Scanning electrochemical microscopy (SECM): localized glucose oxidase immobilization via the direct electrochemical microspotting of polypyrrole-biotin films

This paper describes the successful combination of nanostructured microelectrodes, biotin-avidin chemistry and the direct and generation-collection modes of the scanning electrochemical microscope (SECM) to enable the fabrication, functionalization and characterization of biologically active microspots. The SECM tip was used as an electrochemical “pen” to drive the deposition of a micrometre size spot of biotinylated polypyrrole. Subsequent reaction with avidin and a biotinylated enzyme enabled the construction of a “molecular sandwich” capable of producing H2O2. The SECM tip was then used to “read” the activity of the microspot. A major contribution to this work was the use of mesoporous platinum tips to reliably detect the localized production of H2O2. In contrast to previous approaches this combination of localized deposition, high selectivity of the biotin-avidin binding and reliable imaging only requires one instrument and offers a valuable alternative for the fabrication and characterization of novel multi-analyte biosensor arrays.