Seeds and nanomaterials: seed-assisted synthesis, nanotoxicity, and seed-associated nanotechnology innovations

Abstract

Seeds are the cornerstone of agricultural crop production. They are sources of many valuable materials that can be used to convert bulk materials into nanoforms, thus supporting sustainability in nanomaterial (NM) synthesis and circular farming. The use of seeds in innovative nanotechnology is based on the theoretical knowledge about seed–NM interactions and NM toxicity on seeds. The results show that the internalization of NMs into seeds and their effect on seed physiology depend on several properties of both the NM and the plant species. Nanotechnology innovations including seed-associated strategies for improving abiotic stress tolerance, facilitating pathogen protection, effectively transferring genetic information into embryos, and converting seed oils into biodiesel have been recently developed. This review aims to provide an overview of the current knowledge regarding the complex, multidirectional interactions of seeds with NMs, and suggest directions for future research of seed nanobiology.

Seeds are used for nanomaterial (NM) synthesis. NMs affect seed physiology independently from their penetration in seeds. Seed-based innovations include NM-assisted DNA delivery, seed priming, seed oil transformation and nanosensors.

Introduction

Nanomaterials (NMs) are commonly defined as materials with at least one external dimension or an internal structure in the nanoscale range—typically between 1–100 nanometres (nm). This size range is widely accepted by international standards (International Organization for Standardization and the European Commission). However, this definition is not restricted to size range. In certain cases, materials slightly exceeding 100 nm may still be classified as NMs if they exhibit nanoscale properties due to their high surface area-to-volume ratio, superparamagnetism, quantum effects, or enhanced surface reactivity. As such, functional behaviour and not just size can justify classifying a material as a nanomaterial.

For example, at dimensions less than 5 nm, their catalytic activity is markedly augmented, thereby rendering these materials exceptionally efficient in facilitating chemical reactions. Nanoparticles (NPs) with dimensions under 20 nm have the capacity to transition between hard and soft magnetic states, whereas those smaller than 50 nm undergo modifications in their refractive index properties, which are of paramount importance for optical applications. Furthermore, NMs with dimensions below 100 nm display superparamagnetism a characteristic advantageous in imaging and data storage (Baig et al., 2021). The size range and morphology of the compound are of significance, as they impart unique physical biological and chemical properties such as different electrical and thermal conductivity, light absorbance, and catalytic activity, as well as antimicrobial activity, that differ markedly from those of their bulk counterparts.

When characterizing nanostructures, it is essential to distinguish the number of dimensions a material exhibits on the nanoscale. Zero-dimensional (0D) NMs possess nanoscale dimensions in every aspect, resulting in distinct electronic properties due to quantum confinement (e.g. quantum dots). Nanostructures that exhibit two characteristic dimensions ranging from 1 to 100 nm, while the remaining dimension is not within the nanoscale, are classified as one-dimensional (1D) nanostructures (e.g. nanorods and nanotubes). Two-dimensional (2D) NMs, (including nanofilms, nanolayers, and nanocoatings) comprise thin layers characterized by a minimum thickness of one atomic layer, with numerous atoms present on their surfaces. Materials whose dimensions exceed 100 nm in all aspects are referred to as three-dimensional (3D) nanocubes or nanocages (Tiwari et al., 2012).

NMs are classified into five primary categories based on their composition: carbon-based, inorganic-based, organic-based, composite-based, and bio-based NMs. Carbon-based NMs are present in various configurations and states, including graphene, fullerenes, carbon nanotubes, nanofibers, nanodiamonds, etc. (Kharisov and Kharissova, 2019). Inorganic-based NMs are mainly metal or metal oxide particles with at least one dimension below 100 nm. They are composed of pure precious metals such as gold (Au) or silver (Ag) or being in the form of metallic oxides such as titanium oxide (TiO₂) or zinc oxide (ZnO) nanoparticles. Organic-based NMs are small particles made of organic molecules or polymers like micelles, dendrimers, liposomes, nanogels, polymeric NPs, and layered biopolymers. Composite-based NMs (nanocomposites) are hybrid materials that are produced by mixing of various NMs or blending NMs with larger materials (polymers, ceramic, bulk metals), mostly prepared via in situ growth or polymerization. The structure, composition, interfacial interactions, and the properties of their individual components heavily influence their characteristics. Bionanomaterials (bio-based NMs) are defined as molecular material composed partially or wholly of biological molecules like proteins, antibodies, enzymes, nucleic acids, lipids, poly- and oligosaccharides, viruses, secondary metabolites, etc. These molecules can also be utilized to fabricate complex devices through self-assembly under eco-friendly conditions. In addition to naturally derived materials—sourced either directly from biological systems or engineered to emulate their structural and functional properties, such as chitosan, which is extensively utilized in the food and bioengineering sectors for the encapsulation of bioactive compounds, enzyme immobilization, controlled drug delivery, and as a promoter of plant growth and seed germination—synthetic bionanomaterials, including locked nucleic acids (LNA), peptide nucleic acids (PNA), and xeno nucleic acids (XNA), have been specifically designed for targeted biological and biomedical applications (K.R. Singh et al., 2021; P. Singh et al., 2021).

One of the promising applications of NMs is in the domain of crop production. Nanotechnology’s potential in agriculture spans from seed and plant growth improvement to agrochemical delivery and real-time monitoring of plant and soil health (Kolur et al., 2024). Research in plant nanobiology has been conducted in two primary directions. Besides the evaluation of NM phytotoxicity, the use of NMs in agricultural crop production to increase yield and alleviate environmental pressures has been extensively studied in the past decades (Gowtham et al., 2024; Thabet and Alqudah, 2024).

Seeds as the reproductive units of higher plants are fundamental elements in agricultural plant cultivation and plant diversity maintenance, and play a decisive role in the life cycle of the higher plant (El-Maarouf-Bouteau, 2022). In general, the seed is composed of an embryo surrounded by stored nutrient material and covering layers. As for angiosperms, the seed generally contains the embryo, the endosperm, and the perisperm, the lattermost corresponding to the nucellus and the seed coat (testa). The new individual is represented by the embryo which consists of an embryonic axis and one or two cotyledons. The axis includes the radicle (the embryonic root), the hypocotyl, and the plumule (shoot apex). As a result of desiccation, the final phase of seed development, dry seeds with low water content, a glassy-state cytoplasm, and a low level of metabolic activity are formed. The germination of dry seeds starts with water uptake and ends with radicle protrusion and can be divided into three phases. Rapid water uptake in phase I induces the transition of membranes from gel to a liquid crystal state, and the reorganization of cell structure and molecules required for cell metabolism. In the next germination phase (phase II), water absorption stops and the metabolic activity increases, with intensified gene expression linked to respiration, levels of both hormones and sugars, cell wall metabolism, and protein turn-over enabling the preparation for cell elongation and growth. This metabolic activation is followed by fast water uptake again (phase III) to promote reserve mobilization and metabolism for radicle growth (El-Maarouf-Bouteau, 2022). The successful establishment of the new individual is determined by physiological and biochemical features of the seeds in response to their environment. Distinguished based on seed longevity, orthodox seeds (e.g. Solanum lycopersicum, Phaseolus vulgaris) tolerate drying and freezing, allowing long-term storage in seed banks, recalcitrant seeds (e.g. Populus spp., Theobroma cacao) are sensitive to desiccation and cold which limit their storage capacity, while intermediate seeds (e.g. Citrus spp., Coffea arabica) survive dehydration but die during dry storage at low temperatures (Roberts, 1973; Corbineau, 2024). Inadequate seed germination can result in substantial crop losses, therefore the role of nanotechnology in this regard is to provide solutions and technologies for improving seeds, drawing upon the foundational knowledge offered by ‘nano seed science’.

The objective of this review is to critically evaluate the current knowledge on the relationship between plant seeds and NMs, including NM biosynthesis using seed material, NM interaction with the seed surface and internalization, NM toxicity to seeds, and the application of NMs in seed-related applications.

Biofabrication of nanomaterials with seed extract

The synthesis of different NPs with various properties (such as the size, shape, and high surface area to volume ratio) for wide-ranging applications (e.g. in medicine, industry, and environmental science) has been reported through different methods such as chemical, physical, and biological techniques (Devi et al., 2024). However, the conventional chemical or physical approaches are particularly expensive, energy- and time-consuming, and often involve hazardous reagents. Thus, biological synthesis strategies of NPs have gained significant attention, providing safer and economical alternatives to conventional techniques. These biosyntheses reduce the production of harmful materials by leveraging natural biomolecules to assist the formation of NPs using environmentally-friendly solvents, reducing agents, and capping materials. Various biological sources, including living microorganisms, algae, bacteria, fungi, and plants, or their active components, enzymes, can facilitate the synthesis of metallic NPs by reducing metal ions into NPs within a solution (Salem and Fouda, 2021). These biological agents act as reducing, capping, and stabilizing agents, enabling NP biosynthesis without toxic chemicals. However, microorganism-based synthesis is often slow, requires complex maintenance, and produces polydispersed particles. On the other hand, plant-mediated approaches have emerged as a promising alternative due to their simplicity, biocompatibility, and the diversity of plant metabolites that support the NP formation. The use of various plant extracts from different parts of the plants (leaves, stems, seeds, roost, and fruits) presents a viable, affordable, repeatable, rapid, scalable, and environmentally-friendly approach to the production of NPs. Among these, plant seeds have recently attracted interest due to their rich biochemical composition (Rónavári et al., 2017). Seeds contain high concentrations of biodegradable non-toxic primary and secondary metabolites—including enzymes, proteins, enzymes, amino acids, amides, polysaccharides, vitamins, organic acids, alkaloids, polyphenols, terpenoids, and flavonoids—that serve as biodegradable reducing and capping agents that effectively enhance the reduction of metal salts for NPs synthesis, while preventing agglomeration of NPs by stabilizing them (Ying et al., 2022).

The preparation of seed extracts is a crucial step in the green synthesis of NPs (Ghaffari-Moghaddam et al., 2014). Typically, seeds are washed, dried, and ground into a fine powder. This powder is then subjected to an extraction process using solvents such as water, ethanol, or methanol to obtain bioactive compounds. The extract is filtered and often heated to enhance the release of phytochemicals responsible for NP synthesis. The resulting solution is then mixed with metal precursors, where biomolecules in the extract act as natural reducing and stabilizing agents, leading to the formation of NPs (Villagrán et al., 2024, Fig. 1).

Fig. 1.

Seed-assisted nanomaterial synthesis. Schematic representation of the green way of nanomaterial synthesis using plant seed extract. See explanations in the text. Abbreviations: M, metal. Created in BioRender. Ördögné Kolbert, Z. (2025) https://BioRender.com/cena5x3.

The mechanism of NP generation using plant extracts has been extensively investigated, and it has been determined that multiple biomolecules are responsible for and contribute to metal ion reduction (Rónavári et al., 2021). First, the metal ions interact with the phenolic hydroxyl groups of the biomolecule to create a complex, which then reduces the metal ion. During this process, the biomolecules are oxidized while also often stabilizing the NPs (‘capping’), thus no additional stabilizing agent is needed during synthesis. This process is typically straightforward, requiring only the mixing of a metal salt solution with a natural plant extract, leading to spontaneous extracellular NP formation within minutes to hours (El-Seedi et al., 2019).

Using plant seed extracts for NP synthesis offers several advantages (Rónavári et al., 2017, 2023). Firstly, this method is environmentally friendly, avoiding the need for toxic chemicals, using green chemistry and natural biodegradable products. Moreover, seeds that were traditionally considered waste—such as those from apples, papayas, and mangoes—are now gaining attention for their high phenolic content and antioxidant properties. Additionally, the oils derived from seeds often contain higher concentrations of beneficial phenolic compounds compared to other edible oils, further enhancing their nutraceutical value. Secondly, seed extracts are easy to obtain and process; they do not require special growth conditions or reactors to extract the bioactive components from them. Thirdly, plant extracts contain a number of biomolecules and cellular compounds (e.g. ferulic acid, syringic acid, cinnamic acid, caffeic acid, chlorogenic acid, coumaric acid, (epi)catechin, (epi)gallocatechin, and amino acids) that can serve as reducing and stabilizing agents at the same time, making the synthesis process more efficient (Bhardwaj et al., 2022). Additionally, plant-mediated synthesis leads to the generation of NPs with an enriched spectrum of bioactivities with industrial potential, such as antibacterial, anticancer, antimutagenic, antiviral, and cardioprotective properties, along with improved biocompatibility, making them more suitable for medical and pharmaceutical applications. Furthermore, the cost-effectiveness and scalability of plant-based green synthesis methods make them attractive for large-scale NP production (Magalhães-Ghiotto et al., 2021).

To date, several examples of NPs synthesized using plant seed extracts have been reported in the literature (Table 1). Among these, Ag NPs emerge as the most frequently synthesized nanoparticles. This is likely due to the well-documented antimicrobial, antiviral, and catalytic properties of Ag NPs, which have led to their widespread application in biomedical and environmental fields. In 2008, Nadagouda and Varma, successfully produced Ag and palladium (Pd) NPs through a one-step environmentally friendly biosynthesis method using coffee bean extract (Nadagouda and Varma, 2008). More specifically, the coffee bean extract reacted with an aqueous solution of silver nitrate or palladium(II) chloride solution for a few minutes at room temperature affording stable nanoparticles. It was found that during the reaction, alkaloids and caffeine were the major components involved, and the method could be extended to other noble metals such as Au and platinum (Pt). Ag NPs and copper NPs (Cu NPs) were generated using green coffee beans, demonstrating outstanding antibacterial and catalytic activities (M. Wang et al., 2017; G.Wang et al., 2021). Moreover, Ag NPs were synthesized using extracts from two coffee species, Arabica coffee (Coffea arabica L.) and Robusta coffee (Coffea canephora L.), and their properties were compared, revealing excellent antibacterial activity (Baghaienezhad et al., 2020). Furthermore, drumstick tree (Moringa oleifera) (Katata-Seru et al., 2018) and black mustard (Brassica nigra L.) (Ansar et al., 2021) seeds have explored for the synthesis of Ag and Au NPs due to their antibacterial properties, while cumin (Cuminum cyminum L.) (Rajesh et al., 2018) and fenugreek (Trigonella foenum-graecum L.) (Radini et al., 2018) seeds have been utilized for their enhanced antioxidant properties.

Table 1.

Nanomaterials prepared by seed extracts derived from diverse plant species

Materials	Size	Plant species	Notes	Reference
Silver (Ag) NPs	Mono-dispersed, with a diameter of <100 nm	Sterculia foetida L.	The synthesis of protein-lipid conjugated silver nanoparticles, facilitated by the seed extract functioning as both a reducing and a stabilizing agent	Farsana et al., 2023
	Polydispersed, with size ranged within 10–12 nm	Nigella sativa L.	The seed extract is comprised of numerous active compounds, including terpenoids, proteins, flavonoids, alkaloids, tannins, ketones, aldehydes, and carboxylic acids. These compounds have the potential to serve as stabilizing and reducing agents in the synthesis of Ag NPs	Chand et al., 2021
	Spherical, with diameter of ∼50 nm	Persea americana	The Ag NPs exhibited varying sizes, primarily influenced by the concentration of extract utilized, as the concentration of Persea americana seed extract increased, a corresponding increase in the size of the colloidal Ag NPs was observed	Girón-Vázquez et al., 2019
	NPs were in a range from 5 to 100 with an average of 20 nm	Gardenia jasminoides J.Ellis	The protein and phenolic constituents within the seed extract contribute to the environmentally sustainable synthesis of nanoparticles	Saravanakumar et al., 2018
	Polydispersed, with size range within 28.21–91.28 nm with highest frequency of 37.84 nm	Vigna mungo L.	The extract derived from the hull, removed from the seed utilized in the synthesis of nanoparticles, exhibited outstanding antioxidant and anticoagulant properties	Varadavenkatesan et al., 2017
	Monodispersed, with an average diameter of 38 nm	Cydonia oblonga L.	Biomolecules derived from seed extracts functioned as both capping and stabilizing agents	Zia et al., 2016
	Poly-dispersed, with an average diameter of 20–30 nm	Coffea arabica L.	The seed extract was used as a reducing medium	Dhand et al., 2016
	Stable NPs with average size of 4.6, 10.6, and 41.1 nm	Solanum lycopersicum L.	Three distinct biogenic materials (Multani mitti seeds, Solanum lycopersicum seeds, and Oryza sativa husk) were employed as capping and reducing agents to enhance the reduction rate and stabilization of silver nanoparticles	Dar et al., 2016
	The average sizes of NPs measured at 5, 10, 20, 30, 90, and 180 minutes were 10, 15, 25, 30, 35, and 40 nm, respectively	Dimocarpus longan	The particle size can be modulated by adjusting the quantity of plant extract and the duration of the reaction process	Khan et al., 2016
	Single size distribution with an average diameter of about 7.5 nm	Calendula officinalis L.	The seed extract functions as a reducing agent	Baghizadeh et al., 2015
	The size of NPs increased with increase in irradiation time, leading to the formation of anisotropic nanostructures (1.22 to oversized 150 nm) while increasing the AgNO3 concentration resulted in the formation of Ag nanorods	Piper nigrum L.	Seed extract comprising biomolecules such as vitamins, polysaccharides, proteins, amino acids, enzymes, and organic acids can function both as reducing and capping agents in the environmentally-friendly synthesis of silver nanoparticles and nanorods	Mohapatra et al., 2015
	Spherical shaped NPs with an average size of 6.9 ±0.2 nm	Sterculia foetida L.	The synthesis of protein-lipid conjugated silver nanoparticles, facilitated by the seed extract functioning as both a reducing and a stabilizing agent	Rajasekharreddy and Rani, 2014
	NPs were irregular in shape and different sizes ranging from 3 to 25 nm with 10.78 nm average size	Artocarpus heterophyllus Lam.	The FTIR spectra suggested the involvement of amino acids and amide group I in the reduction process	Jagtap and Bapat, 2013
	Exudate pre-dilution produced single-crystalline hexagonal Ag NPs, and nanotriangles with edge lengths of 86–108 nm, while pH adjustment to 11 resulted in monodispersed ∼12 nm particles	Medicago sativa L.	The initial dilution of the exudate facilitated the synthesis of single-crystalline silver nanoplates, resulting in the formation of hexagonal particles and nanotriangles with edge lengths ranging from 86 to 108 nm. Additionally, the adjustment of pH to 11 yielded monodispersed Ag nanoparticles with an average diameter of 12 nm	Lukman et al., 2011
	The synthesized NPs were spherical; leaf extract produced ∼30 nm spherical NPs, while seed extract yielded larger NPs (92 and 73 nm)	Syzygium cumini L.	The size of nanoparticles was determined to be directly associated with the concentration of polyphenols, which serve as highly polar soluble constituents	Kumar et al., 2010
	Primarily spherical particles, with diameters ranging from 15 to 50 nm	Jatropha curcas L.	In the case of 10−3M AgNO3 solution with 0.2 volume fraction of aqueous seed extract the particles are predominantly spherical in shape with diameter ranging from 15 to 25 nm while larger and uneven shaped particles with diameter 30–50 nm are obtained from 10−2(M) aqueous AgNO3 solution	Bar et al., 2009
Silver and gold (Ag, Au) NPs	Irregularly shaped particles, with an average size of 6 nm and a range of 5–10 nm	Mimosa pudica L.	It is posited that the reduction activity is attributable to the presence of a certain quantity of free reducing sugars liberated by the polymer within the suspension and the polymers facilitate the dispersion of particles within their matrix, thereby contributing to increased stability	Iram et al., 2014
	Particle size of silver was 5–20 nm and gold was 8–30 nm	Plantago ovata L.	Arabinoxylans, derived from the husk of Plantago ovata seeds, consist of reducing sugars capable of reducing gold or silver ions to particulate form, while their hydrogel-like network allows for the dispersion of these particles within the matrix	Amin et al., 2013
Gold (Au) NPs	Spherical or nearly spherical with a uniform particle size of about 34 nm	Vitis vinifera L.	Grape seed extract comprising 95% procyanidin was utilized to enhance the size and uniformity of nanoparticles	Liu et al., 2022
	Circular, triangular, and irregular shapes, 19.45 nm size	Mangifera indica	The seed extract contains a diverse array of phytoconstituents, which function as both reducing and stabilizing agents in the formation of nanoparticles	Donga et al., 2020
	The size of NPs ranged from 3 to 23 nm with average of 11.11 nm	Trachyspermum ammi L.	The majority of nanoparticles were identified as being spherical and spheroidal in shape, exhibiting minimal anisotropy, with an average crystalline dimension of 16.63 nm	Perveen et al., 2021
	Spherical morphology with the formation of aggregates ∼50 nm	Mangifera indica	The synthesis of Au NPs was facilitated through the mediation of phytomolecules, utilizing an aqueous seed extract of Mangifera indica combined with a HAuCl4 solution, wherein the seed extract functions as a reducing and stabilizing agent	Vimalraj et al., 2018
	Polydispersed, spherical particles ranged from 10 to 30 nm with an average size of 20±2 nm	Foeniculum vulgare Mill.	The bioreduction of gold ions to crystalline nanoparticles, exhibiting an average size of 20±2 nm, and the subsequent capping, were mediated by polyphenolic compounds derived from fennel seeds	Choudhary et al., 2017
Gold, silver and selenium (Au, Ag, Se) NPs	Spherical and polydispersed NPs with particle sizes of ∼ 300, 700, and 100 nm for the fabricated Au, Ag, and Se NPs, respectively	Coffea arabica L.	Coffee beans comprise polyphenols, carbohydrates, caffeine, caffeic acid, chlorogenic acid, diterpenes, and trigonelline, which can be employed as reducing and capping biomolecules in inorganic nanoparticles	Abbasian and Jafarizadeh-Malmiri, 2020
Calcium carbonate (CaCO3) NPs	Ellipsoidal in shape with uniform size (<10 nm)	Cicer arietinum L.	Spherically morphed, highly stable CaCO3 (vaterite) crystals are produced, suggesting that the proteins secreted by seedling roots during growth are essential in stabilizing and directing the reaction between aqueous Ca2+ ions and the CO2 produced during the seed growth, thereby facilitating the growth of crystals	Rautaray et al., 2005
Copper (Cu) NPs	Spherical shape, with the size range around 42–90 nm	Persea americana Mill.	The copper nanoparticles synthesized via biological methods present a spherical morphology within the dimensional range of 42 to 90 nm and exhibit notable antimicrobial efficacy against the plant pathogens Aspergillus niger, Aspergillus fumigatus, and Fusarium oxysporum	Rajeshkumar and Rinitha, 2018
	Spherical shape, NPs in the range of 40–80 nm with average particle size of 43.9 nm	Punica granatum L.	The formation of Cu NPs was achieved via the reduction of metal ions, subsequently followed by nucleation facilitated by the seed extract	Nazar et al., 2018
Copper oxide (Cu(II)O) NPs	Calculated average crystalline size was 11 nm	Annona squamosa L.	The seed extract comprises a diverse array of flavonoids, alkaloids, and proteins, which contribute to the prevention of agglomeration and the stabilization of CuO nanoparticles	K.R. Singh et al., 2021; P. Singh et al., 2021
	Spherical shape and ranged in size from 1–100 nm	Elettaria cardamomum L.	The presence of nanoparticles resulted in the observation of Escherichia coli and Staphylococcus aureus resistance zones around each well, exhibiting antimicrobial activity against pathogenic strains	Venkatramanan et al., 2021
	Spherical shape with an average size of 22±1.5 nm	Triticum aestivum L.	The aqueous extract derived from wheat seeds demonstrated a dual role, functioning both as a reducing and a capping/stabilizing agent in the biosynthesis nanoparticles	Buazar et al., 2019
	Spherical in shape with size of ∼26.6 nm	Phaseolus vulgaris L.	In vitro anticancer assays demonstrated that CuO NPs elicited intracellular reactive oxygen species (ROS) generation in a dose-dependent fashion and markedly decreased cervical carcinoma colony formation	Nagajyothi et al., 2017
Lead and copper oxide (Pd/CuO) NPs	NPs average size was around 40 nm	Theobroma cacao L.	The identified chemical constituents of the seed extract, namely epicatechin, catechin, flavonoids, and phenolic acids, function as reducing, stabilizing, and capping agents	Nasrollahzadeh et al., 2015
Iron (Fe) NPs	Crystalline in the size range from 12 to 28 nm	Trachyspermum ammi L.	Various plant extracts play a crucial role in the reduction and stabilization of nanoparticles, alongside specific quantities of polyvinylpyrrolidone (PVP)	Afsheen et al., 2018
Iron(II,III) oxide (Fe3O4) NPs	Crystalline size was ∼14 nm	Syzygium cumini L.	The seed extract functions as a green solvent, as well as a reducing and capping agent, where sodium acetate serves as an electrostatic stabilizing agent	Venkateswarlu et al., 2014
Iron(III) oxide (Fe2O3) NPs	Semi spherical NPs, uniformly distributed and particle size in the range of 25–55 nm	Punica granatum L.	Liquid chromatography-mass spectrometry (LCMS/MS) was conducted to identify the biomolecules present in the extract of pomegranate seeds. Detected compounds include p-hydroxy benzoic acid, gallic acid, methyl gallate, catechin, kaempferol-3-O-sophoroside, 3-deoxyflavonoids, magnolol, ferulic acid, vanillic acid, and pinocembrin, along with other minor constituents. These constituents may contribute to the formation of Fe2O3 nanoparticles (NPs)	Bibi et al., 2019
Platinum (Pt) NPs	Spherical with sizes between 1–6 nm	Nigella sativa L.	The synthesized nanoparticles exhibited a diminutive particle size (3.47 nm) with a spherical configuration	Aygun et al., 2020
Platinum and palladium (Pt, Pd) NPs	Average diameters of Pt NPs, Pd NPs, and Pt–Pd NPs were 20.3±1.9, 22.5±5.7, and 33.5±5.4 nm, respectively	Peganum harmala L.	The study delineates a methodology for synthesizing nanoparticles of platinum, palladium, and bimetallic platinum–palladium. The Pt–Pd nanoparticles demonstrated superior antioxidant properties and significant cytotoxicity towards lung and breast cancer cells	Fahmy et al., 2021
Tin(IV) oxide (SnO2) NPs	The particle size was ∼4 nm	Persia americana Mill.	Nanoparticles were prepared using Persia americana seed methanolic extract by calcining stannous chloride precursors	Elango et al., 2015
Titanium(II) oxide (TiO2) NPs	The particle size was ∼23 nm	Brassica juncea L.	The transmission electron microscopy (TEM) analysis reveals an average particle size of 38 nm, characterized by irregular morphologies and FTIR spectroscopy indicates the presence of functional groups within the extract, including polyphenolic, hydroxyl, and carboxylic groups, which are presumed to play a crucial role in the formation of nanoparticles	Jeyaraj and Mary Saral, 2024
	<100 nm XRD patterns	Cucurbita pepo L.	FTIR analysis demonstrated the presence of diverse functional biomolecules within the seed extract, which served as reducing and capping agents facilitating the transformation of TiO4 into TiO2 NPs	Abisharani et al., 2019
Zinc(II) oxide (ZnO) NPs	Nanocrystals were ∼28.79, 23.90, and 23.94 nm after calcination at 400, 500, and 600 °C	Cydonia oblonga L.	Seed mucilage was employed as a reducing and stabilizing agent at calcination temperatures of 400, 500, and 600 °C, resulting in relatively uniform crystals with an average size of 25 nm	Tabrizi Hafez Moghaddas et al., 2020
	The size range of prepared NPs was 18–27 nm	Eriobotrya japonica L.	The seed extract used as a reducing medium	Shabaani et al., 2020
Carbon dots	Spherical, with average size about 1.45 nm	Carica papaya L.	Papaya seeds served as a biological precursor for the synthesis of carbon dots through a microwave-assisted carbonization process	George et al., 2023
	Quasi-spherical shaped with average size of 6.08 nm	Nigella sativa L.	The seeds were chosen for their naturally occurring organic compounds including carbohydrates, lipids, proteins, and other components such as alkaloids, flavonoids, and terpenoids which, when combined with elements like oxygen, nitrogen, hydrogen, and sulfur, create a conducive environment for the formation of NPs	Ugwuoke et al., 2024.
	Spherical, with a size range of 0.6±0.5 to 2.1±1.8 nm dependent on plant extract composition	Gardenia jasminoides J.Ellis	The study synthesizes three carbon quantum dots variants using a pyrolysis method at 220 °C, with CQDs-3 achieving the highest quantum yield of 4.0%. Characterization confirmed with structural integrity and nanoscale dimensions, alongside excellent biocompatibility and reducing capabilities for synthesizing gold nanoparticles	Fang et al., 2024.
Graphene quantum dots	Planar nanocrystals, with average size from 3.4 to 12 nm	Theobroma cacao L.	Seed extract was both the reducing and capping agent	Anooj and Praseetha, 2019
Reduced graphene oxide	Average thickness of layers was 4.28 nm	Vitis spp.	Seed extract was used as reducing agent	Yaragalla et al., 2016.
Starch nanoparticles	Irregular shaped, with the size range of 30–80 nm	Triticum spp.	The short-chain amylose produced through pullulanase hydrolysis predominantly exhibited V-type crystallinity, and its structural integrity was comparatively less robust than that of the starch nanoparticles derived from acid hydrolysis	Aldao et al., 2018.
Protein-based nanoparticles	Various shapes, with size range from 5 to 250 nm depend of preparation methods	Glycine max L.	The formation process of soy protein-based nanoparticles is a complex system and the assembly process is influenced by many factors	Gong et al., 2024.
Nanosilica	Amorphous, with size from ∼9 to 15 nm	Sorghum spp.	Sorghum is rich in silica content so it can be used as an economically viable raw material for the preparation of silica NPs	Balamurugan and Saravanan, 2012

Similarly, a number of studies demonstrated the preparation of different types of NPs, including Au (Donga et al., 2020; Perveen et al., 2021), iron (Fe) (Afsheen et al., 2018), selenium (Se) (Abbasian and Jafarizadeh-Malmiri, 2020), ZnO (Shabaani et al., 2020; Tabrizi Hafez Moghaddas et al., 2020), CuO (K.R. Singh et al., 2021; P.Singh et al., 2021; Venkatramanan et al., 2021), iron oxide (Fe₃O₄) (Venkateswarlu et al., 2014), and TiO₂ (Abisharani et al., 2019; Jeyaraj and Mary Saral, 2024), by an environmental-friendly, one-step synthesis process using seed extracts from various plant species, such as grapes (Vitis vinifera L.), avocado (Persea americana Mill.), black pepper (Piper nigrum L.), custard apple (Annona squamosa L.), cardamom (Elettaria cardamomum L.), jackfruit (Artocarpus heterophyllus Lam.), kalonji (Nigella sativa L.), and jamun (Syzygium cumini L.). These and further studies have indicated that the biomolecules present in the seed extracts not only facilitate NP formation but also ensure particle stability and size distribution, which is important in biomedicine and environmental applications. For example, the use of the Java olive tree (Sterculia foetida L.) highlights its effective composition in yielding stable Ag NPs, while studies involving jamun, quince (Cydonia oblonga L.), or jackfruit (Artocarpus heterophyllus Lam.) seeds show the potential of producing NPs of narrow size distribution (Kumar et al., 2010; Rajasekharreddy and Rani, 2014; Zia et al., 2016; Farsana et al., 2023). The number and shape of NPs can also be controlled by adjusting the extract volume and dosing rate of the bioreducing agent (Iravani, 2011).

Beyond the well-studied metal and metal oxide nanoparticles, several non-metallic NMs have been synthesized using plant seeds and their extracts. Carbon-based NMs, such as carbon quantum dots (CQDs), have been produced via hydrothermal carbonization of sugar or biomass originating from seed extracts from Nigella sativa L., elm (Ulmus spp.), mustard (Sinapis alba L.), papaya (Carica papaya L.), and gardenia (Gardenia jasminoides L.). Cocoa (Theobroma cacao L.) bean extract-mediated graphene quantum dots synthesis and a green reduction of graphene oxide to reduced graphene oxide using grape seed extract were also demonstrated (Yaragalla et al., 2016; Anooj and Praseetha, 2019; George et al., 2023; Fang et al., 2024; Ugwuoke et al., 2024).

Another significant group of seed-derived NMs is the plant-extracted nanobiopolymers. For example, starch NPs (Aldao et al., 2018) have been obtained from starch-rich seeds (e.g. Zea mays L., Triticum spp.) through acid hydrolysis or nanoprecipitation techniques, offering biodegradable nanocarriers for drug and nutrient delivery. Similarly, protein-based NPs have been synthesized from seed storage proteins, such as globulins and albumins found in soybean (Glycine max L.) and mung bean (Vigna radiata L.), which can self-assemble into nanostructures under desolvation (Gong et al., 2024). Lipid-based nanocarriers have been formulated using oils extracted from flax, soybean, and sunflower seeds, demonstrating potential in encapsulating hydrophobic bioactives (da Silva Santos et al., 2019). Similarly, mango seeds have been successfully processed via acid hydrolysis to isolate cellulose nanocrystals (Henrique et al., 2013). Additionally, polymeric NPs have been developed using seed-derived biopolymers such as starch, cellulose, and proteins, either alone or in combination with biodegradable synthetic polymers, forming nanostructured systems for controlled release and agricultural applications (Machado et al., 2022). Finally, although seeds themselves are not typically rich in silicon, silica NPs have been synthesized by using Sorghum vulgare L. seed (Balamurugan and Saravanan, 2012). In summary, these diverse metallic or non-metallic NMs synthesized from or assisted by plant seeds illustrate the growing potential of seed-based platforms in green nanotechnology.

Green synthesis methods that use plant or seed extracts have gained popularity because they provide eco-friendly solutions with low toxicity and cost-effectiveness. The methods utilize sustainable biological materials through mild reaction environments while eliminating dangerous chemical substances (Jeevanandam et al., 2022). The use of plant seeds for synthesis provides better advantages than microbial systems because plants offer simpler management and faster processing (e.g. no sterile conditions or culture management) and provide inexpensive agricultural raw materials. Recent studies have also explored the use of plant residues and by-products, further enhancing the sustainability and affordability of the process (e.g. leaf litter, fruit peels, seed husks) (Rónavári et al., 2023).

The main obstacle to the industrial adoption of plant-mediated green synthesis is limited scalability (Ying et al., 2022). The industrial adoption of plant-mediated green synthesis faces major barriers because of seasonal availability limitations, low NP yield, batch variability and poor reproducibility, lack of standardization and difficulties with particle property control, and expensive or complex purification procedures. The application of continuous-flow systems and standardized precursor extraction and bio-reactor-based synthesis shows promise to address current limitations but requires additional research to expand their use in agricultural nanotechnology.

NM interaction with the seed coat and their internalization

One of the most exciting and a fundamental issue in seed nanobiology is the role of the seed coat in the interaction of seeds with NPs. The seed coat which usually develops from the integuments of the ovule greatly affects the outcome of seed germination. Due to the imbibition and the active growth of the embryo the seed coat or the pericarp (e.g. in case of caryopsis) gets ruptured to let the new plant emerge (Amen, 1963). It is well known that the water uptake of mature seed depends on the permeability of the seed coat but many other favourable conditions are needed to manage the germination. Even under optimal conditions, the germination of some seeds can be inhibited by a phenomenon called seed dormancy (Amen, 1963). Breaking seed dormancy and facilitating the germination in addition to preparing the offspring for the potential stress factors are the main goals of several nanopriming technologies. Seed nanopriming is the pre-sowing treatment of seeds with NMs to expose plants to mild or moderate stress in order to activate defence responses and prepare the plant for subsequent stress. These applications must be founded on knowledge about seed coat/pericarp characteristics (e.g. surface, anatomy) which might affect the penetration of the NPs into the seeds.

In a recent study, in the embryonic cells of pomegranate (Punica granatum L.) seeds, the presence of TiO₂ NPs as scattered deposits of tetragonal and cylindrical crystals has been observed suggesting NP penetration via the seed coat (Abdelmigid et al., 2022). Moreover, single-walled carbon nanotubes (SWCNTs) have been tested on the seed germination and seedling growth of plants with differently structured seeds (Pourkhaloee et al., 2011). Salvia seeds (Salvia macrosiphon Boiss.) showed the highest germination success in the presence of SWCNTs due to their mucilaginous seed coat (Hellebois et al., 2020), which may facilitate the settlement, availability, and penetration of SWCNTs. Tall fescue (Festuca arundinacea Schreb.) possesses a caryopsis as a propagule in which the seed coat and the pericarp are tightly attached to each other (Rosentrater and Evers, 2018), it germinates much later than salvia seeds probably because of the silica (Si) compounds found in the cell walls of Poaceae family members. It was supposed that Si compounds hamper the penetration of SWCNTs. The presence of SWCNTs on the seed coat surface has been detected by scanning electron microscopy (SEM) (Pourkhaloee et al., 2011; Ratnikova et al., 2015).

Tomato (Solanum lycopersicum L.) seeds have a lignified envelope with a characteristic hairy surface ornamentation (Chaban et al., 2022). Beyond germination induction, the permeability of the tomato seed coat to hydrophilic fullerol and hydrophobic multi-walled carbon nanotubes (MWCNTs) alone or combined with ultrasound (US) has been examined (Kacsó et al., 2022). Bright field, fluorescence, and electron microscopy and micro-Raman spectroscopy provided no evidence for the penetration of fullerol or MWCNT when applied without US. However, US supplementation proved to facilitate the penetration of fullerol or MWCNTs into tomato seeds due to the physical disruption of the seed coat (Kacsó et al., 2022). These results highlight seed coat permeability as a major barrier to the internalization of NMs into seeds of certain species (Ratnikova et al., 2015).

Beyond the seed coat properties, NP internalization is influenced also by the characteristics of the NP itself (e.g. surface charge, size, reactivity). This is supported by the results that fluorescein isothiocyanate (FITC)-labelled zein NPs adhere to the seed coat due to their positive charge, while negatively charged FITC-lignin NPs are present at the exterior and interior layer of the seed coat and the endosperm’s first layer as they enter between the seed coat and cotyledons of soybean seed (Kacsó et al., 2022). The available literature indicates that both smaller (∼10–20 nm) and larger (∼50–80 nm) sized NPs are capable of penetration of the seed coat (Table 2). Despite of the clear difference in the particle sizes of Ag⁰ NPs and Ag₂S NPs (15 and 42 nm, respectively), the higher seed coat penetration of Ag⁰ NPs compared to Ag₂S NPs was explained by their high reactivity with organic molecules like thiol groups (Savassa et al., 2021). At the same time, amine and polycaprolactone-coated and uncoated Fe₃O₄ NPs have been shown to pass through the tomato seed coat suggesting that the particle adsorption was not influenced by surface groups or surface chemistry of the NPs. However, translocation of NPs is different, since more than half of the unfunctionalized NPs are localized in the cotyledons, while NPs with both types of coatings translocate to the cotyledon with a lower efficiency (Lau et al., 2020).

Table 2.

Detection of the presence of NMs in seeds of different plant species

Plant species	Nanomaterial	Treatment	Nanomaterial detection methoda	Seed sample	Main result	Reference
Phaseolus vulgaris L.	Silver nanoparticles (Ag0 NPs) (15 nm)	1, 10, and 100 mg L–1 (1 h)	SEM	Seed surface	Clusters from Ag2S NPs around the hilum, micropyle, and lens were observed	Savassa et al. (2021)
			µ-XRF	Seed cross section	Highest penetration observed for Ag0 NPs and the lowest for Ag2S NPs. The ability of Ag0 NPs to penetrate the seed coat might be related to their high reactivity with organic molecules such as thiol groups
	Silver sulfide nanoparticles (Ag2S NPs) (42 nm)				Ag0 NP treated samples show Ag in parenchyma cells
			μ-XANES		Ag0 NP treatment NPs undergo oxidative dissolution and form thiolate complexes in the internal layer
Phaseolus vulgaris L.	Copper sulfide nanoparticles (CuS NPs) (77.89 nm)	0.3 mg mL–1 (24 h)	PIXE analysis	Seed	CuS NPs were mainly accumulated in the seed coat region, hotspots within the hilum and micropyle regions	Botha et al. (2024)
Solanum lycopersicum L.	C60(OH)20 (fullerol) (1.17±0.36 nm), multiwalled nanotubes (MWNTs) (223.08±38.72 nm) in gallic acid (GA) suspension	50 mg L–1 (0, 5, 10, 30, or 60 min)	SEM	Seed coat	The US-CBNM (ultrasonic irradiation, US) double exposure treatment removed seed coat hairs and eroded the seed coat	Ratnikova et al. (2015)
			Micro-Raman spectroscopy	Cross section	Non-punctured seed coats did not show any Raman signal suggesting that MWNTs did not penetrate through the seed coat. Only punctured seeds showed the presence of MWNTs in the embryo
Solanum lycopersicum L.	Iron oxide nanoparticles (Fe3O4 NPs) (6–13 nm)	0.25, 2.5, and 5 mg mL–1 (24 h)	SEM	Seed surface	Seed morphology was not altered. NPs were trapped inside the fibres on the seed coat	Lau et al. (2020)
			EDX	Seed	Around 0.018−0.029 mg of NPs were loaded onto 1 mg of seed, equivalent to around 1.8−2.9%
			AAS
			μ-XRF	Seed cross section	Most of the NPs remained in the seed coat with minor translocation to the endosperm
Citrullus lanatus (Thunb.) Matsum. & Nakai	Silver nanoparticles (AgNPs) (141.3±0.78 nm)	2.5% suspension of synthesized Ag NPs. One-part TNE was diluted with 10 parts of Nanopure water (12 h)	GC–MS	Seed	Ar-turmerone, a major compound in the turmeric oil nanoemulsion, was internalized in treated seeds	Acharya et al., 2020
			TEM		Confirmed the internalization of Ag NPs in the treated seeds
	Turmeric oil nanoemulsions (TNEs) (171.3±0.52 nm)		INAA
Glycine max L.	Zein nanoparticles (ZNPs) (122.9±0.8 nm)	10 mg NP mL–1 1 mL g–1 of seed (5 min)	FITC	Seed cross section	No translocation was detected; particles adhered to the seed coat surface. ZNP adhered to seed coat because of their positive charge, LNP coated the exterior and interior layer of the seed coat and the endosperm’s first layer due to their negative charge	Kacsó et al. (2022)
	Lignin-graft-poly(lactic-co-glycolic) acid nanoparticles (LNPs) (52.9±0.2 nm)
Pisum sativum L.	Silver nanoparticles (Ag NPs) (18–35 nm) Gold nanoparticles (Au NPs)	(24 h)	TEM	Endosperm	Clusters inside the endosperm	Ahmadov et al. (2020)
Punica granatum L.	Titanium dioxide nanoparticles (TiO2 NPs) biosynthesized from pomegranate extracts (PPE) (85.6 nm) and coffee grounds (CE) (79.6 nm)	40 mg L–1 (24 h)	SEM	Seed surface	Pores with a honeycomb shape were observed on the surface	Abdelmigid et al. (2022)
			EDX		TiO2 NPs were deposited on the seed coat surfaces
			TEM	Seed	Confirmed the presence of TiO2 NPs inside the seed embryos
			XRF	Fine-powdered seeds	Confirmed the assimilation of TiO2 NPs by nanoprimed seeds
			ICP–OES
Triticum aestivum L.	Iron nanoparticles (Fe NPs) (10–80 nm)	5, 10, and 15 mg L–1 (12 h)	TEM	Seed cross section	Showed the presence of Fe NPs inside the seed	Naseer et al. (2022)
			EDX		Confirmed the presence of Fe element
Salvia macrosiphon Boiss	Single-walled carbon nanotubes (SWCNT) (8–15 nm)	10, 20, 30, 40 mg L–1 (20 d in Petri dishes)	SEM	Seed coat	Small SWCNT particles can easily penetrate the seed coats of salvia and pepper	Pourkhaloee et al. (2011)
Capsicum annuum L.
Festuca arundinacea L.

^a Abbreviations: SEM, scanning electron microscopy; TEM, transmission electron microscopy; µ-XRF, micro X-ray fluorescence; XRF, X-ray fluorescence; μ-XANES, micro X-ray absorption near edge structure; EDX, energy dispersive X-ray spectroscopy; PIXE, particle-induced X-ray emission analysis; INAA, instrumental neutron activation analysis; ICP–OES, inductively coupled plasma optical emission spectroscopy; GC–MS, gas chromatography-mass spectrometry; FITC, fluorescein isothiocyanate.

Since, most of the NMs are suspended in water and applied as seed priming agents, we might suppose that NPs probably use the points of water entry to get into the seeds. For instance, some researchers consider that water (and probably the NPs, too) may get into the seed through the entire seed coat, while others think that water absorption occurs only at specific points of the seed, like the hilum or the micropyle (Upretee et al., 2024; Fig. 2). The possibility that NPs use the entry points of water to penetrate the seed coat is supported by the presence of deposited clusters from silver sulfide (Ag₂S) NPs around the hilum, micropyle, and lens of bean (Phaseolus vulgaris L.) seeds. Moreover, the hilum contains branched tracheids with pits where the NPs can remain attached (Savassa et al., 2021).

Fig. 2.

Nanomaterials interact with the seed coat. The comparative structure of the seed coat of flax (Linum usitatissimum) and kidney bean (Phaseolus vulgaris). Both species have orthodox types seeds. Abbreviations: mpyl=micropyle, cut=cuticle, muc=epidermis cells with mucilage, par=parenchyma, stc=stone cells, hil=hilum, mscl=macrosclereids (or palisade layer), oscl=osteosclereids (or hourglass cells), according to Souza and Marcos-Filho (2001) and Upretee et al. (2024). The dark, thick arrows show the real entry points for water during the imbibition, i.e. at the micropyle or the hilum, while light, thick arrows indicate the other potential gates, small dots represent the NPs. Created in BioRender. Ördögné Kolbert, Z. (2025) https://BioRender.com/yzqk8ub.

The interaction between the NPs and the seed coat is bidirectional, since not only do the NPs affect the seed but the seed and its substances may influence the stability, availability, and the uptake of the NPs. The biotransformation along the seed coat depends on the chemical form of the NP, since Ag⁰ NPs undergo oxidative dissolution forming thiolate complexes, while Ag₂S NPs do not show any detectable chemical changes (Savassa et al., 2021). Similar to this, the presence of Cu and S in the hilum and micropyle area of copper(II) sulfide (CuS) NP-exposed bean seeds has been observed indicating a possible uptake mechanism via these specified regions of the seed coat (Botha et al., 2024).

According to the available literature, the penetration of the NPs into seeds may depend both on the physico-chemical properties of the NP and on the morphology, the anatomical structure, and the chemical composition (e.g. presence of flavonoids, polysaccharides, lignin, suberin, wax, or cutin) of the seed coat. Seed nanopriming applications should be preceded by an evaluation of the diverse morpho-anatomical and chemical features of the seeds. For instance, the presence of a polysaccharide mucilage within the seed coat which might facilitate NP uptake or a lignified hard seed coat (sclerotesta) that can act as a barrier should be considered (Fig. 2). Multiple techniques of NM detection [e.g. SEM, TEM, FITC-labelling, Raman spectroscopy, micro X-ray fluorescence (µ-XRF), etc.] in the plant seed matrix have been applied depending on the chemistry of the NM. The representative examples of studies on NM internalization into seeds are presented in Table 2. All of the studies presented above used orthodox seeds, in which the seed coat acts as a physical barrier that protects the embryo, limiting water loss and microbial damage, crucial for long-term storage (Pammenter and Berjak, 2014). In contrast, the majority of recalcitrant seeds, which invest less in defence, have a relatively thin seed coat (Pritchard et al., 2022), and may possibly be less restrictive to NP internalization.

Nanomaterial-caused toxicity in seeds

Independently from their internalization, NMs due to their increased reactivity associated with their large surface area, can have beneficial but also toxic effects on plant systems.

Nanomaterial-triggered phytotoxic effects are extensively reported in seedlings and fully developed plants, and are attributed to biochemical, cellular, metabolic, and molecular pathways (Gowtham et al., 2024). In vegetative stage plants, NMs exert their toxicity by reactive oxygen species- (ROS) and reactive nitrogen species-triggered biochemical modifications including lipid peroxidation, protein carbonylation, protein nitration, and by disruption of primary metabolism (e.g. photosynthesis, phytohormone production) and secondary metabolite production (e.g. flavonoids, phenols) (Gowtham et al., 2024). At the molecular level, high concentrations of NMs lead to genotoxicity (e.g. chromosome aberration, DNA strand breakage) and limit the expression of genes associated, inter alia, with photosystem structure, chlorophyll synthesis, antioxidant system, lignin synthesis, and terpenoid synthesis (Gowtham et al., 2024). Transcriptome analyses in NP-exposed vegetative-stage plants revealed induction of phytohormone signalling (e.g. ethylene, abscisic acid) and mitogen activated protein kinase (MAPK) signalling pathways; however, the low impact of NP exposure on the transcriptome, compared to other environmental stress conditions, suggests that plants might be used as a barrier for bioremediation against ecotoxic effects of NPs (García-Sánchez et al., 2021).

In comparison, most of the molecular mechanisms or pathways of NM toxicity in seeds have not been explored so far which makes our present knowledge about NM-triggered toxicity in seeds very limited and superficial. During testing for NM toxicity, the effect on seeds is usually examined by evaluating germination as being the quantifiable characteristic in the case of seeds. The toxicity of NMs to plant seeds is a complex phenomenon influenced by various factors, including the chemical nature, size, surface area, and coating of the NP, and the concentration and duration of the exposure. The huge amount of literature data on NP phytotoxicity on seed germination has been extensively reviewed by authors including Budhani et al. (2019), Szőllősi et al. (2020), Ranjan et al. (2021), Guo et al. (2022), and Sarkhosh et al. (2022). Regarding NP size as an influencing factor, Fe₃O₄ NPs of 5 nm size significantly reduce germination, while both 10- and 20 nm-sized FeO₄ NPs promote germination of tobacco (Nicotiana tabacum L.) seeds (Alkhatib et al., 2021). The toxic effects of Fe₃O₄ NPs (5 nm) were attributed to deformed epidermis and xylem tissues in the radicles was well as damaged spongy mesophyll and thylakoid loss from chloroplasts in the leaflets of tobacco seedlings (Alkhatib et al., 2021). According to the results published by L.Yin et al. (2012), polyvinylpyrrolidone (PVP)-coated Ag NPs (20 nm) show no germination-influencing effect, while gum arabic coated Ag NPs (6 nm) notably diminished germination of three wetland plant species (Phytolacca americana L., Juncus effusus L., Scirpus cyperinus L.) (L. Yin et al., 2012). Similarly, it was observed that cetyltrimethylammonium bromide (CTAB)-coated Ag NPs exerted a more negative effect on tobacco germination than polyvinylpyrrolidone (PVP)-coated Ag NPs and the CTAB surface coating itself showed inhibiting effects supporting the influence of NP coatings on phytotoxicity (Biba et al., 2020). Beyond NP characteristics, plant species also determines the toxic NP effects. For instance, seed germination of head lettuce, romaine lettuce, and asparagus lettuce is not affected by the cerium oxide (CeO₂) NP exposure, but the same treatment decreases the germination rate of cucumber, radish, and wheat (P. Zhang et al., 2015). Recently, Au NPs synthesized using Brazilian red propolis (BRP) extract [BRP-GNPs (gold nanoparticles), 6.34±2.01 nm] have been found to exhibit both positive and negative effects on plant germination, depending on the concentration and the plant species tested. For example, lower concentrations of BRP-GNPs improve wheat germination, but the same concentrations of BRP-GNPs limit the germination of soybean (Botteon et al., 2025). The effects of NPs of the same size and concentration may differ depending on the developmental stage of the same plant species as was observed in Fe₃O₄ NP (5 nm) exposed tobacco seedlings in their early and later developmental stages (Alkhatib et al., 2019, 2021). However, the examination of germination-modifying effects of TiO₂ and CeO₂ NPs in 10 plant species indicated that the observed effects do not always relate to the exposure concentration, therefore early root growth may be a more sensitive indicator of potential effects from NM exposure than germination (Andersen et al., 2016). Besides the lack of concentration dependency observed in some studies, the inhibitory effect on germination is mild or absent in some cases, or occurs at high NP concentrations, while seedling growth is more sensitive to NP presence (Pan et al., 2024). All these can be explained by the presence of the seed coat which may protect the seeds from direct NP interaction.

The molecular mechanism of the germination limiting effect of NPs can be considered as multi-layered. It has been shown that the presence of carbon NMs, including fullerenol and multi-walled nanotube-gallic acid (MWNT-GA), can result in the physical impairment of the coat of tomato seeds (Ratnikova et al., 2015) possibly leading to leakage of valuable seed materials and/or internalization of toxic substances (Basahi, 2021). Similarly, pea (Pisum sativum L.) seeds exposed to TiO₂ NPs showed decreased water content in the embryo associated with increased solute leakage from the seeds. TiO₂ NPs-triggered glutathione peroxidase, and catalase activities were not able to compensate probable ROS production and oxidative stress (indicated by NADPH oxidase activation and malondialdehyde content elevation). Based on these, oxidative stress-induced lipid peroxidation and consequently solute leakage were identified as principal mechanisms of TiO₂ NPs-related toxicity in pea seeds (Basahi, 2021). Recently, the photosynthetic performance in seed tissues of Inga laurina (Sw.) Willd. exposed to CuO NPs has been evaluated, and chlorophyll fluorescence as a non-destructive tool to evaluate NP impact on photosynthetic activity in seed tissues has been reported (Graciano et al., 2024). Interestingly, CuO NPs do not trigger ROS production or Cu accumulation within the seed. At the same time, CuO NPs affect the steady-state maximum chlorophyll fluorescence, the photochemical efficiency of photosystem II, and non-photochemical quenching of Inga laurina seeds over time. Additionally, the results indicated that CuO NPs disturb the circadian clock of the seeds which is suggested by the CuO NP-associated changes in oscillatory rhythms of energy dissipation. The authors concluded that the negative effects on photosynthetic activity of CuO NPs could be attributed to energy dissipation due to physical interactions of NPs or the physical obstruction of photosynthesis but not to ROS production or Cu accumulation (Graciano et al., 2024).

A further molecular level mechanism of NM-associated seed toxicity is that the presence of certain NMs may result in a reduction in the availability of nutrients in the seed and seedling. For example, during germination, MWCNT exposure reduced Zn translocation from the cotyledons to the seedling possibly due to internal micronutrient immobilization and caused Zn deficiency in the later stages of plant development (Zaytseva, 2016; Zaytseva et al., 2017).

Regarding the relationship between nanomaterial-caused seed toxicity and nanotechnological applicability, it should be noted that both small and large NPs present trade-offs between efficacy and toxicity on seeds. Smaller sized NPs may be more effective at stimulating germination, but toxicity risk increases with size reduction and dose, while larger NPs are safer but may be less effective. Therefore, for effective seed treatment, it is crucial to use low concentrations of small NPs, and to apply coated or functionalized NPs (e.g. biopolymer-wrapped) to mitigate toxicity, as well as to tailor NP size based on the target plant species, seed coat properties, and intended priming effect.

Seed-associated nanotechnology innovations

Based on knowledge regarding NM biofabrication, NM-seed coat interaction, and the positive or negative effects of NMs on seed physiology, scientists have created seed-associated strategies to prime seeds for better seed vigour and germination, improve abiotic stress tolerance, facilitate pathogen protection, effectively transfer genetic information, and efficiently convert seed oils into biodiesel (Fig. 3). Furthermore, nanosensors for monitoring seed health have also been developed. Current advances in nanotechnology-based seed priming have been extensively reviewed (see Patra et al., 2024; Shelar et al., 2024; Aggarwal et al., 2025; Mahra et al., 2025; Yadav and Mathur, 2025), therefore our review focuses on not yet reviewed NM applications for gene delivery to embryos, enhancing seed safety, seed oil transformation, and monitoring seed health as novel trends in seed nanotechnology.

Fig. 3.

Seed-based nanotechnological innovations include nanopriming, nano gene delivery, nanopesticides, and biodiesel production. These innovations offer promising solutions for global challenges like climate change, genetic improvement, food and feed safety, and sustainable energy production, respectively. At the same time, there are numerous factors (e.g. size and toxicity trade-off, environmental risk, biosafety, lack of regulations, etc.) which currently limit the wide-scale application of nanomaterials (NMs) in seed technology. Created in BioRender. Ördögné Kolbert, Z. (2025) https://BioRender.com/7h85b4u.

NM-assisted gene delivery to embryos

Conventional plant gene delivery approaches can be divided into three main categories: biological (Agrobacterium-mediated transformation), physical (biolistic and electroporation), and chemical (polyethylene glycol- or liposome-mediated) (Shivashakarappa et al., 2025). Besides their advantages, these methods have also drawbacks including genotype-dependence, random gene integration, low gene transfer efficiency, tissue damage, and time-consuming labour-intensive plant regeneration protocols. However, due to their high DNA binding ability, the application of NMs in gene-delivery systems may exhibit improved transformation efficiency and compatibility with biological systems, protect cargos, and enhance plant regeneration capacity (Fig. 3; Shivashakarappa et al., 2025). Furthermore, one main advantage of NM-mediated gene delivery is the efficient protection of transferred DNA from nucleases provided by the nanocarriers (Niazian et al., 2021). As for seed tissues, carbon nanotube (CNT)-mediated plasmid DNA delivery into rice has been reported by infiltration of leaf cells and excised-embryos with reporter genes. The CNT-facilitated plasmid DNA delivery in rice leaf and embryo tissues has been verified by transient green fluorescent protein (GFP), yellow fluorescent protein (YFP), beta-glucuronidase (GUS) expression (Dunbar et al., 2022). However, efficient in planta DNA delivery and strong protein expression without transgene integration can be achieved by using SWCNT (Demirer et al., 2019), these NMs are highly persistent in organisms or in the environment. Recently, biocompatible and optimizable arginine-functionalized nanohydroxyapatites (R-nHAs)-based DNA delivery into seeds has been developed to deliver DNA plasmids for genetic transformation in planta (Izuegbunam et al., 2021). The expression of GUS activity in developing embryonic tissues of wheat, barley, and field mustard suggest that the R-nHA-based plasmid DNA delivery system has high potential for stable genetic transformation of germline tissues in seeds without any observable negative effects on germination (Izuegbunam et al., 2021). Recently, a plasmid DNA delivery platform using phyto-synthetized iron NPs has been developed for gene transformation in okra (Abelmoschus esculentus L.) embryos via the magnetofection process (Farooq et al., 2022). According to the results, a DNA-to-iron NP ratio of 1:20 results in the highest gene transformation efficiency with rotating (800 rpm, 5 h) the mixture of plasmid DNA, iron NPs, and seed embryos (Farooq et al., 2022).

The examples presented highlight the potential of NM-mediated strategies to improve transformation efficiency in plants. However, they also reveal key limitations that must be addressed to advance the practical use of these technologies (Fig. 3). A central challenge is the plant cell wall, a rigid and multilayered structure composed of cellulose, hemicellulose, pectin, and lignin (Fuertes-Rabanal et al., 2025), which contrasts with the flexible lipid membranes of animal cells. With pore sizes typically ranging from 5–20 nm (Pei, 2022), the wall restricts passive entry of most NPs and macromolecules, limiting delivery efficiency (Cunningham et al., 2018; Y.Zhang et al., 2024). To bypass this barrier, protoplasts have been explored (Panda et al., 2024). While they permit easier DNA uptake, challenges with regeneration and maintenance make this approach impractical for many species and limit its use in crop improvement efforts. Beyond physical barriers, NM-mediated delivery is also constrained by issues related to NP size, cargo capacity, and biosafety (Wu and Li, 2022). Achieving effective delivery without damaging plant tissues requires precise optimization of concentration. This trade-off between efficacy and safety remains a critical limitation. Another unresolved issue is the limited cargo capacity of nanocarriers. While strategies such as using functionalized SWCNTs have improved DNA delivery to chloroplasts (Santana et al., 2022), the delivery of larger CRISPR/Cas9 vectors remains rare (Kandhol et al., 2025), hindering broader application. Finally, systemic movement of NPs in plant tissues may result in accumulation in edible organs, raising biosafety concerns regarding potential transfer into the food chain (Wu et al., 2021; Gao et al., 2023). These issues underscore the need for continued research into safe, efficient, and scalable nanocarrier systems for plant biotechnology.

Seed nanoapplications in relation to food safety

Through its use in seed treatment, nanotechnology has the potential for improving food safety. Creating advanced seed treatments using NMs that protect seeds and seedlings against pathogen infections and pests can lessen the need for conventional pesticides (Fig. 3). Conventional agrochemicals possess multiple disadvantages including poor solubility, low bioavailability, photosensitivity, organic solvent pollution, and excess toxicity (Shelar et al., 2023). Nanopesticides include nanofungicides which can be applied in seeds in order to limit the infection in the seed or seedling stage. Mostly metal or metal oxide-based nanofungicides (e.g. CuO, TiO₂, ZnO, Fe or Si NPs) have been developed and applied in seeds (reviewed by Shelar et al., 2023; Venugopal et al., 2024). More recently, a nanofungicide containing the metal–organic framework UiO-66 carrier, the fungicide ipconazole (IPC), and a tannic acid (TA)-ZnII coating has been developed and applied to rice seeds. This formulation provides a controlled release of IPC and efficiently regulates the proliferation of Fusarium fujikuroi spores, with good penetration ability into both rice roots and fungal mycelia. Furthermore, the developed nanofungicide exhibits high antifungal activity and low biotoxicity (Q. Zhang et al., 2024). Similarly, in rice seeds, the newly developed nanocomposite containing sodium alumino silicate synthesized by neem leaf extract causes no reduction in seed germination but effectively limits seed rot caused by Aspergillus flavus and decreases toxin concentration in rice varieties suggesting effective antifungal properties during seed storage of rice (N. Singh et al., 2025).

Maintenance of seed health during storage can be achieved by newly developed nanoinsecticide formulations. For instance, sphere-shaped polyvinylpyrrolidone-coated zein-zipped herbal molecules infused nano colloids (PZCA-NCs, 151 nm, containing curcumin and azadirachtin) have been fabricated and tested on black gram (Vigna mungo) seed viability (Madhan et al., 2025). A toxicity study on the storage insect Callosobruchus maculatus indicates efficient insecticide activity of PZCA-NCs (Dubey et al., 2024). Moreover, PZCA-NCs show antifungal activity tested on Macrophomina phaseolina suggesting that PZCA-NCs can be applied to maintain seed health due to their combined insecticide and fungicide properties (Madhan et al., 2025).

Beyond seed treatments, nanopesticides are increasingly viewed as promising tools for enhancing pest control efficiency and reducing the environmental burden associated with conventional pesticides (Shangguan et al., 2024). However, despite these benefits, critical knowledge gaps remain regarding their long-term ecological impact and regulatory oversight (Fig. 3).

Due to their nanoscale dimensions and unique physicochemical properties, nanopesticides can interact with biological systems in complex and sometimes unpredictable ways (Ji et al., 2024). Studies have reported toxic effects on non-target organisms, including soil microbes, aquatic life, and pollinators (Du et al., 2025; T. Zhang et al., 2025). For example, silver- and copper-based nanopesticides have been shown to alter microbial diversity and cause toxicity in both plants and animals (Vignardi et al., 2020; Fernández-Bertólez et al., 2024; Gajardo et al., 2025). Such disruptions may impair key soil functions like nitrogen fixation and organic matter decomposition, with cascading effects on plant health and ecosystem processes (Ding and Yu, 2025). Nanopesticide mobility also poses environmental risks. After application, NPs may leach through soil layers and contaminate groundwater or surface waters (L. Zhang et al., 2024; T. Zhang et al., 2025). In aquatic systems, they can accumulate in organisms and enter food webs, raising concerns about bioaccumulation and trophic transfer. Some engineered NMs have been found to trigger oxidative stress and reproductive toxicity in aquatic species (L. Zhang et al., 2024; T.Zhang et al., 2025), although the broader environmental fate of these materials remains poorly understood.

Current toxicity studies are typically short term and conducted under controlled conditions, often using concentrations far higher than those applied in agricultural settings. This limits the ecological relevance of their findings and highlights the need for long-term, field-based studies that better reflect real-world scenarios. Additionally, the behaviour of nanopesticides is highly dependent on soil pH, organic matter, and moisture, factors that influence their mobility, transformation, and bioavailability (Islam, 2025). Another major barrier to the safe and widespread adoption of nanopesticides is the lack of tailored regulatory frameworks. Most agencies still apply conventional pesticide regulations to nanoformulations, despite their distinct properties (Kumari et al., 2023). A core issue is the absence of a unified definition of nanopesticides, some definitions restrict particle size to under 100 nm, while others extend this to 1000 nm based on functional properties (J. Yin et al., 2023). This inconsistency hinders product registration, safety evaluation, and international harmonization.

Efforts have been made by organizations such as the European Food Safety Authority (EFSA), the U.S. Environmental Protection Agency (EPA), and the International Organization for Standardization (ISO) to develop guidelines for the assessment and safe use of NMs in agriculture (Kumari et al., 2023). However, these frameworks are still evolving and often lack harmonization across jurisdictions. Key challenges include the need for standardized testing protocols, validated analytical methods for NP detection and characterization, and models that account for the unique behaviours of NMs in complex environmental matrices. The absence of these tools hampers accurate risk assessments and limits the ability to implement effective regulatory oversight.

In parallel, public scepticism around the term ‘nano’ and unclear communication about product safety can impede market acceptance (Atanda et al., 2025). Transparent, evidence-based outreach is essential to improve trust. From a commercial standpoint, the production and scaling-up of nanopesticides involve high costs related to synthesis, formulation optimization, and compliance with safety regulations (Atanda et al., 2025). These costs can deter small- and medium-sized enterprises and limit accessibility for resource-limited farming communities, particularly in developing countries. To address these challenges, research should focus on developing cost-effective, sustainable, and biologically inspired synthesis methods. One such example is the use of green synthesis (e.g., with the application of plants, microbes) for nanomaterial production potentially reducing environmental risks and production costs while aligning with circular economy principles (Atanda et al., 2025).

Nanosensors for seeds

It has been known for decades that both wet and dry seeds emit volatile organic compounds (VOC), mainly methanol, acetaldehyde, ethanol, and acetone, during their aging process (Jorgensen, 2001; Selvarani et al., 2025), and recently VOCs have been considered as reliable markers for seed quality (Mira et al., 2016; Selvarani et al., 2025). VOCs can be perceived by gas sensors showing resistance changes with the cross flow of a certain gas which transforms to an electrical signal that forms the fingerprint pattern for gas detection (Hajivand et al., 2024). Improved versions of VOC sensors are composed of NPs such as ZnO or NiO/ZnO nanowires (Kaur et al., 2018) and their utilization in plant disease diagnosis and stress management has been extensively reviewed (e.g. Ang and Lew, 2022; Vyas et al., 2023; Hajivand et al., 2024); however, there is a significant knowledge gap regarding nanosensing of seed VOCs.

NM-assisted biodiesel production from seed oil

Biodiesel production from non-edible seed oils offers a powerful solution to the problems associated with the increasing energy demand due to overpopulation. Sustainability is supported by the fact that this approach reuses non-edible seeds as agricultural waste. A recent innovation is the utilization of NPs as catalysts for seed-derived biodiesel production (Fig. 3). For example, CuO NPs synthesized with aqueous leaf extract of Portulaca oleracea L. have been used to catalyse biodiesel formation from oils of Citrus medica L. seeds having high oil content (Rozina et al., 2022b). In a similar study by the same research group, aqueous leaf extract of Silybum marianum (L.) Gaertn. has been applied to biofabricate Ag NPs, which have been used as a catalyst for the conversion of seed oil of Zanthoxylum armatum DC. into biodiesel (Rozina et al., 2022a).

Conclusion and perspectives for future research

Seeds play a fundamental role in plant cultivation. However, in many cases seeds are unnecessary by-products and as such provide a promising alternative to traditional methods for NP production. Seed-based approaches have many advantages, such as sustainability, biocompatibility, and low-cost, while also utilizing the biochemical richness of plants to produce NPs with specific properties (e.g. size, shape, surface charge, and stability) for different purposes. Moreover, the utilization of agricultural green waste for NM biofabrication may support regenerative agricultural practices. However, further development is needed to identify plants that are widely available and suitable for industrial-scale synthesis. Additionally, as the green material used in synthesis can strongly influence the physical, chemical, and biological characteristics of the resulting NMs, it is essential to comprehensively evaluate these products before their application to delineate their behaviour and fate in the presence of living systems.

The seed coat is the first point where the NMs interact with the seed. The diverse morpho-anatomical and chemical features of the seed coat highly influence the NP–seed interaction, and such features should be considered when treating seeds of different plant species with NPs. Orthodox seeds benefit directly from nanopriming, which may be the reason that the interactions of NPs with seed coat have been extensively examined in plant species having orthodox seeds. NP–seed coat interactions and the effects of nanopriming in recalcitrant seeds are little explored areas with promising opportunities. For instance, NMs with antioxidant features may have the potential to improve post-freezing viability in recalcitrant seeds, and this possibility is worthy of examination in future nano seed research. NMs in the plant seed matrix have been detected using diverse imaging techniques and further experimental data showing the possible internalization of NMs depending on particle size, chemical nature, shape, concentration, and plant species is needed.

NM-associated toxicity in seeds depends on several factors relating to the NM and also to the plant species, and the main molecular mechanisms involve ROS overproduction, oxidative damage, and nutrient deficiency in the seed/seedling tissues. There is undoubtedly a lack of knowledge regarding the adverse NM effects on physiological and molecular mechanisms in the seeds, thus we urge detailed studies on, for example, seed ROS metabolism, macromolecule damage, phytohormone metabolism, etc. Additionally, omics technologies have the potential to shift the research on plant-NP interactions from low-throughput bioassays to high-throughput discovery which may have application in NM toxicological studies in relation to seeds.

Exciting nano-innovations have been emerged recently related to genetic modification, improvement of seeds, protection against pathogens, and utilization of seeds. These innovative approaches offer solutions to global issue such as climate change-related crop losses, food security, the oil crisis, and sustainability in agriculture. At present, certain applications of NMs in seeds appear to be overpromoted, particularly when considering the existing technological, regulatory, and safety limitations. While science has shown exciting potential, the real-life adoption of nanotechnology in seed treatment faces several practical and ethical constraints including the lack of solid proof of scalability and reproducibility in field environments, unexplored long-term impacts on non-target organisms, soil microbiota, or seed genetics, and the lack of specific regulations for NP use in agriculture or seed technology (Fig. 3). Therefore, evaluating the long-term effects on the environment and human health, and creating standards for the safe and efficient application of nanotechnology in agriculture should be main goals of future study. With the continued in-depth exploration of nascent research areas, seed nanotechnology is poised for significant advancement in the foreseeable future.

Author contribution

TB, GF, DK, SK, RS, AR and ZSK: writing—original draft; TB, AR, RCDS, ZK, ZSK: writing—review & editing; TB, RS, ZSK: visualization; ZSK: conceptualization, supervision, and funding acquisition.

Funding

This work was supported by the National Research, Development and Innovation Office of Hungary under grant no. K 135303 (ZSK) and by the ‘Lendület’ MOMENTUM Project of the Hungarian Academy of Sciences (LP2023-14/2023). The manuscript is prepared with the professional support of the University Research Scholarship Program of the Ministry of Culture and Innovation, Financed from the National Research, Development and Innovation Fund (EKÖP-24-3-SZTE-521).