Preparation And Properties Of Bacterial Cellulose/Gelatin Porous Scaffolds

Extracellular matrix?ECM?, which is composed of mutual crisscross nanofibers with both microporous and nanofibrous three-dimensional network structure, is the main place for cell adhesion, growth and proliferation. Therefore, the key to design a tissue engineering scaffold as ECM substitute is to simulate both the structure and function of ECM. Gelatin?Gel? is an ideal material for tissue engineering scaffold due to its microporous structure, strong cell adhesion ability, biodegradability and unique sol-gel reversible transformation. However, the lack of nanofibers, poor mechanical properties and fast degradation rate of pure gelatin scaffold limit its application in tissue engineering.In this article, bacterial cellulose?BC?, which shares similar nanofibrous three-dimensional network structure to ECM, is selected as a reinforced material to gelatin scaffolds in order to achieve its optimum combination with microporous gelatin scaffolds and fabricate a more ideal scaffold for tissue engineering. The detailed works are listed as follows:?1? The vacuum freeze drying technology was used to prepare gelatin three-dimensional porous scaffolds. The influence of solution concentration on the pore structure of gelatin scaffolds was studied. SEM results showed that the pore diameter of scaffolds decreased with the increase of the concentration of gelatin solutions. With the concentration of 1 wt%, the gelatin scaffold possessed a regular morphology and interconnected pores, the average diameter and porosity of which was 229±25 ?m and 83.02± 4.7 %, respectively. This concentration was selected for further study.?2? Bacterial cellulose/gelatin porous scaffolds were prepared by fiber homogenization method. The experimental results showed that the composite scaffolds had both the microporous structure and nanofibrous three-dimensional network, which is similar to ECM. The average pore diameter of Gel:BC?6:4?, Gel:BC?5:5? and Gel:BC?4:6? was 111±24 ?m,100 ± 9 ?m and 84 ± 15 ?m, respectively, which indicated that with the increase of BC nanofiber contents, the pore diameter of composite scaffolds decreased. The compressive modulus of Gel:BC?4:6? was 1.48±0.23 MPa, which was 4.5 times of gelatin scaffold?0.33±0.07 MPa?. The addition of BC significantly improved the mechanical properties of gelatin scaffolds. In the degradation experiments, the mass loss of the composite scaffolds in 56 days?8 weeks? was around 30 % and compared to the gelatin scaffold?68.9±6.2 %?, they maintained the structure stability for a long time. It indicated that we can adjust the mechanical properties and degradation rate of scaffolds by changing the BC nanofiber contents in the composites according to specific requirements of different organs and tissues. Wall roughness of the scaffolds was also improved due to the existence of BC nanofibers. BC/Gel composite scaffolds had better biological performance and were more conductive for cell adhension, proliferation and growth.?3? Two methods, H₂SO₄ hydrolysis and TEMPO catalytic oxidation, were used to modify BC. And then modified BC/Gel composite scaffolds?BCNW/Gel and TOBC/Gel? were prepared. The results showed that this two methods reduced the size of BC in nanometer scale and further improved the dispersion of BC nanofibers in the composites. Both BCNW/Gel and TOBC/Gel composite scaffolds had the microporous and nanofibrous three-dimensional network structure, which is similar to BC/Gel scaffold. What's more, their pore regularity had been improved and the pore diameters also got increased. The average diameters of BCNW/Gel and TOBC/Gel scaffolds were 126±23 ?m and 146 ± 35 ?m, respectively. In addition, this two kinds of modification methods increased the compressive modulus and degradation rate of the composite scaffolds. The TEMPO catalytic oxidation method introduced more hydrophilic carboxyl groups to BC nanofibers, which can further accelerate the degradation of the composite scaffold and improve the degradation problem of BC in vivo. ADSCs cells sticked closely on TOBC/Gel scaffold, which indicated that scaffold had better biological activity and TOBC/Gel scaffold can be further applied in degradable tissue engineering scaffolds.