Cosme Rodríguez-Valencia

Novel selenium‐doped hydroxyapatite coatings for biomedical applications

Nowadays there is a short-term need of investigating in orthopedic implants with a greater functionality, including an improved osseointegration and also antibacterial properties. The coating of metallic implants with hydroxyapatite (HA) remains to be the main proposal, but superior quality HA coatings with compositions closer to natural bone apatites, including carbonates, trace elements are required. Selenium is an essential nutrient in biological tissues and, at the same time, it also presents antibacterial properties. A pioneering study on the fabrication of selenium-doped carbonated hydroxyapatite (iHA:Se) coatings by Pulsed Laser Deposition (PLD) is presented. Different proportions of selenium were incorporated to obtain the iHA:Se coatings. Their physicochemical characterization, performed by SEM/EDS, FTIR, FT-Raman, Interferometric Profilometry and XPS, revealed typical columnar growth of HA in globular aggregates and the efficient incorporation of selenium into the HA coatings by the, most probably, substitution of SeO(3)(2-) groups in the CO(3)(2-) sites. Biological evaluation illustrated the absence of cytotoxicity when an amount of 0.6 at.% of Se was added to the iHA:Se coatings and excellent proliferation of the MC3T3-E1 preosteoblasts. Antibacterial properties were also proved with the inhibition of P. aeruginosa and S. aureus from establishing bacterial biofilms.

In vitro response of pre-osteoblastic cells to laser microgrooved PEEK

Polyetheretherketone (PEEK) is currently being used in implants as an alternative to titanium, due to its mechanical properties, cytocompatibility and inertness. Several studies have demonstrated that certain patterning on the implants promotes the oriented cell growth of osteoblasts, favouring the formation of bone tissue. This patterning improves the implants osteointegration in the bone and its mechanical stability. Therefore, the objective of this work is to micro-structure PEEK by laser radiation and to carry out an exhaustive study of the orientation of pre-osteoblast cells that grow on this material. Parallel microgrooves were obtained using an ArF excimer laser coupled with a mask projection unit with distances of 25, 50, 75 and 100 µm between grooves. The cell growth on these PEEK surfaces was studied, in order to compare the effect of different distances between grooves on the biological response of MC3T3-E1 pre-osteoblastic cells. Preferential cell orientation was observed for all studied distances, which was more pronounced in the 25 and 50 µm ones.

Human mesenchymal stem cells response to multi-doped silicon-strontium calcium phosphate coatings

The search for apatitic calcium phosphate coatings to improve implants osteointegration is, nowadays, preferentially focused in the obtaining of compositions closer to that of the inorganic phase of bone. Silicon and strontium are both present in trace concentrations in natural bone and have been demonstrated, by separate, to significantly improve osteoblastic response on calcium phosphate bioceramics. This work aims the controlled and simultaneous multi-doping of carbonated calcium phosphate coatings with both elements, Si and Sr, by pulsed laser deposition technique and the biological response of human mesenchymal stem cells to them. A complete physicochemical characterization has been also performed to analyze the coatings and significant positive effect was obtained at the osteogenic differentiation of cells, confirming the enormous potential of this multi-doping coating approach.

The improved biological response of shark tooth bioapatites in a comparative in vitro study with synthetic and bovine bone grafts.

Autologous bone is considered to be the gold standard for bone tissue regeneration, providing more highly efficient functional responses compared to synthetic materials, and avoiding the rejection risks of allogenic grafts. However, it presents limitations for certain types of surgery due to its high resorption levels and donor site morbidity. Different biphasic synthetic composites, based onnon-apatitic calcium phosphates enriched with apatitic phases-such as hydroxyapatite, and bioderived bone grafts of bovine and porcine origin-are proposed as lower resorption materials due to their higher crystalline structure. The present work proposes two new sources of bioapatites for bone filler applications obtained from the dentine and enameloid of shark teeth, respectively. These bioapatites each present a characteristic apatite-based composition and additional enrichments of specific trace elements, such as magnesium and fluorine, with proven roles in bone metabolism. Their processing and physicochemical characterization (SEM, FT-Raman and XRD) is presented, together with an in vitro evaluation of osteogenic activity compared to a commercial bovine mineralized matrix and synthetic HA/β TCP grafts. The results proved the globular morphology (0.5-1.5 μm) and porosity (~50 μm and ~0.5-1 μm) of shark dentine bioapatites with biphasic composition: apatitic (hydroxyapatite and apatite-(CaF)), non-apatitic (whitlockite), and an apatitic phase (fluorapatite), organized in oriented crystals in enameloid bioapatites. An evaluation of the pre-osteoblast MC3T3-E1 morphology revealed the colonization of pores in dentine bioapatites and an aligned cell growth in the oriented enameloid crystals. A higher proliferation (p  <  0.01) was detected at up to 21 d in both the shark bioapatites and synthetic biphasic graft with respect to the bovine mineralized matrix. Finally, the great potential of porous biphasic dentine bioapatites enriched with Mg and the aligned fluorapatite crystals of enameloid bioapatites in promoting greater osteogenic activity was confirmed with a significantly increased ALP synthesis (p  <  0.01) compared to the commercial grafts.

Nanonstructural Analysis of Hydroxyapatite Thin Films Using HRTEM/FIB Techniques

Hydroxyapatite, with a composition that resembles the mineral phase of bone, is often used as a coating of metallic prostheses to improve the adhesion and osseointegration of implants in different parts of the skeleton [1]. Among the available techniques that allow the deposition of this material on metallic substrates, Pulsed Laser Deposition (PLD) is capable of producing high quality and highly biocompatible coatings with excellent final attachment [2,3].