Table 2.

Examples of electrochemical biosensors that detect miRs in blood

Detection platform	Detection target	Specificity and mismatches	Detection time	Detection range/ Detection limit	Detection media	Publication year
Electrode: flat gold E/chitosan/origami‐ssDNA	miR‐21: 5′‐UAG CUU AUC AGA CUG AUG UUG A‐3′	vs. (1)δ: 5′‐UAG CUU AUC AGA CUG AUG UUG C ‐3′ (2)δ: 5′‐UAG CUU AUC G GA CUG AUG UUG A‐3′ (3) miR‐192: 5′‐CUG ACC UAU GAA UUG ACA GCC‐3′	N/A	0.1 pM to 10.0 nM/79.8 fM	spiked into 1% human serum	Shuo Han, 2019[ 65 ]
Electrode: DNA–Au@MNPs Collector: flat gold E using a magnet	miR‐21: 5′‐UAG CUU AUC AGA CUG AUG UUG A‐3′	vs. (1)δ: 5′‐UAG CUU AUC A A A CUG AUG UUG A‐3′	30 min	10 aM to 1 nM	(1) spiked unpurified serum (2) spiked 50% blood	R. Tavallaie, et al., 2018[ 66 ]
Label: Fe3O4/CeO2 @Au MNPs Electrode: GCE electrodeposited AuNPs	miR‐21: 5′‐UAG CUU AUC AGA CUG AUG UUG A‐3′	vs. (1) miR‐141: 5′‐CAU CUU CCA GUA CAG UGU UGG A‐3′, (2) miR‐155: 5′‐UUA AUG CUA AUC GUG AUA GGG GUU‐3′ (3) miR‐199: 5′‐CCC AGU GUU CAG ACU ACC UGU UC‐3′	100 min	1 fM to 1 nM/0.33 fM	Spiked into 10‐fold‐diluted human serum	Sihan Liu, et al., 2018[ 67 ]
Labels: 1) Au/TMC/Fe3O4, 2) CdSe@CdS/TMC/Fe3O4 Electrode: PTh/rGO/SPCE	(1) miR‐106a: 5″‐AAA AGU GCU UAC AGU GCA GGU AG‐3″ (2) miR let‐7a: 5″‐UGA GGU AGU AGG UUG UAU AGU U‐3″	vs. (1) miR‐15a: 5″‐UAG CAG CAC AUA AUG GUU UGU G‐3″ (2) miR‐21: 5″‐UAG CUU AUC AGA CUG AUG UUG A‐3″ (3) miR‐200c: 5′‐CGU CUU ACC CAG CAG UGU UUG G‐3	N/A	Serial dilutions of targets: 0.1 fM‐5 pM/ miRNA‐106a: 0.06 fM miRNA let‐7a: 0.02 fM	Spiked human blood plasma	Maryam Daneshpour, et al., 2018[ 68 ]
Labels: 1) biotin‐MB1‐AuNPs, 2) biotin‐MB2‐AgNPs Electrode: Neutravidin/GCE	(1) miR‐21: 5′‐UAG CUU AUC AGA CUG AUG UUG A‐3′ (2) miR‐141: 5′‐UAA CAC UGU CUG GUA AAG AUG G‐3′	vs. (1) simultaneous detection of miR‐21 and miR‐141 (2) miR‐205: 5′‐UCCUUCAUUCCACCGGAGUCUGU‐3′ (3) miR‐221: 5′‐AGC UAC AUU GUC UGC UGG GUU UC‐3′	N/A	miRNA‐21: 0.5–1000 pM/0.3 pM miRNA‐141: 50−1000 pM / 10 pM	spiked serum sample	Sawsen Azzouzi, et al. 2019[ 69 ]
Amplification: combined CESA with template‐free DNA extension reaction Electrode: flat gold E	miR‐196a: 5′‐UAG GUA GUU UCA UGU UGU UGG G‐3′	vs. (1)δ: 5′‐UAG GUA GUU ACA UGU UGU UGG G‐3′ (2) miR‐196b:5′‐UAG GUA GUU UCC UGU UGU UGG G‐3′ (3): 5′‐UAG CUU AUC AGA CUG AUG UUG A‐3′	60 min	0.05 fM to 50 pM/15 aM	Spiked plasma	Jing Guo, et al., 2018[ 70 ]

E: electrode; GCE: glassy carbon electrode; SPCE: screen printed carbon electrode. Au@MNPs: gold‐coated magnetic nanoparticles; Au MNPs: gold magnetite nanoparticles; AuNPs: gold nanoparticles; AgNPs: silver nanoparticles; TMC: N‐trimethylchitosan (TMC) polymer; PTh: Polythiophene; rGO: reduced graphene oxide; CESA: cyclic enzymatic signal amplification; biotin‐MB: biotinylated molecular beacon; ssDNA: single‐stranded DNA; ^δsingle‐mismatch base‐pair: bold‐underlined letter.