Development of Microdrip Enzyme Device Using Carbon-Coated Porous Silica Spheres

Abstract

Carbon-coated porous silica spheres (C/PSSs) are particles with uniform particle and mesopore sizes, on which a thin layer of carbon is uniformly deposited on the surface by chemical vapor deposition. The continuous carbon deposit over the mesopore network allows the C/PSS to be electrically conductive and more chemically stable over its traditional counterparts, such as PSS, porous carbons, and carbon electrodes. As homogeneous particles, C/PSS can also be arranged uniformly on an electrode by screen printing to construct macroscopic networks that facilitate the diffusion of substances. Herein, C/PSS was synthesized and fabricated into a working electrode for a prototype glucose enzyme sensor to perform electrochemical measurements on a sample size of 20 μL. We selected the two enzymes, glucose dehydrogenase (GDH) and glucose oxidase (GOD), and water-soluble mediators, quinoline-5,8-dione (QD), to demonstrate the functionality of the sensor. The GDH sensor achieved a linear response up to 75 mM glucose concentration much higher than commercial sensor strips and the GOD sensor up to 25 mM. The results proved that the response current was mainly controlled by glucose diffusion. We succeeded in developing a sensor chip with C/PSS arranged on the surface with high efficiency by selecting a mediator that can smoothly transfer electrons to and from carbon, which enables various sensing applications. This work is the demonstration of the triple pore structure of the C/PSS electrode for enzyme electrode reactions.