Electrochemically Inspired Copper(II) Complex on Disposable Graphite Pencil Electrode for Effective Simultaneous Detection of Hypoxanthine, Xanthine, and Uric Acid

Review on recent advances in fabrication of enzymatic and chemical sensors for hypoxanthine

Hypoxanthine is an important product of the nucleotide degradation pathway. It has been considered as a potential marker for assessing meat freshness and clinical diagnosis. In the review, we focus on advancement made in the fabrication of hypoxanthine sensors. Several traditional methods are being utilized for the detection of hypoxanthine, but these methods are expensive, complex, require pretreatment of the sample which is time-consuming and trained persons to operate. Sensors have emerged as simple, rapid, economic, disposable, and portable tools for hypoxanthine detection in biological samples. In particular, the review describes the significant role of hypoxanthine in clinical and food applications. Classification of sensors into enzymatic and non-enzymatic sensors along with the different methods used for xanthine oxidase immobilization and type of transducers used for hypoxanthine detection are briefly explained.

Synthesis, characterization and electrochemical properties of some biologically important indole-based-sulfonamide derivatives

A new series of indole-based-sulfonamide derivatives (A1–A8) was synthesized by treating 5-fluoro-1H-indole-3-carbohydrazide with different aryl-sulfonyl chloride in the presence of pyridine. All synthesized derivatives (A1–A8) were characterized by different analytical methods. The electrochemical behavior of these compounds (A1–A8) was investigated in detail using cyclic voltammetry (CV) and square wave voltammetry (SWV) at the pencil graphite electrode (PGE). In the present study, the redox behavior of all derivatives varies due to the nature of substitutions in the indole sulfonamide moiety. Various fundamental electrochemical parameters, including the standard heterogeneous rate constants (k_s), and the electroactive surface coverage (Г) were calculated from the obtained CVs. The obtained results shed light on the understanding of structure–activity relationships of this class of compounds.

A simple electrochemical approach to fabricate functionalized MWCNT-nanogold decorated PEDOT nanohybrid for simultaneous quantification of uric acid, xanthine and hypoxanthine

Medical diagnostics and detection of food spoilage require estimation of hypoxanthine (HX), xanthine (XN), and uric acid (UA). A selective sensing platform has been proposed for simultaneous detection of all these species. Functionalized multi-walled carbon nanotube (fMWCNT) stabilized nanogold decorated PEDOT:TOS polymeric nanocomposite (Au-PEDOT-fMWCNT) was synthesized through rapid one-step electropolymerization to enhance conductivity and active surface area by several folds. Electrochemical activities of the proposed sensing platform were analyzed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS). Analyses through SEM, FESEM and TEM were performed to explore the surface morphology and elemental analysis of the polymeric nanohybrid was investigated by XPS, Raman, FTIR, XRD spectroscopy. Electro-catalysis of UA, XN and HX occurred at low oxidation potentials i.e. 0.082, 0.463 and 0.808 V, respectively in the optimized conditions. The uniquely designed simple, interference free Au-PEDOT-fMWCNT/GCE sensor exhibited high selectivity, good reproducibility, reusability (∼180 times) and stability (∼3 month) with excellent sensitivity of 1.73, 14.31 and 3.82 μA μM^-1 cm^-2 for UA, XN and HX, respectively. The sensor exhibited linear ranges of detection as 0.1-800, 0.05-175 and 0.1-150 μM with detection limits of 199.3, 24.1 and 90.5 nM for quantification of UA, XN and HX respectively. The performance of the proposed sensor was validated by addition of UA, XN and HX in human serum, urine and fish samples by comparing to those using HPLC. The results indicated good applicability of the proposed sensor for simultaneous detection of UA, XN, HX in real biological fluids.