Physical, Mechanical, and Biological Properties of PMMA-Based Composite Bone Cement Containing Silver-Doped Bioactive and Antibacterial Glass Particles with Different Particles Sizes

Abstract: In the present work, antibacterial composite bone cement was designed by introducing a bioactive and antibacterial glass into a commercial formulation. The effect of glass particles’ addition on the curing parameters of the polymeric matrix was evaluated; moreover, the influence of the glass particle size on the glass dispersion, compressive and bending strength, bioactivity, and antibacterial effect was estimated. The results evidence a delay in the polymerization kinetics of the composite cement, which nevertheless complies with the requirements of the ISO standard. Morphological characterization provides evidence of good dispersion of the glass in the polymeric matrix and its exposition on the cement surface. The different glass grain sizes do not affect the composites’ bioactivity and compressive strength, while a slight reduction in bending strength was observed for samples containing glass powders with greater dimensions. The size of the glass particles also appears to have an effect on the antibacterial properties, since the composites containing larger glass particles do not produce an inhibition halo towards the S. aureus strain. The obtained results demonstrate that, by carefully tailoring the glass amount and size, a multifunctional device for artificial joint fixing, temporary prostheses, or spinal surgery can be obtained

Digital light processing stereolithography of hydroxyapatite scaffolds with bone-like architecture, permeability, and mechanical properties

AbstractThis work deals with the additive manufacturing and characterization of hydroxyapatite scaffolds mimicking the trabecular architecture of cancellous bone. A novel approach was proposed relying on stereolithographic technology, which builds foam‐like ceramic scaffolds by using three‐dimensional (3D) micro‐tomographic reconstructions of polymeric sponges as virtual templates for the manufacturing process. The layer‐by‐layer fabrication process involves the selective polymerization of a photocurable resin in which hydroxyapatite particles are homogeneously dispersed. Irradiation is performed by a dynamic mask that projects blue light onto the slurry. After sintering, highly‐porous hydroxyapatite scaffolds (total porosity ~0.80, pore size 100‐800 µm) replicating the 3D open‐cell architecture of the polymeric template as well as spongy bone were obtained. Intrinsic permeability of scaffolds was determined by measuring laminar airflow alternating pressure wave drops and was found to be within 0.75‐1.74 × 10−9 m2, which is comparable to the range of human cancellous bone. Compressive tests were also carried out in order to determine the strength (~1.60 MPa), elastic modulus (~513 MPa) and Weibull modulus (m = 2.2) of the scaffolds. Overall, the fabrication strategy used to print hydroxyapatite scaffolds (tomographic imaging combined with digital mirror device [DMD]‐based stereolithography) shows great promise for the development of porous bioceramics with bone‐like architecture and mass transport properties

Micro-CT imaging and finite element models reveal how sintering temperature affects the microstructure and strength of bioactive glass-derived scaffolds

: This study focuses on the finite element simulation and micromechanical characterization of bioactive glass-ceramic scaffolds using Computed micro Tomography ([Formula: see text]CT) imaging. The main purpose of this work is to quantify the effect of sintering temperature on the morphometry and mechanical performance of the scaffolds. In particular, the scaffolds were produced using a novel bioactive glass material (47.5B) through foam replication, applying six different sintering temperatures. Through [Formula: see text]CT imaging, detailed three-dimensional images of the scaffold's internal structure are obtained, enabling the extraction of important geometric features and how these features change with sintering temperature. A finite element model is then developed based on the [Formula: see text]CT images to simulate the fracture process under uniaxial compression loading. The model incorporates scaffold heterogeneity and material properties-also depending on sintering temperature-to capture the mechanical response, including crack initiation, propagation, and failure. Scaffolds sintered at temperatures equal to or higher than 700 [Formula: see text]C exhibit two-scale porosity, with micro and macro pores. Finite element analyses revealed that the dual porosity significantly affects fracture mechanisms, as micro-pores attract cracks and weaken strength. Interestingly, scaffolds sintered at high temperatures, the overall strength of which is higher due to greater intrinsic strength, showed lower normalized strength compared to low-temperature scaffolds. By using a combined strategy of finite element simulation and [Formula: see text]CT-based characterization, bioactive glass-ceramic scaffolds can be optimized for bone tissue engineering applications by learning more about their micromechanical characteristics and fracture response

Materials for Healthcare Applications Symposium, EUROMAT 2011 (Montpellier, France, 12–15 September 2011)

The advancement of the healthcare and biomedical sectors requires the improvement of traditional biomaterials and the development of new and multifunctional biomaterial combinations with enhanced structural and biological performance. The need for biomaterials to help tackle the health problems of an increasing elderly population is continuously growing. Biomaterials science and technology is highly interdisciplinary, which involves not only the established materials science disciplines but also scientific fields such as chemistry, biology, bioengineering and medicine. The increasing impact of nanotechnology in the medical field must also be noted as this implies the development of biomimetic surfaces, nanostructured biomaterials and miniaturized devices. At the last European Congress and Exhibition on Advanced Materials and Processes (EUROMAT 2011: http://euromat2011.fems.eu) held in Montpellier, France in September of last year, the topic of materials for healthcare was covered in three focused symposia, namely: i) bioactive coatings and material-tissue interfaces, ii) smart and biomimetic materials for biomedical applications and tissue engineering and iii) mechanical characterization and modeling of tissues and biomedical materials at all length scales. The oral and poster presentations reflected novel research on biomaterials covering new areas of processing, properties and applications of materials in the biomedical field. A broad variety of topics were presented, ranging from biomaterials for bone replacement, bioactive surfaces and coatings, nanocomposites and tissue engineering scaffolds, bioinspired biocomposites and antibacterial coatings. The eight papers [1–8] published in this special issue of Biomedical Materials were selected from contributions presented at EUROMAT 2011 in the Materials for Healthcare Symposia, specifically for their focus in biomaterials for tissue engineering. It is recognized that successful biomaterials and structures for tissue engineering are those that closely mimic the composition chemistry and hierarchical structure of the native tissues to be replaced and regenerated, including the possibility of adaptation to the biological changes during the healing process, and which exhibit specific mechanical and biological functions to enable rapid new tissue regeneration. The papers selected for this special section went through the normal peer-review process of the journal and cover numerous novel biomedical materials, including a range of inorganic and functionalised bioactive coatings for prosthetic and bone regeneration applications, a series of advanced biodegradable polymer-inorganic composites for tissue engineering and engineered nanocarriers for gene delivery also discussing the interaction of scaffolds with different stem cells. As guest editors of this special section in Biomedical Materials, we are grateful to all authors and reviewers, who have supported this publication with their efforts and hard work, contributing to its timely publication

Fe-doped sol-gel glasses and glass-ceramics for magnetic hyperthermia

This work deals with the synthesis and characterization of novel Fe-containing sol-gel materials obtained by modifying the composition of a binary SiO2-CaO parent glass with the addition of Fe2O3. The effect of different processing conditions (calcination in air vs. argon flowing) on the formation of magnetic crystalline phases was investigated. The produced materials were analyzed from thermal (hot-stage microscopy, differential thermal analysis, and differential thermal calorimetry) and microstructural (X-ray diffraction) viewpoints to assess both the behavior upon heating and the development of crystalline phases. N2 adsorption–desorption measurements allowed determining that these materials have high surface area (40–120 m2/g) and mesoporous texture with mesopore size in the range of 18 to 30 nm. It was assessed that the magnetic properties can actually be tailored by controlling the Fe content and the environmental conditions (oxidant vs. inert atmosphere) during calcination. The glasses and glass-ceramics developed in this work show promise for applications in bone tissue healing which require the use of biocompatible magnetic implants able to elicit therapeutic actions, such as hyperthermia for bone cancer treatment

Injectable Osteoinductive bone cements

The present invention concerns an injectable composition for the use in bone-filling and bone-consolidation in surgery and therapy. In particular, the invention relates to the field of injectable bone cements, for both treating of factures caused by osteoporosis or trauma and filling gaps due, for example, to the decrease of bone mass after removal of tumors or cysts

In vitro cytocompatibility of antibacterial silver and copper-doped bioactive glasses

Fighting the formation of bacterial biofilm and simultaneously providing a bioactive environment for bone regeneration during the treatment of orthopedic infections is one of the greatest challenges in surgery. Moreover, the major global threat of rapidly increasing antimicrobial resistance calls for non-antibiotic alternatives. Bioactive glasses doped with antibacterial metal ions silver (Ag), or copper (Cu), offer a potential solution. However, an added challenge is the cytocompatibility of these antimicrobial biomaterials, which could be compromised due to the possible cytotoxic effect of the dopants. This work evaluates the cytocompatibility of two bioactive glasses, SBA2 and SBA3, either doped with Ag- (Ag-SBA2) or Cu-ions (Cu-SBA3) via ion-exchange process. The viability, proliferation, and morphology of human adipose stem cells (hASCs) were evaluated using different culture conditions: i) direct culture on glass discs, with and without pre-incubation, and ii) in medium containing glass dissolution byproducts. The release kinetics of the doped ions was evaluated in α-MEM and during cell culture. Moreover, the effect of protein adsorption on the cell response was studied by introducing a layer of fibronectin on the glass discs before direct culture with hASCs. Ag-SBA2 and Cu-SBA3 both initially inhibited the hASC viability in direct cell culture. However, cells remain viable with healthy morphology when cultured directly on pre-treated discs, or indirectly with the glass dissolution byproducts. This suggests that the cytotoxicity effect seems to arise from the contact toxicity between the cells and the material surface. Fibronectin adsorption significantly improved the cytocompatibility of Ag-SBA2, while Cu-SBA3 requires further optimization. To conclude, Ag-SBA2, through its contact toxicity, has the potential for treating early infection, without compromising long-term cytocompatibility and bioactivity. However, further optimization of the Cu-SBA3 glass is needed due to its cytotoxicity towards hASCs.Peer reviewe

Resorbable Glass-Ceramic Phosphate-Based Scaffolds for Bone Tissue Engineering: Synthesis, Properties and In Vitro Effects on Human Marrow Stromal Cells

Highly porous bioresorbable glass-ceramic scaffolds were prepared via sponge replication method by using an open-cell polyurethane foam as a template and phosphate-based glass powders. The glass, belonging to the P2O5-SiO2-CaO-MgO-Na2O-K2O system, was synthesized by a melting-quenching route, ground, and sieved to obtain powders with a grain size of less than 30\u2009\u3bcm. A slurry containing glass powders, polyvinyl alcohol, and water was prepared to coat the polymeric template. The removal of the polymer and the sintering of the glass powders were performed by a thermal treatment, in order to obtain an inorganic replica of the template structure. The structure and properties of the scaffold were investigated from structural, morphological, and mechanical viewpoints by means of X-ray diffraction, scanning electron microscopy, density measurements, image analysis, and compressive tests. The scaffolds exhibited a trabecular architecture that closely mimics the structure of a natural spongy bone. The solubility of the porous structures was assessed by soaking the samples in acellular simulated body fluid (SBF) and Tris-HCl for different time frames and then by assessing the scaffold weight loss. As far as the test in SBF is concerned, the nucleation of hydroxyapatite on the scaffold trabeculae demonstrates the bioactivity of the material. Biological tests were carried out using human bone marrow stromal cells to test the osteoconductivity of the material. The cells adhered to the scaffold struts and were metabolically active; it was found that cell differentiation over proliferation occurred. Therefore, the produced scaffolds, being biocompatible, bioactive, resorbable, and structurally similar to a spongy bone, can be proposed as interesting candidates for bone grafting

Mechanical Properties of Robocast Glass Scaffolds Assessed through Micro-CT-Based Finite Element Models

In this study, the mechanical properties of two classes of robocast glass scaffolds are obtained through Computed micro-Tomography (micro-CT) based Finite Element Modeling (FEM) with the specific purpose to explicitly account for the geometrical defects introduced during manufacturing. Both classes demonstrate a fiber distribution along two perpendicular directions on parallel layers with a (Formula presented.) tilting between two adjacent layers. The crack pattern identified upon compression loading is consistent with that found in experimental studies available in literature. The finite element models have demonstrated that the effect of imperfections on elastic and strength properties may be substantial, depending on the specific type of defect identified in the scaffolds. In particular, micro-porosity, fiber length interruption and fiber detaching were found as key factors. The micro-pores act as stress concentrators promoting fracture initiation and propagation, while fiber detachment reduces the scaffold properties substantially along the direction perpendicular to the fiber plane.publishedVersionPeer reviewe