Papers by Author: Herman S. Mansur

Abstract: There is a constant need for bone substitutes. This work was focused on evaluating morphological characteristics of new bioceramic three-dimensional scaffold for bone tissue engineering based on Portland cement with air-voids introduced by outgassing reaction product from lime and aluminum powder. Pores morphology was observed using scanning electron microscopy (SEM). Bulk density, apparent density, and apparent porosity were measured by Archimedes method. Water absorption by total immersion and by capillarity was also investigated. The results have indicated that cement based scaffolds exhibit a hierarchical structure with interconnected macropores and a micropores framework that indicate potential use of the developed porous materials as bone substitutes.

Abstract: Bioactive glasses are materials that have been used for the repair and reconstruction of diseased bone tissues, as they exhibit direct bonding with human bone tissues. However, bioactive glasses have low mechanical properties compared to cortical and cancellous bone. On the other hand, composite materials of biodegradable polymers with inorganic bioactive glasses are of particular interest to engineered scaffolds because they often show an excellent balance between strength and toughness and usually improved characteristics compared to their individual components. Composite bioactive glass-polyvinyl alcohol foams for use as scaffolds in tissue engineering were previously developed using the sol-gel route. The goal of this work was the synthesis of composite foams modified with higher amounts of PVA. Samples were characterized by morphological and chemical analysis. The mechanical behavior of the obtained materials was also investigated. The degree of hydrolysis of PVA, concentration of PVA solution and different PVA-bioactive glass composition ratios affect the synthesis procedure. Foams with up to 80 wt% polymer content were obtained. The hybrid scaffolds obtained exhibited macroporous structure with pore size varying from 50 to 600 µm and improved mechanical properties.

Abstract: A variety of types of organic polymers have been employed in the synthesis of hybrids with silica. In this work the sol-gel method was used for preparation of macroporous 3D hybrid scaffolds based on silica and chitosan in various compositions (10, 20 and 30% wt). The hybrids were analyzed by Scanning Electron Microscopy (SEM), X-ray Diffraction (DRX) and Infra-red Spectroscopy (FTIR) and the effect of addition of the polymer was evaluated. The foams obtained by sol-gel process were appropriate to produce hybrids based on chitosan-silica and showed large pore size distribution and porosity, except for hybrids with higher polymer content. The FTIR spectroscopy showed a band relative to Si-O-C bond that was also found to increase with the increasing the amounts of chitosan in the hybrid. This fact can suggest an interaction between the organic-inorganic phases in the material and provide new insights on the advantages of chitosansilica hybrid materials produced via sol-gel methodology.

Abstract: Bioactive glass/polymer hybrids are promising materials for biomedical applications because they combine the bioactivity of these bioceramics with the flexibility of polymers. In previous work hybrid foams with 80% bioactive glass and 20% polyvinyl alcohol (PVA) were prepared by the sol-gel process for application as scaffold for bone tissue engineering. In this work it was evaluated the effect of increasing the PVA content of the hybrids on structural characteristics and mechanical properties of hybrid foams produced by this method. The hybrids were prepared with inorganic phase composition of 70%SiO2-30%CaO and PVA fractions of 20 to 60% by the sol-gel method. The structural and mechanical characterization of the obtained foams was done by FTIR, SEM, Helium Picnometry, and compression tests. To reduce the acidic character of the hybrids due to the catalysts added, different neutralization solutions were tested. The immersion of hybrids in a calcium acetate solution was the most adequate neutralization method, avoiding calcium loss while maintaining pH nearly 7,0 and low PVA loss. The foams presented porosity of 60-85% and pore diameters of 100-500μm with interconnected structure. The pore structure varied with the polymer content in the hybrid. The compression tests showed that an increase of PVA fraction in the hybrids improved their mechanical properties.

Abstract: Porous scaffolds have been developed in many forms and materials, but few have reached the combination of adequate physical, biological and mechanical properties. In previous works hybrid foams bioactive glass polyvinyl alcohol (PVA) were prepared by the sol-gel process for application as scaffold for bone tissue engineering. We observed that synthesis parameters such as PVA hydrolysis grade, PVA solution concentration, and PVA content in the hybrids affected both synthesis results and structural characteristics of the obtained foams. A marked change in foaming behavior occurs for PVA contents around 60%. In this work we analyze the effect of different compositions and synthesis parameters on the mechanical behavior of PVA-bioative glass foams. The compression tests showed that an increase of PVA fraction changes the mechanical behavior due to different mechanisms leading to cell collapse. For hybrids with lower PVA contents (20 to 30%) the cell collapse is due to brittle crushing. For intermediate polymer content (40-60%) the contribution of plastic yielding in the plateau region increases and it becomes the predominant mechanism of cell collapse for samples with higher polymer content (70-80%).

Abstract: The aim of this study was to characterize phospholipids bilayers deposited through Langmuir-Blodgett (LB) using Fourier Transform Infrared Spectroscopy (FTIR) and Quartz Crystal Microbalance (QCM) sensor. Phospholipids dimyristoylphosphatidylcholine (DMPC), dimyristoylphosphatidylethanolamine (DMPE), dipalmitoylphosphatidylethanolamine (DPPE) bilayers were deposited. Also, hybrid monolayer of DMPC/Cholesterol (DMPC/CHOL) was prepared. Phospholipid with concentration of 1 mg.ml-1 in chloroform solution was spread at the air-water interface of a Teflon-made LB trough containing a subphase of Milli-Q water using the single-shot method. Phospholipid monolayers were transferred onto the QCM crystal and ZnSe crystals as planar solid support for FTIR measurements using the vertical dipping method. Homogeneous molecular LB films of DMPC, DMPE, DPPE phospholipids and DMPC/CHOL hybrid were produced and characterized by isotherms (Π-area), transfer ratio (θ) and QCM frequency changes results. Also, FTIR spectra results have also indicated the surface molecular organization and packing with the presence of major vibration bands.

Abstract: Polyvinyl alcohol (PVA) is a unique synthetic biocompatible polymer and it has a large number of hydroxyl groups that can react with many kinds of functional groups. In the present work, nanostructured PVA/TEOS hybrids were characterized by Small-angle X-ray Scattering (SAXS) associated with Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) techniques. We have synthesized hybrids based on the reaction of PVA with tetraethoxysilane (TEOS). PVA/TEOS hybrids were also modified in the nanometer-scale by crosslinking with glutaraldehyde (GA) during the synthesis involving hydrolysis and condensation of PVA/TEOS network. FTIR spectra showed major vibration bands associated with organic-inorganic chemical groups present in the hybrid composite PVA/TEOS. XRD coupled to FTIR results have indicated the presence of semi-crystalline domains embedded in amorphous PVA matrix. SAXS results were presented as plots with experimental scattering intensity, I(q), as a function of the modulus of the scattering vector, q. SAXS curves showed quite different trend on vector q with the scattering intensity I(q) corresponding to samples PVA, PVA/GA and PVA/TEOS/GA. Pure PVA sample showed a “knee” type curve, with maximum value q=0.04 Å-1. These results have indicated different nano-ordered disperse phases for PVA, PVA/TEOS hybrid and PVA/TEOS/GA chemically crosslinked hybrid.

Abstract: In the present work, we aimed to investigate the immobilization of Bovine Serum Albumin (BSA) into poly (vinyl alcohol) (PVA) network. PVA hydrogels with BSA were characterized by Synchrotron SAXS radiation associated with Fourier Transform Infrared Spectroscopy (FTIR). We synthesized hydrogels by dissolving PVA in aqueous solution (5.0 wt%) and crosslinked with glutaraldehyde (GA). PVA and PVA/GA hydrogels samples were immersed in BSA aqueous solution for protein immobilization. FTIR spectra showed major vibration bands associated with PVA and GA chemical groups, and BSA protein amides. Regarding to SAXS characterization, the slope of the log I(q), scattering intensity, as a function of log q, the scattering vector, provided important information about the morphology of entities present in the system. Two different scattering patterns were obtained for PVA (slope = 3.5) and PVA/BSA (slope=1.5 and 3.0). These results have given strong evidence of nano-ordered dispersed globular BSA immobilized into chemically crosslinked PVA hydrogel network. SAXS analyses have indicated that the scattering q-vector maximum value was shifted by altering PVA polymer hydrogel with GA crosslinker and also with BSA incorporation into the network.

Abstract: In the present work, a novel biocomposite has been developed based on lignin (Lig) and HA/b-TCP bioceramic materials. The Lig/HA and Lig/b-TCP systems were investigated by Scanning Electron Microscopy coupled to EDX microprobe (SEM/EDX). Lignin is a lignosulfonate natural polymer with complex random coupling and the exact chemical structure is yet unknown. FTIR spectroscopy is an important tool for lignin characterization based on several major vibration bands associated with generally found chemical groups. Consequently, FTIR spectroscopy was used to evaluate the chemical functionalities and major components present in the material. SEM photomicrographs of biocomposites Lig/HA and Lig/b-TCP have shown uniform dispersion of the natural polymer binder in the bioceramic matrix. Also, chemical composition obtained by EDX spectra have indicated lignin evenly distributed in the HA and b-TCP compounds. Novel biocomposites based on lignin/HA and lignin/b-TCP were developed with porosity ranging from 50 to 100 µm. These results have confirmed the high potential application of lignin as a non-toxic natural polymer binder to be used as 3D scaffold template for biomedical applications.

Abstract: In the present work, natural coral from Brazilian reefs were studied according to their crystallography by X-ray diffraction and microstructure by Scanning Electron Microscopy (SEM/EDX). FTIR spectroscopy was also used to evaluate the chemical functionalities and major components present in the material. The SEM morphology results have shown a tri-dimensional coral structure with porous ranging from 50 to 200 µm. Aragonite was identified as the major crystalline phase through XRD analysis and FTIR spectroscopy. Strontium calcium carbonate, (Sr,Ca)CO3, was also identified by XRD analysis. After sintering at 900º/1h, the conversion from aragonite to CaO and calcite was observed. These results have endorsed the high potential application of natural coral materials as 3D scaffolds for biomedical application, because of calcium carbonate compounds can be converted to HA by hydrothermal and biomimetic coating processes.