RESUMEN
The critical performance factors such as selectivity, sensitivity, operational and storage stability, and response time of electrochemical biosensors are governed mainly by the function of their key component, the bioelectrode. Suitable design and fabrication strategies of the bioelectrode interface are essential for realizing the requisite performance of the biosensors for their practical utility. A multifaceted attempt to achieve this goal is visible from the vast literature exploring effective strategies for preparing, immobilizing, and stabilizing biorecognition elements on the electrode surface and efficient transduction of biochemical signals into electrical ones (i.e., current, voltage, and impedance) through the bioelectrode interface with the aid of advanced materials and techniques. The commercial success of biosensors in modern society is also increasingly influenced by their size (and hence portability), multiplexing capability, and coupling in the interface of the wireless communication technology, which facilitates quick data transfer and linked decision-making processes in real-time in different areas such as healthcare, agriculture, food, and environmental applications. Therefore, fabrication of the bioelectrode involves careful selection and control of several parameters, including biorecognition elements, electrode materials, shape and size of the electrode, detection principles, and various fabrication strategies, including microscale and printing technologies. This review discusses recent trends in bioelectrode designs and fabrications for developing electrochemical biosensors. The discussions have been delineated into the types of biorecognition elements and their immobilization strategies, signal transduction approaches, commonly used advanced materials for electrode fabrication and techniques for fabricating the bioelectrodes, and device integration with modern electronic communication technology for developing electrochemical biosensors of commercial interest.
RESUMEN
In this work, the diffusion of thiocholine ion into an enzyme-loaded polypyrrole film was evaluated by different methods, and the results were compared to identify the most suitable method. The enzyme-loaded polypyrrole film was coated with a thin layer of gelatin and gluteraldehyde so as to prevent enzyme leaching. Diffusion coefficients under normal and prepolarized conditions were calculated by five different methods, namely, the Cottrell method, the method of Peerce and Bard, the theoretical impedance model, the electrochemically stimulated conformational relaxation (ESCR) method, and the direct impedance measurement method. The theoretical model of Vortynstev was used to calculate the parameters from the impedance spectra using simplex technique in MATLAB. The results indicate that under normal unpolarized condition the ESCR method gives a diffusion coefficient close to that given by Vortynstev method, but under polarized conditions the Cottrell method can provide a better value of diffusion coefficient than ESCR. The diffusion coefficient of thiocholine in PPy composite film from an electrolytic background of phosphate buffer of pH 7.4 was found to be 1.00 × 10(-8) cm(2) s(-1) based on Vortynstev method. The mechanism of thiocholine diffusion into the positively charged/polarized matrix is attributed to be through the formation of a dinegative ion between thiocholine and phosphate anion via electrostatic attraction.