Abstract
Antibacterial cerium-doped hydroxyapatite (Ce-HAp) layers have been researched sparingly in recent years. The Ce-HAp powder, Ca10−xCex(PO4)6(OH)2 with xCe = 0.05, was obtained by an adapted chemical co-precipitation method at room temperature. The target was prepared using the Ce-HAp (xCe = 0.05) powder sintered in air at 600 °C. The coatings on the Ti substrate were generated in plasma using a radio frequency (RF) magnetron sputtering discharge in an Ar gas flow in a single run. To collect the most complete information regarding the antimicrobial activity of cerium-doped hydroxyapatite with xCe = 0.05, (5Ce-HAp), antimicrobial studies were carried out both on the final suspensions and on the coated surfaces. The target was tested using ultrasound measurement, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), glow-discharge optical emission spectroscopy (GDOES), and X-ray photoelectron spectroscopy (XPS). The present study exhibited for the first time results of the homogeneous coatings of hydroxyapatite doped with cerium using a radio frequency magnetron sputtering technique. In addition, this study highlighted for the first time the stability of the cerium-doped hydroxyapatite gels used in the creation of the coating. Ultrasound measurements on the concentrated suspension of 5Ce-HAp showed a good stability compared to double distilled, water which was chosen as the reference fluid. Particles with spherical shape were observed by both TEM and SEM analysis. The broadening of the IR bands in the IR spectrum of the 5Ce-HAp film in comparison with the IR spectrum of the precursor target indicate the formation of interlinked bonds into the layer bulk. XPS analysis revealed that the mixture of Ce3+ and Ce4+ ions in the hydroxyapatite (HAp) structure of the coatings could be due to the deposition process. The surface of 5Ce-HAp coatings was homogenous with particles having a spherical shape. A uniform distribution of all the constituent elements on the surface the 5Ce-HAp layer was revealed. The antimicrobial assays proved that both 5Ce-HAp suspensions and 5Ce-HAp coatings effectively inhibited the development of colony forming units (CFU) for all the tested microbial strains. Moreover, the antimicrobial assays emphasized that the 5Ce-HAp suspensions had a biocide effect against Escherichia coli (E. coli) and Candida albicans (C. albicans) microbial strains after 72 h of incubation.
Highlights
The most pressing problem from the health system is the emergence of multi-drug resistant microorganisms and the appearance of infections with these microorganisms [1,2,3,4].The alarming and rapid increase in the appearance of drug-resistant microbial-related infections have forced researchers to focus their attention to the development of unconventional alternatives for treating microbial infections [1,2,3]
In our previous study on cerium-doped hydroxyapatite nanoparticles synthesized by the co-precipitation method, we showed that cerium-doped hydroxyapatite may be prepared by the co-precipitation method at low temperatures, and Ce ions can enter into the HAp structure by substitution with calcium ions [35,36]
For the most complete information regarding the antimicrobial activity of cerium-doped hydroxyapatite with xCe = 0.05 (5Ce-HAp), antimicrobial studies were carried out on the final suspensions, on the pressed powder, and on the coated surfaces
Summary
The most pressing problem from the health system is the emergence of multi-drug resistant microorganisms and the appearance of infections with these microorganisms [1,2,3,4]. The alarming and rapid increase in the appearance of drug-resistant microbial-related infections have forced researchers to focus their attention to the development of unconventional alternatives for treating microbial infections [1,2,3]. One of the most studied materials for its outstanding antimicrobial properties is synthetic hydroxyapatite (HAp), having the chemical formula Ca10 (PO4 ) (OH) , which is considered an essential inorganic material, very similar with human hard tissues that can be found in dentine, enamel, and bones [7,8]
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