Amperometric glucose biosensor based on sol-gel-derived metal oxide/Nafion composite films

Amperometric glucose biosensors have been developed based on the encapsulation of glucose oxidase in the nanoporous composite films of sol-gel-derived metal oxide (titania and silica) and perfluorosulfonated ionomer, Nafion, on a platinized glassy carbon electrode. The presence of Nafion polymer in the sol-gel-derived metal oxide not only prevents the cracking of the pure sol-gel-derived metal oxide film but also improves the sensitivity and long-term stability of the biosensor. Analytical performance of the glucose biosensor based on the titania/Nafion composite is superior to that of the biosensor based on the silica/Nafion composite in terms of response time, sensitivity, and long-term stability. The glucose biosensor based on the titania/Nafion composite film can reach 95% of steady-state current less than 2 s. The biosensor responds to glucose linearly up to 7 mM with a sensitivity of 15 μA/mM. The biosensor retained 80% of its initial activity after 4 months of storage in 0.05 M phosphate buffer at pH 7. Sol-gel-derived titania/Nafion composite can also be used for the preparation of second-generation (mediator-based) biosensor by immobilizing the positively charged mediator such as N,N′-dimethylaminomethyl ferrocene in the composite film via electrostatic and hydrophobic interactions.