Cobalt doped biphasic calcium phosphate ceramics for bone regeneration applications: Assessment of in vitro antibacterial activity, biocompatibility, osteogenic and angiogenic properties

The influence of cobalt ion dopant on the in vitro biological properties of biphasic calcium phosphate (BCP) was investigated with an aim to develop an effective scaffold for bone tissue engineering applications. Cost-efficient wet chemical method was used to prepare in-situ cobalt doped BCP and XRD, FTIR, Raman spectroscopy, FESEM analyses were performed for detailed physico-chemical characterizations. It has been observed that pure BCP is comprised of 98 vol% of beta-TCP and 2 vol% of beta-CPP, whereas incorporation of cobalt leads to 58.8 vol% of beta-TCP and 41.4 vol% of beta-CPP. Moreover, Co-doped BCP exhibited relatively larger particle size when compared to pure BCP as observed in FESEM analysis. Furthermore, cobalt doped BCP showed enhanced antibacterial activity and the zone of inhibition was prominent compared to pure BCP. The release of cobalt ions from doped BCP was analyzed by Inductively Coupled Plasma (ICP) mass spectrometry at different time points (up to 28 days) and sustained release of cobalt ions warrants its benefits in native tissue regeneration. Both pure and Co-doped BCP showed excellent hemocompatibility as the percentage of hemolysis was below 2 %. Cell viability was found to be marginally higher with incorporation of trace amount of cobalt in BCP. Notably, in vitro angiogenic activity assessment results confirmed that VEGF-A and HIF-1 alpha gene expression was significantly enhanced in case of doped BCP compared to pure BCP, signifying that the cobalt doping considerably improved the expression of angiogenic factors. Over the study, results demonstrated that incorporation of cobalt as dopants can effectively improve the in vitro biological properties of biphasic calcium phosphate based bioceramics and might be considered as a new generation bone grafts in bone regeneration applications.