Core-Shell Palladium Telluride Quantum Dot-Hemethiolate Cytochrome Based Biosensor for Detecting Indinavir Drug

Indinavir is a first-generation HIV protease inhibitor anti-retroviral (ARV) drug. Due to interindividual differences in the rate of indinavir metabolism, clinicians and pharmacologists have expressed urgent need for sensor devices that will enable real time determination of appropriate dosage. In this study, an indinavir biosensor was developed by the functionalization of a cysteamine-modified gold (Cyst|Au) electrode with biocompatible core-shell 3-mercaptopropionic acid (3-MPA)-capped palladium telluride quantum dot (PdTeQD) and the heme-thiolate cytochrome P450-3A4 (CYP3A4) enzyme. The PdTeQD was capped with 3-mercaptopropionic acid (3-MPA) to improve its reactivity, biocompatibility and thermal stability. Small angle X-ray scattering (SAXS) studies revealed that the 3-MPA-PdTeQD particles formed core-shells with diameters of 4.7 nm. Fourier transformed infrared spectroscopy (FTIR) experiments confirmed the formation of 3-MPA-PdTeQD by the presence of specific COOH and CH₂ FTIR signature bands. Ultraviolet-visible (UV-Vis) spectrophotometric analysis of the quantum dot, exhibited a broad characteristic band at ~320 nm, corresponding to a band gap energy (E_g) value of 3.87 eV, indicating that the QD is a semiconducting material. Cyclic voltammetry (CV) responses of the biosensor (i.e., CYP3A4|3-MPA-PdTeQD|Cyst|Au) indicated that 0.26 V was the suitable potential for measuring indinavir metabolism. The biosensor has a sensitivity, dynamic linear range (DLR) and limit of detection (LOD) values of 0.0218 μA/nM, 0.0004-0.01 nM (i.e., 3×10^-7 -7×10^-6 mg L^-1) and 0.023×10^-7 mg L^-1, respectively, for indinavir. The LOD value was lower than the maximum plasma concentration (C_max) value (0.13-8.6 mg L^-1) of indinavir which is normally measure 8 h after intake. The low DLR value makes the biosensor suitable for application at point-of-care, where indinavir concentration is expected to be in ng L^-1 level in physiological samples within a few minutes of the drug administration.

Electrochemical Aptatoxisensor Responses on Nanocomposites Containing Electro-Deposited Silver Nanoparticles on Poly(Propyleneimine) Dendrimer for the Detection of Microcystin-LR in Freshwater

A sensitive and reagentless electrochemical aptatoxisensor was developed on cobalt (II) salicylaldiimine metallodendrimer (SDD-Co(II)) doped with electro-synthesized silver nanoparticles (AgNPs) for microcystin-LR (L, l-leucine; R, l-arginine), or MC-LR, detection in the nanomolar range. The GCE|SDD-Co(II)|AgNPs aptatoxisensor was fabricated with 5' thiolated aptamer through self-assembly on the modified surface of the glassy carbon electrode (GCE) and the electronic response was measured using cyclic voltammetry (CV). Specific binding of MC-LR with the aptamer on GCE|SDD-Co(II)|AgNPs aptatoxisensor caused the formation of a complex that resulted in steric hindrance and electrostatic repulsion culminating in variation of the corresponding peak current of the electrochemical probe. The aptatoxisensor showed a linear response for MC-LR between 0.1 and 1.1 µg·L-1 and the calculated limit of detection (LOD) was 0.04 µg·L-1. In the detection of MC-LR in water samples, the aptatoxisensor proved to be highly sensitive and stable, performed well in the presence of interfering analog and was comparable to the conventional analytical techniques. The results demonstrate that the constructed MC-LR aptatoxisensor is a suitable device for routine quantification of MC-LR in freshwater and environmental samples.