Non-mulberry silk fibroin grafted PCL nanofibrous scaffold: Promising ECM for bone tissue engineering

A comparative study of nanofibrous scaffolds with inclusion of nonmulberry silk protein fibroin is presented for application in bone tissue engineering. Introduction of silk fibroin into the scaffolds is carried out in two ways: by electrospinning blend of poly(epsilon-caprolactone) (PCL) and by grafting fibroin on aminolyzed electrospun nanofibrous PCL. Verification of aminolysis was provided by confocal laser microscopy of rhodamine B isothiocyanate tagged substrates. Absorbance spectroscopy of the products of the reaction between NH2 groups and ninhydrin was used for quantification of aminolysis. Presence of nitrogen on the substrates was established using energy dispersive X-ray while scanning electron microscopy was used to substantiate their nanofibrous morphology. Evaluation of ATR-FTIR results showed that secondary structure of fibroin was preserved in the respective substrates. Presence of fibroin improves hydrophilicity, measured by dynamic contact angle, and surface roughness, topography viewed by atomic force microscopy. These characteristics support cell growth and proliferation. The mechanical strength of the scaffolds is enhanced due to presence of fibroin. Different biophysical characterizations indicate better hydrophilicity, higher nitrogen content, and higher surface roughness of the fibroin grafted scaffolds. Both fibroin-grafted and fibroin-blended scaffolds successfully support activity and viability of human osteoblast like cells. Cell cycle analysis, alkaline phosphatase assay and Alizarin red S staining are used to substantiate cell cycle pattern, proliferation and resultant neo-matrix generation on the scaffolds respectively. The results show that fibroin grafted matrices are better at supporting cell adhesion, growth, and proliferation. The findings demonstrate advantages of fibroin blended and grafted matrices for use in bone tissue engineering applications. (C) 2015 Elsevier Ltd. All rights reserved.