Hydrophobic Modification Of Agarose And Its Application In Tissue Engineering

Agarose is a natural biomaterial with abundant resource and biocompatibility, but the strong hydrophilic with a lot of hydroxyl groups and poor processing properties limits its application in biomedical engineering. So modifying agarose with more hydrophobic and easier processed is a key issue of constructing high porosity scaffolds, it has vital significance to broaden application of agarose in tissue engineering.Objective:In order to improve organic solubility for the further application of agarose in biomedical materials fields, agarose acetate was synthesized and then was to constitute tissue engineered scaffolds by electrospinning technique or solvent-leaching method. The main results and conclusions are described as follows.Methods:agarose acetate was prepared by acylation reaction; the substitution degree of agarose acetate was measured by chemical titration method; the molecular weight of agarose or agarose acetate was measured by viscosimetry; the structures of products were characterized with FT-IR and 13C-NMR and atomic force microscope (AFM). Cell adhesion experiment was performed to evaluate the biocompatibility of agarose acetate.To test the degradation properties and tissue compatibility of agarose acetate, the in vivo degradation behaviors of agarose acetate have been systematically investigated up to 22 weeks. The fibrous agarose acetate mats was prepared by electrospinning, Pararmeters of elecrtospinning process were optimized, especially solvent and concentration of solution. The fibrous mats were further characterized by swelling in distilled water. The agarose and agarose acetate scaffolds with 3D structure were fabricated via porogen leaching methods and the surface morphology was observed under SEM. In vivo study was conducted to assess the biocompatibility.Results:agarose with different substitution degrees was obtained by the certain reaction condition. Titration analysis proved that the substitution degree of agarose acetate was 2.67 and 3.75 respectively. Results of the viscosity method indicated that molecular weight of agarose acetate was about 200 thousand. Strutures of agarose and agarose acetate were proved with FT-IR,13C-NMR; Under AFM, it was found that the surface of agarose acetate membrane was able to form nodular structures, and with the increase of substitution degree, the average diameter of the nodules and the roughness rate tend to decrease. The result of cell adhesion showed that agarose acetate could improve cell proliferation. The in vivo degradation test showed that agarose degraded slowly and the inflammation was gradually diminished with time after agarose acetate of DS2.67 were implanted into subcutaneous of mice, and contrary results with agarose acetate of DS3.75. But the agarose acetate degraded slowly in any DS. The optimal condition for electrospinning reaction was as follows:acetone/DMAc=2:1, C(agarose acetate)=5%. Swelling test revealed that the fibers swelled appreciably for 24h but the physical integrity of the fibrous structure remained intact. SEM results showed the scaffolds have porous structure and favorable interporous connectivity, the porosities was 90%. The test of planting in the body indicated that agarose acetate had good biocompabibility.In conclusion, agarose acetate is easily processed into porous scaffold, and is hopful to be applied bone regeneration.