Development of a functionalized MCM-41 biosensor modified with selenium nanoparticles for glucose determination

Abstract

A novel biosensor for glucose determination had been developed in this study. Glucose biosensor is a good example of a commercial biosensor. It uses glucose oxidase (GOx), a redox enzyme to break down glucose to hydrogen peroxide and coupled with amperometric detection. For the construction of such a biosensor, a broad applicable method in the immobilization of enzyme is critically needed. One way to go about this is through the development of a new carrier such as nanoparticles. Here, a silica-based material, MCM-41, was used as enzyme support material, functionalized and modified with selenium (Se) nanoparticles and then fabricated into a biosensor. MCM-41 was synthesized and characterized to analyze the structural, morphological, elemental and physicochemical characteristics. It was later confirmed that MCM-41 of high purity and high surface area was synthesized. Pristine and unmodified MCM-41 may not be suitable as enzyme support material because it cannot provide the necessary sites for enzyme attachment. Therefore, two types of MCM-41 supports were produced: f-MCM- 41 and f-SeMCM-41. The first one, f-MCM-41 was modified for immobilization of GOx and minimum leaching of the enzyme by functionalizing with amino groups using 3- aminopropyl triethoxysilane (APTES), followed by attachment of aldehyde group using glutaraldehyde. The latter, f-SeMCM-41, was co-functionalized with amino group during selenium nanoparticles (SNs) attachment onto the silicate framework to increase sensitivity and electrical conductivity for a better response. The product was then functionalized with glutaradehyde. Selenium nanoparticles (SNs) were successfully synthesized using a simple, cost effective and non-hazardous procedure where selenious acid was reduced using ascorbic acid, ultrasonicated and aged for 24h. Characterization showed that SNs of hexagonal crystalline type with high purity of more than 95.0% was produced. The incorporation process of SNs onto MCM-41 did not alter the structure of MCM-41 or even the SNs as observed by X-Ray Diffraction Spectroscopy (XRD). It was found that GOx-f-Se-MCM-41 was more efficient than GOx-f-MCM-41 as determined by the specific activity of GOx immobilized onto them. The optimum pH for immobilization of GOx onto both functionalized MCM-41 and Se-MCM-41 was determined to be pH 6.0 and the optimum initial GOx concentration was 2.0 mg/mL. GOx-f-MCM-41 and GOx-f-Se-MCM-41 were used in the fabrication of carbon paste electrodes (CPE) and the efficiency examined. GOx-f-Se-MCM-41/CPE electrode was more sensitive and efficient as compared to GOx-f-MCM-41/CPE electrode, as evaluated using cyclic voltammetry. GOx-f-Se-MCM-41/CPE can detect very low range of glucose between 3.69 µM to 16.25 µM. Normal human glucose level is between 3.3 to 3.8 mM but this biosensor can detect much lower levels making it an excellent biosensor for clinical and industrial use. Hence, the newly developed functionalized MCM-41 support with immobilized glucose oxidase with Se attached to it, GOx-f-Se-MCM-41/CPE offers the potential exploitation of a suitable glucose biosensor.