Glucose and lactate biosensors based on redox polymer/oxidoreductase nanocomposite thin films

Glucose and lactate enzyme electrodes have been fabricated through the depo sition of an anionic self-assembled monolayer and subsequent redox polymer/ enzyme electrostatic complexation on gold substrates. These surfaces were f unctionalized with a negative charge using 11-mercaptoundecanoic acid (MUA) , followed by alternating immersions in cationic redox polymer solutions an d anionic glucose oxidase (GOX) or lactate oxidase (LAX) solutions to build the nanocomposite structure. The presence of the multilayer structure was verified by ellipsometry and sensor function characterized electrochemicall y. Reproducible analyte response curves from 2 to 20 mM (GOX) and 2-10 mM ( LAX) were generated with the standard deviation between multiple sensors be tween 12 and 17%, a direct result of the reproducibility of the fabrication technique. In the case of glucose enzyme electrodes, the multilayer struct ure was further stabilized through the introduction of covalent bonds withi n and between the layers. Chemical cross-linking was accomplished by exposi ng the thin film to glutaraldehyde vapors, inducing linkage formation betwe en lysine and arginine residues present on the enzyme periphery with amine groups present on a novel redox polymer, poly[vinyl-pyridine Os(bisbipyridi ne)(2)Cl]-co-allylamine. Finally, an initial demonstration of thin-film pat terning was per formed as a precursor to the development of redundant senso r arrays. Microcontact printing was used to functionalize portions of a gol d surface with a blocking agent, typically 1-hexadecanethiol. This was foll owed by immersion in MUA to functionalize the remaining portions of gold wi th negative charges. The multilayer deposition process was then followed, r esulting in growth only on the regions containing MUA, resulting in a "posi tive"-type pattern. This technique may be used for fabrication of thin-film redundant sensor arrays, with thickness under 100 Angstrom and lateral dim ensions on a micrometer scale.