Table 3. Optical biosensors used in infectious disease detection, showing target biomarkers, sensing techniques, and detection limits across various diseases.

Disease	Target biomarker	Biosensor type/technique	Key features/detection limit	References
COVID-19	Anti-SARS-CoV-2 antibodies, RBD antigen, viral RNA	Fluorescence, SPR, SERS, colorimetry, photoluminescence	Low-cost, fast, visual detection, femtomolar-level sensitivity	70 and 71
HIV-1	gp120 protein, HIV-1 DNA (preantibody stage)	SPR, photonic crystal hydrogel sensor	48 fM (SPR), 4 viral particles per mL (hydrogel)	72 and 73
Hepatitis B	HBV DNA, HBsAg, HBeAg	Lateral flow (colorimetry), graphene–gold hybrid, chemiluminescent optical fiber	0.3–8.5 pM (DNA/HBsAg), 50 pg mL−1 (HBsAg), 0.01 fg mL−1 (HBeAg)	74, 75 and 76
Tuberculosis	TB antigens in sputum, nucleic acids	SPR, OLED-based sandwich hybridization, Raman spectroscopy	63 pg mL−1, rapid detection from processed sputum	77, 78 and 79
Malaria	PfGDH, PfLDH, infected RBC refractive index	SPR, antibody-aptamer plasmonic sensor, smartphone-based fiber-optic aptasensor	<30 fM (PfLDH), 264 pM (PfGDH), visual detection in <1 h	4, 81, 82 and 83
Ebola virus	Soluble glycoprotein (sGP), VP40, glycoproteins	Optofluidic nanoplasmonic, nanoantenna, SOI nanowire sensor	220 fg mL−1 (sGP), response in <5 min, real-time detection	84, 85 and 86
E. coli	Whole bacterial cells	Interferometric reflectance imaging (SP-IRIS)	Single-cell level, label-free, works in unprocessed samples	87