Bioactive glasses (BGs) are being used in several biomedical applications, one of them being as antibacterial materials. BGs can be produced via melt-quenching technique or sol-gel method. Bactericidal silver-doped sol-gel derived mesoporous silica-based bioactive glasses were reported for the first time in 2000, having the composition 76SiO-19CaO-2PO-3AgO (wt%) and a mean pore diameter of 28nm. This review paper discusses studies carried out exploring the potential antibacterial applications of drug-free mesoporous silica-based BGs. Bioactive glasses doped with metallic elements such as silver, copper, zinc, cerium and gallium are the point of interest of this review, in which SiO, SiO-CaO and SiO-CaO-PO systems are included as the parent glass compositions. Key findings are that silica-based mesoporous BGs offer a potential alternative to the systemic delivery of antibiotics for prevention against infections. The composition dependent dissolution rate and the concentration of the doped elements affect the antibacterial efficacy of BGs. A balance between antibacterial activity and biocompatibility is required, since a high dose of metallic ion addition can cause cytotoxicity. Typical applications of mesoporous BGs doped with antibacterial ions include bone tissue regeneration, multifunctional ceramic coatings for orthopedic devices and orbital implants, scaffolds with enhanced angiogenesis potential, osteostimulation and antibacterial properties for the treatment of large bone defects as well as in wound healing.
Porous composite scaffolds with decoupled ion release of copper and strontium were fabricated and characterized: a reproducible and cost-effective approach to obtain constructs with tailored release profiles and promising biological properties.
Soluble Ga/Ce-doped phosphate glass fibres exhibiting controlled release of ions were developed and characterised for wound healing applications. Fibres did not disturb the proliferation and migration of cells and showed antibacterial properties.
Phosphate-based glasses (PBG) have low melting temperatures and can be obtained by meltquenching and sol-gel methods. The most significant characteristic of PBG is their ability to dissolve completely in aqueous solution within different timeframes. This solubility can reduce the need for revision surgeries and makes PBG well-suited for soft tissue regeneration. Phosphate glass fibres (PGF) due to their geometry and volume-surface area ratio are the subject of a growing number of studies on resorbable composites. Medical applications include bone fixation devices, nerve tissue scaffolds and wound healing. PBG can be doped with various ions to enhance their biological, chemical and structural properties allowing the preparation of fibres with designed properties and with the ability to release biologically active ions upon degradation. The aim of this review is to look in detail at the influence of different dopants on PGF behaviour, both at a structural and biological level.
Due to the threat posed by the rapid growth in the resistance of microbial species to antibiotics, there is an urgent need to develop novel materials for biomedical applications capable of providing antibacterial properties without the use of such drugs. Bone healing represents one of the applications with the highest risk of postoperative infections, with potential serious complications in case of bacterial contaminations. Therefore, tissue engineering approaches aiming at the regeneration of bone tissue should be based on the use of materials possessing antibacterial properties alongside with biological and functional characteristics. In this study, we investigated the combination of polyhydroxyalkanoates (PHAs) with a novel antimicrobial hydroxyapatite (HA) containing selenium and strontium. Strontium was chosen for its well-known osteoinductive properties, while selenium is an emerging element investigated for its multi-functional activity as an antimicrobial and anticancer agent. Successful incorporation of such ions in the HA structure was obtained. Antibacterial activity against Staphylococcus aureus 6538P and Escherichia coli 8739 was confirmed for co-substituted HA in the powder form. Polymer-matrix composites based on two types of PHAs, P(3HB) and P(3HO-co-3HD-co-3HDD), were prepared by the incorporation of the developed antibacterial HA. An in-depth characterization of the composite materials was conducted to evaluate the effect of the filler on the physicochemical, thermal, and mechanical properties of the films. In vitro antibacterial testing showed that the composite samples induce a high reduction of the number of S. aureus 6538P and E. coli 8739 bacterial cells cultured on the surface of the materials. The films are also capable of releasing active ions which inhibited the growth of both Gram-positive and Gram-negative bacteria.
Novel cerium‐ (Ce) and gallium (Ga)‐doped phosphate glasses (PGs) are successfully obtained by the peroxidation method. The new glasses are characterized using Fourier‐transform infrared spectroscopy (FTIR), Raman spectroscopy, X‐ray diffraction, inductively coupled plasma‐optical emission spectroscopy (ICP‐OES), and pH measurements. A strong correlation between glass properties and their composition is found. The incorporation of Ga/Ce in the glass structure is confirmed by peak shifts in Raman and FTIR spectra. Degradation tests conducted in water confirm the soluble character of the PGs and reveal the influence of Ga and Ce on the degradation rate. Ga‐doped glasses are found to be less soluble than Ce‐doped ones (43%, 33%, 21%, and 16% of dry mass remained after 7 weeks for 7Ga, 5Ga, 5Ce, and 7Ce, respectively). Biological evaluation using ST‐2 cells shows adequate cell response with a cell viability of 80% measured using the indirect contact method depending on the composition. The cell viability decreases with an increase in Ga content and increases with Ce content. The antibacterial character of Ga/Ce‐doped PGs is confirmed by turbidity measurements against Escherichia coli and Staphylococcus carnosus. The novel Ce/Ga‐doped PGs exhibiting antibacterial properties and biocompatibility reported here are interesting for tissue engineering and wound healing applications.
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