Carbon Nanotube–Bilirubin Oxidase Bioconjugate as a New Biofuel Cell Label for Self-Powered Immunosensor

We demonstrated a biofuel cells (BFCs)-based self-powered sensing system for the detection of Nε-(carboxymethyl)lysine (CML), in which the bilirubin oxidase (BOD)-carbon nanotube (CNT) bioconjugate modified with antibody acted as a biocatalyst for enhancing O2 reduction in the biocathode, as well as the transducing enzyme for signaling magnification. With an increase in the concentration of CML, the amount of BOD labels on biocathode surface increases, thus leading to the higher output of the as-prepared BFCs. This novel BFCs-based self-powered sensor showed a wide linear range for analyzing CML from 1 nM to 100 μM with a detection limit of 0.2 nM, which was 50 times more sensitive than that determined from the conventional ELISA. Most importantly, our new self-powered sensing platform can determine the level of CML in serum samples from multiple healthy donors and multiple sclerosis patients, being well in accordance with that from the commercial ELISA analysis.