Injectable collagen/RGD systems for bone tissue engineering applications

Imbalance crosslink density and polymer concentration gradient is formed within the traditional alginate hydrogel using calcium chloride as a crosslinking agent in external gelation for instantaneously process. In this studying, type I collagen (Col I) blended calcium salt form of poly(γ-glutamic acid) (γCaPGA) was mixing with RGD-modified alginate with convenient gelation process and suitable for practical use. The hydrophilicity of the resulting hydrogels was evaluated through swelling tests, water retention capacity tests, and water vapor permeation tests. Mineralization was qualitatively evaluated by alizarin red dyeing at day 14, verifying the deposition of calcium. The in vitro osteogenic differentiation is monitored by determining the early and late osteocalcin (OCN) and osteopontin (OPN) markers with MG63 cells. Obtained results demonstrated that no extremely changes in mechanical properties. After 14 days of culture, hydrogels significantly stimulated OCN/OPN gene expressions and MG63 cell proliferation. Unusually, γCaPGA with RGD-modified alginate appeared better calcium deposition in 14 days than the other. However, addition of Col I can counterpoise RGD effect in blood coagulation and platelet adhesion made the hydrogel more flexibility and selectively in use. This studying provided that non-covalently crosslinked hydrogel by γCaPGA with alginate can be upgrading by RGD and Col I in water uptake capability, obviously effective for MG63 cells and are remarkably biocompatible and exhibited no cytotoxicity. Moreover, results also displayed the injectable process without complicated procedure, have high cost/performance ratio and have great potential for bone regeneration.