Elechiguerra et al., demonstrated the antiviral activity against HIV-1 virus [187]; Rogers et al. studied against monkeypox virus [188]; Orlowski et al., against herpes simplex virus [189]; Xiang et al., against H1N1 influenza virus [190], and so on, indicating potential option for disinfection of SARS-CoV-2 as well. Similarly, Gusseme et al. [191], and park et al. [192], also demonstrate the antiviral activity of AgNPs by disinfecting viral contaminated water, signifying a better option for disinfection of SARS-CoV-2 from the contaminated surface as well. In addition to this, the antimicrobial activity of CuNPs has also been well established, which could be suitable technique to combat various viruses. In one study, Murray et al. demonstrate potential antiviral efficacy of Cu against poliovirus [193]. Moreover, Warnes et al., further examined viral inhibitory efficacy of CuNPs against HuCoV-229E corona virus. The study showed that CuNPs could efficiently inhibit viral growth, which further inhibits SARS-CoV-2, when used as disinfectant [194].

8. Toxicological aspects of nanoparticles

However, nanoparticles emerge as novel tools for bio-imaging, diagnosis and delivery of immense pharmacotherapeutic moieties against many deadliest diseases. In the meantime, potential investigation for its toxicological perspective seems to be equitability in respect to its use during delivery of multi cargos. Notably, various studies have been approached to confine the threatful adverse effects of nanoparticles on cardiovascular, neurological, pulmonary, cytological and other various epidemiological toxicities [195], [196], [197]. Numerous studies demonstrated that the toxic effect of such inorganic nanoparticles occurs through physicochemical (dispersity, size, shape and surface chemistry) and biochemical (cellular and molecular) mechanisms as shown in Fig. 6 . More specifically, the cellular mechanism involves lysosomal impairment, mitochondrial dysfunctions, mitophagy, endoplasmic reticulum (ER) stress and endoplasmic reticulum autophagy, while molecular mechanism particularly associated with autophagy-related to signaling pathway, hypoxia-inducible factors and oxidative stress [198], [199], [200].

Fig. 6.

Schematic representation of the toxicological effect of nanoparticles via the physicochemical and biochemical mechanism.

Additionally, many researchers have investigated the potential pathway for toxicological aspects of inhaled or administered nanoparticles. Fortunately, most of the synthetic organic, supra-molecular and polymeric-based NPs showed bearable or no toxicity due to their biodegradable and biocompatible natures [201,202]. On other hand, the undesirable and unbearable toxicity of inorganic NPs is mainly due to apoptosis, necrosis, oxidative stress and autophagy [203,204]. Further, autophagy is the prime root for causing significant toxicities which mainly follows microautophagy, macroautophagy and chaperone-mediated autophagy. Microautophagy involves the direct engulfment of cytoplasmic components into lysosomes in non-selective manners whereas macroautophagy is associated with the formation of autophagosomes initially, followed by fusion of autophagosomes into lysosomes and hence its degradation, leading to cell death shown in Fig. 7 . Similarly, chaperone-mediated autophagy is a degradative phenomenon of translocated cytosolic soluble proteins through chaperone-dependent selecting manners without the formation of additional vesicles [205], [206], [207]. In one investigation, Yu et al., elucidated that autophagic cell death was observed due to silica NPs in hepatoma HepG2 cell lines, which were then markedly inhibited by autophagy inhibitor [208]. Similarly, Liu et al., and park et al., further examined the autophagic cell death in A549 lung cell lines and BEAS-2B bronchial cell lines respectively, due to the toxicological effect of single-walled carbon nanotubes [209,210]. Moreover, Sun et al., highlighted the copper oxide NPs inducible autophagy in A549 cell lines, which was inhibited by autophagic inhibitors like wortmannin and 3-methyladenine [211]. In addition, Yu et al., and Johnson et al., further investigated the efficient toxicity of zinc oxide NPs leading to autophagic cell death [212,213]. Besides, cationic poly-amidoamine dendrimers also may cause intolerable adverse effects like liver injury, lung damage and neuronal dysfunctions associated with autophagic cell death [214], [215], [216]. In the next study, wang et al., confirmed the lysosomal dysfunctional associated autophagic cell death in hepatocytes due to silica NPs [217]. Importantly, Fe₃O₄ NPs exhibited potential lysosomal functional impairment, mitochondrial damage, ER and Golgi body stress, where after such destructive effect was mitigated by PLGA-coated Fe₃O₄ NPs [218].

Fig. 7.

Nanoparticles induced macroautophagy pathway following three different steps: (1) formation of double membraned autophagosomes from cytoplasmic constituents (misfolded proteins or damaged organelles), (2) formation of autolysosomes by the fusion between autophagosomes and lysosomes, (3) degradation of autophagosomes leading to cell death.

9. Conclusions

After the outbreak of SARS-CoV-2 throughout the world, millions of people were infected with the virus and lost their life. Notably, the Shortage of advanced technological diagnostic kits and lack of effective treatment alternatives further contribute to disastrous health and economic issues. Although, worldwide’ s health organizations, pharmaceutical industries, and many groups of scientists have collaborated to find out efficient approach for the prevention of COVID 19, but still facing multiple challenges to shout the pandemic. In contrast, nano-technological strategies for diagnosis via bio-sensing, treatment via medicinal delivery and prevention via vaccine delivery create an emerging hope for the entire world. The rapid, highly sensitive and more accurate potentiality of this diagnostic nano-technological equipment strongly provides arrays for early detection of COVID 19. Additionally, higher drug internalization, greater target ability, reduced dosing frequency and hence toxicities and cost-effective method of Nano-medicinal and vaccine delivery further helps in the treatment and prevention of corona virus. Subsequently, upcoming deadliest viral infections can also be easily diagnosed, treated and prevented through a nano-technological approach. However, limited potent toxicities associated with administered NPs, equally need to be focused on and comprehensively investigated but the beneficial outcomes of this novel nano-technological backbones greatly overcome the hurdles and barriers associated with drug delivery. Therefore, in the current situation, this Nano-medicinal based pathway may significantly draw the attention of entire global scientists.

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Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper