Study On The Stability And Cytotoxicity Of The Biosynthesized Gold Nanoparticles Using Catclaw Buttercup

Gold nanoparticles (AuNPs) with large surface area, quantum effect and smallsize effect, exhibiting excellent characters in many different fields, such as optics,optoelectronics, drug delivery system, disease and gene therapy, catalysis and medicalimaging, and so on. At present, AuNPs are mainly synthesized by chemical reductionmethod. The produced naked AuNPs are easy to agglomerate, and usually modifiedwith organic molecules such as PEG on the surface to improve stability for the furtherapplication. However, when these AuNPs interact with cells, organic molecules candisrupt the cell membrane or the cell cycle, thus leading to the cell death. This greatlylimits the deep application of AuNPs in biomedical research. Recently, thebiosynthesis of AuNPs, which is non-toxic, safe, eco-friendly, green, and economical,paves a new way to solve the problem. Biological compositions of the biosynthesizedAuNPs not only have bioactivity and reducibility, but also possess carboxyl andhydroxyl groups to protect AuNPs and thus improve its stability. In this thesis, aimingat the study on the preparation and biomedical application of the biosynthesizedAuNPs, we investigated the preparation feasibility and optimization of thebiosynthesized AuNPs using catclaw buttercup. And on this basis, we further studiedthe colloid stability and cytotoxicity of this biosynthesized AuNPs. The main worksare summarized as follows.1. Preparation optimization and characterization of the biosynthesized AuNPsusing catclaw buttercupSelecting catclaw buttercup as the raw material, the biosynthesized AuNPs weredirectly prepared through the incubation of the catclaw buttercup powder and HAuCl4.The influence of the reaction time, temperature and mass ratio of HAuCl4/catclawbuttercup on AuNPs synthesis was investigated. The AuNPs obtained under theoptimized conditions was then characterized by UV-Vis, XRD, HRTEM, EDX，ICPand FTIR. Results showed that when the preparation condition was50/1as the ratio ofcatclaw/HAuCl4buttercup,37C as the reaction temperature, and4hours as thereaction time in25mL reaction liquid, we could get the maximum output of89.6%,and the obtained AuNPs was well-dispersed, spherical and gold crystal structure withthe diameter of17nm. This biosynthesis method provides a novel, green, eco-friendly,and economical route for AuNPs preparation. 2. Study on the colloid stability of the biosynthesized AuNPs using catclawbuttercupUsing UV-Vis spectroscopy, we investigated the colloid stability of thebiosynthesized AuNPs in NaCl, LiCl and acid solutions with a series ofconcentrations, the protein and sugar compositions of the biosynthesized AuNPs wereanalyzed by SDS-PAGE, Improved-lowry Protein Assay Kit and anthrone-sulfuriccolorimetric method respectively. Results showed that in contrast to thechemosynthesized AuNPs, the biosynthesized AuNPs were more stable, which werestill well-dispersed even in the saturated NaCl or LiCl solutions and the pH=1acidsolution. There was no sugar detected, and the protein was existed, which might playan important role in the remarkable stability.3. Study on the cytotoxicity of the biosynthesized AuNPs using catclawbuttercup and its application in dark-field imagingSelecting L-02human normal liver cell line and MCF-7breast cancer cell line asstudy objects, the cytotoxicity of the biosynthesized AuNPs was investigated throughMTT, Cell Titer Blue, as well as DAPI staining, and then compared with that of thechemosynthesized AuNPs. Results revealed that the chemosynthesized AuNPs showedstrong cytotoxicity to both L-02and MCF-7. However, the biosynthesized AuNPsshowed little influence on MCF-7at certain concentration, and could promote thegrowth of L-02, which suggested the good biocompatibility of the biosynthesizedAuNPs. Moreover, when the biosynthesized AuNPs were used for dark-field imagingof MCF-7, the satisfying effect of dark field imaging demonstrated the preservation ofunique absorption characteristic and scattering property of AuNPs after co-incubationwith cells, which endows them potential for application in the field of biomedicine,such as nanocarriers, dark field imaging of cells and so on.