Impact of bone extracellular matrix mineral based nanoparticles on structure and stability of purified bone morphogenetic protein 2 (BMP-2).

Bone Morphogenetic Protein 2 (BMP-2) is an osteoinductive protein which has been overexpressed, refolded (Refolding is often the bottle-neck step in producing recombinant proteins from inclusion bodies of Escherichia coli, especially for dimer proteins) and purified by using Heparin affinity chromatography. Refolding of BMP-2 was based on gradient dialysis in presence of lower urea concentration. The main objective of the present work is to unravel the impact of the extracellular matrix components on BMP-2 conformation and stability. We tried to elucidate the interaction of the bone matrix minerals in the form of nanoparticles with the bone protein. We chose hydroxyapatite nanoparticles (HAp NPs) which is the most abundant bone mineral and the other being a trace mineral in our bones i.e., zinc oxide nanoparticles (ZnO NPs) as the potential nanoparticles for this study. The isolated protein is found to be a β- sheet type with melting temperature being approximately 70.66 °C. Upon interaction with HAp NPs and ZnO NPs, the absorbance and the fluorescence intensity indicates the interaction with the protein as there was an upsurge in both the cases. Circular Dichroism (CD) spectroscopy revealed that ZnO NPs are having more dominant secondary structure and thermal stabilizing effect as compared to HAp NPs.