Silk scaffolds with gradient pore structure and improved cell infiltration performance.

Electrospun scaffold with three-dimensional (3D) geometry and appropriate pore structure is an important challenge to mimic natural tissues such as skin, cartilage, etc. In this work, 3D silk fibroin (SF) electrospun scaffolds with gradient pore size were prepared by combining multi-step electrospinning with low temperature (LTE) collecting. The LTE electrospun scaffolds achieved 3D macro-structure with large pore size. The effects of relative humidity (RH), collecting temperature on the morphology of the scaffolds were investigated by scanning electron microscopy and computed tomography. The pore size of the scaffolds was tailored by adjusting SF concentration, electric field, flow rate, needle gauge and collector temperature during electrospinning at 50% RH. L929 cell infiltration results of the scaffolds showed that conventional electrospun scaffolds with small pore size (average diameter 5.9 ± 1.4 μm) restrained cell proliferation and infiltration. On the contrary, LTE electrospun scaffolds with medium pore size (average diameter 11.6 ± 1.4 μm) improved cell proliferation obviously. Large pore size scaffolds (average diameter 37.2 ± 12.9 μm) was beneficial to cell infiltration depth in the thickness direction of the scaffolds. The scaffolds, which were integrated with layers of small, medium and large pores, are promising in the repair of tissue with gradient pore structures.