Xinyi Shi, Taihua Wang, Jianjun Qiao
This paper explores the fabrication of hydroxyapatite-capsaicin nanocomposite coatings on Mg-Ag alloy by the electrophoretic deposition (EPD) method at different deposition times and voltages. The microstructure, surface chemistry, hardness, corrosion behavior, and cell proliferation of the deposited layers at different deposition times and voltages were examined. Based on microstructural observations, the deposited layers became denser at higher deposition time and voltage. In addition, the hydroxyapatite-capsaicin nanocomposite became thicker at higher EPD voltage. FTIR and XPS analyses confirmed the successful incorporation of capsaicin into the HAP coating with partial retention of CAP-derived surface functionalities after annealing. Also, the hardness of the coated layer increased with voltage and time. However, EPD voltage was more effective in increasing the hardness. The maximum hardness of 141 HV was obtained at a deposition voltage of 160 V. The hardness profile of the deposited composite showed greater fluctuations with increasing deposition voltage. Electrochemical polarization tests demonstrated that corrosion resistance improved with increasing deposition voltage and time. Furthermore, cell growth was improved at higher EPD time and voltage. MTT assay results confirmed the enhanced cytocompatibility of the HAP-CAP coatings. Also, the Mg2+ ion release rate and pH variation decreased as the deposited layer became thicker and denser. The minimum Mg2+ ion release rate of 5.2 ppm h-1 was obtained at a deposition voltage of 160 V. Compared with conventional HAP coatings, incorporation of capsaicin enhanced the biological performance while preserving the structural stability of hydroxyapatite, which thus provides a promising strategy for the development of multifunctional biodegradable implant coatings.