In vitro biocompatibility study of EDC/NHS cross-linked silk fibroin scaffold with olfactory ensheathing cells

In this paper, we investigated silk fibroin (SF) cross-linked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) and its biocompatibility with olfactory ensheathing cells (OECs). After cross-linked with different concentrations of EDC/NHS solutions, SF scaffolds were analyzed by different techniques such as scanning electron microscopy, Fourier transform infrared spectra, x-ray diffraction, tensile machine and water contact angle assay. As to their structures, we found 4.5% EDC/NHS cross-linked SF possessed a more significant increase of β-sheet and a decrease of α-helix than 1.5% group. These changes helped SF achieve excellent mechanical properties. While more remarkable improvement of hydrophilicity was seen in 1.5% EDC/NHS treated SF. Immunofluorescence, MTT, Annexin-V/PI and ELISA analysis were then conducted to determine the states and functions of OECs on the scaffolds. OECs on 4.5% EDC/NHS cross-linked SF seemed insufficient to spread, and the proliferation was limited on 4 and 6 days. Moreover, 4.5% EDC/NHS exerted adverse effects on cell survival and nerve growth factor (NGF) secretion at day 4, but not 1.5% EDC/NHS. Taken together, SF scaffolds showed improved physical and hydrophilic properties through cross-linking. 1.5% EDC/NHS cross-linked SF scaffolds showed significant advantages between mechanical property and the states and functions with OECs, which has the potential to be used for neural repairing.