Table 9.

Summary of the SERS applications in the biomedical field presented in this review (indirect protocol).

$\mathbf{Analyte}$	Recognition Unit	SERS Substrate	Ref.
Viral DNA	DNA Hairpin	Au NPs	[470]
RSAD2 gene	DNA Hairpin	Nanowave Chip	[471]
microRNA	Molecular Beacon	Ag NPs	[472]
miR-21	ssDNA	Au NRs on Au substrate	[473]
ssDNA		AuNPs@SiNWAr	[474]
Modifications in ssDNA	DNA targeting BRCA1	Au-coated magnetic NPs on rGO on Au electrode	[475]
Bacterial DNA	Probe, target, and reporter DNA	Au NP-on-wire	[476]
CEA, AFP	Antibodies	Sandwich Au honeycomb array + Au nanostars	[477]
Pathogenic bacteria	Antibiotics	Nanoscopic Ag substrate + electrodeposited Ag-Au layer	[478]
Intracellular pH	Mercaptobenzoic acid (MBA)	Ag-MBA@SiO2	[479]
Intracellular pH	(Cr(CO)3–ATP)	Au-coated planar substrate	[480]
Intracellular and extracellular redox potential of neural cells	Dopamine	ITO electrode + hexagonally packed Au nanodots	[481]
Pancreatic cancer biomarker (MUC4)	MUC4 Antibody	Au NPs	[482,483]
CEA, human IgG	4-mercaptobenzoic acid (4-MBA) + antibody	Ag NR arrays on glass	[484]
VEGF	DNA Aptamer	Si-encapsulated hollow Au nanospheres and an Au-patterned microarray substrate	[485]
PSA	Antibody	MWCNTs/IL/chitosan + AuNPs-PAMAM	[486]
PSA	PSA Aptamer	Core-satellite magnetic NP (core)/Au NPs satellites	[487]
PSA	PSA Antibody	Sandwich Au Nanospheres on Au substrate	[488]
p53 and EGFR	P53 + EGFR antibodies	Si substrate + Ag nanopillars	[489]
PSA, thrombin, and Mucin-1	Aptamers	Self-assembled Ag NP pyramids on SERS substrate + SERS tags	[490]
Anti-gp41 antibody (HIV biomarker)	gp41	Microfluidic chip encoded with 2D LSPR structures of Au NPs	[491]

AFP: α-fetoprotein; AuNPs@SiNWAr: Silicon nanowire arrays decorated with Au nanoparticles; HIV: Human immunodeficiency viruses; CEA: carcinoembryonic antigen; EGFR: epithelial growth factor receptor; IgG: Immunoglobulin G; IL: Ionic liquid; ITO: Indium tin oxide; LSPR: Localized surface plasmon resonance; MWCNT: Multiwalled carbon nanotube; PAMAM: Poly(amidoamine); PSA: Prostate specific antigen; rGO: Reduced graphene oxide; VEGF: Vascular endothelial growth factor.