RESULTS

1

Phase 1: Optimization of the c-PLD deposited structures from the compositional, morphological and structural point of view

Thin films of calcium phosphates (hydroxyapatite, HA and β-tri-Calcium phosphate, β-TCP) doped with Se and Sr (HA/β-TCP:SeSr) have been synthesized by combinatorial pulsed laser deposition (c-PLD) using a excimer laser source KrF* (λ = 248 nm, τFWHM ≤ 25 ns). The surface morphology and growth mode of the c-PLD coatings were evaluated using scanning electron microscopy (SEM). Furthermore, the elemental composition and the chemical states of HA/β-TCP:SeSr coatings were determined by energy dispersive X-ray spectroscopy (EDXS) and X-ray photoelectron spectroscopy (XPS) which evidenced the existence of a Se and Sr compositional gradient. The integrity of the chemical functions and stoichiometry of the as-deposited coatings were evaluated by Fourier transform infrared spectroscopy (FTIR). The as-obtained results allow thus the subsequent phases of the project to be carried out and the effective achievement of intended objectives.
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Phase 2: Evaluation of the c-PLD thin films composition with respect to structural and solubility properties, corrosion resistance and biological performances

The c-PLD synthesis of new coatings from composite biomaterials based on biphasic calcium phosphates (HA and β-TCP) and doped with Se and Sr (HA/β-TCP:SeSr) which combine both the Se property to induce the cancerous cell apoptosis and the Sr to accelerate the osseointegration was reported. HA/β-TCP:Se/Sr thin films were fabricated using a excimer laser source KrF* (λ = 248 nm, τFWHM ≤ 25 ns). Targets and deposited nanostructures were characterized from the structural point of view by X-ray diffraction (XRD), and the latter morphologically by SEM, following the solubility tests. The films were subsequently evaluated in vitro by electrochemistry, solubility and cytocompatibility tests. The presence of β-TCP (known for its increased solubility) in the composition of c-PLD coatings, in conjunction with the variation of Se and Sr content, determine the achievement of different rates of release of active Se and Sr ions in the cellular environment and thus a different biological response.
HA/β-TCP:SeSr films turned out to be biocompatible for mesenchymal stem cells (h-MSC) due to their lack of cytotoxicity, making them promising for rapid implant integration. On the other hand, the behavior of human osteosarcoma cells (SaOS2) tested on the surfaces of c-PLD coatings indicated a decrease in cell viability compared to the material used as a control. Moreover, the presence of osteoprogenitor cells in the co-cultures caused an intensification of the pro-inflammatory cytokine IL-1β signal with the increase in Sr content (S3-S5).

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Phase 3: Validation of the optimized HA/β-TCP:Se/Sr coatings

Simple and doped HA/β-TCP thin films were fabricated by PLD using a KrF excimer laser source KrF* (λ = 248 nm, τFWHM ≤ 25 ns). Optimized PLD conditions were selected for coatings with rough morphologies, suitable for good cell adhesion and good replication of the source target composition.
The surface morphology and topography of PLD coatings was evaluated by SEM and AFM which highlighted the presence of fine nanometric grains, uniformly distributed and in patches organized in the form of particles (typical to HA deposited by PLD). The crystalline structure of films was evaluated by XRD, which emphasized the amorphous nature of the deposited material. The Ca/P molar ratio and the presence of Se and Sr ions were determined using EDS, while the chemical state of the component elements of the HA/β-TCP, HA/β-TCP:Se2Sr8 and HA/β-TCP:Se3Sr7 coatings was analyzed by XPS.
Solubility/bioactivity tests were performed by immersing the samples in DMEM culture medium for up to 28 days and revealed a good resistance to degradation and even the biomineralization capacity of the films. The coatings cytotoxicity was evaluated using three different cell lines: SaOS2, h-MSC and L929. The antimicrobial efficiency of HA/β-TCP based coatings was evaluated against E. coli strain.

Contact

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Str. Atomistilor 409, PO BOX MG-36, Magurele, ILFOV
RO-077125
ROMANIA                         

Email

gianina.popescu@inflpr.ro   

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