The Preparation Of Starch Derivatives With Different Charges And The Study Of Their Protein Resistance

Nonspecific protein adsorption is the key issue in various fields, such as bio-implants, biosensors and marine hull. It is reported that about 80% of the failure of bio-implants is ascribed to the bio-adhesion, which is initiated by the nonspecific protein adsorption on the bio-implants. Despite extensive studies, there are still a very limited number of protein resistant materials that meet the various challenges of practical applications, particularly in applications involving complex media such as blood. Thus, the development of new protein resistant materials remains an important focus of research. The main objectives of this thesis are: First, synthesize new nonflouling materials possessing both protein resistance and biocompatibility. Second, investigate the mechanism of their protein resistance, as follows.Zwitterionic group, which is famous for its protein resistance, was attached to starch, and zwitterionic 3-dimethyl(propyl) ammonium propanesulfonate starch(Z-Starch) with different substitution degrees of the zwitterionic groups(DSZM) was obtained. Z-Starch hydrogel was prepared with poly(ethylene glycol) diglycidyl ether(PEGDE) as a crosslinker. HRP-conjugated goat antihuman IgG(HRP-IgG) was used as a model protein to examine the protein resistance of the Z-Starch hydrogel. MCF-7 and human vascular endothelial cells(HUVECs) were included to assess the cytotoxicity and cell resistance of the Z-Starch hydrogel. The results are: HRP-IgG adsorption on Z-Starch hydrogel shows a dependence on DSZM and the amount of protein adsorption decreases as the DSZM increasing. Adsorption kinetics of HPG-Ig G on Z-Starch hydrogel illustrate a secondary adsorption kinetics. HRP-IgG adsorption on Z-Starch hydrogel also exhibits a dependence on ionic strength, which is related to the zwitterionic assocaitions. Cell cytotoxity and adhesion assays suggest that Z-Starch is safe and can resist cell adhesion effectively.Non-fouling materials bind water molecules via either hydrogen bonding or ionic solvation to form a hydration layer which is responsible for their resistance to protein adsorption. Three ionic starch-based polymers, namely a cationic starch(C-Starch), an anionic starch(A-Starch) and a zwitterionic starch(Z-Starch), were synthesized via etherification reactions to incorporate both hydrogen bonding and ionic solvation hydration groups into one molecule. Further, C-, A- and Z-Starch hydrogels were prepared via chemical crosslinking. A ternary system of protein, water and polymer was constructed. Three model protiens with different net charges(HRP-IgG, lysozyme and pepsin) and two model cells(L929 and HUVECs) were used to evaluate their protein and cell resistance. The results are: These three polymers have a strong affinity to bind water molecules and they have an effect to stablilize protein in solutions. Protein adsorption assay displays that the protein resistance of these three materials follows the order: Z-Starch ≥ A-Starch>C-Starch. Cell adhesion assay demonstartes that the Z- and A-Starch hydrogels resist cell adhesion effectively, while the C-Starch hydrogel induces cell adhesion. This is consistent with their ability to resist protein adsorption.Incorporating both ionic solvation and hyrodrogen bonding groups into one molecule provides us a way to design and syntheize new protein resistant materials. Meanwhile, the Z- and A-Starch hydrogels are safe and possess excellent protein and cell resistance. These imply that the Z- and A-Starches have potential applications in drug delivery carriers, tissue engineerings and coatings of implanted sensors where protein resistance is needed.