Synthesis of Novel Chitosan Derivatives and Surface Functionalization of Titanium with HACC
|School||Shanghai Jiaotong University|
|Keywords||quaternary chitosan derivatives phosphonium chitosan derivatives titanium surface modification x-ray photoelectron spectroscopy (XPS)|
Chitosan, a well-known abundant natural polycationic macromolecule with good biodegradability, biocompatibility and so on, gets much attention currently for biomedical application.Firstly, varies of 2-Hydroxypropyltrimethyl ammonium chloride chitosans (HACC) with different degree of substitution (DS: 6%, 18%, 37%, 54% and 81%) were synthesized by the reaction of chitosan with glycidyltrimethylammonium chloride (GTMAC), and characterized by FT-IR and 1H-NMR spectroscopy. Their properties such as water solubility, aqueous solution stability upon pH and moisture absorption ability were studied, following with the film-forming capability and the antibacterial property of films. Results indicated that the water solubility, aqueous solution stability upon pH and moisture absorption ability increased with increasing DS of HACC. Additionally, HACC films, prepared by tape casting with their dilute solutions, were presented as transparent films with favorable mechanical performance and better antibacterial property against Staphylococcus aureus and Escherichia coli than chitosan film.Secondly, HACC functionalized titanium was prepared by treating the pristine titanium with piranha acid oxidation, silanization procedure, glutaraldehyde reaction and HACC (DS: 18%) deposition successively. Each kind of chemical treated titanium was characterized by x-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared attenuated total reflection (FT-IR/ATR). The results showed that with each reaction occurred, the atomic ratio of C/Ti and O/Ti gradually increased. Following the reaction of glutaraldehyde treated titanium with HACC, the atomic ratio of N/Ti rised from 0.212 to 1.088. With each reaction occurred, the content of O 1s attributed to TiO2 became smaller and smaller, from 81%, 72%, 61% to 40%. Also with each reaction carried out, the electron peak of Ti 2p at 453.4 eV due to Ti base gradually turned smaller and the peak almost diappearred after the titanium was treated with glutaraldehyde and HACC. Additionally, series infrared absorption bands were observed on the surface of HACC funtionalized titanium, including 3365cm-1 (-OH), 1664cm-1 (Amide I), 1165cm-1 (νas, C-O-C bridge) and the absorption bands between 958cm-1and 1155cm-1 (skeletal vibrations involving the C-O stretching of saccharide structure of HACC). All these results indicated that HACC was successfully covalently attached to medical titanium surfaces.Eventually, novel Water Soluble Phsophonium Chitosan Derivatives (WSPCS) were synthesized with differing degree of substitution (3.6% and 4.2%) of quaternary phosphonium by reacting chitosan with (2-Carboxyethyl) triphenylphosphonium chloride in a homogeneous system. At the same time, novel Organo Soluble Phosphnium Chitosan (OSPCS) were prepared with differing degree of substitution (54.5% and 81.7%) using chitosan-sodium dodecyl sulfate polyelectrolyte/surfactant complex in an organo system. All these compounds were characterized by FT-IR, 1H-NMR, 31P-NMR and x-ray diffraction (XRD). The results suggested that both WSPCS and OSPCS contained element of phsophonium. The crystallinity of not only WSPCS but also OSPCS was significantly influenced by the introduction of triphenylphosphonium group to chitosan backbone. WSPCS also showed improved water solubility, while the resulting OSPCS showed enhanced organo solubility compared to original chitosan.