B. Wang, I-. Kang
Keywords: chitosan-gold nanoshell, mercaptopropionic acid, γ-Aminobutyric acid, surface-enhanced Raman scattering
Summary:A Surface-enhanced Raman Scattering (SERS) can be used to detect the concentration change of γ-Aminobutyric Acid (GABA) as the principle for enhancing Raman scattering by molecules adsorbed on rough metal surfaces or by nanostructures. GABA plays such key role in declining neuronal excitability throughout the nervous system, and is the mainly inhibitory neurotransmitter in the mammalian central nervous system in the human body. After adding Mercaptopropionic Acid(MPA), the very strong S–Au bond was formed between gold surface and MPA. Chitosan is the natural polysaccharide and is thought as the largest biomaterial after cellulose ,when the utilization and distribution is concerned. With the feature of nontoxic, biodegradable, polycationic, antibacterial, and biocompatible, chitosan has attracted much attention and has extensive use in biotechnology, food, pharmaceutical, cosmetics, textile, and agricultural industries. With those large number of advantages, chitosan is going to be considered as a new materials for the biosensor. To form the uniform nanoparticles, the linear polymer chitosan in the acid condition can have the protonated amine group attracted the TPP which has the polyanion groups at the same time. The electrostatics attraction between these positive amine groups and negative polyanion groups supports for the ionic cross-linking process of TPP with chitosan to form chitosan nanoparticles. Gold nanoparticles, however, because of the merit of the metal, biocompatibility and unique plasmonic properties, can be applied as diagnostic and therapeutic agentia for cancer cells. In this study, the gold ion was reduced by the ascorbic acid in the alkaline condition, which combined with chitosan nanoparticles immediately to cover chitosan nanoparticles. 3-Mercaptopropionic Acid(MPA), which has S-H bond at the end of the compound, can easily modify chitosan-gold nanoshell particles to obtain new function group. On the particles, and the S-Au is so strong that it can be easily detected by Raman which can be controlled flexibly as well. So it is meaningful to creative a biosensor which can convert the results from physical signal to chemical reaction. In this study, the surface enhanced Raman scattering(SERS) analytical technology was used to detect the chemical bond vibration between the modified chitosan and absorbed GABA. As the same time, the optimum condition of the MPA was detected and the intensity tendency of the different concentration of GABA. In other hand, the carboxyl group, the other end of the MPA, can easily absorb the GABA. For the SERS sensitivity (counts), the calibration curve of as determined by the concentration levels of GABA which was absorbed onto the modified chitosan-gold nanoshell on the peak of 1600cm-1 was as follow: y=1591X+1972.2(R2=0.9484) along with the peak at 500cm-1 as follow: y=1591X+1972.2(R2=0.9484). On the basis of the aforementioned two sets of data it was confirmed that the analysis of GABA by using modifying chitosan nanoparticles had a high level of SERS sensitivity. In this study, DLS, SEM, SERS were used to detect the products for obtaining the conclusion.