Enzymes, biosensors gold nanoparticles, activity

Enzyme sensors are another important application of metal nanoparticles in CMEs besides nonenzyme sensors. Many enzymes can keep their activity when anchored onto gold nanoparticles. A novel method for fabrication of a biosensor based on the combination of sol-gel and self-assembled techniques has been introduced very recently. For example, the gold nanoparticles and enzyme horseradish peroxidase (HRP) can be successfully immobilized on gold electrode by the help of sol-gel with thiol groups, and the direct electrochemistry of HRP has been achieved and the biosensor thus prepared exhibits fast response, good reproducibility, and long-term stability. 

Monoamine oxidase amperometric biosensor based on SPE were also modified with MWCNT by using the drop casting technique for the determination of antidepressants in model solutions and dosage forms. The authors used BSA protein which provided a matrix for the immobilization of the enzyme and protection of the enzyme activity when glutaraldehyde is used as a linker. Serafin et aZ. developed a label free dual immunosensor for the determination of human growth and prolactin hormones. The electrochemical immunosensor was based on CNT modify carbon SPE platform with the presence of poly(ethylene-dioxythiophene) (PEDOT) and gold nanoparticles. Again, the hybrid nano-material composite facilitated a proper immobilization of the antibody on the electrode matrix. 

On a different setup, Du et al. [31] cast sol-gel silica/gold nanoparticle nanocomposite films on a glassy carbon electrode, which was then impregnated with an acetylcholinesterase (AChE) enzyme (Figure 46.10). The construct was used as a biosensor for organophosphorus pesticide detection. In this system, gold nanoparticles not only offered a biocompatible microenvironment to retain the activity of adsorbed enzyme molecules but also acted as a wire to enhance the direct electron transfer rate between the enzyme active centers and the electrode surface, which otherwise would be blocked by the thick protein shell of the enzyme chemical structure. 

Nanostructured interfaces between the bare electrode and DNA, formed by various nanomaterials such as gold nanoparticles and carbon nanomaterials (e.g., SWCNTs, multi-walled carbon nanotubes, carbon nanofibers, graphene, and graphene oxide nanosheets) [54-63], represent another approach to the enhancement of the biosensor response due to inherent electroactivity, effective electrode surface area, etc. [35, 64]. Nanometer scale complex films of DNA, enzymes, polyions, and redox mediators were suggested for tests of genotoxic activity of various chemicals [65]. 

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