| In this thesis, chitosan was adopted as raw material to prepare its derivative which has excellent water-soluble property through malayacylierung. Due to the incorporation of the malay acyl, not only the original outstanding characteristics of the chitosan was retained, but also the water-solubility of chitosan was greatly improved. The acidic condition of dissolving chitosan was expanded to a wider pH range. In addition, the modified product exhibited the characteristics of polyampholyte due to the introduction of carboxyl group. Meanwhile, reactive functional group C=C was also incorporated onto chitosan backbone, whichprovided a possibility for the subsequent modification and application of maleic chitosan (CSM).A series of multi-responsive chitosan-based hydrogels were prepared by changing the environmental conditions, forming polyelectrolyte complexes or interpenetrated network with other polymer. All based on the water-solubility of maleic chitosan. In this paper we examined in vitro release of the gels to explore the possibility of utilizing CSM as a material for controlled drug delivery. The major results were shown as following:1. Water-soluble maleic chitosan was obtained through acylation by using pyridine as a catalyst. FTIR, XRD, UV and thermal gravimetric analysis results confirmed that the product was the expected one.2. Maleic chitosan gels were prepared by changing the concentration, environmental pH, and temperature as well as the formation of polyelectrolyte complexes. Bovine hemoglobin (HB) was selected as model drug to examine the release properties of drug-loaded gels. The results indicated that all of the gels had compact structure and achieved sustained release of drug.3. Alginate microspheres were prepared by emulsification/internal gelation. Multilayer composite microspheres were obtained by an LBL method. Surface properties of the microspheres were characterized by EA, XPS, VSM, SEM and laser particle size analyzer. EA and XPS analysis results together indicated alternate immersion is an effective methord for the preparation of multilayer composite microspheres. VSM, SEM and laser particle size analysis results showed all of the microspheres had good dispersion, uniform particle size and superparamagnetic. The in vitro drug release properties were studied by using HB and Coomassie Brilliant Blue G250as modle drugs, and the results showed that the release rate was slowed down with increasing the layers. In addition, the macromolecules behaved more evident sustained release than small molecule drugs did.4. Well-defined PVA was synthesisd by RAFT living polymerization and alcoholysis, and then covalently combined with CSM via thiol-ene Click reaction. The drug-loaded gel was produced with freezing-thawing method. CSM/PVA blend was taken as control to inverstigate the in vitro release performance of CSM-PVA gel. The results showed that the drug release performance of CSM-PVA gel is superior to that of blend one. |
