| Soft materials as well as the liquid crystalline state are widely existed in nature by mostorganisms, from the view of bionic point, the acquisition of soft material characteristics withcertain mechanical properties and the materials with properties of flowability and directionalorder as well as the study of interaction with cells through the combination of these two commonforms of organisms is of great significant for soft tissue engineering and stem cell therapy.Chitosan physical hydrogels were obtained by replacing1,2-propanediol with alkalinesolution, and double physical crosslinked hydrogels were obtained by supplementingtripolyphosphate(TPP) ionic crosslinking. The states of chitosan and water in hydrogels and theeffect of the concentration of alkali and the pretreatment with tripolyphosphate(TPP) on themicrostructure and the mechanical properties of hydrogels were investigated byXRD/POM/SEM/DSC and mechanical analysis. The result of XRD and POM showed thatchitosan in hydrogel presented amorphous state which including some anisotropic orderedstructure. The DSC results showed that the freezing water and the non-freezing water could beco-existed in the hydrogel and their percentage lied on alkali treatment, and the ratio of the bothwould be no longer affected by alkali concentration after TPP ionic crosslinking. The SEMimages showed that the microstructure of hydrogels displayed a three-dimensional network withrich-nanofibers. The pretreatment of ionic crosslinking had effects on the internal structure of thehydrogels. The unconfined compressive test and the dynamic mechanical analysis showed thatwhen the concentration of NaOH was lower than4mol/L, the mechanical properties ofhydrogels without ionic-crosslinked increased with the increasing of the NaOH concentrationand reached the best at4mol/L. The mechanical properties of the hydrogels crosslinked with TPPfirstly then treated by NaOH got decreased, which showed the best at2mol/L. The two kinds ofphysical crosslinking used in this study was competitive in the formation of hydrogels.Macromolecular biological liquid crystal was synthesized for chitosan/luiquid compositehydrogel. PPC, BPC and OPC were synthesized through the esterification reaction betweenpropionyl chloride/butyryl chloride/caprylyl chloride and HPC. The structure and properties ofthe products were detected using FTIR,1H-NMR, POM and XRD. The result showed that theintroduction of flexible acyl side-chain would make products contained both rigid mesogenic unit and flexible chain fragment to produce thermotropic cholesteric liquid crystallinemacromolecules in room temperature. The length of acyl side-chain had great effects on theorder and flowability of hydroxypropyl cellulose ester liquid crystal.The liquid crystal was introduced into chitosan solution by using nebulization, and thechitiosan/liquid crystal composite hydrogel was prepared through displacement of alkalinesolution. SEM and AFM observation demonstrated that composite hyrogel showed an island-likesurface structure and independent disperse homogeneous liquid crystal domain was formed inhydrogel. The density of liquid crystal domain increased as the increase of liquid crystal content,and then linked with each others. The size of liquid crystal domain was normally4-10um.The cell compatibility of the chitosan hydrogel and complex hydrogel were investigated byusing3T3cell and New Zealand rabbits chondrocyte as cell models. The result showed that goodadhesion and proliferation of3T3cells was observed on the surfaces of pure hydrogels andcomplex hydrogels with different type and proportion of liquid crystals. The cells have hadentered the logarithmic growth phase of cells after contacting the materials for3days. The cellsshowed good status and good activity and secreted a large amount of extracellular matrix. Theadhesion and proliferation of the cells and the secretion of extracellular matrix on complexhydrogels were better than that on pure LC film and chitosan hydrogel. Synergistic effecthappened between chitosan hydrogel and liquid crystal can promote the growth and proliferationof the cells. Of all the hydrogels, CS/OPC composite hydrogel showed optimal biocompatibility.Chondrocyte on this type of hydrogel could maintain the round or oval shape, and presentedmitotic spindle. Composite hydrogel had a excellent biocompatibility in whole.The physical cross-linked and double physical cross-linked chitosan hydrogel weresuccessfully constructed and then the chitosan/liquid crystal composite hydrogel were obtained.The composite hydrogel had good biocompatibility and would have potential application in softtissue engineering field. |
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