Biocompatible Palladium Telluride Quantum Dot-Amplified Biosensor for HIV Drug

Indinavir (IDV) is a potent and well-tolerated protease inhibitor antiretroviral (ARV) drug used as a component of the highly active antiretroviral therapy (HAART) of human immunodeficiency virus (HIV). It undergoes hepatic first-pass metabolism that is catalysed by microsomal cytochrome P450-3A4 enzyme (CYP3A4), which results in pharmacokinetics that may be favourable or adverse. Therapeutic drug monitoring (TDM) of IDV during HIV treatment is therefore critical, in order to prevent the adverse effects of its first-pass metabolism and optimise an individual’s dosage regime. Biosensors are now the preferred diagnostic tools for TDM assessment at point-of-care, due to their high sensitivity and real-time response. An electrochemical biosensor for IDV was prepared by depositing a thin film of CYP3A4 (a thiolate enzyme) and thioglycolic acid-capped palladium telluride quantum dot (TGA-PdTeQD) on a cysteamine-functionalised gold disk electrode (Cyst|Au) using a combination of thiol and carbodiimide covalent bonding chemistries. The electrochemical signatures of the biosensor (CYP3A4|TGA-PdTeQD|Cyst|Au) were determined by cyclic voltammetry (CV) that was performed at a scan rate of 500 mV s −1 , and the sensor responses at the characteristic reduction peak potential value of − 0.26 V were recorded. The sensitivity, linear range ( LR ) and limit of detection ( LOD ) values of the indinavir biosensor were 4.45 ± 0.11 μA nM −1 IDV, 0.5–1.0 nM IDV (i.e. 3.6 × 10 −4 –7.1 × 10 −4 mg L −1 IDV) and 4.5 × 10 −4 mg L −1 IDV, respectively. The values of the two analytical parameters ( LR and LOD ) of the biosensor were by up to four orders of magnitude lower than the maximum plasma concentration ( C max ) values of indinavir (0.13–8.6 mg L −1 IDV). The IDV biosensor was successfully used to detect IDV in human serum samples containing dissolved indinavir tablet. This, therefore, indicates the indinavir biosensor’s suitability for TDM applications, using samples obtained within 1–2 h of drug intake at point-of-care, for which very low levels of the drug are expected. Graphical abstract