Table 2.

Comparison of MEF-based nanobiosensors for nucleic acid detection.

Detection Strategy	Fluorescent Dye/Enhancer	Wavelengths (Ex, Em)	Target	Required Time	Detection Limit	Ref
Detection of DNA by using engineered substrates to increase the emissivity of the fluorophore (proximity of surface plasmons (<100 Å))	Cy3, Cy5/Ag-nanostructure	Ex: 549 nm, 646 nm Em: 562 nm, 663 nm	DNA	<3 h	-	[83]
By applying neutravidin-coated fluorescent nanospheres to biotinylated Au-nanorods, the signal enhancement under the fluorescence microscope using Ag zigzag nanorods (ZNR) arrays	Alexa 488/Ag zigzag nanorod	Ex: 488 nm Em: 525 nm	DNA	<3 h	0.01 pM	[84]
Induction of localized surface plasmon resonance effect (LSPR) of highly ordered monolayer Au-nanorods; Distance-dependent MEF effect between extinction and enhancement	Quasar670/Au-nanorod	Ex: 664 nm Em: 670 nm	ssDNA	<20 min	10 pM	[85]
Detection of DNA by using Ag vertical nanorod (VNR) arrays fabricated via the glancing angle deposition (GLAD) method	Cy5/Ag vertical nanorods	Ex: 635 nm Em: 670 nm	Kallikrein (KLK7)	>12 h	-	[86]
Bimetallic structures (containing Au and Ag 2 nm and 50 nm thick) are used to maximize the MEF effect; Detection of amplified target DNA using polymerase chain reaction (PCR).	SYBR Green I/Au-Ag	Ex: 470 nm Em: 535 nm	dsDNA	-	400 fg/μL	[87]
Fix with capture DNA of magnetic nanoparticles implanted with silver nanoparticles; After introduction of target DNA, sandwich structure formation by hybridization reaction and isolation of barcode DNA from silver nanoparticles and fluorescence enhancement	FAM/NMP-AgNP	Ex: 495 nm Em: 518 nm	DNA	>10 min	1 pM	[88]
Increase the signal-to-background ratio by using the high quenching efficiency of AuNPs; Distance-dependent MEF effect and high specificity of target fluorescein isothiocyanate-tagged DNA-HMNC and target DNA hybridization	FITC/Magnetic NP/nanogold clusters	Ex: 488 nm Em: 520 nm	DNA	>2 h	0.01 μM	[89]
Amine-functionalized Fe3O4 nanoparticles bind with amine-gold bonding reaction and form magnetic Au-nanoclusters; After binding of target DNA, distance-dependent MEF effect between AuNP and FITC	Flu, Rho 6G, Cy5/MOF-based nanoprobes	Ex: 494, 525, and 646 nm Em: 513 nm, 553 nm, 664 nm	DNA	<30 min	20 fM	[90]
Quenching of AuNPconjugated Cy5 by AuNP, complementary binding of target DNA with capture DNA on AuNP and other DNA on Au-nanorod, AuNP or Au@AgNP, and enhancement of fluorescence signal.	Au-NP-conjugated Cy5/Au@AgNP	Ex: 410 nm Em: 660 nm	DNA	>12 h	3.1 pM	[91]
Length optimization of dsDNA and attachment of Au-nanoparticles (AuNPs) to the surface; Activation of CRISPR-Cas12a complex by target cfDNA, degradation of AuNP and fluorophore ssDNA, and generation of red-violet fluorescence	FITC/DNA-functionalized AuNP	Ex: 490 nm Em: 520 nm	breast cancer gene-1 (BRCA-1)	<30 min	0.34 fM	[92]
Annealing of target RNA and DNA anchor probes tagged with silver nanoparticles and fluorophores on a solid surface and enhancement of fluorescence signal	TAMRA/AgNP	Ex: 532 nm Em: 585 nm	β-globin mRNA	30–60 min	25 fM	[93]
Fabrication of sandwich structure using 484-mer RNA and 15-mer complementary RNA attached to Flower-like silver film; Enhanced fluorescence emission of TAMRA-tagged 15-mer RNA; Shortening the spacing distance between N-CD and CeO2 and significantly quenching the fluorescence of N-CD; Fluorescence recovery of quenched probes in the presence of target miRNAs	(DNA1-NCDs)/Flower-like Ag	Ex: 390 nm Em: 462 nm	miR-210, miR-21	15 min	0.03 fM, 0.06 fM	[94]
FAM-MB formed a hairpin structure and the fluorescence reduction of 6-FAM and AgNPs; Upon target miRNA hybridization, increasing the distance between 6-FAM and AgNPs and Fluorescence enhancement	FAM-tagged MB/AgNRs	Ex: 488 nm Em: 520 nm	miR-21	60 min	1 pM	[95]
Fluorescent dye (FAM) tagging of chemically synthesized gold triangular nanoprisms (Au TNPs); When the target miRNA hybridizes with the molecular beacon, the distance between the FAM and AgNP increases and the fluorescence intensity of the FAM increases.	FAM/Au TNPs	Ex: 488 nm Em: 520 nm	miR-10b, miR-96	120 min	1.13 pM, 30 fM	[96]
Fluorescence enhancement using biotin-functionalized lanthanide nanoparticles as signal enhancers and capture of target miRNAs of surface-modified molecular labels; Detection of Biotin-NPs-probe hybridized with miR in a sandwich structure.	Biotin-NPs/Ln3+-nanoprobe	Ex: 340 nm Em: 617 nm	miR-21	>2 h	1.38 fM	[97]
The miR-124 specific MB (molecular beacon) attachment on magnetic plasmonic nanorods; Immunomagnetic isolation and enrichment of exosomes in cell culture medium collection, non-destructive analysis of exosome miR-124 expression.	FAM/plasmonic AuNRs	Ex: 490 nm Em: 520 nm	miR-124	30 min	1 pM	[98]