Development of Cerium-Doped Hydroxyapatite Coatings with Antimicrobial Properties for Biomedical Applications

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.

Physico-Chemical Properties and In Vitro Antifungal Evaluation of Samarium Doped Hydroxyapatite Coatings

“…These results are in good agreement with previously reported studies regarding the lack of antimicrobial properties of hydroxyapatite [20,59,60]. Moreover, previous studies [15,[56][57][58][59][60][61][62][63][64] reported that the antifungal effect of samarium could be explained by the fact that samarium ions have the ability to attach to the cell membrane leading to changes of its permeability. Furthermore, samarium ions that are released from the composite matrix could disrupt the bacterial membrane integrity thus affecting a multitude of cellular processes such like adhesion, ion conductivity and cell signaling [61].…”

Chitosan–Hydroxyapatite Composite Layers Generated in Radio Frequency Magnetron Sputtering Discharge: From Plasma to Structural and Morphological Analysis of Layers

“…In this context, the adding of chitosan to hydroxyapatite (in the synthesis process), for its future use as a sputtering target in rf magnetron discharge, leads to different surface morphologies of HApCs coatings (see Figure 5 a,b) in comparison with those of HAps [ 10 , 12 ]. Thus, on the surface of HApCs layers, grain-like structures with spherical shapes and various sizes are formed that can be assigned to the coagulation of macromolecules of HApCs (produced in the magnetron plasma), on the substrate.…”

“…In our previous works, we showed that at low radio frequency (rf) working powers, in magnetron sputtering plasma discharges, bioceramic multicomponent coatings for biomedical applications can be synthetized [ 10 , 11 , 12 ]. In [ 10 ], we showed that in rf magnetron discharge at about 1.2 × 10 −2 mbarr and 50 W rf power, after 4 h deposition time, regular granular-like structures on the surface of calcium phosphate layers deposited on Ti substrates can be generated.…”

Investigation of Spin Coating Cerium-Doped Hydroxyapatite Thin Films with Antifungal Properties

“…Therefore, the obtaining of novel cerium-doped hydroxyapatite materials for the development of medical device coatings could contribute with important advances in the area of antimicrobial agents. In a previous study, we presented cerium-coated hydroxyapatite (x Ce = 0.05) coatings obtained by plasma by RF magnetron sputtering [24].…”