Table 2.

Therapeutic drug monitoring using optical biosensors.

Type of Biosensor	Type of Drug	Drug	Biosensor Characteristics	Matrix	Limit/Detection Range	Results	Ref.
Fibre optic	Anticonvulsant	Phenytoin	Autonomous reversible immunosensor: mouse monoclonal IgG	Blood and plasma	4.45 µM	Viability for quantifying phenytoin in blood, applicable for other haptens in blood	[134]
	Bronchodilator	Theophylline	Fluorescence-based autonomous reversible immunosensor: mouse monoclonal IgG	Serum	55 µM	Analyte concentrations give rise to a change in the antibody binding equilibrium with changes in fluorescence	[135]
SPR	Antibiotic	Vancomycin and Chloroeremomycin	Covalent bacterial wall peptide coupling to a self-assembled monolayer (SAM) on a gold film	Solution buffer	20 mM 2.5 mM	Chloroeremomycin is related to bacterial wall peptides, thereby facilitating quantification	[142,143]
		Ciprofloxacin	SPR with a molecularly imprinted polymer (MIP)	Solution buffer	0.08 µg/L	Sensitive technique for quantifying this type of molecule	[144]
		Ampicillin	SPR operated in flow conditions	Solution buffer	10−3 M to 10−1 M	Technique requiring less time (20 min) without losing sensitivity	[145]
		Gentamycin	SPR with a Doppler laser using UV-Vis spectroscopy	Solution buffer	0.05 ng/mL	Lower detection limit compared to ELISA	[146]
	Anticancer	MTX	LSPR with functionalized gold nanoparticles with folic acid (FA-AuNPs) in completion with MTX	Serum	28 nM	Lower detection limit than that reported for LSPR biosensors (155 Nm)	[125]
	Anticoagulant	Heparin	Using prolamine and polyethyleneimine as affinity surface	Plasma	0.2 U/mL	Lower detection limit than that found for previously cited techniques	[149]
	Opioid	Morphine	Immunoassays using polyclonal antibodies from New Zealand rabbits	Urine	762–24,4000 pg/mL	This technique enables the sensitive and specific quantification of different opioids such as heroin and morphine	[150]
LSPR	Anticancer	MTX	LSPR with functionalized gold nanoparticles with folic acid (FA-AuNPs)	Plasma	155 nM	This technique provides a new index for quantifying this drug by this type of biosensor	[127]
	Antibiotic	Tobramycin	Transmission localized surface plasmon resonance (T-LSPR), using DNA aptamers	Serum	0.34 µM	This modification enables the direct detection (without using labels) of a small molecule in a complex matrix	[155]
	Anticoagulant	Megalatran	LSPR integrated with a microfluidic chip	Solution buffer	0.9 nM	A pioneering study regarding the use of enantioselective biosensors	[141]
	Anti-arrhythmic	Digoxin	LSPR with gold nanoparticles	Solution buffer	2 ng/mL	This device enables the direct low-cost detection of digoxin, as well as being a device that is easy to make and use	[160]
SERS	Anticancer	5-fluorouracil	SERS with silver nanoparticles	Saliva	150 ng/mL	This study provides a great opportunity since it enables one to quantify a highly toxic drug with genetic variations in its metabolism	[162]
	Antibiotic	Ampicillin	SERS with silver on nanoparticles using hydroxylamine—HCl	Solution buffer	27 ng/mL	This technique has been compared to LC/MS, with greater sensitivity. It provides an index for quantifying drugs with this type of device	[163]
		Penicillin G			29 ng/mL
		Carbenicillin			30 ng/mL
		Penicilloic acid			28 ng/mL