Marcia S. Sader

Microstructure of ceramic coating on titanium surface as a result of hydrothermal treatment

Hydroxyapatite coating on commercially pure titanium has been produced by a biomimetic method in order to improve osteointegration for medical implant purposes. A specific chemical treatment by etching titanium substrate with different concentrations of NaOH aqueous solution at 130 °C in an autoclave, followed by heat treatment at 600 °C was selected to obtain an activated titanium substrate. The microporous surface obtained has allowed the nucleation and growth of a calcium phosphate layer by soaking the substrate in a simulated body fluid (SBF). Scanning electron microscopy (SEM) together with energy dispersive analyzer for X-ray (EDS), X-ray diffraction (XRD) as well as Fourier transform infrared spectroscopy (FT-IR) were employed to evaluate the hydroxyapatite coating. A homogeneous structure coating without cracks defined the chemical treatment condition of the substrate.

Response of osteoblastic cells to titanium submitted to three different surface treatments

In the complex process of bone formation at the implant-tissue interface, surface properties are relevant factors modulating osteoblastic function. In this study, commercially pure titanium (cp Ti) samples were prepared with different surface characteristics using chemical attack with a sulfuric acid/hydrochloric acid based solution (treatment A); chemical attack plus anodic oxidation using phosphoric acid (treatment B); and chemical attack plus thermal oxidation followed by immersion in a sodium fluoride solution (treatment C). The samples were characterized by scanning electron microscopy (SEM), contact profilometry and contact angle. The biological performance of the prepared surfaces was evaluated using mice osteoblastic cell cultures for up to 21 days. Cells seeded on the different titanium samples showed similar behavior during cell attachment and spreading. However, cellular proliferation and differentiation were higher for samples submitted to treatments A and C (p < or = 0.05; n = 3), which were less rough and showed surface free energy with smaller polar components.

Simultaneous incorporation of magnesium and carbonate in apatite: effect on physico-chemical properties

Synthetic apatites are widely used both in the dental and the orthopaedic fields due to their similarity in composition with the inorganic phase of hard tissues. Biologic apatites are not pure hydroxyapatite (HA), but are calcium-deficient apatites with magnesium and carbonate as minor but important substituents. The aim of the present study was to produce a more soluble biomaterial through the simultaneous substitution of magnesium and carbonate in the apatite structure to accelerate the degradation time in the body. The physico-chemical and dissolution properties of unsintered magnesium and carbonate-substituted apatite (MCAp) with similar Mg/Ca molar ratio (0.03) and varying C/P molar ratio were evaluated. The resultant powders were characterised using several techniques, such as FTIR, TGA, XRD, ICP and SEM, while the release of calcium ions in a pH 6 solution was monitored using a Ca-ion selective electrode. The results showed a decrease of crystallite size and an increase in the release of calcium to the medium as the carbonate content in the samples increased.

Hydroxyapatite coating by sol–gel on Ti–6Al–4V alloy as drug carrier

In this study Ti–6Al–4V samples were used as substrates and Ca–P layers were deposited using sol–gel technique and covered by spin-coating. The efficiency of hydroxyapatite (HA) coatings as drug carrier was also evaluated by immersion in gentamicin sulphate solution and the release profiles were obtained by cumulative method of the coating samples. Three non-linear mathematical methods were employed in order to discuss a possible mechanism to lead the drug release. Physical chemical techniques showed the presence of the typical absorption bands of calcium phosphates by infrared spectroscopy while X-ray diffraction peaks matched up with hydroxyapatite patterns. Microstructural techniques (SEM, EDS) help to confirm the hydroxyapatite coating by surface aspect and Ca/P ratio (1.64). The best fitting according statistical results explained each stage of the released profiles and correspond to a mixture of short initial burst effect plus drug dissolution with a specific kinetic and the diffusion of the gentamicin solid particles.

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.

Comparative study of hydroxyapatite coatings obtained by Sol-Gel and electrophoresis on titanium sheets

A comparative study of two coating methods on titanium (Ti) substrates, sol-gel and electrophoresis processes, was performed. Before coating, two different surface treatments were employed. The hydroxyapatite (HA) powder were characterized by infrared spectroscopy (FTIR) and X-ray diffraction (XRD) while coated samples were examined by using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). Both techniques seem to be suitable to coat Ti. A previous surface treatment on metallic titanium seems to be fundamental to enhance coat uniformity and adhesion that was estimated by the adhesive tape test. The decrease in calcination temperature did not affect the coating adhesion.

Can inorganic bovine bone grafts present distinct properties

The aim of this study was to evaluate the physicochemical characteristics of 3 mineralized bovine inorganic biomaterials and correlate them with the dissolution rate. Bio-Oss(r), GenoxInorgânico(r), and Bonefill(r) were examined using field emission gun scanning electron microscopy (FEG-SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), specific surface area (BET), calcium/phosphorous molar ratio and a dissolution assay. Bio-Oss(r) showed a micro- and nanoporous structure consisting of 15-nm hydroxyapatite (HA) crystallites; Genox(r), a microporous structure composed of 39-nm HA crystallites; and Bonefill(r), micro- and nanoporous structure of indeterminable crystallite size. FTIR analysis showed that Bio-Oss(r) and Genox(r) were composed of calcium phosphate. The absorption bands of phosphate were poorly defined in Bonefill(r). By XRD, Bio-Oss(r) was shown to contain peaks related to the carbonated HA, whereas Genox(r) only contained peaks corresponding to HA. The broad bands in Bonefill(r) indicated low crystallinity. Bio-Oss(r) showed a greater surface area and calcium release rate than that of Genox(r). Although all biomaterials were of bovine origin, the different manufacturing processes result in materials with different physicochemical properties and may influence the biological and clinical response.

Rietveld Refinement of Sintered Magnesium Substituted Calcium Apatite

The incorporation of magnesium in the synthetic apatite has been associated with biomineralization process and osteoporosis therapy in human and animals. Magnesium easily replaces calcium in the apatite lattice and influences or controls the hydroxyapatite crystallization processes. In this work, Mg-substituted calcium deficient apatite, with Mg/Ca ratio = 0.1, 0.15 and 0.2 were synthesized by precipitation method. Then, sintered at 1000 oC and compared with a commercial product labeled as tricalcium phosphate sintered at the 1000 oC. The sintered products showed tricalcium phosphate (β-TCP) structure. The Mg2+ substitution in the Ca(4) and Ca(5) sites of β-TCP and the lattice parameter changes were estimated using the Rietveld method. Using this method, the formulas Ca2.73(Mg0.27)(PO4)2, Ca2.71(Mg0.29)(PO4)2 and Ca2.70(Mg0.23Mg0.07)(PO4)2 were calculated for the samples with Mg/Ca ratio = 0.1, 0.15 and 0.2 respectively.

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

Beta-tricalcium phosphate (β-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 β-TCP structure (β-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 β-TCP and β-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 β-TCP and β-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 β-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 (β-TCP), beta tricalcium phosphate substituted by magnesium (β-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 β-TCP, β-TCMP, and BCMP colloidal inks. The sintered scaffolds were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Archimedes 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.