Piezoelectric 3-D Fibrous Poly(3-hydroxybutyrate)-Based Scaffolds Ultrasound-Mineralized with Calcium Carbonate for Bone Tissue Engineering: Inorganic Phase Formation, Osteoblast Cell Adhesion, and Proliferation.

Elaboration of novel biocomposites providing simultaneously both biodegradability and stimulated bone tissue repair is essential for regenerative medicine. In particular, piezoelectric biocomposites are attractive because of a possibility to electrically stimulate cell response. In the present study, novel CaCO3-mineralized piezoelectric biodegradable scaffolds based on two polymers, poly[( R)3-hydroxybutyrate] (PHB) and poly[3-hydroxybutyrate- co-3-hydroxyvalerate] (PHBV), are presented. Mineralization of the scaffold surface is carried out by the in situ synthesis of CaCO3 in the vaterite and calcite polymorphs using ultrasound (U/S). Comparative characterization of PHB and PHBV scaffolds demonstrated an impact of the porosity and surface charge on the mineralization in a dynamic mechanical system, as no essential distinction was observed in wettability, structure, and surface chemical compositions. A significantly higher (4.3 times) piezoelectric charge and a higher porosity (∼15%) lead to a more homogenous CaCO3 growth in 3-D fibrous structures and result in a two times higher relative mass increase for PHB scaffolds compared to that for PHBV. This also increases the local ion concentration incurred upon mineralization under U/S-generated dynamic mechanical conditions. The modification of the wettability for PHB and PHBV scaffolds from hydrophobic (nonmineralized fibers) to superhydrophilic (mineralized fibers) led to a pronounced apatite-forming behavior of scaffolds in a simulated body fluid. In turn, this results in the formation of a dense monolayer of well-distributed and proliferated osteoblast cells along the fibers. CaCO3-mineralized PHBV surfaces had a higher osteoblast cell adhesion and proliferation assigned to a higher amount of CaCO3 on the surface compared to that on PHB scaffolds, as incurred from micro-computed tomography (µCT). Importantly, a cell viability study confirmed biocompatibility of all the scaffolds. Thus, hybrid biocomposites based on the piezoelectric PHB polymers represent an effective scaffold platform functionalized by an inorganic phase and stimulating the growth of the bone tissue.

A biodegradable AZ91 magnesium alloy coated with a thin nanostructured hydroxyapatite for improving the corrosion resistance.

The main aim of this study was to investigate the properties of an AZ91 alloy coated with nanostructured hydroxyapatite (HA) prepared by radio frequency (RF) magnetron sputtering. The bioactivity and biomineralization of the AZ91 magnesium alloy coated with HA were investigated in simulated body fluid (SBF) via an in vitro test. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) analyses were performed. The samples were immersed in SBF to study the ability of the surface to promote the formation of an apatite layer as well as corrosion resistance and mass change of the HA-coated AZ91 alloy. Electrochemical tests were performed to estimate the corrosion behaviour of HA-coated and uncoated samples. The results revealed the capability of the HA coating to significantly improve the corrosion resistance of the uncoated AZ91 alloy.

Surface wettability and energy effects on the biological performance of poly-3-hydroxybutyrate films treated with RF plasma.

The surface properties of poly-3-hydroxybutyrate (P3HB) membranes were modified using oxygen and an ammonia radio-frequency (RF, 13.56 MHz) plasma. The plasma treatment procedures used in the study only affected the surface properties, including surface topography, without inducing any significant changes in the crystalline structure of the polymer, with the exception being a power level of 250 W. The wettability of the modified P3HB surfaces was significantly increased after the plasma treatment, irrespective of the treatment procedure used. It was revealed that both surface chemistry and surface roughness changes caused by the plasma treatment affected surface wettability. A treatment-induced surface aging effect was observed and resulted in an increase in the water contact angle and a decrease in the surface free energy. However, the difference in the water contact angle between the polymers that had been treated for 4 weeks and the untreated polymer surfaces was still significant. A dependence between cell adhesion and proliferation and the polar component of the surface energy was revealed. The increase in the polar component after the ammonia plasma modification significantly increased cell adhesion and proliferation on biodegradable polymer surfaces compared to the untreated P3HB and the P3HB modified using an oxygen plasma.

Enhancement of the mechanical properties of AZ31 magnesium alloy via nanostructured hydroxyapatite thin films fabricated via radio-frequency magnetron sputtering.

The structure, composition and morphology of a radio-frequency (RF) magnetron sputter-deposited dense nano-hydroxyapatite (HA) coating that was deposited on the surface of an AZ31 magnesium alloy were characterized using AFM, SEM, EDX and XRD. The results obtained from SEM and XRD experiments revealed that the bias applied during the deposition of the HA coating resulted in a decrease in the grain and crystallite size of the film having a crucial role in enhancing the mechanical properties of the fabricated biocomposites. A maximum hardness of 9.04 GPa was found for the HA coating, which was prepared using a bias of -50 V. The hardness of the HA film deposited on the grounded substrate (GS) was found to be 4.9 GPa. The elastic strain to failure (H/E) and the plastic deformation resistance (H(3)/E(2)) for an indentation depth of 50 nm for the HA coating fabricated at a bias of -50 V was found to increase by ~30% and ~74%, respectively, compared with the coating deposited at the GS holder. The nanoindentation tests demonstrated that all of the HA coatings increased the surface hardness on both the microscale and the nanoscale. Therefore, the results revealed that the films deposited on the surface of the AZ31 magnesium alloy at a negative substrate bias can significantly enhance the wear resistance of this resorbable alloy.

The release of nickel from nickel-titanium (NiTi) is strongly reduced by a sub-micrometer thin layer of calcium phosphate deposited by rf-magnetron sputtering.

Thin calcium phosphate coatings were deposited on NiTi substrates (plates) by rf-magnetron sputtering. The release of nickel upon immersion in water or in saline solution (0.9% NaCl in water) was measured by atomic absorption spectroscopy (AAS) for 42 days. The coating was analyzed before and after immersion by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). After an initial burst during the first 7 days that was observed for all samples, the rate of nickel release decreased 0.4-0.5 ng cm(-2) d(-1) for a 0.5 mum-thick calcium phosphate coating (deposited at 290 W). This was much less than the release from uncoated NiTi (3.4-4.4 ng cm(-2) d(-1)). Notably, the nickel release rate was not significantly different in pure water and in aqueous saline solution.

[Thin calcium-phosphate coatings produced by high frequency magnetron sputtering and prospects for their use in biomedical engineering].

Thin calcium-phosphate coatings with thickness less than 2.7 m were prepared by radio-frequency magnetron sputtering technique on the surfaces of pure titanium, titanium alloy Ti6A14V and stainless ASTM 316. Results of scanning electron microscopy showed that all coatings were dense and poreless and did not have any visible defects or microcracks. Rutherford backscattering (RBS) revealed a prepared coating consisting only of calcium 33.6 (1.6 at%, phosphorous 16.5 (1.5 at%, and oxygen 48.6 (1.2 at%. The concentration of each above-mentioned element through the coating was almost constant. The physicomechanical properties of the prepared coatings were investigated using a nanoindentation technique. The values of nano-hardness and Young's modulus calculated on the basis of the obtained data were 10 GPa and 113 GPa, respectively. These values were higher than that of non-coated substrates, except titanium alloy due to the sputtering mechanism. It was found that the coating with a thickness less than 1.6 ?m possessed more adhesion strength than coatings with greater value of thickness. However, we suggest that all coatings have great cohesive resistance that does not depend on the coating thickness.