Insulator semiconductor structures coated with biodegradable latexes as encapsulation matrix for urease

A new urea biosensor for clinical applications was obtained by immobilization of urease within different latex polymers functionalized by hydroxy, acetate and lactobionate groups. Responses of these biosensors based on pH–ion-selective field effect insulator–semiconductor (IS) systems to urea additions were evaluated by capacitance measurements. UV–visible spectroscopy was used to check the urease activity in various matrixes. A good retention of the catalytic urease activity in the case of the cationic polymers was observed. In addition, rotating disk electrode experiments were carried out to determine the matrix permeability characteristics. Under optimal conditions, i.e. buffer capacity corresponding to 5 mM phosphate buffer, the urea enzyme insulator semiconductor (ENIS) sensors showed a linear response for urea concentrations in the range 10−1.5 to 10−4 M. Furthermore, kinetic parameters for the immobilized urease were obtained from Lineweaver–Burk plot. Clearly, a fast response and a good adhesion for the urease–acetate polymer composite films, prepared without using glutaraldehyde as cross-linking agent was observed.