E. Peón

Enhancing in vitro biocompatibility and corrosion protection of organic–inorganic hybrid sol–gel films with nanocrystalline hydroxyapatite

Application of novel organic-inorganic hybrid sol-gel coatings containing dispersed hydroxyapatite (HAp) particles improves the biocompatibility, normal human osteoblast (NHOst) response in terms of osteoblast viability and adhesion of a Ti6Al4V alloy routinely used in medical implants. The incorporation of HAp particles additionally results in more effective barrier proprieties and improved corrosion protection of the Ti6Al4V alloy through higher degree of cross-linking in the organopolysiloxane matrix and enhanced film thickness.

Application of New Statistical Approach to Study Drug Release from OCP Coating on Titanium Sheets

In this study, commercially pure titanium (Ti-cp) discs were used as substrates. Octacalcium phosphate (OCP) layers were deposited by immersion of Ti-cp discs up to 7 days into Solution for Bioactivity Evaluation (SBE) and characterized by SEM-EDS and XRD. The OCP coatings were doped with cephazolin or cefalexin by individual immersion in 300 ppm of each solution for 24 h at room temperature. The non-existence of mathematical models to explain drug release from these matrixes made the choosing of correct model, a complex process. Five non-linear mathematical methods were employed in order to identify the possible drug release mechanism using Akaike and Bayesian Information Criterion (AIC and BIC respectively) and its derivatives. The best model was Peppas & Sahlin that consider two stages in release: pure diffusion in first stage, and drug dissolution and migration through the porous matrix at second stage.

Biocompatibility and Corrosion Protection Behaviour of Hydroxyapatite Sol-Gel-Derived Coatings on Ti6Al4V Alloy

The aim of this work was to prepare hydroxyapatite coatings (HAp) by a sol-gel method on Ti6Al4V alloy and to study the bioactivity, biocompatibility and corrosion protection behaviour of these coatings in presence of simulated body fluids (SBFs). Thermogravimetric/Differential Thermal Analyses (TG/DTA) and X-ray Diffraction (XRD) have been applied to obtain information about the phase transformations, mass loss, identification of the phases developed, crystallite size and degree of crystallinity of the obtained HAp powders. Fourier Transformer Infrared Spectroscopy (FTIR) has been utilized for studying the functional groups of the prepared structures. The surface morphology of the resulting HAp coatings was studied by Scanning Electron Microscopy (SEM). The bioactivity was evaluated by soaking the HAp-coatings/Ti6Al4V system in Kokubo’s Simulated Body Fluid (SBF) applying Inductively Coupled Plasma (ICP) spectrometry. 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and Alamar blue cell viability assays were used to study the biocompatibility. Finally, the corrosion behaviour of HAp-coatings/Ti6Al4V system was researched by means of Electrochemical Impedance Spectroscopy (EIS). The obtained results showed that the prepared powders were nanocrystalline HAp with little deviations from that present in the human bone. All the prepared HAp coatings deposited on Ti6Al4V showed well-behaved biocompatibility, good bioactivity and corrosion protection properties.

Multifunctional sol-gel derived thin film based on nanocrystaline hydroxyapatite powders

The aim of this work was to prepare bioactive hydroxyapatite coatings by sol-gel method and to study the effect of thermal treatment temperature upon the bioactivity and corrosion protection of these coatings on Ti6Al4V alloy. The application of (DTA/TGA) and (XRD) has provided valuable information about the phase transformation, mass loss, identification of the phases developed, crystallite size and degree of crystallinity. (SEM/EDX) has been applied to study the surface morphology of coated samples before and after immersion in simulated body fluid (SBF) to detect the biomimetic precipitation of the bone- like apatite. The obtained results show that all the prepared samples are ceramic nanocrystalline with crystal structure and composition like hydroxyapatite, with little deviations from that present in the human bone. The bioactivity of the studied samples is found to be closely related to the thermal treatments applied. That is, the bioactivity decreases as the temperature of the thermal treatment increase. Coatings from such prepared hydroxyapatite sol have been accomplished by dip-coating technique on non-toxic Ti6Al4V alloy for biomedical applications. The corrosion behaviour of the resulting hydroxyapatite coatings in a (SBF) has been studied by electrochemical impedance spectroscopy (EIS). The hydroxyapatite coated Ti6Al4V alloy displayed excellent bioactivity when soaked in the (SBF) and acceptable corrosion protection behaviour.

Processing and Characterization of Ti-6Al-4V Samples Manufactured by Selective Laser Melting

Titanium and its alloys are well known as one of the best in-vitro and in-vivo bone replacement metallic biomaterial due to its excellent balance between biomechanical and biofunctional properties. The selective laser melting (SLM) method has a lower cost and shorter manufacturing time than the conventional routes used in the fabrication of titanium alloys. In this work, Ti6Al4V sheets were manufactured by SLM (LM samples) and subsequently annealed for stress relief at 750 oC for 10 min (LM-A samples). SEM, XRD and contact profilometry measurements were carried out to characterize the elemental composition, phases and surface morphology of different samples. A micro-tribo-mechanical evaluation was also performed by micro-indentation and scratch tests. The resulting surface was rough (Ra = 9.1 ± 0.5 μm) for all samples, showing protuberances with spherical morphology. For annealed samples, an oxide layer composed of rutile and Al2O3 was observed that increased the micro-hardness of the surface in LM-A sheets. However, after removing this oxide layer, the micro-hardness of the LM-A sheets was reduced when compared to LM samples as a result of the stress relief. A direct relationship between Vickers micro-hardness and scratch resistance was always observed. Therefore, LM-A sheets showed higher scratch resistance at low loads (oxidized surface effect) than LM samples, but lower resistance at high loads (bulk effect).

Sistemas de Liberación Controlada de Fármacos a Partir de Materiales para la Restauración del Tejido Óseo

Nowadays, two of the most important problems are the high incidence of bone infections and the inflammatory response of the human organism when an implant is used. For this reason, the inclusion of drugs in materials for bone restoration is an interesting and promising approach to solve this problem. On this paper, drug delivery systems from bone restoration materials making little modifications to classic materials such as calcium phosphate cements, PMMA acrylic cements and coating metals were prepared, characterized and evaluated. All the prepared matrixes showed no-interaction between main components of formulation allowing the composition to lead the behavior of drug profile. The modifications made to classic bone materials on hydrophilicity and porosity, two important characteristics, helped to improve the drug delivery capacity. The ending results of delivery moved between 40-95 % in different time ranges according to composition which allows different possible application of these materials.

Controlled Rate Thermal Analysis (CRTA) as New Method to Control the Specific Surface in Hydroxyapatite Thin Coatings

The control of the texture in synthetic hydroxyapatite ceramics had limited their appli‐ cation in the field of the materials for bone implantation, even more when it is used as a filling in cements and other formulations in orthopedic surgery. The present article shows preliminary results demonstrating the effectiveness of a modification of the con‐ trolled rate thermal analysis (CRTA), developed by J. Rouquerol, used for the prepara‐ tion of ceramic materials with controlled textural characteristics, during the formation of ceramic powders of synthetic hydroxyapatite at low temperatures. The thermal treat‐ ments of the hydroxyapatite were carried out in a device connected to a computer, to control temperature and pressure system, keeping the decomposition speed constant. Results, reported when preparing ceramic powders of hydroxyapatite at 300 and 850°C under controlled pressure, using synthetic hydroxyapatite with a Ca/P molar ratio equal to 1.64, were checked using IR spectroscopy and X‐ray diffraction, showed that the formed phase corresponds to that of crystalline hydroxyapatite, even at 300°C of maxi‐ mum temperature. Values of specific surface (BET) between 17 and 66 m2/g, with pore size in the range of 50–300 Å in both cases are obtained by N 2 absorption isotherms, when analyzing the isotherms of nitrogen absorption.

Recubrimientos de hidroxiapatita nanocristalina - Preparación, caracterización y evaluación de la bioactividad

The coating of metallic alloys with bioactive ceramics aims to accelerate bone formation around implant, contributing to its fixation. In this paper, the deposition of bioactive hydroxyapatite ceramic by sol-gel method on Ti-6Al-4V alloy sheets was studied. Coatings prepared from hydroxyapatite sol have been accomplished by dip-coating technique on non-toxic Ti-6Al-4V alloy for biomedical applications. The coating layer was characterized by X-ray diffraction provided valuable information about the phase transformation, identification of the phases developed and degree of crystallinity. Scanning electron microscopy was applied to study the surface morphology and coating adhesion to substrate was evaluated by shear testing (ASTM F 1044-05). The obtained results show that all the prepared samples are ceramic nanopowders with crystal structure and composition like hydroxyapatite, with small deviations from the one present in the human bone. The corrosion behavior of the resulting hydroxyapatite coatings in a simulated body fluid (SBF) was studied by electrochemical impedance spectroscopy. The hydroxyapatite coated Ti-6Al-4V alloy displayed excellent bioactivity when soaked in the SBF and acceptable corrosion protection behavior. The citocompatibility test according to ISO 10993-5 standard shows that sol-gel coating did not provoke cell dead.