Nanofabrication of biodegradable enzyme-based glucose and organophosphorus pesticide biosensors

The goal of this project is to construct biosensors using polyhydroxyalkanoate (PHA), a biodegradable plastic, as a base material, for detecting organophosphorus pesticides that are as durable and effective as synthetic plastics. To test PHA for durability, a degradation study and tensile test were performed. The PHA substrate was found to degrade at an average rate of approximately 0.1434 g per day during the first 28 days, 0.02179 g per day during days 28-63 and 0.002041 g per day during days 63-98. The modulus of elasticity and the yield strength of PHA were 2.43 x 10(-7) and 2000 psi, respectively, while the maximum stress to fracture the PHA was 6703 psi. The PHA was patterned with a nanofabricated inter-digitated array (IDA) gold electrode using a combination of thermal evaporation, photolithography and etching processes. Acetylcholinesterase was immobilized onto the IDA by a conventional sol-gel process using tetraethylorthosilicate (TEOS) and polydimethylsiloxane (PDMS) as precursors. The biosensor was sensitive to concentrations in the range of 0.1 mM- 50 mM in 0.05 M Tris-HCl buffer at pH 7.2 using a Hewlett Packard 4192A Impedance Analyzer. Preliminary results suggest that the coupling of the sol-gel immobilization method with photolithography technology can offer mass production of a resilient organophosphorus pesticide biosensor from PHA.