Osteogenic effect of tricalcium phosphate substituted by magnesium associated with Genderm® membrane in rat calvarial defect model.

Beta-tricalcium phosphate (ß-TCP) is one of the most widely employed bioresorbable materials for bone repair since it shows excellent biological compatibility, osteoconductivity and resorbability. The incorporation of divalent cations such as magnesium onto the ß-TCP structure (ß-TCMP) may improve the biological response to the material through the release of bioactive ions. The objective of this study was to evaluate, on a rat calvarial critical size grafting model, the bone regeneration process using ß-TCP and ß-TMCP granules by histomorphometric analysis. Results demonstrated that six months after bone grafting, the association of GBR (guided bone regeneration) using a membrane (GenDerm®) and granules of ß-TCP and ß-TCMP significantly improves bone repair in the treatment of critical-size defect in rat skulls, in comparison to untreated defects or GBR alone, leading to a bone level approximately four to five-fold greater than in the blood clot group. The ß-TCMP+GenDerm® membrane group presented 40.5% of the defect area filled by newly-formed bone, even at the central part of the defect, rather than only at the border, as seen in the other experimental groups.

Beta-type calcium phosphates with and without magnesium: From hydrolysis of brushite powder to robocasting of periodic scaffolds.

Several approaches have attempted to replace extensive bone loss, but each of them has their limitation. Nowadays, additive manufacture techniques have shown great potential for bone engineering. The objective of this study was to synthesize beta tricalcium phosphate (ß-TCP), beta tricalcium phosphate substituted by magnesium (ß-TCMP), and biphasic calcium phosphate substituted by magnesium (BCMP) via hydrolysis and produce scaffolds for bone regeneration using robocasting technology. Calcium deficient apatites, with and without magnesium were obtained by hydrolysis, calcined and physico-chemically characterized. Colorimetric cell viability assay, calcium nodule formation, and the expression of alkaline phosphatase, osteocalcin, transforming growth factor beta-1 and collagen were assessed using a mouse osteoblastic cell line (MC3T3-E1). Direct-write assembly of cylindrical periodic scaffolds was done via robotic deposition using ß-TCP, ß-TCMP, and BCMP colloidal inks. The sintered scaffolds were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Archimede's method, and uniaxial compression test. According to the cell viability assay, the powders induced cell proliferation. Calcium nodule formation and bone markers activity suggested that the materials present potential value in bone tissue engineering. The scaffolds built by robocasting presented interconnected porous and exhibited mean compressive strength between 7.63 and 18.67 MPa, compatible with trabecular bone.

Production and in vitro characterization of 3D porous scaffolds made of magnesium carbonate apatite (MCA)/anionic collagen using a biomimetic approach.

3D porous scaffolds are relevant biomaterials to bone engineering as they can be used as templates to tissue reconstruction. The aim of the present study was to produce and characterize in vitro 3D magnesium-carbonate apatite/collagen (MCA/col) scaffolds. They were prepared by using biomimetic approach, followed by cross-linking with 0.25% glutaraldehyde solution (GA) and liofilization. Results obtained with Fourier-transform infrared spectroscopy (FT-IR) confirmed the type-B carbonate substitution, while by X-ray diffraction (XRD), a crystallite size of ~10nm was obtained. Optical and electron microscopy showed that the cylindrical samples exhibited an open-porous morphology, with apatite nanocrystals precipitated on collagen fibrils. The cross-linked 3D scaffolds showed integrity when immersed in culture medium up to 14 days. Also, the immersion of such samples into an acid buffer solution, to mimic the osteoclastic resorption environment, promotes the release of important ions for bone repair, such as calcium, phosphorus and magnesium. Bone cells (SaOs2) adhered, and proliferated on the 3D composite scaffolds, showing that synthesis and the cross-linking processes did not induce cytotoxicity.

Human osteoblasts adhesion and proliferation on magnesium-substituted tricalcium phosphate dense tablets.

Tricalcium phosphate (TCP) is recognized as a promising bone replacement material due to its high bioactivity and resorbable properties. To mimic biological apatites, incorporation of magnesium (Mg) in TCP was proposed. Mg-substituted TCP (beta-TCMP) and beta-TCP dense tablets were obtained by pressing and sintering at 1,000 degrees C Mg-substituted calcium deficient apatite (Mg-CDA) and commercial TCP, respectively. The materials were characterized using X-ray diffraction, infrared spectroscopy and electron microscopy. Human osteoblast cells (SaOs2) were seeded onto the sintered tablets for 4 h, 24 h and 7 days. Results showed that Mg-CDA was completely transformed into beta-TCMP. Moreover, beta-TCMP stimulated adhesion and proliferation of human osteoblast cells. Consequently, the magnesium incorporation on calcium deficient apatites followed by sintering at 1,000 degrees C seems to be a useful path to obtain biocompatible and non cytotoxic dense tablets with TCP structure with potential application on bone engineering.

SEM/EDS analysis and characterization of gunshot residues from Brazilian lead-free ammunition.

The exposition to heavy metal-rich airborne due to fire practicing has forced to the development of heavy metal-free environmental ammunition primers all over the world. Here we characterize the GSR elements present in the Brazilian lead-free ammunition produced by Companhia Brasileira de Cartuchos (CBC) and commercialized by MagTech in the U.S. and Europe under the name CleanRange centerfire cartridges. Both first and second generations of CleanRange in calibers 9 mm Luger, .40 S&W, .380 AUTO and .38 SPL were analyzed and compared to regular Brazilian CBC ammunition by scanning electron microscopy/energy dispersive spectroscopy. Differences in composition and morphology of GSR particles from the two generations of CleanRange were observed. The first generation ammunition (found in Europe) presented spherical particles, being strontium the only unique element detected. The second generation (found in the U.S.) produced irregular particles composed mostly by potassium, aluminum, silicon and calcium. We can conclude that identification of GSR derived from CBC second generation lead-free ammunition in suspects' hands may be impossible without the addition of a distinct metallic taggant in the primer composition by the manufacturer.

Improvement of in vitro titanium bioactivity by three different surface treatments.

OBJECTIVE: Dental implants are usually made from commercially pure titanium or titanium alloys. The aim of this investigation was to determine the influence of surface treatments of commercially pure titanium samples on in vitro bioactivity. METHODS: Commercially pure (cp) titanium (Ti) sheets were submitted to three different surface treatments, including, for all samples, etching with an HCl/H(2)SO(4) solution. Part of each etched sample was further submitted either to anodic oxidation by using an H(3)PO(4) solution or to thermal oxidation. Treated and non-treated samples were analyzed by using scanning electron microscopy (SEM), profilometry and photoelectron X-ray spectroscopy (XPS). The in vitro assessment was carried out through the immersion of samples in simulated body fluid (SBF). In vitro testing was carried out by SEM and by the determination of calcium (Ca) content in solution by atomic absorption spectrometry (AAS). The non-treated titanium samples were used as the control group. RESULTS: This study has shown that, after up to 7-day exposure, a calcium phosphate layer precipitated only on samples submitted to at least one of the three treatments used. This result, based on SEM images, is in good agreement with Ca content and XPS analysis, in which remarkable effects of surface modifications on Ti samples are highlighted. SIGNIFICANCE: These results suggest that suitable surface treatments, such as employed here, may improve in vitro titanium bioactivity in a SBF solution at 37 degrees C. This behavior suggests a possibility of a further favorable in vivo response.