Electrolytic deposition of lithium into calcium phosphate coatings

Objectives: Lithium ions stimulate the Wnt signaling pathway and the authors previously demonstrated that lithium enhances the proliferation of tissue cultured human mesenchymal stem cells. The aim of this study was to prepare and characterize a calcium phosphate/lithium coating by means of electrolytic deposition. It was hypothesized that the hybrid coatings would enhance the proliferation of MG63 osteoblast-like cells in vitro. Methods: Calcium phosphate coatings were electrolytically deposited in electrolytes containing 0, 0.5 and 5 g/L lithium chloride, respectively. They were characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The coating thickness, lithium content and release profile were also measured. The cell attachment and cell-doubling index of MG63 cells on these coatings were determined through a Cell Counting Kit-8. Results: Lithium inhibited calcium phosphate deposition in a dose-dependent manner. Both crystallinity and thickness of the coatings were reduced with increasing lithium concentration in the electrolyte. The incorporation of lithium was 2.2 and 5.5 μg/mg, respectively. The hybrid coatings demonstrated a burst lithium release within half an hour upon immersion into simulated physiological solution. Both attachment and early proliferation of MG63 cells on these hybrid coatings were enhanced. Significance: These results suggest that lithium can be effectively incorporated into calcium phosphate coatings. The incorporation of lithium interferes with calcium phosphate deposition; however, it enhances the biocompatibility of the coatings.