The Preparation And Characterization Of Gelatin/Alginate Composite Hydrogel Microsphere Scaffolds

Microsphere assembled scaffolds have attracted extensive research attention dueto their three-dimensional interconnected pore channels and adjustable performance.Poly(lactic acid-co-glycolic acid)(PLGA) is one of the most widely studiedmicrosphere material. However, PLGA microsphere scaffold has several problems,such as the acidic degradation products may be adverse to tissue growth, lack of cellrecognition sites due to the hydrophobic nature of PLGA, and toxic solvents residuein the scaffold preparation.Gelatin has excellent biocompatibility, biodegradability and abundant cellrecognition sites with low immunogenicity. Alginate also has good biocompatibility.Therefore, natural biopolymers, gelatin and alginate, were combined to construct thethree dimensional composite hydrogel microsphere scaffold.The main contents of the this dissertation are as follows:(1) Gelatin/alginate composite hydrogel microsphere preparationThe gelatin/alginate composite microspheres with rough surface mesh holes wereprepared by W/O emulsion-crosslinking method. The influence of preparationparameters such as water concentration, stirring speed, water oil ratio, dosage ofemulsifier, and emulsifying temperature on microspheres particle size and distributionhave been investigated. The target particle sizes yield ratio and the uniformity ofparticle size distribution are used as the dual indices for the optimization ofpreparation parameters. The orthogonal analysis reveals that emulsificationtemperature and emulsifier have almost the same effect on the microspheres particlesize and the particle size distribution.(2) Gelatin/alginate composite hydrogel microsphere scaffold constructionChemical crosslinking method was adopted to bond the hydrogel microspherespacked scaffold. Calcium chloride was used to crosslink the sodium alginate in themicrosphere, then genipin was used to crosslink the gelatin in the microsphere. Theoptimized crosslinking condition was obtained as follows:2%（w/v） genipin wasdissolved in the ethanol/water (30v/v%) solution, the mass ratio of cross-linked sodium alginate microspheres and genipin solution was1:2.8, crosslinkingtemperature and time were30oC and48h, and then air dried to maintain the scaffoldmorphology.(3) In vitro biological evaluation of the scaffoldPBS soaking test was used to study the biodegradability of the microspheresscaffold, and the results showed that it has good biodegradable property. The scaffoldstructure was stable and there was less than50%degradation after soaking for4weeks. In addition, pores gradually appeared on the microsphere surface with thesoaking time. Live/dead dying and CCK8tests were used to compare the cellcompatibility of the scaffold and the bulk hydrogel. Biological test results showed thatthe microsphere scaffold has better cell adhesion and proliferation than the bulkhydrogel. Simulated body fluid was used to test the in vitro activity of microspherescaffold, and the results showed that the scaffold surface is rapidly deposited withcalcium phosphate, which indicated that the microsphere scaffold may be potentiallyused in bone repair.