Biomineralised interpenetrating network hydrogels for bone tissue engineering

Hydrogels are attractive for tissue engineering applications due to their incredible versatility, but their use is limited by inadequate mechanical strength and poor biocompatibility. In this study, to better mimic the mineral component and the mechanical strength of natural bone, two biocompatible materials, 2-hydroxyethyl agarose and poly(ethylene glycol) diacrylate, were combined with nanocrystalline hydroxyapatite (nHAp)-coated poly(lactic-co-glycolic acid) (PLGA) microspheres. A novel composite interpenetrating network (IPN) hydrogel scaffold was created to investigate its mechanical and osteoconductive performance for bone tissue engineering-related applications. The inclusion of nHAp-coated PLGA microspheres in an IPN hydrogel led to an increase in compressive modulus. In the absence of nHAp-coated microspheres, cell viability dropped to 59·1% at 3 weeks post-encapsulation. However, by incorporating nHAp-coated microspheres, cell viability improved to 80·6%. The capacity of composite IPN hydrogels to promote bone formation in cell culture was assessed. In the presence of mineralised microspheres, a composite IPN gel showed a significant increase in alkaline phosphatase activity and calcium (Ca) deposition following 3 weeks of incubation when compared with plain IPNs. This technology may be also applied to other cell-based applications where the improved mechanical integrity and osteoconductivity of cell-containing IPN hydrogels may be used to mimic bone tissue replacement.