Table 1.

Summary of nanobody-based immunoassay methods for SARS-CoV-2 detection.

Nanobody name	Nanobody target	Affinity to target (KD)	Method	Sample source	Specificity	Sensitivity	Sample to-result time	Features	References
NTD-E4, NTD-B6	N protein	23.8 ± 2.1 nM (NTD-E4), 46.5 ± 2.6 nM (NTD-B6)	ELISA	Nasal swabs	–	–	Several hours	–	[51]
E2, B6, C2	N protein	0.8 nM (E2), 1.6 nM (B6), 1.1 nM (C2)	ELISA	–	–	LOD of 50 pg/mL for N and 1.28 × 103 pfu/mL for the killed virus	Several hours	–	[50]
C5, F2	S protein	99 pM (C5), 40 pM (F2)	ELISA	–	–	103 ffu/ml for inactivated virus	Several hours	–	[116]
–	RBD of S protein	–	ELISA	Saliva, nasopharyngeal swabs	100 %	Saliva - 93.3 % (Ct ≤ 30), 87.5 % (Ct ≤ 35), 86 % (Ct ≤ 40); Nasopharyngeal swabs - 90 % (Ct ≤ 30), 80 % (Ct ≤ 35), 88 % (Ct ≤ 40)	Several hours	–	[117]
–	S protein		Photoelectrochemical (PEC) immunosensor	–	–	LOD = 2.8 × 10−17 M (5 fg/mL)	30 min	Label-free, convenient, rapid, low cost	[44]
RBD8/ RBD10	RBD of S protein	–	Nanobody-functionalized nanoparticles for rapid, electronic detection (Nano2RED)	Serum, blood	–	LOD=∼1.3 × 10−12 M, for RBD in diluted human serum	5–20 min	Label-free, rapid detection, low cost	[45]
VHH72-C13	RBD of S protein	12.1 nM	Nanobody-functionalized electrochemical platform	Saliva, nasopharyngeal swab	Saliva-85 %, nasopharyngeal swab-90 %	Saliva-80 %, nasopharyngeal swab-90 %, LOD = 1.2 × 104 viral RNA copies mL−1, 2 × 10−17 M	10 min	Portable, quick, accurate, user-friendly	[47], [118]
VHH72	RBD of S protein	23 nM	Organic electrochemical transistors (OECTs)	Saliva, nasopharyngeal swab, serum	–	Single-molecule, sensitivity comparable to RT-PCR, saliva (LOD = 1.2 × 10−21 M), nasopharyngeal swab (LOD = 1.9 × 10−14 M)	<15 min	Label-free, rapid, sensitive, reusable, simple, robust	[46], [118]
Ty1	RBD of S protein	24.9 ± 10.3 nM	Alternating current electrothermal flow (ACET) integrated OECT-based immunosensor	Saliva	–	LOD = 1 × 10−16 M	∼2 min	Label-free, partially reusable, speedy detection	[48]