Effect of decorating titanium with different self-assembled monolayers on the electrodeposition of calcium phosphate

Calcium phosphate (CaP) ceramics are used in orthopedics and dentistry due to their excellent osseointegration and biocompatibility. The electrodeposition of CaP on titanium alloy covered with self-assembled monolayers (SAMs) was studied with respect to the influence of chain length, end-group charge, and anchoring group. SAMs with end-groups similar to the functional groups on the side chains of collagen were selected. This study is divided to three parts: (1) studying the effects of SAMs on the titanium substrate, (2) studying the process of nucleation and growth of the CaP on specific SAMs, and (3) characterizing the CaP coatings using various surface analytical techniques. It was concluded that the nucleation and growth behavior of CaP changed in the presence of the SAMs. Different surface energies and crystallographic phases were associated with this change. Although the nucleation remained progressive, the growth changed from three-dimensional on bare surfaces to two-dimensional on SAMs-covered surfaces. Moreover, the deposition kinetics was slower on SAMs-covered surfaces, with phases containing a higher Ca/P ratio. Examination of the coating revealed that different SAMs lead to different surface morphologies of the coating while maintaining its degree of crystallinity. Yet, the phase content changes from hydroxyapatite and octacalcium phosphate (HAp + OCP) on the bare electrode to OCP only on the SAMs-covered electrode. These changes may have a substantial effect on the in vivo behavior by changing the coating's solubility and surface morphology, thus affecting cell adhesion, proliferation, and differentiation processes.