Conductive Ag-Based Modification of Hydroxyapatite Microtubule Array and Its Application to Enzyme-Free Glucose Sensing

Plenty of biomineralized hydroxyapatite (BioHAP) matrix microtubules (named dentin tubules) with regular arrangement are inside mammal tooth dentin. Herein, electrically conductive polyaniline (PANI) is applied to modify the microtubule array to assemble a PANI/BioHAP composite through an in-situ polymerization method. On this basis, a sensor (PANI/BioHAP/AgHg) is assembled with PANI/BioHAP and silver amalgam, and further applied to enzyme-free glucose sensing. The inner-wall of the tubules is treated in advance with p-methylbenzene sulfonic acid to alter its hydrophilism into hydrophobicity. The treatment contributes to improve the diffusibility of aniline monomer in the tubules and to form a PANI conductive network on the wall. Meanwhile, a large quantity of active sites on the surface of BioHAP matrix performs both adsorption and concentration to glucose molecules. The special array structure helps to shield undesired electrochemical signals, and also increases the current response of glucose electro-catalytic oxidation.