Tuning the sol-gel microenvironment for acetylcholinesterase encapsulation

The effect of the sol-get microenvironment on the activity of acetylcholinesterase, an enzyme of high bio-analytical interest, is presented and is correlated to the overall analytical performance of corresponding biosensors. The sol-gel membranes are initially optimized with respect to the catalyst and the TEOS:H2O ratio (r), for mechanical stability, porosity, and hydrophobicity as well as in terms of enzymatic activity. FT-IR and electrochemical impedance spectroscopy (EIS) are used to probe the configuration and rotational mobility of the enzyme within the sol-gel matrices. Overall, it is observed that the rotational mobility of the protein can be correlated with the sensitivity of the biosensor. Optimum biosensor performance is obtained for base-catalyzed sol-gels with r values close to 2. The biosensor has sensitivity or 2.5 mu A/mm, a linear range of response between I and 3 mm, response time of about 30s, and sensor-to-sensor reproducibility (RSD) of 3%. These analytical characteristics are far superior to previously reported sol-gel biosensors. (c) 2005 Elsevier Ltd. All rights reserved.