Preparation And Characterization Of Chitosan-Based Controlled-Release Material

Chitosan (CS) is one derivative of chitin, obtained by deacetylation, there are a number of polargroups on the chain, such as amin, hydroxyl etc. Because of good hydrophility, non-toxicity, biocompatibility and high adhesion, it is a new natural medical polymer, largely used in different applications as solutions, fibers, gels and films.Chitosan can be used as a main candidate for the durg release carrier. CS has sol performance of special structure like sponge, through the proper cross-linking reactions and preparation methods, we can control drugs out continuely to improve the drug solubility and absorption, achieving the ideal of release rate.But in the solid state, chitosan is a semicrystalline polymer, molecular arrangement is loose, so the performance of pure CS sample is poor:poor water resistance, easily brittle and degradable, bad mechanical properties, limit the long-term application of control-released carrier.Therefore consider by introducing new chemical groups to improve chitosan performance., forming complexes.Polyvinyl Alcohol(PVA) is easily souble in hot water, with excellent fiber and film formation. It contains much-OH, which can complex with the introduced group, and enhances the mechanical property of the composite.The research used CS as matrix, for the activity of amine and hydroxyl on the CS chain, introducing new groups, choosing material components, ratio, blending mode and structure design, to control the complex biodegradation and dynamic parameters design of functional material release. This research is how to choose appropriate molding process, through solution blending prepare CS/PVA composite membrane, CS/SS composite membrane, CS/PVA composite fluffy network, pure CS fluffy network and pure CS film, and characterize the degrade performance.The degradation mechnical property of films in the SBF were tested by the fabric tensile strength tester, macro-and micro-structure of the samples were investigated by Optical microscope and SEM, quantitatively represented the degradation performance with weightlessness rate curve, qualitatively analysis the degradation component change of samples by Fourier Transform Infrared Spectrometer (FT-IR). The experimental results show that:1. The optimized technical parameters were as follows:the concentration of acetic acid is 3%. For CS fluffy network:20w(DD:97%),2%, coagulation bath is 15%(w/v) NaOH and 10%(v/v) ethanol, dry at 40℃(12h); For CS film:15w,2% and 2.5%,3%NaOH(remover); For CS/PVA film: c(PVA):c(CS) is 8/2 and 12/2, V:V=1:1, dry at 40℃,3% NaOH(remover); For CS/SS film: c(CS):c(SS) is 2:2.2 and 2:3.7, V(CS):V(SS) is 2:1, mix at 70℃; For CS/PVA fluffy network: c(PVA):c(CS) is 10/3, mixed coagulation bath, Spinning temperature is 20-25℃, high speed.2. The degradation speed of film is related to materials (molecular weight), concentration, and thickness. Film, which is small molecular weight, low concentration and thin, degraded fast. In SBF, macro performance for membrane is gradually broken into pieces, volume reduced, and the microscopic view is fracture decomposition for bonds.3.Choose appropriate raw material molecular weight, the speed of coagulation bath to prepare high strength, fineness uniform fiber, then natural accumulate to form network structure. The poros in the network provided diffusion channels in the process of drug release.4.The CS complex mixed with other polymer, such as PVA and SS, can change the degradation speed in SBF. For CS/PVA film, the hydroxyl on PVA chain and amino on CS chain formed numerous hydrogen bond within and between the moleculer, PVA supported power and enhanced the mechnical property, so the film don't degrade for long time.For CS/SS composite film, the degradation speed becomes slower because of the introduction of SS, SS becomed the regulation adsorption degradation center in the CS/SS film and control degradation speed. Sort the samples according to degradation speed:CS film>CS/SS film>CS/PVA film; CS fluffy network>CS/PVA fluffy network.The traditional drug usually easily overrun blood drug concentration during early period, then may fail because of lower concentration. The carrier in the composite can be controlled to degrade in SBF. Matrix is biodegradable, structure becomes loose, and diffusion resistance reduced gradually and finally achieves constant release.The complex formation can get chitosan better comprehensive property than pure CS. Analysis different degradation mechanism and speed of complex to provide new basis formulations for long-term drug release system.