Superior performance of a carbon-paste electrode based glucose biosensor containing glucose oxidase enzyme in mesoporous silica powder

Recent advances in glucose-oxidase-based nanocomposites for diabetes diagnosis and treatment

Glucose oxidase (GOx) has attracted a lot of attention in the field of diabetes diagnosis and treatment in recent years owing to its inherent biocompatibility and glucose-specific catalysis. GOx can effectively catalyze the oxidation of glucose in the blood to hydrogen peroxide (H2O2) and glucuronic acid and can be used as a sensitive element in biosensors to detect blood glucose concentrations. Nanomaterials based on the immobilization of GOx can significantly improve the performance of glucose sensors through, for example, reduced electron tunneling distance. Moreover, various insulin-loaded nanomaterials (e.g., metal-organic backbones, and mesoporous silica nanoparticles) have been developed for the control of blood glucose concentrations based on GOx catalytic chemistry. These nano-delivery carriers are capable of releasing insulin in response to GOx-mediated changes in the microenvironment, allowing for a rapid return of the blood microenvironment to a normal state. Therefore, glucose biosensors and insulin delivery vehicles immobilized with GOx are important tools for the diagnosis and treatment of diabetes. This paper reviews the characteristics of various GOx-based nanomaterials developed for glucose biosensing and insulin-responsive release as well as research progress, and also highlights the current challenges and opportunities facing this field.

Integration of enzyme-encapsulated mesoporous silica between nanohole array electrode and hydrogel film for flow-type electrochemical biosensor

We herein propose a simple and sensitive electrochemical flow biosensor platform without an external flow device. The sensing unit comprises a platinum nanohole array electrode deposited on a nanoporous track-etched membrane (PtNH/NPM), a packed-layer of glucose oxidase-encapsulated mesoporous silica particles (GOD/MPS), and bovine serum albumin hydrogel film (BSA gel film). This sensing unit was fixed at the open window at the side of the plastic container with internal solution containing NaCl as osmotic reagent. When the sample glucose solution (0.10 mL) was pipetted at the sensing unit, a portion of the sample solution (5 μL) was spontaneously transferred into the BSA gel film. The concentration gradient of NaCl between the internal solution and the BSA gel film induced osmotic flow of water toward the internal solution. This osmotic flow assisted delivery of glucose to the GOD/MPS and enzymatically generated H₂O₂ to the PtNH/NPM. The proposed sensor could be used repeatedly and produced a linear current response for glucose, with a limit of detection of 16 μM. These sensor performances confirmed availability of the sensor design utilizing the osmotic flow.

Functional Channel of SWCNTs/Cu2O/ZnO NRs/Graphene Hybrid Electrodes for Highly Sensitive Nonenzymatic Glucose Sensors

The hybrid electrode of single-wall carbon nanotubes (SWCNTs)/Cu₂O/ZnO nanorods (NRs)/graphene used on the current-response nonenzymatic glucose sensor was investigated herein, regarding the mechanism of the formation of functional channel. The synthesis of the hybrid electrode involved four steps. First, the graphene was grown by chemical vapor deposition (CVD) and then wet-transferred onto indium transparent oxide (ITO) glass. Second, a zinc oxide (ZnO) seed layer was sputtered onto the graphene/ITO glass, and ZnO NRs were gradually grown by the hydrothermal method. Third, the ZnO NRs were clad with cuprous oxide (Cu₂O) by the electrochemical method. Fourth, the SWCNTs were dropped onto the Cu₂O surface, with a Nafion surfactant. X-ray diffraction spectra, scanning electron microscopy spectra, Raman spectra, cyclic voltammograms, and amperometric response diagrams were used to verify the performance of the device. Results showed that sensitivity increased significantly from 11.2 to 289.8 μA mM^-1 cm^-2, linear range increased significantly from 0.6 to 11.1 mM, and the coefficient of determination (R²) increased from 0.9766 to 0.9923, all by the addition of the SWCNTs/Cu₂O functional channel mechanism and without graphene. When the graphene was added to the functional channel electrode, sensitivity increased again from 289.8 to 466.1 μA mM^-1 cm^-2 at low concentrations.

Development of amperometric biosensor in modified carbon paste with enzymatic preparation based on lactase immobilized on carbon nanotubes

Abstract

The variety of products derived from milk, without or with lactose, encourages the development of more effective analytical techniques that can be applied to the quality control of both the production line and the final products. Thus, in this work an efficient and minimally invasive method for the detection of lactose was proposed, using a biosensor containing the enzyme lactase (LAC) immobilised on carbon nanotubes (CNTs) that, when reacting with lactose, emit an electrochemical signal. This biosensor was connected to a potentiostat, and its electrochemical cell was composed of the following three electrodes: reference electrode (Ag/AgCl), auxiliary electrode (platinum wire), and working electrode (biosensor) on which graphite (carbon) paste (CP), CNTs, and LAC were deposited. The transmission electron microscopy and scanning electron microscopy were used in the characterisation of the composite morphology, indicating excellent interactions between the CNTs and LAC. The sensitivity of the CP/LAC/CNT biosensor was determined as 5.67 μA cm^-2.mmol^-1 L and detection limits around 100 × 10^-6 mol L^-1 (electrode area = 0.12 cm²) and an increase in the stability of the system was observed with the introduction of CNTs because, with about 12 h of use, there was no variation in the signal (current). The results indicate that the association between the CNTs and LAC favoured the electrochemical system.

Graphic Abstract