Table 2.

List of some recently reported sensing systems for SARS-CoV-2.

Category	Bioreceptor	Target	Detection Method	Immobilization/Fabrication	Support Material	Detection Limit	Time	Ref.
	CRISPR/ Cas12a	N-gene	Colorimetric	Liquid-phase detection using AuNP-labeled ssDNA	N/A	1 copy µL−1	90 min	[13]
	CRISPR/ Cas13a	N-gene RNA	Fluorescence	Liquid-phase detection in microchamber array device	N/A	10 fM	<5 min	[91]
CRISPR-based	CRISPR/ Cas12a	N-gene RNA	Nanopore sensor	Liquid-phase detection	N/A	22.5 aM	>30 min	[114]
	CRISPR/ Cas12a	RdRp gene (RNA dependent RNA polymerase)	Electrochemiluminescence (ECL)	DNA tetrahedron immobilized on functionalized glassy carbon electrode for ECL signal	N/A	23.7 aM	>60 min	[115]
	CRISPR/ Cas12a	Open reading frame 1ab (ORF1ab) and N-gene	LFA	Analyte-biocomponent reaction in liquid-phase	N/A	7 copies per reaction	~60 min	[116]
	CRISPR/ Cas12b	Open reading frame 1ab (ORF1a/b) and N-gene	LFA	Analyte-biocomponent reaction in liquid-phase	N/A	10 copies per reaction	60 min	[117]
	CRISPR/ Cas12b	ORF1ab, N- and O- gene	Colorimetric (magnetic pull-down)	Analyte-biocomponent reaction in liquid-phase	N/A	50 copies per reaction	>50 min	[118]
	Antibody for N protein	N protein	SWV	N protein immobilized on cotton-tipped SPE	nanofiber-modified SPE	0.8 pg mL−1	> 20 min	[119]
	Antibody for S protein	S protein	FET sensor	Antibody for S protein immobilized on the graphene sheets of FET (immobilization on channel)	Graphene with Au/Cr electrode layer	1 fg mL−1	/	[120]
	Antibody for S protein	S protein	Chronoamperometry	Antibody immobilization by conjugation with DNA liker with a tethered ferrocene probe	Gold coated chip	1 pg mL−1	5 min	[121]
Immunosensors	Antibody for S protein	S protein	DPV	Antibody immobilized by EDC/NHS on cysteamine-modified Au electrode	Gold-modified laser scribed graphene	2.9 ng mL−1	~4 min	[122]
	Antibody for N protein	N protein	Amperometry	Capture antibody immobilized on screen-printed gold electrode, while sensing probe prepared by dually labeling magnetic bead with HRP and anti N protein antibody	screen-printed gold electrode and magnetic beads	10 pg mL−1 (in diluted serum)	<1 h	[123]
	Antibody for N protein	N protein	Chemiluminescence	Antibody immobilized on magnetic beads functionalized with -AuNP and modified with Co2+	Gold nanoparticle-functionalized magnetic beads	69 fg mL−1	20 min	[124]
	Antibody for N protein	N protein	Chemiluminescence	Antibody immobilized on AuNP attached to N-(4-aminobutyl)-N-ethylisoluminol and Co2+-functionalized MBs	Functionalized magnetic beads	21 fg mL−1	25 min	[125]
	DNA aptamer	S protein	EIS	Aptamer immobilized on functionalized gold electrode	Gold electrode	1000 viral particles per mL (in saliva sample)	<10 min	[106]
	DNA aptamer	S protein	Photoelectrochemical sensing	DNA aptamer immobilized on photoactive material (Au NPs/Yb-TCPP) coated on a glass carbon electrode	Au NPs/Yb-TCPP composite [Ytterbium Tetrakis(4-carboxyphenyl) porphyrin (Yb-TCPP)]	72 ng mL−1	>70 min	[126]
Aptasensors	DNA aptamer	S protein	Proximity ligation assay	Liquid-phase detection coupled with qPCR	N/A	37.5 pg mL−1	~2 h.	[127]
	DNA aptamer	S protein	Surface plasmon resonance (SPR)	Aptamer immobilized on polyethylene glycol interfaced gold nano-film deposited on optical fiber	Gold nano-film immobilized on optical fiber	36.7 nM	~10 min	[128]
	DNA aptamer	S1 subunit of S protein	Localized Surface Plasmon Resonance	Biotinylated aptamer immobilized on nano-gold surface by biotin-streptavidin interaction	Gold surface	0.26 nM	~16 min	[129]