Hydroxyapatite coatings electrodeposited at near-physiological conditions

• Electrodeposition of a uniform coating on Ti–6Al–4V at 37 °C, pH=7.4.
• The coating is comprised of hydroxyapatite and octacalcium phosphate.
• The coating is similar to that formed by chemical deposition.
• The coating is more biomimetic than coatings currently used in orthopedics.
• The coating may be loaded with biological matter and/or antibiotics.

Calcium phosphate (CaP) ceramics are used in orthopedics and dentistry due to their excellent biocompatibility and osseointegration. Plasma spraying has been the most common process for application of hydroxyapatite (HAp) coatings. Although electrodeposition (ED) has many potential advantages, very little has been published on ED of HAp at near-physiological conditions. Here we report the ED of uniform HAp–OCP (octacalcium phosphate) coatings on Ti–6Al–4V substrate at 37 °C, pH=7.4, following surface pretreatment. Thermodynamic calculations were first used to predict which CaP phases may precipitate from solution under different experimental conditions. Microscopic observation revealed that the coating formed in this study is similar to that formed by chemical deposition, and better mimics the biological apatites in terms of structure and phase content than coatings currently used in orthopedics.