Ena A. Aguilar-Reyes

Preparation and Characterization of 45S5 Bioactive Glass‐based Scaffolds Loaded with PHBV Microspheres with Daidzein Release Function

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) microsphere loaded 45S5 bioactive glass (BG) based scaffolds with drug releasing capability have been developed. PHBV microspheres with a mean particle size 4 ± 2 μm loaded with daidzein were obtained by oil-in-water single emulsion solvent evaporation method and applied to the surface of BG scaffolds by dip coating technique. The morphology, in vitro bioactivity in simulated body fluid (SBF), mechanical properties and drug release kinetics of microsphere loaded scaffolds were studied. The microspheres were shown to be homogeneously dispersed on the scaffold surfaces. It was confirmed that hydroxyapatite crystals homogeneously grew not only on the surface of the scaffold but also on the surface of the microspheres within 3 days of immersion in SBF. The daidzein release from the microsphere loaded scaffolds lasted almost 1 month and was determined to be diffusion controlled. The microsphere loaded BG scaffolds with daidzein releasing capability obtained in this study are a candidate for bone tissue engineering.

Synthesis and characterisation of β-TCP/bioglass/zirconia scaffolds

ABSTRACT Tricalcium phosphate scaffolds reinforced with bioglass were characterised morphologically, physically, and mechanically. The scaffolds were fabricated through powder technology and the polymer foaming technique using 80 wt-% of β-TCP and 20 wt-% of phosphate-based bioglass doped with zirconia in various amounts (0, 0.25, 0.5, 0.75, and 1.0 wt-%). The foaming agent was varied (1, 1.5, 2, 2.5, and 3 wt-%) to determine the optimal amount that ensured an interconnected porosity and pore size suitable for increasing osteoconduction and cell attachment. Promising samples for tissue engineering applications showed a pore size ranging from 1.41 to 303 μm, total porosity of 50–53%, compressive strength values between 0.6 and 1 MPa, Young’s modulus from 357 to 574 MPa, and excellent interconnectivity.

Formation of Calcium-Phosphate Coatings on Ti6Al4V Substrates by an Autocatalytic Deposition Route

The aim of this research is to develop a methodology to obtain bioactive coatings on Ti6Al4V substrates pretreated with NaOH 5M for 24 h, by an autocatalytic route using an acid bath. The autocatalytic bath was developed in order to produce bioactive coatings with a Ca/P molar ratio of 1.2 by dissolving the appropriate amounts of CaCl2 and NaH2PO2 as precursors and C4H4Na2O4·6H2O as a reducing agent in distilled water, at pH values of 5.5 and 6.0, temperatures of 80 and 90°C, and two immersion times of 60 and 180 min. It was observed that the thickness and morphology of the coating changed according to the processing conditions.

Fabrication and Characterization of Highly Ordered Porous Alumina Templates by a Two-Step Anodization Process

Highly ordered through-hole anodic porous alumina membranes were fabricated by electrochemical oxidation of aluminum in a controlled two-step process. A teflon dispositive was used to ensure single side anodization. Under the most appropriate condition for the fabrication of ideally ordered anodic aluminum oxide (AAO), the voltage used was 15 V during 24 h in a 15 % w/v sulfuric acid solution. SEM, TEM and FESEM characterization shows that the as-fabricated AAO film has a defect-free array of straight parallel channels perpendicular to the surface. The thickness of the porous membrane is 20 microns, approximately. The ordered channels are formed in a honey comb arrange with a pore diameter in the range 20-30 nm, wall thickness of 10-20 nm, interpore distance of 40 nm, and high aspect ratio of 850. The pore density, quantified by image analysis, is 5.4×1010 pore/cm2; perfect ordering was maintained in the full depth of the membrane. Dimensions of this porous structure provide a convenient way to precision engineer the nanoscale morphology.

In Vitro Characterization of 3D Beta-Tricalcium Phosphate Scaffolds Reinforced with Phosphate Based-Bioactive glass for Bone Replacement

Bone tissue engineering is an excellent alternative to reduce bone disorders and conditions, by inducing new functional bone regeneration starting from the synthesis of the biomaterials and then the combination of cell and factor therapy. In the present contribution, the scaffolds were made with a ratio of 80 wt.% of β-TCP and 20 wt. % of phosphate-based bioglass, in addition the phosphate-based bioglass was reinforced with zirconia in different amounts (0, 0.5 and 1.0 mol%) with the aim to reduce the dissolution rate, improve the osteoconduction and the osteogenesis of the bone tissue. The results obtained by μCT of the scaffolds containing zirconia showed a wide pore size distribution between 1.5 and 303 μm. AlamarBlue assays showed that the cell proliferation of MC3T3-E1 preosteoblasts scaffolds were sixfold increase in relation to the number of the initial cells. FE-SEM helped to observe the cauliflower structure of HA and DRX showed that crystalline phases formed after heat treatment were (NaCaPO4 and NaZr5PO4) owing both to the crystallization and combination of the bioglass and β-TCP .

Densification Study of Cu-Al-SiC Composite Powders Prepared by Mechanical Milling

This work involves the preparation of Cu-Al-SiC composite powders by a high-energy milling process and the study of their densification behavior by cold compaction. The goal of the milling process is to get embedded the ceramic particles in the metal matrix to enhance the distribution of the metal and ceramic phases in the compacts, an important condition to derive in isotropic properties of consolidated materials. For comparison purposes, compressibility tests of a Cu-5Al matrix prepared by high-energy milling were performed; while additions of 1, 5 and 10 vol.% SiC were added to the matrix. It was found that the high-energy milling process leads to Cu-Al-SiC composite powders with a homogeneous distribution of the reinforcement in the matrix. Compressibility essays showed that densification of the powders decreased with SiC content; a densification of 73.7% was obtained for composites with 10% SiC compared to 76.0% for samples with 1% SiC at the maximum load applied. Milling time reduced the plastic deformation capacity of the matrix leading to fracture of the cold welded aggregates; the fracture process was accelerated by the addition of the hard reinforcement particles. Thus, morphology of the powders changed from laminar, to fine fragments and coarse aggregates, affecting the compaction behavior.

Structural Characterization of Aluminum Foams Obtained by Powder Metallurgy

The porous structure of aluminum foams was quantitatively monitored in terms of pore density, pore area, and shape and size distribution using image analysis; then, related to density and expansion profiles by interrupted experiments. This practice offers important information in the control and reproducibility of foams. The aluminum foams were produced by the powder compact melting method at 800°C. The foamable precursors consisted in uniaxial cold pressed Al-TiH 2 mixtures compacted at 387 MPa; the pressure applied and particle size distribution of the mixture originated preforms with 95.9% densification. This procedure eliminated the traditional hot-compaction step; besides, the amount of foaming agent was kept to a minimum of 0.5 wt.% TiH 2 . A volume expansion of 215 to 236% and densities from 0.7730 to 0.8206 g/cm 3 were obtained in a time window of 420 to 570 s. The calculated shape factors and Feret diameters defined how the roundness of pores varies with size all along the foaming process.

Heat Treatment Effect on Properties of Ni-P-Al 2 O 3 Composite Coatings

Ni-P and Ni-P-Al 2 O 3 composite coatings are obtained by electroless plating on steel substrates. Alumina particles with an average particle size of 5 microns are added to the bath in loads of 5, 10, 15 and 20g/L. It is found a maximum retention of 18.2 vol.% Al 2 O 3 for a ceramic load of 10g/L. The composition of the binary Ni-P deposits is 9.3 wt.% P and the balance nickel. The addition of ceramics to the electroless solution induces a reduction of phosphorous content to 9.0, 8.3, 7.9 and 7.3%, respectively. The deposited coatings are heat-treated in the temperature range between 100 and 500°C and holding times from 30 to 300 minutes. A maximum hardness of 1600 HV0.1 is obtained for composite coatings containing 18.2 vol.% Al 2 O 3 treated at 400 °C/1h. The uniform distribution of ceramics and precipitation of fine Ni 3 P and Ni 12 P 5 precipitates are responsible of the hardening of the nickel matrix.