M. Satyanarayana

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

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.

Carbon nanotube ensembled hybrid nanocomposite electrode for direct electrochemical detection of epinephrine in pharmaceutical tablets and urine.

An efficient electrochemical sensor for selective detection of the neurotransmitter, epinephrine (Epn), has been fabricated with the aid of a functionalized multiwall carbon nanotube-chitosan biopolymer nanocomposite (Chit-fCNT) electrode. Multiwall carbon nanotubes (CNT) were successfully functionalized with the aid of nitric acid and confirmed by the Raman spectral data. Functionalized carbon nanotubes (fCNT) were dispersed in chitosan solution and the resulting bio-nanocomposite was used for the fabrication of sensor surface by drop and cast method. Electrochemical characteristics of the fabricated sensor were understood using cyclic, differential pulse voltammetry (CV, DPV) and electrochemical impedance analysis for the detection of Epn in phosphate buffer (pH7.4). CV and impedance analysis revealed that the Chit-fCNT modified electrode enhances the electrodic reaction of Epn and facilitated the electron transfer more readily compared to that of bare electrode. Applying DPV for the detection of Epn, achieved 30nM as the lowest detection limit in the determination range of 0.05-10μM and the analytical time as low as 10s. Selective determination of Epn against the coexistence of a number of biological electroactive interferents and reproducible results for the determination of Epn were demonstrated. The present biosensor has been found efficient for successful direct determination of Epn from pharmaceutical adrenaline formulations and urine samples.

Biopolymer protected silver nanoparticles on the support of carbon nanotube as interface for electrocatalytic applications

In this research, silver nanoparticles (SNPs) are prepared on the surface of carbon nanotubes via chitosan, a biopolymer linkage. Here chitosan act as stabilizing agent for nanoparticles and forms a network on the surface of carbon nanotubes. Synthesized silver nanoparticles-MWCNT hybrid composite is characterized by UV-Visible spectroscopy, XRD analysis, and FESEM with EDS to evaluate the structural and chemical properties of the nanocomposite. The electrocatalytic activity of the fabricated SNP-MWCNT hybrid modified glassy carbon electrode has been evaluated by cyclic voltammetry and electrochemical impedance analysis. The silver nanoparticles are of size ∼35 nm and are well distributed on the surface of carbon nanotubes with chitosan linkage. The prepared nanocomposite shows efficient electrocatalytic properties with high active surface area and excellent electron transfer behaviour.