Multiwall carbon nanotube ensembled biopolymer electrode for selective determination of isoniazid in vitro

Abstract

A reagent-free electrochemical biosensor is fabricated for the sensitive determination of the important anti-tubercular drug isoniazid (INH). The electrochemical response of the fabricated multiwall carbon nanotube (MWCNT)–chitosan (chit) nanocomposite modified glassy carbon electrode (MWCNT–chit/GCE) towards the detection of INH is investigated by cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The carbon nanotube–chitosan nanocomposite electrode exhibits an excellent electrocatalytic effect towards the oxidation of INH. The overpotential for the electrochemical oxidation is greatly reduced by ∼800 mV, to + 0.17 V vs. Ag|AgCl at MWCNT–chit/GCE compared to + 0.97 V vs. Ag|AgCl at the bare GCE, and the electrocatalytic current is enhanced by nearly four orders of magnitude. Applying the DPV method under optimized conditions, a linear calibration plot is achieved over the concentration range of 1.0 × 10⁻⁷ M to 1.0 × 10⁻⁵ M INH and the biosensor could detect concentrations as low as 5.5 × 10⁻⁸ M INH in ∼12 s. The modified electrode shows very good selectivity towards the specific recognition of INH in the presence of important biological interferents. The electrochemical biosensor detects INH in vitro directly from spiked drug formulations and undiluted urine samples at concentrations as low as 5 × 10⁻⁷ M with recovery limits of 102% and 101.4%, respectively.