Collagen and elastin hydrolysates hydrogels cross-linked by dialdehyde starch and pectin

Abstract

Introduction. Collagen is the main structural protein of the various connective tissues in mammals. Collagen, in the form of elongated fibrils, is mostly found in fibrous tissues such as tendons, ligaments and skin. The amino acid composition of collagen is unusual for proteins, mostly because of its high hydroxyproline content. Elastin is a protein which can be mostly found in connective tissues. It is elastic and allows many tissues in the body to resume their shape after stretching or contracting. The chemical composition of elastin is also unusual for proteins, because of desmosine and isodesmosine content. Cross-linking process of the materials was designed to improve its properties, like mechanical strength, porosity and susceptibility to degradation. Aim of the study. The aim of our study was to investigate the influence of dialdehyde starch (DS) and pectin (P) on the properties of collagen/elastin hydrogels. DS is a polysaccharide derived by chemical modification from natural starch. It is prepared by periodate oxidation of starch. Pectin is a complex polysaccharide consisting mainly of esterified D-galacturonic acid resides in an alpha-(1-4) chain. Materials and methods. Collagen was obtained from rat tail tendons. Elastin hydrolysates were isolated from porcine aorta. 1% solution of collagen in 0.1 M acetic acid and 1% solution of elastin hydrolysates in water were prepared. Mixtures of the proteins were prepared in different volume ratios (Coll 100 %; Coll 95%-El 5%; Coll 90 %-El 10%) and were then cross-linked with DS and P. After that, a dialysis against deionised water was performed. Obtained gels were then analysed. Results and conclusions. The FTIR spectra show that the collagen and elastin structure was not changed by cross-linking with dialdehyde starch or pectin. The mechanical properties of the collagen and elastin material cross-linked by DS were improved, while the use of pectin causes deterioration of these properties. The lyophilized gels exhibit porous structure. The various size is observed. The in vitro study demonstrates that the materials are attractive for cells. The addition of dialdehyde starch and pectin causes formation of cross-linking bonds in the collagen and elastin materials and the transparent, hydrogels are obtained. However, the gels containing DS are much stiffer than materials with P. The results show that DS is better cross-linking agent than P. Dialdehyde starch is a suitable cross-linking agent for protein materials for medicine and tissue engineering applications. Acknowledgments. The authors would like to thank the National Science Centre (NCN, Poland, Grant no: UMO-2011/03/D/ST8/04600) for providing financial support to this project.