Preparation And Characterization Of Chitosan/Heparin Self-Assembed Films

Chitosan is a biopolymer, it is mainly obtained from the deacetylation of chitin extracted from shells of shrimps, crabs, and squids. It is produced in the amount of one hundred billion tons per year in nature. The most distinguishing chitosan propertise are its non-toxicity, biodegradability and biocompatibility, which makes it a green polymer. Also important is that chitosan is the only positively charged, naturally occurring polysaccharide, for chitosan may then interact strongly with negatively charged entities. Heparin is a glycosaminoglycan present in the human body, but it is often obtained from porcine intestinal mucosa., which commonly used as anticoagulant in clinical. It has the highest negative charge of all biological polyanions because of its high content of sulfonate and carboxyl groups.The surface modification is significant for biomedical applications, because the intact materials can be engineered for specific bioaffinities. With regard to Layer-by Layer technique (LbL), the polyelectrolyte multilayer films at solid surfaces appears as a versatile surface functionalization method with applications in blilogical applications such as anti-infective medical implants. In the present study, multilayer films were formed with natural polysaccharides chitosan (CS) and heparin (HEP) on glass surface with LbL technique. The morphology of the films were characterized by atomic froce microscope(AFM), and the growth of CS and HEP was analyzed. Finally, the anti-coagulant activity of these films againsrt whole human blood was studied by the immersion of a substrate into bolld for1h incubaton time at37℃,and are therefore promsing coatings for medical implants.1. Chitin was extracted from the shells of crabs back, and then was used to parpare chitosan by microware-alkali liquor method. The deacetylation degree of chitosan was determinated by potentiometric tiration method, and the molecular weight of chitosan was determinated by Ostwald viscometer method, which were compared with two commercial products at the same time. As a result, the degree of deacetylation of extrated chitosan samples was77.49%, while the degree of deactylation of chitosan purchased from Juyuan. Co. Ltd and Guoyao.Co.Ltd were 84.93%、81.69%, respectively; the viscosity average molecular weight of extraeced chitosan was8.1×106, while the viscosity average molecular weight of chitosan purchased from Juyuan.Co.Ltd and Guoyao.Co.Ltd were2.2×105,5.7×105, respectively. The infrared results show the molecular structure of chitosan, and AFM images of films prepared from chitosan purchased from Guoyao.Co.Ltd were best, which was choosed to prepare polyelectrolyte multilayer films.2. Glutaraldehyde-modified substrate were obtained by three-step prossing method of chemical modification on glass, and were characterizated by contact angle, AFM, and infrared method. CS/HEP self-assembled multilayer films were prepared by spontaneous adsorption of lmg/ml, pH=3.0CS solution and1ml/ml, pH=6.9HEP solution on the glutaraldehyde-modified substrate. AFM was used to observe the morphology of the films, the contace angle was used to observe the film surface wettability, while the small angle X-ray diffraction was used to detect the growth of the films.3. Well-controlled poly N-methylol acrylamide moleculars brush grafted glass surface were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) and characterized by contact angle instrument and AFM. Then CS/HEP self-assembled multilayer films were prepared by alternately adsorption of1mg/ml, pH=3.0CS solution and lml/ml, pH=6.9HEP solution on the molecular brushs-modified substrate. AFM、contact angle measurement were used to characterizated the multilayer films.4. The preliminary anti-coagulation properties of perpared assembly of CS/HEP multiayer films were explored.