Preparation of silk fibroin-chitosan scaffolds and their properties

Objective: To prepare the silk fibroin (SF)-chitosan (CS) scaffolds by adjusting the mass ratio between CS and SF, and test and compare the properties of the scaffolds at different mass ratios.

Methods: According to the mass ratios of 6:4 (group A), 6:8 (group B), and 6:16 (group C) between SF and CS, CS-SF scaffolds were prepared by freeze-drying method, respectively. The material properties, porosity, the dissolubility in hot water, the modulus elasticity, and the water absorption expansion rate were measured; the aperture size and shape of scaffolds were observed by scanning electron microscope (SEM). Density gradient centrifugation method was used to isolate the bone marrow mesenchymal stell cells (BMSCs) of 4-week-old male Sprague Dawley rats. The BMSCs at passage 3 were seeded onto 3 scaffolds respectively, and then the proliferation of cells on the scaffolds was detected by MTS method.

Results: The results of fourier transform infrared spectroscopy proved that with the increased content of CS, the absorption peak of random coil/alpha helix structure (1 654 cm(-1) and 1540 cm(-1)) constantly decreased, but the absorption peak of corresponding to beta-fold structure (1628 cm(-1) and 1516 cm(-1)) increased. The porosity was 87.36% +/- 2.15% in group A, 77.82% +/- 1.37% in group B, and 72.22% +/- 1.37% in group C; the porosity of group A was significantly higher than that of groups B and C (P < 0.05), and the porosity of group B was significantly higher than that of group C (P < 0.05). The dissolubility in hot water was 0 in groups A and B, and was 3.12% +/- 1.26% in group C. The scaffolds had good viscoelasticity in 3 groups; the modulus elasticity of 3 groups were consistent with the range of normal articular cartilage (4-15 kPa); no significant difference was found among 3 groups (F=5.523, P=0.054). The water absorption expansion rate was 1 528.52% +/- 194.63% in group A, 1 078.22% +/- 100.52% in group B, and 1320.05% +/- 179.97% in group C; the rate of group A was significantly higher than that of group B (P=0.05), but there was no significant difference between groups A and C and between groups B and C (P > 0.05). SEM results showed the aperture size of group A was between 50-250 microm, with good connectivity of pores; however, groups B and C had structure disturbance, with non-uniform aperture size and poor connectivity of pores. The growth curve results showed the number of living cells of group A was significantly higher than that of groups B and C at 1, 3, 5, and 7 days (P < 0.05); and there were significant differences between groups B and C at 3, 5, and 7 days (P < 0.05).

Conclusions: The CS-SF scaffold at a mass ratio of 6:4 is applicable for cartilage tissue engineering.