IN VIVO SAFETY AND EFFICACY TESTING OF A THERMALLY TRIGGERED INJECTABLE HYDROGEL SCAFFOLD FOR BONE REGENERATION AND AUGMENTATION

Background We have reported an injectable L-pNIPAM-co-DMAc hydrogel with hydroxyaptite nanoparticles (HAPna) which promotes mesenchymal stem cell (MSC) differentiation to bone cells without the need for growth factors. This hydrogel could potentially be used as an osteogenic and osteoconductive bone filler of spinal cages to improve vertebral body fusion. Here we investigated the biocompatibility and efficacy of the hydrogel in vivo using a proof of concept femur defect model. Methods Rat sub-cut analysis was performed to investigate safety in vivo. A rat femur defect model was performed to evaluate efficacy. Four groups were investigated: sham operated controls; acellular L-pNIPAM-co-DMAc hydrogel; acellular L-pNIPAM-co-DMAc hydrogel with HAPna; L-pNIPAM-co-DMAc hydrogel with rat MSCs and HAPna. Following 4 weeks, defect site and organs were histologically examined to determine integration, repair and inflammatory response, as well as Micro-CT to assess mineralisation. Results No inflammatory reactions o...