Table 2.

Biosensors for heavy metal monitoring with detection limits and response time.

Heavy metals	Configuration of biosensors	Electrodes/Materials		Environmentalmatrix	Detection limits	Response times	Remarks	Refs.
		Anode	Cathode
Cu, As, Cr, Hg	Double chamber MFC	Carbon fiber	Carbon fiber	Municipal wastewater	0.5–10 mg L–1	5 min	MFC as a heavy metal biosensor	[83]
Pb, etc.	A dual-chamber self-powered MFC	Graphite felts	Graphite felts	Water containing heavy metal ions	2 mg L–1	N/A	A simple, cheap and sensitive	[101]
Cr	Sediment MFC	Carbon cloth	Graphite felt	Industrial wastewater	0.2–0.7 mg L–1	18.3 min	Real-time in-situ detection	[106]
Hg	Doublechamber MFC	Graphitefelt	Graphitepaper	Artificial water	200 mg L–1	N/A	Environmentally friendly method	[108]
Pb, Cd, Cu	Magnetoelastic (ME) biosensor	ME ribbon		Heavy metal ions solutions	0.23–0.33 µM	5 min	High-sensitive	[109]
Pb	Micromechanicalbiosensor	A silicon membrane		Lead ions solutions	10 µM	N/A	Based on 8–17 DNAzyme	[130]
Hg, Ag, Cu, Pb	DNA-based electrochemical biosensors	Gold, SPGE, PGE, ITO, magnetic beads, etc.		Environmental matrices	0.0001–300 nM	N/A	Providing a platform for heavy metal detection	[99]
Cu, Cr, Zn, Ni	Reusable single-chambered cylindrical MFC	Graphite sheet	Graphite sheet	Industrial wastewater	5–20 mg L–1	N/A	Cost-effective	[100]
Cd, Cu,Zn	Whole-cell bacterial biosensor	Sol-gel matrices (a thin film of sol-gel)		Soilenvironment	1.42 × 10−4–3.16 × 10−4 mg L–1	4–7 h	A green fluorescent protein	[40]
Hg	DNA-based electrodes	Gold nanoparticles, MWCNT		Water samples	1 × 10−6 nM	N/A	A time and cost-effective	[127]
Se, Sn, Cr	Bacterial molecular biosensors	Acinetobacter baylyi ADP1 Tox2		River water	Low	30 min	Respond at low levels	[71]
Hg, Zn, Cu, Cd	A bacterial whole-cell biosensor	A. baylyi Tox2biosensor		Seawater	0.02–1.0 mg L–1	A quick	Rapid detection, sensitive biosensor	[70]
Cu, Hg, Zn, Fe, Cr, Cd	MFC-based biosensors	Graphite, carbon cloth, stainless steel	Graphite, carbon cloth, platinum	Water, wastewater, sewage sludge	0.0125–200 mg L–1	Short time	Cost-effective	[110]
Cu	A single-chamber MFC	Carbon brush	Carbon cloth	Artificial solution	0.5–12.5 mg L–1	N/A	A cost-effective	[105]
Pb	Light-up biosensor	Micro-spin column (Bio-Rad)		Water, serum samples	60.7 nM	N/A	A simple, facile, and cost-effective	[111]
Hg	SERS-based biosensor	Magnetic nanoparticles, SWCNT substrate and CoFe3O4@Ag		Aqueous solution	8.4 × 10−4 nM	N/A	Good sensitivity, selectivity, simplicity, and rapidity	[112]
Pb, Ni, Cd, etc.	Biosensor cells	A novel marine luminescentbacterium Vibrio sp. MM1		Aquatic environments	0.97–14.54 mg L–1	N/A	High sensitivity	[78]
Hg	DNAzyme-based biosensors	Nanomaterial-assisted DNAzymes		Tap, river, lake, wastewater, etc.	5 × 10−5–100 nM	N/A	Highly selective and sensitive recognition	[103]
Pb	A self-cleaning electrochemical biosensor	Cu-TCPP nanofilm and DNAzymes		Artificial solution	1.7 nM	N/A	High sensitive and selective	[123]
Hg, Ag	Novel conductometric biosensor	Three-enzyme system (invertase, mutarotase, glucose oxidase)		Artificial solution	1.25 mM	10–20 min	High sensitivity	[113]
Cd	A novel signal amplification biosensor	Agarose gel electrophoresis, oligonucleotides DNA		Artificial solution	19.93 nM	N/A	A satisfactory recovery rate, high sensitive	[138]
Hg	Whole-cell biosensors	A gas reporting biosensor system		Artificially contaminated soil	5 μM	45 min	On-site detection, saving time and costs	[102]

Remarks: MFC: Microbial fuel cell, PGE: Polycrystalline gold electrode, SPGE: Screen-printed gold electrode, ITO: Indium tin oxide, ME: Magnetoelastic, DNA: Deoxyribonucleic acid, MWCNT: Multi-walled carbon nanotube, SERS: Surface enhancement Raman spectrum, SWCNTs: single-walled carbon nanotubes, TCPP: Tetrakis (4-carboxyphenyl) porphyrin.