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Tuberculosis (TB) is one of the deadliest diseases in Africa and it is classified as a serious global health problem. A new threat associated with the disease is the emergence of multidrug-resistant TB (MDR-TB), which results from improper dose or non-compliance with a treatment regime. It is, therefore, important to determine a patient’s rate of TB drug metabolism at a point-of-care, in order to enable appropriate dose prescription. This work presents a novel enzymatic nanobiosensor for real-time determination of isoniazid (INH), which is a highly prescribed drug for TB treatment. The nanobiosensor consists of a cytochrome P450-2E1 (CYP2E1) isoenzyme covalently attached to a screen printed or disk gold electrode (Au), functionalized with thioglycolic acid-capped gold nanoparticle (TGA-AuNP). The nanomaterial was green-synthesized with banana peel extract (BPE) as the reducing agent. It exhibited an ultraviolet-visible spectroscopy (UV–Vis) signature absorption band for AuNP at 536 nm and a direct bandgap energy (Eg) value of 2.00 eV. Fourier transform infra-red spectroscopy (FTIR) was used to confirm the reduction of Au3+ to Au0. High-resolution transmission electron microscopy (HR-TEM) and high-resolution scanning electron microscopy (HR-SEM) studies indicated that TGA-AuNPs were polydisperse and exhibited spherical morphology. Bovine serum albumin (BSA) and CYP2E1 were attached to the TGA-AuNPs-modified Au electrode using glutaraldehyde (Glu) as binder, to form the nanobiosensor (BSA/CYP2E1/Glu/TGA-AuNPs/Au). Differential pulse voltammetric (DPV) responses of the nanobiosensor for INH were determined in 10 mM phosphate buffer (pH 7.4). The limit of detection (LOD) and the limit of quantification (LOQ) values of the nanobiosensor were 0.0556 μM INH and 0.1683 μM INH, respectively.
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