Study of protein adsorption on octacalcium phosphate surfaces by molecular dynamics simulations

This study numerically studies absorption of human serum albumin (HSA) and basic protein lysozyme (LSZ) on crystallographic planes of octacalcium phosphate (OCP), an essential bioactive calcium phosphate. The molecular simulations include constructing atomic structure of OCP crystallographic planes and representative segments of HSA and LSZ with three different initiate orientations respect to OCP planes. The simulation reveals the dynamic process of the protein absorption. The absorption behavior of proteins is quantified by the interaction energy between proteins and OCP planes and the strain energy of proteins in absorption. The results show that absorption interaction energy of basic LSZ is higher than that of acidic HSA, which indicates that LSZ is more favorable to adsorb onto OCP surface than HSA. The interaction energies change with the OCP crystallographic planes, the trend of changes for both proteins are similar, that is OCP (001) > OCP (111) > OCP (110) > OCP (100), which is corrected with surface energy variation of crystallographic planes. The strain energy strongly depends on the orientations of the proteins before absorption, but weakly depends on crystallographic planes. The simulation results provide useful significant information for predicting/designing interface between bioceramic materials and organic tissues as well as for understanding the mechanism of the osteoinductivity at an atomic level.