Prussian Blue based screen printed biosensors with improved characteristics of long-term lifetime and pH stability

The promising advantages of Prussian Blue (PB) as catalyst and of the thick film screen printing technology have been combined to assemble sensors with improved characteristics for the amperometric determination of H2O2, PB-modified screen printed electrodes were applied to detect H2O2 at an applied potential of -0.05 V versus the internal screen printed Ag pseudoreference electrode, showing a detection limit Of 10(-7) Mol 1(-1), a linearity range from 10(-7) to 5 x 10(-5) mol 1(-1), a sensitivity of 234 muA mmol 1(-1) cm(-2), and a high selectivity. Improved stability at alkaline pH values was also observed, which made possible their use with enzymes having an optimum basic pH. Then, the immobilisation of a single enzyme (glucose oxidase (GOD) or choline oxidase (ChOX)) or of two enzymes, acetylcholinesterase (AchE) coimmobilised with ChOX, has been performed on the surface of PB modified screen-printed electrodes (SPEs) using glutaraldehyde and Nafion((R)). ChOX has been selected as an example of enzyme working at alkaline pH. The choline biosensors showed a detection limit of 5 X 10-7 Mol 1(-1), a wide linearity range (5 x 10-7 10(-4) Mol 1(-1)), a high selectivity and a remarkable long term stability of 9 months at 4 degreesC, and at least 4 weeks at room temperature. Similar analytical characteristics and stability were observed with the acetylcholine biosensors. (C) 2002 Elsevier Science B.V. All rights reserved.