Mechanical & cell culture properties of elastin-like polypeptide, collagen, bioglass, and carbon nanosphere composites.

Collagen, the most commonly used extra-cellular matrix protein for tissue engineering applications, displays poor mechanical properties. Here, we report on the preparation and characterization of novel multi-component composite systems that incorporate a genetically engineered, biocompatible polymer (elastin-like polypeptide, ELP), biodegradable ceramic (45S5 bioglass), carbon nanosphere chains (CNSC), and minimal amount (~25% w/w) of collagen. We hypothesized that incorporation of bioglass and CNSC would improve mechanical properties of the composites. Our results showed that the tensile strength and elastic modulus nearly doubled after addition of the bioglass and CNSC compared to the control ELP-collagen hydrogels. Further, MC3T3-E1 pre-osteoblasts were cultured within the composite hydrogels and a thorough biochemical and morphological characterization was performed. Live/dead assay confirmed high cell viability (>95%) for all hydrogels by day 21 of culture. Alkaline phosphatase (ALP) activity and osteocalcin (OCN) production assessed the pre-osteoblast differentiation. Normalized ALP activity was highest for the cells cultured within ELP-bioglass-collagen hydrogels, while normalized OCN production was equivalent for all hydrogels. Alizarin red staining confirmed the mineral deposition by the cells within all hydrogels. Thus, the multi-component composite hydrogels displayed improved mechanical and cell culture properties and may be suitable scaffold materials for bone tissue engineering.