Local Bio-Sensitization of Nanocrystalline Boron Doped Diamond Surfaces with Biotin Using Electrospotting

This contribution deals with localized surface functionalization of metallic-conductive Boron Doped Diamond (BDD) electrodes. In such a context, we chose to graft biotin probes on to diamond surfaces as a biological model. Biotin was attached onto polycrystalline BDD surfaces using a four-step chemical-modification. The latter protocol involves surface electrografting of nitrophenyl groups using electrochemical reduction of p-nitrobenzene diazonium salts. Then, the nitrophenyl primers are chemically reduced and the resulting aminated surfaces are further chemically functionalized with biotin through two successive chemical steps. The localization of the biotin layer is ensured during the first electrochemical step using electrospotting. This procedure utilises a mobile electrochemical micro-cell that allows surface derivatization with spots of few hundreds micrometer diameter. In such a context, we primarily focused this study on this first grafting step to investigate grafting parameters such as the diazonium salt concentration and electrografting time. The characterizations used are XPS and AFM to confirm the presence of electrografted nitrophenyl groups and their organization on the diamond surface. Finally, following the further chemical steps, the effectiveness of diamond surface biotinylation was addressed through fluorescence microscopy owing to the biotin-avidin recognition using a streptavidin-R-phycoerythrin conjugate. The derivatized diamond surface has been demonstrated to be fully renewable thus providing a versatile and robust platform for surface bio-sensitization dedicated to biosensor design.