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Layer-by-Layer Assembly of Enzyme-Coated Single-Walled Carbon Nanotubes and Redox Polymers

Ta-Wei Tsai1, Gustavo Heckert1, and David W. Schmidtke2. (1) University of Oklahoma Bioengineering Center, University of Oklahoma, 100 East Boyd, Norman, OK 73019, (2) School of Chemical, Biological, and Materials Engineering, University of Oklahoma, 100 East Boyd, EC Rm. T-335, Norman, OK 73019

A sodium cholate suspension-dialysis method was used to adsorb two different redox enzymes, glucose oxidase (GOX) and horseradish peroxidase (HRP), onto single-walled carbon nanotubes (SWNT). By this method, solutions of highly dispersed and debundled SWNTs were prepared, that remained stable for 30 days and which retained 70% of the native enzymatic activity. We demonstrate incorporation of these enzyme-SWNT conjugates into amperometric biosensors through a layer-by-layer (LBL) self-assembly process. Incorporation of SWNT-enzyme conjugates resulted in a 5-fold increase in the sensitivity as compared to films without SWNTs. In the case of the GOX-based sensors, current densities as high as 400 &muA/cm2 could be reached, with the sensitivity of the sensors being controlled by varying the number of multilayers.