An interference-free new xanthine biosensor based on immobilized enzyme-nanogold conjugate on carbon nanotube doped poly (3,4-Ethylenedioxythiophene) composite film

A new design of biosensor based on polymeric nano(bio)composite has been proposed for the selective detection of xanthine to be used in the clinical analysis as well as food quality control. The xanthine oxidoreductase (XOR) gene of Pseudomonas aerogenosa strain CEBP1 was cloned to obtain purified enzyme through affinity chroma-tography. fMWCNT doped PEDOT was electrodeposited on the working electrode to enhance the sensitivity and selectivity of the biosensor. Bio-synthesized gold nanoparticles conjugated XOR (Au-XOR) was covalently immobilized on the polymeric nanocomposite. The enzymatic activity was enhanced 1.12 times with increased substrate affinity. The surface morphology and structural properties of the polymeric layer were investigated using SEM, FESEM, TEM. Electrochemical characteristics were performed by cyclic voltammetry, differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy. Xanthine was oxidized (pH 7.0) on the uniquely designed polymeric nano(bio)composite modified electrode at a lower anodic potential of + 0.446 V vs. Ag/AgCl (3 M NaCl) at optimized DPV conditions. The simple, newly designed Au-XOR/fMWCNT-PEDOT/GCE exhibited interference-free reproducibility and stability (~4 months) with excellent sensitivity of 16.075 mu A.mu M- 1.cm(-2) for the quantification of xanthine in biological samples such as blood, tissue, urine. The applicability of the biosensor was validated by comparing the sensing results for the real biological fluidic solutions with HPLC data (RE = 0.5-3.1%).

Automated summary

A new design of biosensor based on polymeric nano(bio)composite has been proposed for the selective detection of xanthine. The biosensor showed enhanced enzymatic activity and improved sensitivity and selectivity. The performance of the biosensor was validated using various characterization techniques and comparison with HPLC data.