The effect of incorporating different types of carbon nanotubes into composite films of a redox polymer (FcMe(2)-C3-LPEI) and; glucose oxidase (GOX) was investigated. The composite films were constructed by first forming a high-surface area. network film of either single-walled carbon nanotubes (SWNTs) or multiwalled carbon nanotubes (MWNTs) on a glassy carbon electrode (GCE).by solution casting of a suspension of Triton-X-100;dispersed SWNTs. Next a glucose responsive redox hydrogel was formed on top of the,nanotube-modified electrode by cross-linking FcMe(2)-C-3-LPEI with glucose oxidase via ethylene-glycol diglycidyl ether (EGDGE). Electrochemical and enzymatic measurements showed that composite films made with (7,6) SWNTs- produced a higher response 0.3 mA/cm(2)) to glucose than films made with (6,5) SWNTs (1.8 mA/cm(2)) or MWNTs (1.2 mA/cm(2)) Or films made without SWNTs (0.7 mA/cm2). We also show that the response of the composite films could be systematically varied by" abricating SWNT films with different weight. ratios' of (7,6), and (6,5) SWNTs. Optimization of the (7,6) SWNTs loading and "the redox polymer-enzyme film produced a shicose-response of 11.2 mA/cm(2). Combining the optimized glucose firms with a platinum oxygen breathing cathode.into biofuel cell produced a maximum power density output of 343 mu W/cm(2).