Study On Biodegradable Chemical-crosslinked Alginate Hydrogels

Alginate, as a natural linear polysaccharide, has been widely used in various fields such as medicine industry for its good biocompatibility. However, alginate itself has a very slow degradation rate especially when there is no enzyme in human body to digest it, releasing high molecular weight strands that may have difficulty being cleared from the body. Besides, ionically cross-linked alginate hydrogels have uncontrollable mechanical properties and degradation behavior as the ions in gels would make exchanges with those in its environmental solutions. Considering the demands for biomaterials, the drawbacks above definitely limits its application in tissue engineering.In this paper, partially oxidized alginate was prepared by using sodium periodate, the structure of the yielding materials was characterized by FT-IR, and the change of molecular weights before and after oxidation was tested through viscosity measurement. From all the results, the appearance of aldehyde group was confirmed, and the decrease in molecular weight was observed. Simultaneously, aminated gelatin and modified heparin were made with ethylenediamine using water-soluble carbodiimide. The relationship between the content of amino groups and the use of ethylenediamine was obtained by TNBS assay. Then Schiff's base was formed between the aldehyde groups in the oxidized alginate and the amino groups in the aminated gelatin, which resulted in covalent cross-linking and gel formation. Material properties and biocompatibility of the hydrogels were characterized.Heparin, as a kind of glycosaminoglycan, is component of extracelluar matrix and is able to make distinctive combination with growth factors such as bFGF. In this work, a little of modified heparin was introduced into chemically cross-linked alginate hydrogels through the reaction between modified heparin and oxidized alginate. Control release of growth factors is thus expected after they are embedded in gels by combining with modified heparin beforehand, which may promote the growth and proliferation of cells in tissue engineering. FITC-BSA was employed as the model protein in this work to investigate the release properties of the hydrogels.Polymer scaffolds made from oxidized alginate and gelatin were prepared through the covalently cross-linking hydrogel forming mechanism. Results reveals that the microstructures and properties of the scaffolds could be modulated by adjusting the mass contents, pre-freezing temperatures, and the addition of calcium ion. Importantly, treatment after preparation would not be needed and the scaffolds with relatively good biocompatibility are endowed with potential applications in tissue engineering.