Study On Surface Modified By Quaternary Ammonium Salt And Its Antibacterial Property

Antibacterial materials have attracted increasing attention for their application in biomedical materials fields. In the recent decades, various methods have been applied to endow materials antibacterial activity. The antimicrobial can be immobilized onto the surfaces through kinds of ways such as embedding, blending, coating, and grafting. In this work, polycations were covalently tethered onto the surfaces using "graft from" strategy followed by quaternary ammoniation to give the resulted surfaces good antibacterial activity. This surface modification exhibited several advantages including less consumption of antibacterial agents, longer stability of antibacterial properties, no release of toxic substances, and no destroy of the physical and chemical properties of bulk materials. Here two typical materials of great importance in biomedical application, (PU) and silicon nanowire arrays (SiNWAs) were used as model substrates for the modification and their antibacterial activity was investigated. The detailed research works were summarized as follows:1. PU has been widely applied in biomedical materials field due to its excellent mechanical properties and good biocompatibility, and antibacterial modification will extend its potential application. In this work, vinyl groups were first introduced to PU surfaces by a simple chemical method and then surface-initiated radical polymerization of dimethyl amino ethyl methacrylate (DMAEMA) was conducted using azobisisobutyronitrile (AIBN) as the initiator. Finally, the grafted poly(dimethyl amino ethyl methacrylate) (PDMAEMA) brushes were quaternized to give the resulted surfaces antibacterial activity. The modified surfaces were characterized by water contact angle measurement, fluorescein sodium salt assay, and antibacterial analysis. After quaternization the color of the modified surfaces turned deeper and the modified surfaces became more hydrophilic, suggesting the successful quaternization process. The results of antibacterial activity analysis indicated that more than 95% adhered bacterial could be killed on the quaternized PDMAEMA modified PU surfaces.2. Silicon nanowire arrays (SiNWAs) not only have the special properties as a semiconductor and surface effect, small-size effect, quantum-size effect and macroscopic quantum tunneling effect as a typical one-dimension nanomaterial, especially they exhibit special effects on surface modification. In this work, SiNWAs were prepared using chemical etching method. Then DMAEMA was graft polymerized on SiNWAs by atom transfer radical polymerization (ATRP) followed by quaternization. The modified surfaces were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), water contact angle measurement, fluorescein sodium salt assay, and antibacterial analysis. Incubation of Escherichia coli on the substrates resulted in 95% cell death on the quaternized nanowire material compared to less than 45% on the quaternized smooth silicon. The results suggest that silicon nanowire array modified with quaternized pDMAEMA is a highly effective antibacterial material due to a high density of antibacterial polymer and consequent high bacterial adhesion and killing.