Preparation Of Bio-functional Materials Using Sulfated Chitosan Modified Silicon Substrate

Sulfated polysaccharides widely exist in vivo, They present in the structure ofcell/tissue and regulate cell growth and blood anticoagulation conditions. In humanbody, most of the sulfated polysaccharides are heparin and heparan, among which theeffect of heparin is the most remarkable. It has been shown in previous studies that thebiological activity of heparin is achieved due to the specific binding activity of theprotein. Heparin can generate a strong interaction with antithrombin, growth factorsand lysozyme, which further influences the biological functions of these proteins.Therefore, heparin has a wide range of potential applications in the biomedical field.However, heparin has a complex structure and different source of heparin has differentbiological activity. It is found that heparin derivatives prepared by regioselectivesulfation of heparin display similar bioactivities and functions as compared to heparin,including antioxidant, antivirus, antitumor, anticoagulant and antibacterial, etc.. Thus,these heparin derivatives have a wide range of applications in the field of biomedicine.Modifying biomaterial surfaces with regioselective sulfated chitosan can endowthe surface with unique biological activities and funtions. Due to the fact that the3,6-O-sulfated chitosan (36S) and6-O-sulfated chitosan (6S) exhibit specific bindingactivity with lysozyme, in the present study, we proposed the project where materialswith unique bioactivities and biofunctions by grafting36S and6S to silicon substrates.The main content is as follows:1. Regioselectively sulfated chitosan was prepared by chlorosulfonic acid, NPC(p-nitrophenol chloroformate) method was used to graft sulfated chitosan to thematerial surface. The wettability and charge distribution of surfaces prepared under different pH, concentration, reaction time and temperature were studied. The resultsshowed that the surface with the best properties can be obtained when the reactionwere carried out in phosphate buffer (PB, pH=5.7) containing1.0mg/ml sulfatedchitosan at30℃for24h.2. A recyclable antibacterial material can be prepared by silicon grafted with3,6-O-sulfated chitosan, with the method of NPC. Because the modified surfaceexhibited very high bonding activity of lysozyme, and can maintain full hydrolyticactivity, the materials can achieve the antibacterial functionality with high efficiency.Meanwhile, this bonding affinity can be desorbed in salt solution of high concentration.Therefore, the modified surface can be recycled by4.0M NaCl solution and reused asan antibacterial material.3. SiNWAs (silicon nanowire arrays) with multi-functionalities was prepared bychemical etching method using HF solution etching Si substrate, and then modifiedwith6S. First, nano-material exhibited increasing amount and activity of surface boundLyz due to its large specific surface area, which in turn greatly improved itsantibacterial property; besides, this modified material showed good biocompatibility,and can support the adhesion and growth of both L929and Hela cells; furthermore,with the physical penetrating effect of nanowires and the binding ability of6S withDNA/PEI complexes, the modified SiNWAs can efficiently load and release exogenousDNA, and improve the gene transfection efficiency towards different cell lines (Helacells and stem cells).In summary, in the present work, we designed several bio-functional surfacesbased on Silicon substrates modified with sulfated chitosan. Various characterizationtechniques were used to study the structure and biological functionality of the modifiedsurface and it is discovered that the modified surface exhibits excellent antibacterialproperty and can be reused. Besides, a multi-functional nano-material can be obtainedby modifying SiNWAs with6S and the modified material shows improvedantibacterial property, good biocompatibility and enhanced gene delivery efficiency.The properties and bio-functions of the synthesized material were investigated with various characterization techniques. Therefore, our work can provide bothexperimental evidence and theoretical guidance for designing novel biomaterials.