Study Of Inorganic Nanomaterials-based Biosensors

1. Development of Amperometric Biosensor for Glucose Based on a Novel Attractive Enzyme Immobilization Matrix: Calcium Carbonate NanoparticlesCalcium carbonate nanoparticles (nano-CaCO₃) may be a promising material for enzyme immobilization owing to their high biocompatibility, large specific surface area and their aggregation properties. This attractive material was exploited for the mild immobilization of glucose oxidase (GOD) in order to develop glucose amperometric biosensor. The GOD/nano-CaCO₃ based sensor exhibited a marked improvement in thermal stability compared to other glucose biosensors based on inorganic host matrixes. Amperometric detection of glucose was evaluated by holding the modified electrode at 0.60 V (vs. SCE) in order to oxidize the hydrogen peroxide generated by the enzymatic reaction. The biosensor exhibited a rapid response (6 s), a low detection limit (0.1μM), a wide linear range of 0.001-12 mM, a high sensitivity (58.1 mA cm-2 M-1), as well as a good operational and storage stability. In addition, optimization of the biosensor construction, the effects of the applied potential as well as common interfering compounds on the amperometric response of the sensor were investigated and discussed herein.2. Calcium Carbonate Nanoparticles: A Host Matrix for the Construction of Highly Sensitive Amperometric Phenol BiosensorWe report on the utilization a novel attractive nanoscaled calcium carbonate (nano-CaCO₃)-polyphenol oxidase (PPO) biocomposite to create a highly responsive phenol biosensor. The phenol sensor can be easily achieved by casting the biocomposite on the surface of glassy carbon electrode (GCE) via the cross-linking step by glutaraldehyde. The special three dimensional structure, porous morphology, hydrophilic and biocompatible properties of the nano-CaCO₃ matrix result in high enzyme loading, and the enzyme entrapped in this matrix retains its activity to a large extent. The proposed PPO/nano-CaCO₃ exhibited dramatically developed analytical performance such as such as a large determination range (6×10^-9 - 2×10^-5 M), a short response time (less than 12 s), high sensitivity (474 mA M^-1), subnanomolar detection limit (0.44 nM at a signal to noise ratio of 3) and excellent long-term stability (70% remains after 56 days). In addition, effects of pH value, applied potential, temperature and electrode construction were investigated and discussed.3. Layered double hydroxides inorganic matrix materials: Characterization and application to the design of amperometric xanthine biosensorA type of amperometric xanthine biosensor based on layered double hydroxides inorganic matrix casting the biocomposite on the surface of by glutaraldehyde. The composite films have been characterized by Fourier transform infrared (FT-IR). The results indicate that xanthine oxidase retains the essential feature of its native structure in the composite film. The enzyme electrode provided a linear response to xanthine over a concentration range of 1～200μM with a sensitivity of 0.18 AM^-1cm^-2 and a detection limit of 1μM based on S/N = 3. The apparent Michaelis-Menten constant (KMapp) for the sensor was found to be 1.1 mM. The activation energy for enzymatic reaction is calculated to be 8.4 kJ mol^-1. Furthermore, the biosensor exhibited excellent long-term stability and satisfactory reproducibility.