The Biological Effects Of Gold Nanoparticle Layer

The application of surfaces with micro-/nano structures in biomedical fields has drawn increasing attention in recent years, especially their notable advantages in innovative sensors and tissue engineering materials. However, it has long been difficult and costly in the preparation of such materials. Hence, developing a convenient method to form micro/nano structures on many materials of different nature is highly desirable, which will enable the transformation process of those surfaces in biomedical researches and applications.The main focus of this thesis is to build micro/nano topographical structures comprised of gold nanoparticle layer (GNPL) on material surfaces via a convenient glucose reduction process. And we first investigated the performances of GNPL modified ELISA plate in the applications of both indirect and sandwich format ELISA. Moreover, we modified the GNPL with protein-repellent polymer brush and conjugated it with GRGDY peptide, and studied the influence of GNPL roughness on the specific binding of L929fibroblasts. Finally, we conjugate tumor cell-specific aptamers (APT) TD05to GNPLs through surface self-assembly, and investigated its performances in selective capturing of specific tumor cells.First, we prepared micro/nano three dimensional GNPL on various materials by using glucose reduction method, and studied the performances of the GNPL modified ELISA plate in ELISA applications. Metallographic microscope and field emission scanning electron microscope (FESEM) were used to characterize the morphology of GNPL. And isotope labeling was used to monitor fibrinogen (Fg), human serum albumin (HSA) and lysozyme (LYZ) adsorption on GNPLs, and also, the activity of adsorbed LYZ was measured. Then, we studied the performances of the GNPL modified ELISA plates in ELISA by using cancer marker carcinoembryonic antigen (CEA), human antithrombin (AT), rabbit immonoglobulin (IgG), and human fibroncetin (Fn) as model analytes. We found that the morphologies of GNPL and the amount of adsorbed bioactive protein could be tuned simply by controlling the amount of reaction solution used. It is also shown that two opposite wetability states (superhydrophilic and superhydrophobic) of GNPLs can be formed, and the superhydrophilic state of GNPL was optimal in ELISA. The performances of GNPL in both indirect and sandwich ELISA showed the improved method can significantly enhanced the sensitivity and lowered the limit of detection. This improved method is convenient, universal and effective, and could be an ideal supplement to the conventional ELISA.In the second part of the thesis, we prepared low-fouling GNPL with cell-specific binding abilities. And investigated the effect of surface roughness on the specific binding between L929fibroblasts and the modified GNPLs. We modified GNPLs with poly(oligo(ethylene glycol) methyl ether methacrylate)(POEGMA) brush as spacers via surface-initiated atom transfer radical polymerization (SI-ATRP), and conjugate them with cell-specific peptide glycine-arginine-glycine-aspartic acid-tyrosine (GRGDY). FESEM, water contact angle, surface roughmeter, ellipsometry and X-ray photoelectron spectroscopy (XPS) were used to characterize the GNPLs before and after modifications. Isotope labeling was used to monitor Fg adsorption onto GNPLs before and after modification, and ELISA was used to study the Fn adsorption from human plasma. L929cells were used to investigate the specific binding between cells and GNPLs-POEGMA-GRGDY surface, and the effects of GNPLs roughness on this interaction. The results showed the pristine micro/nano rough structures significantly inhibited L929cell growth; however, after modification with POEGMA-GRGDY, the micro/nano structures greatly enhanced L929cell-specific interactions and improved the cell compatibility of surfaces while maintaining superior low-fouling ability compared with planar gold. Our findings demonstrated a promising and effective surface modification strategy for investigations and applications based on cell-surface interactions.Finally, we modified GNPLs of different roughness with TD05aptamers, a kind of tumor cell specific aptamer via self-assembly. And the selective binding effects of the functionalized GNPLs on the target tumor cell under serum-free and serum-containing culture conditions were investigated. Water contact angle and ellipsometry were used to characterize surface wetability and the thickness of polymer brush coatings on GNPLs before and after modification. The results demonstrated that the two kinds of tumor cells prefer to adhere on pristine GNPL surfaces compared to planar gold regardless of the presence of serum, and Ramos cells outnumbered slightly. More importantly, after the modification with TD05aptamer, the selective binding ability of GNPLs increased as surface roughness increased, especially, the number of adhered Ramos cells was18times higher than the CEM cells under serum-free conditions. Our results indicate that the properly functional ized GNPL holds great promise in future applications in cancer diagnosis, rare cell separation etc.In conclusion, this thesis mainly focused on the conveniently prepared GNPL modified surfaces, and investigated its universality on different materials, and the influence of the volume of reaction solution on the GNPL morphologies. The influence of GNPL on protein adsorption and activity were also investigated. Moreover, the performances of GNPL modified ELISA plate were studied detailedly, and satisfactory results were obtained. Furthermore, the influence of GNPL roughness on the specific binding between L929fibroblasts and GNPL surfaces, and the performances of APT functional ized GNPL in selective tumor cell binding were also investigated. Our work indicate that GNPL modified surfaces could find wide applications in biomedical research and applications.