Studies On Sodium Alginate Modified By The Polymer Containing POSS Structure

A multi-hydroxy Polyhedral Oligomeric Silsequioxane (POSS-(OH)32) was synthesized firstly. The POSS-(OH)32 was used as an initiator for ring-opening polymerization of lactide. A star polylactic acid (SPLA) was obtained through the polymerization. The SPLA was used to modify sodium alginate hydrophobically by physical blending, and SPLA/calcium alginate composite gel beads were obtained after cross-linking with calcium chloride. The swelling property of composite gel beads was investigated. Ibuprofen was used as the model drug for release behavior study. The results showed that SPLA/calcium alginate composite gel beads didn't swell in deionized water or pH1.2 HCl, but swelled in pH7.2 PBS, and the swelling rate decreased as SPLA/sodium alginate ratio increased; the drug loading rate could be improved and the release rate was postponed with the increase of SPLA content or SPLA molecular weight in the carries. The release mechanism gradually changed from the first-order to the zero-order pattern after the modification.In the second part of this study, amphiphilic graft copolymer was prepared by esterification between alginate and SPLA using carbodiimide hydrochloride as the catalyst. Chemical structure and physical properties of the product were characterized by FTIR, TGA, DSC and XRD. Self-aggregation behavior of the product was investigated in the aqueous phase by fluorescence analysis, and the critical aggregation concentrations (CAC) of ALG-14 and ALG-22 were 0.01g/L and 0.005g/L respectively, and the results show that the CAC is closely related to the content of hydrophobic side chains. The micelle was prepared by using this amphiphilic graft copolymer through self-aggregation. The morphology of the micelle was characterized by TEM. It was discovered that the micelles formed rod-like structure, and their average size was about 1um. Additionally the amphiphilic graft copolymer was made into a thin film through calcium cross-linking. Contact angle analysis showed that the contact angle increased with the increase of grafting rate.Finally, the synthesized alginate/SPLA amphiphilic graft copolymer was used as a drug carrier. The drug-loaded gel beads were prepared by using bovine serum albumin (BSA) as a model drug. The swelling properties were studied by using the method described above. The surface morphology of the gel beads was observed by SEM, and the results showed that the sizes of the hole structure were associated with grafting ratio of alginate. Compared with alginate gel beads, the drug release rate of amphiphilic graft copolymer gel beads slowed down significantly in pH6.8 PBS and physiological saline. The activity of BSA was tested by CD spectra, the results show that the activity of BSA was not affected during the preparation process of gel beads. The amphiphilic graft copolymer was potetially used as a drug carrier materials for peptides and proteins.