INTRODUCTION: Bacterial antibiotic resistance increases every year, creating an urgent need to develop new antibacterial materials. Gallium has been studied since the 1970s as an effective treatment for bone diseases and has recently shown antibacterial activity against different bacterial strains. Therefore, gallium doped hydroxyapatite (GaHAp) could be used as an antibacterial agent. The aim of the study was to investigate the effect of gallium on hydroxyapatite properties and P. aeruginosa growth.
METHODS: GaHAp was synthesized with a wet chemical precipitation method with a concentration of gallium 2wt%, 4wt%, 6.3wt% and 8wt%. CaO, H3PO4 and Ga(NO3)3*xH2O were used as raw materials. Synthesis was performed at 45 °C and final pH was 6.95±0.05. GaHAp was characterised with X-ray Diffraction analysis (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Specific Surface Area (SSA) was measured with N2 adsorption system BET method. Ion release in Dulbecco’s Modified Eagle Medium (DMEM) was measured for 18 days by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). P. aeruginosa growth was conducted in Tryptic soya broth (TSB) with GaHAp concentrations of 1, 2 and 4 mg/mL (dry sample). The growth curves were obtained by monitoring the absorbance (optical density) at 600 nm (OD600) for 18 hours and subtracting starting OD600-t=0 from all measurements.
RESULTS: The obtained GaHAp showed characteristic apatite peaks on XRD with decreased crystallinity. Additional gallium compound phases were not observed. The obtained GaHAp compared to HAp has a higher specific surface area, indicating a decrease in particle size. Ga3+ ions were constantly released over 18 days with a release range of ~ 40%. The antibacterial test showed that 4 mg/mL of GaHAp suspension induced a total inhibition of P. aeruginosa.
CONCLUSIONS: Gallium ions inhibit hydroxyapatite crystal formation. GaHAp allows a sustained release kinetic of Ga3+ ions. Also, GaHAp has the potential of P. aeruginosa bacteria growth inhibition.
ACKNOWLEDGEMENTS: This research is funded by the EuroNanoMed III project “NANO delivery system for one-shot regenerative therapy of peri-implantitis” (ImlpantNano).
Authors acknowledge financial support from the European Union’s Horizon 2020 research and innovation programme under the grant agreement No 857287.