Table 1.

Different applications of capacitive biosensors developed for different targets.

	Target	Sensor Preparation Method	Dynamic range (M)	Limit of Detection (M)	Selectivity	Stability	Ref.
Proteins	Cholera toxin (CT)	Immobilization of anti-CT antibodies on self-assembled monolayer (SAM) of lipoic acid and 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)	1.0 × 10−13 –1.0 × 10−10	1.0 × 10−14uiu	N/D	N/D	[9]
	Cholera toxin (CT)	Immobilization of anti-CT on gold nanoparticles incorporated on a poly-tyramine layer	0.1 × 10−18–10 × 10−12	9.0 × 10−20	N/D	Up to 36 times with an RSD of 2.5%	[10]
	HIV-1 p24 antigen	Immobilization of anti-HIV 1 p24 antigen on gold nanoparticles incorporated on a poly-tyramine layer	10.1 × 10−20–10.1 × 10−17	3.32 × 10−20	N/D	N/D	[11]
	VEGF	Immobilization of anti-VEGF aptamer first capturing the VEGF protein then, sandwiching with antibody-conjugated magnetic beads	13 × 10−14–2.6 × 10−11	N/D	N/D	N/D	[12]
Nucleic acids	25-mer oligo C	Covalent attachment of 25-mer oligo C on poly-tyramine modified electrode	10−8–10−11	10−11	Oligo-T was used as the competing agent, when the temperature was increased from RT to 50 °C, the ΔC value decreased from 48 nF·cm−2 to 3 nF·cm−2	N/D	[13]
	ssDNA	Thiol modified oligonucleotides were immobilized on Au and 3-glycidoxypropyl-tri-methoxy silane (GOPTS)	0.5 × 10−6–1.0 × 10−3	N/D	N/D	GOPTS functionalized surfaces were more stable at 4 °C. Ten-fold decrease in fluorescence intensity after 1 week even when the substrates were stored at 4 °C.	[14]
	Nampt	Immobilization of ssDNA aptamers on SAM of mercaptopropionic acid (MPA)	0–45 × 10−10	1.8 × 10−11	N/D	N/D	[15]
	Target DNA	Immobilization of pyrrolidinyl peptide nucleic acid probes (acpcPNA)	1.0 × 10−11–1.0 × 10−10	6–10 × 10−12	Complementary DNA provided a much higher ΔC compared to single and double mismatched DNA	Could be reused for 58–73 times with an average residual activity of ≥98%	[16]
Cells	Total bacteria	Based on the interaction between E. coli and concanavalin A immobilized on a modified gold surface	12 CFU·mL−1–1.2 × 10−6 CFU·mL−1	12 CFU·mL−1	N/D	For the first 35 cycles, the residual activity was 95% ± 3% (RSD = 3.2%). After 35 cycles, it was 85%.	[17]
	E. coli	E. coli cells immobilized on SAM of Mercaptopropionic acid (MPA)	8 × 105 CFU·mL−1–8 × 107 CFU·mL−1	N/D	N/D	N/D	[18]
Heavy metals	Hg(II), Cu(II), Zn(II), Cd(II)	Immobilization of metal resistance and metal regulatory proteins on gold electrode	10−15–10−3	N/D	N/D	N/D	[19]
	Cu(II), Cd(II), Hg(II)	1. Immobilization of whole bacterial cell to emit a bioluminescent/fluorescent signal in the presence of heavy metal ions	0–200 × 10−6	1.0 × 10−6	N/D	84% of the activity loss within 6 days	[20]
		2. Immobilization of heavy metal binding proteins	10−15–10−1			Stable over 16 days
Saccharides	Glucose	Immobilization of ConA on gold nanoparticles incorporated on the tyramine modified gold electrode	1.0 × 10−6–1.0 × 10−2	1.0 × 10−6	Small sugars including D-fructose, D-mannose, D-maltose, methyl-α-D-glucopyranoside, methyl-α-D-mannopyranoside also bound instead of glucose	A neglectable loss in sensitivity after 10 cycles (7.5%)	[21]
	Glucose	Immobilization of ConA and replacement of small glucose with the large glucose polymer	1.0 × 10−5–1.0 × 10−1	1.0 × 10−6	Small molecules and high molecular weight dextran also bound instead of glucose	N/D	[22]
Small molecules	Metergoline	Immobilization of molecularly imprinted spherical beads on modified gold electrode	1–50 × 10−6	1.0 × 10−6	Cross reactant contribution was maximum 1.3 nF	N/D	[23]
	Aflatoxin B1	Bioimprinting	3.2 × 10−6–3.2 × 10−9	6.0 × 10−12	Competing agents’ binding was significantly lower than aflatoxin B1	Little variation over 28 injections with non-reduced Schiff’s bases	[24]
	Ochratoxin A (OTA)	Monoclonal anti-OTA immobilization on Si3N4 substrate combined with magnetic nanoparticles (MNPs)	2.47–49.52 × 10−12	4.57 × 10−12	Differences for ochratoxin B and aflatoxin B1 were not significant	N/D	[25]