Table 3.

Promising applications and challenges of various biosensor detection techniques for WBE.

Detection technique	Applications in WBE	Challenges	Ref
Indirect (PCR, CRISP, and genome sensing)	Commonly used technique to detect nucleic acids; Precise and sensitive detection of SARS-Cov-2 RNA; examine complex wastewater or biofluids.	Require trained personnel otherwise false negative; specialized equipment to interpret results for disease circulation; human health risks; inconsistency of sample strains vs. reference.	[[163], [164], [165], [166]]
Surface-enhanced Raman scattering (SERS) based biosensors (liquid, paper-based, microfluidic, magnetic)	Highly sensitive, low cost, rapid; detect at environmentally relatable concentrations; wastewater monitoring due to active SERS substrates; handheld systems appropriate for field analysis.	SERS substrate heterogeneity; weak SERS signals; require additional data analysis; reproducibility; challenge in detecting in complex wastewater at nano concentrations.	[167,168]
Electrochemical and field-effect transistor (FET) sensors	Simple lab on a chip integration; detect at environmentally relatable concentrations; portable; compatible for on-site analysis; simple operation.	Non-specific adsorption of interfering molecules and electrochemical signals in unstable physiological conditions in operation for the complex wastewater analysis.	[169,170]
Spectroelectrochemical (SEC) sensors	Capable of detecting single-molecule; feasible in using in complex wastewater media as complementary data allows to resolve overlapping signals coming from interfering molecules.	Device reproducibility with EC-SERS substrates; complexity in data analysis and interpretation; appropriate design needed for on-site analysis.	[171,172]