Urea amperometric biosensors based on a multifunctional bipolymeric layer: Comparing enzyme immobilization methods

This paper outlines the results obtained with biosensors designed for urea amperometric detection. The incorporation of urease into a bipolymeric substrate consisting of poly(pyrrole) and poly(5-amino-1-naphthol) was performed through four different approaches: direct adsorption, entrapment in cellulose acetate layer, cross-linking with glutaraldehyde, and also covalent attachment to the polymeric matrix. Poly(pyrrole) acts as amperometric transducer in these biosensors, while poly(5-amino-1-naphthol) drastically reduces the interference signal of agents such as ascorbic and uric acids. The biosensors containing urease covalently attached to the substrate provided interesting results in terms of sensitivity towards urea (0.50 μA cm−2 mmol−1 L), lifetime (20 days) and short response times, due to the enzyme immobilization method used. All biosensors analyzed showed also a wide linear concentration range (up to 100 mmol L−1) and low detection limits (0.22–0.58 mmol L−1).