Glucose, lactate, and pyruvate biosensor arrays based on redox polymer/oxidoreductase nanocomposite thin-films deposited on photolithographically patterned gold microelectrodes

Glucose, lactate, and pyruvate sensor arrays were fabricated by depositing electrostatically complexed monolayers on lithographically patterned, individually addressable, gold microelectrodes. Standard photolithographic techniques combined with metal deposition were used to fabricate gold arrays on both SiO₂/Si and flexible Mylar substrates. These gold arrays were then functionalized with a negative surface charge through chemisorption of 11-mercaptoundecanoic acid (MUA) followed by the electrostatic assembly of a nanocomposite thin-film of a cationic osmium redox polymer and anionic oxidoreductases, either glucose oxidase, lactate oxidase, or pyruvate oxidase. When tested electrochemically, glucose, lactate and pyruvate sensors exhibited analyte sensitivities of 0.26, 0.24 and 0.133 μA/(cm² mM) respectively. Responses to analytes proved to be linear in the physiologically relevant concentration ranges for glucose (0-20 mM), lactate (0-10 mM), and pyruvate (0-2 mM). Standard deviations between individual electrodes of ∼18% (glucose) and 20% (lactate) were determined for the enzyme electrode arrays with five array members. Furthermore, the potential problem of sensor cross-talk was investigated by subsequently testing one array member and then array members adjacent to that sensor. The response from a pair of electrodes was approximately twice than that of a single electrode, demonstrating that the individual sensors are free of cross-talk.