Influence of Si substitution on the reactivity of α-tricalcium phosphate.

Silicon substituted calcium phosphates have been widely studied over the last ten years due to their enhanced osteogenic properties. Notwithstanding, the role of silicon on α-TCP reactivity is not clear yet. Therefore, the aim of this work was to evaluate the reactivity and the properties of Si-α-TCP in comparison to α-TCP. Precursor powders have similar properties regarding purity, particle size distribution and specific surface area, which allowed a better comparison of the Si effects on their reactivity and cements properties. Both Si-α-TCP and α-TCP hydrolyzed to a calcium-deficient hydroxyapatite when mixed with water but their conversion rates were different. Si-α-TCP exhibited a slower setting rate than α-TCP, i.e. kSSA for Si-TCP (0.021g·m-2·h-1) was almost four times lower than for α-TCP (0.072g·m-2·h-1). On the other hand, the compressive strength of the CPC resulting from fully reacted Si-α-TCP was significantly higher (12.80±0.38MPa) than that of α-TCP (11.44±0.54MPa), due to the smaller size of the entangled precipitated apatite crystals.

Oleic acid surfactant in polycaprolactone/hydroxyapatite-composites for bone tissue engineering.

Bone substitutes are required to repair osseous defects caused by a number of factors, such as traumas, degenerative diseases, and cancer. Autologous bone grafting is typically used to bridge bone defects, but suffers from chronic pain at the donor-site and limited availability of graft material. Tissue engineering approaches are being investigated as viable alternatives, which ideal scaffold should be biocompatible, biodegradable, and promote cellular interactions and tissue development, need to present proper mechanical and physical properties. In this study, poly(ε-caprolactone) (PCL), oleic acid (OA) and hydroxyapatite (HAp) were used to obtain films whose properties were investigated by contact angle, scanning electron microscopy, atomic force microscopy, tensile mechanical tests, and in vitro tests with U2OS human osteosarcoma cells by direct contact. Our results indicate that by using OA as surfactant/dispersant, it was possible to obtain a homogenous film with HAp. The PCL/OA/Hap sample had twice the roughness of the control (PCL) and a lower contact angle, indicating increased hydrophilicity of the film. Furthermore, mechanical testing showed that the addition of HAp decreased the load at yield point and tensile strength and increased tensile modulus, indicating a more brittle composition vs. PCL matrix. Preliminary cell culture experiments carried out with the films demonstrated that U2OS cells adhered and proliferated on all surfaces. The data demonstrate the improved dispersion of HAp using OA and the important consequences of this addition on the composite, unveiling the potentially of this composition for bone growth support. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1076-1082, 2016.

Novel hybrid membrane of chitosan/poly (ε-caprolactone) for tissue engineering.

We investigated the potential use of 3D hybrid membrane: poly (ε-caprolactone) (PCL) mesh using rotary jet spinning with subsequent chitosan (CH) coating. The morphological examinations by scanning electron microscopy (SEM) were proved the efficiency of this technique on obtaining relative homogeneous PCL fiber mats (15,49±4,1µm), with high surface porosity (1,06±0,41µm) and effective CH coating. The feasibility of rotary jet spinning allowed the solvent evaporation during the process; this fact was verified by differential scanning calorimetry (DSC), indeed also had verified changes in thermal properties on the hybrid membrane, since the present of CH. It was investigated the mechanical properties of the hybrid membrane and CH film, the data were that the samples presents good tensile modulus but low strain at the break. In addition, it was verified the biocompatibility properties in vitro using Vero cells. PCL mesh demonstrated cells more spread vastly in the pore surface, with attachments in between fibers indicating the potential for cell adhesion. The films samples (CH and hybrid membrane) resulted in a cells layer on the surfaces with an intense staining (metachromasy), which is the result of cells more active. The cell counting -5 days of culture- and the MTT assay -21 days of culture- demonstrated that the materials tested proved to be different from the positive control and equal to each other and this fact, in our view, this indicates a satisfactory proliferation. Thus, based on the results here, this novel hybrid membrane provides an attractive material for tissue engineering applications.

Injectable biodegradable polycaprolactone-sebacic acid gels for bone tissue engineering.

Tissue engineering constitutes a promising alternative technology to transplantation medicine by creating viable substitutes for failing tissues or organs. The ability to manipulate and reconstitute tissue function has tremendous clinical implications and will most likely play a key role in cell and gene therapies in the coming years. In the present work, a novel injectable and biodegradable biomaterial is reported that could be injected on the human body with a surgical syringe. The material prepared is a blend of polycaprolactone (PCL), a biodegradable and elastic biomedical polymer, and sebacic acid, a natural polymer part of castor oil with low molecular weight to accelerate the slow degradation rate of PCL. The biocompatibility of the blend was evaluated in vitro and its in vivo behavior was also assessed through subcutaneous and bone implantation in rats to evaluate its tissue-forming ability and degradation rate. The results allowed the conclusion that the gel is biocompatible, promotes the differentiation of mesenchymal stem cells, and presents an adequate degradation rate for use in bone tissue engineering. In vivo the gel blends promoted tissue regeneration and adverse reactions were not observed on subcutaneous and bone implants.

Biocompatibility and biodegradation of polycaprolactone-sebacic acid blended gels.

Tissue engineering aims at creating biological body parts as an alternative for transplanting tissues and organs. A current new approach for such materials consists in injectable biodegradable polymers. Their major advantages are the ability to fill-in defects, easy incorporation of therapeutic agents or cells, and the possibility of minimal invasive surgical procedures. Polycaprolactone (PCL) is a promising biodegradable and elastic biomaterial, with the drawback of low-degradation kinetics in vivo. In this work a biodegradable injectable gel of PCL blended with sebacic acid (SA) was prepared, to improve the degradation rate of the biomaterial. SA is known for its high degradation rate, although in high concentrations it could originate a pH decrease and thus disturb the biocompatibility of PCL. Degradation tests on phosphate buffered saline were carried out using 5% of SA on the blend and the biomaterial stability was evaluated after degradation using differential scanning calorimetry, dynamical mechanical analysis, and scanning electronic microscopy. After degradation the elastic properties of the blend decreased and the material became more crystalline and stiffer, although at a lower extent when compared with pure PCL. The blend also degraded faster with a loss of the crystalline phase on the beginning (30 days), although its thermal and mechanical properties remained comparable with those of the pure material, thus showing that it achieved the intended objectives. After cell assays the PCL-SA gel was shown to be cytocompatible and capable of maintaining high cell viability (over 90%).

Poly(ε-caprolactone) and poly(D,L-lactic acid-co-glycolic acid) scaffolds used in bone tissue engineering prepared by melt compression-particulate leaching method.

Porous bioresorbable polymers have been widely used as scaffolds in tissue engineering. Most of the bioresorbable scaffolds are aliphatic polyesters and the methods employed to prepare the porous morphology may vary. This work describes and evaluates the in vitro degradation of porous and dense scaffolds of poly(ε-caprolactone) (PCL) and poly(D,L-lactic acid-co-glycolic acid) (50/50) (PLGA50) prepared by particulate leaching-melt compression process. Biological evaluation was carried out using osteoblast cell cultures. The results showed an autocatalytic effect on the dense samples. Osteoblasts presented intermediate adhesion and the cell morphology on the surface of these materials was dispersed, which indicated a good interaction of the cells with the surface and the material.

Effects of pH on the electrochemical behaviour of titanium alloys for implant applications.

The electrochemical behaviour of two commercial titanium alloys Ti-6Al-4 V (ASTM F136) and Ti-13Nb-13Zr (ASTM F1713) was investigated in Ringer physiological solution at two pH values (5.5 and 7.0). The corrosion properties were examined by using electrochemical techniques: Potentiodynamic anodic polarization, cyclic polarization and electrochemical impedance spectroscopy (EIS). The electrochemical corrosion properties of both alloys at different conditions were measured in terms of corrosion potential (E (corr)), corrosion current density (i (corr)) and passivation current density (i (pass)). Equivalent electrical circuits were used to modulate EIS data, in order to characterize alloys surface and better understanding the pH effect on the interface alloy/solution.

Glutaraldehyde-treated bovine pericardium: effects of lyophilization on cytotoxicity and residual aldehydes.

This work assesses the effect of lyophilization on the cytotoxicity and residual aldehyde concentration of glutaraldehyde-treated and lyophilized bovine pericardium (group A), comparing it to conventional glutaraldehyde-treated bovine pericardium (group B). Cytotoxicity was measured by incubating a pericardium sample from each group in saline and assessing the eluant's influence on cellular growth. Residual aldehydes were measured by HPLC. Although both groups' eluants exhibited some cytotoxicity, the eluant from group A was less cytotoxic, with a cytotoxicity index (IC50(%)) of 41%. Group B eluants all had marked cytotoxic effects; cell growth was 24.15% of the negative control at the most dilute eluant concentration (6.25%). The mean residual glutaraldehyde level was less in group A than in group B (2.36 +/- 0.11 and 9.90 +/- 3.70 g/l, respectively; n=3, P < 0.05), but residual formaldehyde levels did not differ. These results demonstrate that compared with conventional glutaraldehyde-treated bovine pericardium, lyophilized pericardium is less cytotoxic, with fewer glutaraldehyde residues.

Resposta da musculatura de ratos e partículas de polisulfona / Muscle response of rats by polysulphone particles

Neste trabalho foi estudada a resposta da musculatura triceps de ratos Wistar a particulas de uma poliétersulfona fabricada pela AMOCO e vendida sob o nome comercial UDELTM P-1800 implantadas na forma de particulas por um período de até 52 semanas. Ao final do período de implante, näo foi observado pelos autores nenhum indício que indicasse toxicidade do material

Desenvolvimento de uma protese de ventrículo artificial implantável / Development of a prosthesis of implanted artificial ventricle

O objetivo deste trabalho foi o desenvolvimento de uma prótese de ventrículo artificial implantável (VAI), para utilização em pacientes com insuficiência cardíaca profunda que necessitam de assistência circulatória mecânica, como ponte para transplante de coração. Foi utilizado um programa CAD (Microstation) para o projeto mecânico do VAI. O dispositivo apresenta uma membrana livre fixada entre duas crianças de titânio, seu acionamento é do tipo pneumático. O dispositivo foi projetado para ser implantado na cavidade abdominal e conectado ao coração nativo via ápice do ventrículo esquerdo e aorta, por meio de cânulas confeccionados em silicone, acopladas a válvulas biológicas de pericárdio bovino.

Abstract - This paper describes the design of an implantable artificial ventricular assist device to support the heart as a bridge to heart transplantation, in patients with profound cardiac failure. The artificial ventricle presented has a free floating membrane, dividing two titanium carcass. The driving unit is pneumatic. Two silicone cannulae are used to conect the device to the patient's heart ( left ventricle apex and aorta). Each cannula is eqquiped with one bovine pericardium valve. A computer program (Microstation) was utilized to provide volumetric calculus, bidimensional and tridimensional visualization to optimize the design