Preparation Of New Crosslinking Agents And Studying On Crosslinking Of Collagen With Them

Collagen is the most abundant protein and a primary component of extracellular matricesin mammalian connective tissue. It has better biodegradability and biocompatibility, weakantigenicity and low toxicity with broad applications. However, the weak mechanicalproperties, low thermal stability and high biodegradation rate of native collagen are notsufficient for its application in vivo or in vitro. These defects of collagen have seriouslyrestricted the development of good characteristics, and limited the application of collagenmaterials.The cross-linking of collagen is a way to improve the defects mentioned above. Howeverphysical methods for crosslinking does not result in an adequate degrees of crosslinkingalthough they avoid the potentially cytotoxicity. For chemical crosslinking, the most widelyused crosslinkers contain glutaraldehyde (GA), N-ethyl-N-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) or genipin. But these conditional crosslinkers alwaysexhibited evident defect, such as cytotoxicity, insufficient crosslinking effect or somechromogenic reaction. Therefore, it is necessary to develop an alternative crosslinker whichshowed excellent crosslinking efficiency as well as cytocompatibility.With the summary on all kinds of chemical method in the modification of collagenbefore, in this paper, two new crosslinking agents: β-Cyclodextrin aldehydes (β-CD-DA) andβ-Cyclodextrin polyrotaxane multiple aldehydes (β-CD-PR-4) have been prepared tomodify the collagen. And we have proved the synthesis of β-CD-DA through FTIR, Raman,1H NMR and alkali consumption method. We have preliminary proved the synthesis ofpoly(pseudo) rotaxanes by FTIR, TG and XRD. Though the elemental analysis,1H NMR andRaman spectra, we have determined the number of β-CD on the polyrotaxane and the C6-OHhave been replaced by the aldehyde group.Then these two types of crosslinking agent were used to crosslink with collagenrespectively, and the property of crosslinked collagen have been characterized subsequently.The maximum crosslinking degree are around81.4%and87.1%respectively, which was littlehigher than that of EDC and GA at the same concentration. β-CD-DA and β-CD-PR-4couldimprove the thermal stability of the collagen effectively and the thermal denaturation temperature have increased16.9and23.6℃,, respectively. The biodegradation rate have alsoreduced a lot and the relative enzymatic degradation were28.2%and23.1%respectively. Thecompression strength has been significantly improved and the maximum compressionmodulus of collagen were31.32and116.07KPa respectively. In addition, β-CD-DA andβ-CD-PR-4exhibit low cytotoxicity to L929cells and also have no chromogenic reaction. Ithas nearly no effect on cell growth when the concentration of these two types of crosslinkingagent is less than0.1mg/ml. The cytotoxicity of collagen which crosslinked with these twocrosslinker is almost same as the EDC modified collagen.At last, we have successfully prepared CD-capped polyrotaxanes multi-aldehydes withdifferent molecular weights by changing the reaction conditions and the weight ratio of rawmaterials. It can be used as the bio-crosslinker or other functional materials.