Surface characterization of silver-doped bioactive glass

Tellurium-Doped Bioactive Glass Induces Ferroptosis in Osteosarcoma Cells Regardless of FSP1

Human osteosarcoma (OS) is a rare tumor predominantly affecting long bones and characterized by a poor prognosis. Currently, the first line of intervention consists of the surgical resection of primary tumors combined with radiotherapy and chemotherapy, with a profound impact on the patient's life. Since the surgical removal of OS frequently results in a large resection of bones, the use of biomaterials to sustain the stability of the remaining tissue and to stimulate bone regeneration is challenging. Moreover, residual neoplastic cells might be responsible for tumor recurrence. Here, we explored the potential of tellurium-ion-doped bioactive glass as a novel therapeutic intervention to both eradicate residual malignant cells and promote bone regeneration. Bioactive glass (BAG) has been extensively studied and employed in the field of regenerative medicine due to its osseointegration properties and ability to improve bone tissue regeneration. We found that the incorporation of tellurium (Te) in BAG selectively kills OS cells through ferroptosis while preserving the viability of hBMSCs and stimulating their osteodifferentiation. However, the mechanism of Te toxicity is still unclear: (i) Te-BAG generates lipid-ROS through LOXs activity but not iron overload; (ii) Te-dependent ferroptosis is mediated by GPX4 down-regulation; and (iii) the anti-ferroptotic activity of FSP1 is abrogated, whose expression confers the resistance of OS to the canonical induction of ferroptosis. Overall, our data show that Te-doped bioglass could represent an interesting biomaterial with both pro-ferroptotic activity towards residual cancer cells and pro-osteoregenerative activity.

Tailoring of bioactive glass and glass-ceramics properties for in vitro and in vivo response optimization: a review

Bioactive glasses are inorganic biocompatible materials that can find applications in many biomedical fields. The main application is bone and dental tissue engineering. However, some applications in contact with soft tissues are emerging. It is well known that both bulk (such as composition) and surface properties (such as morphology and wettability) of an implanted material influence the response of cells in contact with the implant. This review aims to elucidate and compare the main strategies that are employed to modulate cell behavior in contact with bioactive glasses. The first part of this review is focused on the doping of bioactive glasses with ions and drugs, which can be incorporated into the bioceramic to impart several therapeutic properties, such as osteogenic, proangiogenic, or/and antibacterial ones. The second part of this review is devoted to the chemical functionalization of bioactive glasses using drugs, extra-cellular matrix proteins, vitamins, and polyphenols. In the third and final part, the physical modifications of the surfaces of bioactive glasses are reviewed. Both top-down (removing materials from the surface, for example using laser treatment and etching strategies) and bottom-up (depositing materials on the surface, for example through the deposition of coatings) strategies are discussed.

Tailoring antimicrobial characteristic and mechanical behavior with silver in leucite–glass–ceramics for hard tissue engineering

Leucite glass–ceramics are excellent dental restorative materials, but they have relatively poor fracture toughness and high hardness, which leads to lower damage tolerance and counter‐tooth wear, respectively. These materials are also susceptible to bacterial infections and biofilm formations. Here, we report a versatile material leucite–silver‐based glass–ceramic to address the aforementioned shortcomings. Silver was incorporated in leucite (K2O·Al2O3·4SiO2) glass–ceramic to improve the fracture toughness, reduce hardness, and impart antibacterial characteristics. Silver (2, 5, 10, and 15 wt.%) was added into the leucite glass matrix by two approaches, that is, using silver nanoflakes (AgNFs) and using precursor (AgNO3), via thermal decomposition, followed by a sintering process. The incorporation of silver was confirmed by X‐ray diffraction, transmission electron microscopy, and energy‐dispersive spectroscopy. Results showed that the hardness of the leucite‐silver composite material was reduced by 30% and indentation toughness improved by 47% as determined by Vickers indentation. Antibacterial characteristics of the material were investigated against Staphylococcus aureus and Escherichia coli bacteria. Scanning electron microscopy was done to see the morphology of damaged bacteria and colonies. Further, antibacterial activity was quantified using the colony formation unit counting method. All the samples showed antibacterial activity and the sample with the highest silver content, that is, 15 wt.% showed maximum potential to damage the bacteria. Inductively coupled plasma‐atomic emission spectroscopy analysis is done in phosphate buffer saline solution to quantify the amount of silver leached out from the leucite‐silver glass–ceramic samples. It was seen that the cumulative leached‐out silver over 3 days was less than 4 μg/cm2 which is well within the daily tolerance limit (5 μg/kg/day) of silver for the human body. Further, to confirm the cell viability, a cytocompatibility test is performed using L929 fibroblast and AW8507 oral cell lines. Cell viability of more than 80% was achieved, suggesting their suitability for biomedical applications. It is believed that the developed material can be a potential candidate for various applications like dental restorations, implants, and coating material for different substrates (SS 304, SS 316, Ti6Al4V, etc.) to protect them from bacterial infections and biofilm formation, etc.

Removal of Toxic Lead from Wastewater by Lupinus albus Seed Hull

In this work, we address two concerns at once: waste reduction and the development of a lead removal adsorbent. The potential of Lupinus albus seed hull (LSH) powder as an efficient, innovative, and economical adsorbent for Pb(II) absorption was examined in this study. Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy investigations were used to determine the structural and morphological properties of the LSH adsorbent. The adsorption process was studied in batch mode with multiple process variables (adsorbent dosage of 4.0-20 g/L; solution pH of 1.5-5.5; contact time of 15-70 min). By fitting the equilibrium data to the Langmuir isotherm model, the maximum adsorption capacity of Pb(II) was 357.14 mg/g at optimized pH (5.5), LSH dose (0.4 g), and interaction time (60 min) with starting Pb(II) concentration of 50 mg L-1. As for the reaction kinetics, the pseudo-second-order model was shown to be a convenient match. LSH can be reused after four desorption/adsorption cycles and has a high potential for eliminating Pb(II) from wastewater.

Zinc Oxide-Doped Antibacterial Soda Lime Glass Produced as a Glass Container

The aim of this study is to produce and characterize glass materials, which have an enhanced antibacterial property by the conventional melting method. Container glass compositions including different amounts of zinc oxide (ZnO) (5.0, 7.5, and 10.0%) were prepared and melted to be able to obtain the antibacterial glass. The Release and antibacterial tests, which were performed after the melting process, showed that the glass doped with 5% ZnO was the most appropriate composition according to test results (99.82% Escherichia coli inactivation) and its raw materials' costs. Physical, thermal, and mechanical properties such as thermal expansion coefficient (86.1 × 10^-7/°C), density (2.523 g/cm³), refractive index (1.5191), hardness (596 kg/mm²), and elastic modulus (5.84 GPa) of the glass doped with 5% ZnO were determined, and the results showed that the obtained antibacterial glass sample is suitable to be used as a glass container. HighTemperature Melting Observation System studies were performed on the produced antibacterial glass composition, and it was found that the antibacterial glass can be produced in soda lime glass furnaces without changing any furnace design and production parameters. This antibacterial glass can be a remarkable product for the pharmaceutical and food industries.

Investigating the structure, solubility, and antibacterial properties of silver- and copper-doped hydroxyapatite

Hydroxyapatite (HA) powders were synthesized by the wet precipitation method in which two experimental compositions were synthesized (10 mol% Ag-HA and Cu-HA) where the CaNO₃ content was partially substituted with AgNO₃ and Cu(NO₃ )₂ . X-ray diffraction (XRD) was employed to characterize changes to the HA structure as the dopants (Cu²⁺ , Ag⁺ ) were incorporated into the materials structure. Energy-dispersive X-ray spectroscopy (EDS) determined confirmed the compositions and found that the Ca/P ratio was 1.63 for the control (HA) while Ag-HA and Cu-HA exhibited (X + Ca)/P ratios of 1.79 and 1.65, respectively. Antibacterial efficacies were evaluated against E. coli and S. aureus, as a function of surface area and incubation time. The more prominent antibacterial effects were observed with both Ag-HA and Cu-HA and the materials antibacterial influence was maintained with respect to time. Ion release studies of each HA composition (15, 30, and 45 days) showed that Cu-HA released significantly more Cu²⁺ (36.1 ± 5.1 mg/L) than Ag⁺ (2.9 ± 1.2 mg/L) from Ag-HA. Analysis of each composition incubated in simulated body fluid (SBF) exhibited surface depositions that are likely calcium phosphate (CaP). Cytocompatibility testing in MC 3T3 Osteoblasts showed slight reductions in cell viability when tested using MTT assay, however cell adhesion studies were positive for each composition.

Sol-gel silicate glass doped with silver for bone regeneration: Antibacterial activity, intermediate water, and cell death mode

The hydration state of bioactive glass materials and its relationship with their biocompatibility have been receiving attention. In this research, silver-containing bioactive glasses (BGAgs) (Ag contents of 0.25, 0.5, and 1.0% in the glass system) were developed using the sol-gel method. Their physicochemical properties, size, morphology, and surface area were characterized by conducting X-rays diffraction (XRD), Fourier transform infrared (FTIR), Transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) surface area analyses. The surface charges of the developed BGAgs were evaluated using the Nano Zetasizer. Moreover, the antibacterial activities and intermediate water (IW) contents of hydrated BGAgs were determined. Finally, BGAgs disks were tested against osteosarcoma (MG63) cell line to evaluate their death modes. The physicochemical characteristics of the BGAgs revealed no modifications after Ag doping. In comparison, relative changes were recorded in the particle size (20-33 to 16-29 nm), surface area (4.3 to 3.7 m²/g), and particle charge (-24 to -14.6 mV). Doping the current glass system with silver produced impressive amounts of IW, consistent with recorded proliferation rates of the cells when treated with BGAgs. The determined hydration states correlated with other findings in this research might be helpful in predicting and assessing the biological behaviors of BGAgs.

Structural, biological investigation of metal (Fe, Cu, Ag)-ceramic composites

In the present study, five composites based on metals (Ag, Fe, Cu) and ceramic; named as 0.2 Ag, 0.2 Cu, 0.2 Fe, 0.1Ag-0.1Cu, and 0.1Ag-0.1Fe were prepared by the solid-state sintering method. Two different phases of wollastonite: β-wollastonite (JCPDS No.: 01-076-0186), and α-wollastonite (JCPDS No.:00-031-0300) were identified in all composite. The in vitro bioactivity assay performed in simulated body fluid showed the bioactive behavior of all composites except one having >0.1% Ag concentration. The antibacterial activity test was performed against two pathogenic bacteria Staph. Aureus and Staph. Epidermidis using the agar well diffusion method. Results of antibacterial assays showed that all samples showed antibacterial activity except the 0.2 Fe sample. It was observed that the addition of Ag and Cu provided the inhibitory ability to composites, 0.1Ag-0.1Cu and 0.1Ag-0.1Fe composites are regarded as an optimum composite having better bioactive and antibacterial efficacy as compared to all other composites.

Titanium-Containing Silicate-Based Sol-Gel Bioactive Glass: Development, Characterization, and Applications

Bioactive glasses are surface-reactive glasses that, when placed in physiological fluid, undergo a transformation from glass to hydroxyapatite. Doping the bioactive glass with metallic ions can impart desirable and unique properties that are not inherent to natural hydroxyapatite. Once such ion is titanium. Titanium exists in trace amounts in native dental enamel, and its presence has been correlated with increased tooth hardness and brightness, both desirable clinical properties. Synthetic titanium-substituted hydroxyapatite exhibits better mechanical and antibacterial properties and demonstrates potential for an improved cellular response when compared to unmodified hydroxyapatite with applications in the broader field of bone tissue engineering. In this work, we use the sol-gel method to synthesize a titanium-containing silicate-based bioactive glass aimed at generating titanium-substituted hydroxyapatite on the glass surface upon immersion in body fluid. Titanium is homogeneously distributed throughout our glass, which keeps its amorphous nature. After 14 days of immersion in simulated body fluid, the glass forms a titanium-substituted hydroxyapatite on its surface. Enamel surfaces treated with the titanium-containing glass show significantly increased microhardness compared to enamel surfaces treated with a control glass, confirming the potential for the proposed glass in enamel remineralization. We also show that the presence of titanium in the glass promotes cell differentiation toward bone formation, suggesting further applications for this material in the broader field of bone tissue engineering.

Buffering capacity and antibacterial properties among bioactive glass-containing orthodontic adhesives

This study was to evaluate the acid-buffering capacity and antibacterial properties of orthodontic adhesives containing bioactive glasses (BAGs) (45S5, 45S5F, S53P4), Hydroxyapatite, beta-tricalcium phosphate, and Canasite. Fillers comprising 15 wt% bioactive glasses, HAp, β-TCP, and Canasite incorporated with 55 wt% silanated glass were added to a mixture of UDMA/TEGDMA. Acid-buffering capacity was tested by exposing disc-shaped samples of each adhesive to medium of bacteria-produced acids, and pH changes were recorded at 24 and 48 h. Antibacterial properties were assessed by indirect testing by exposing polymerized adhesive samples to a medium and direct testing by immersing the specimens in solutions containing S. mutans and S. sanguinis. A significant buffering capacity was shown by the 45S5, 45S5F and S53P4 BAG adhesives. The antibacterial properties were not significant in all experimental adhesives. Therefore, the experimental orthodontic adhesives containing BAGs demonstrated a significant buffering capacity but did not show significant antibacterial properties against S. mutans and S. sanguinis.

Employing waste to manage waste: Utilizing waste biomaterials for the elimination of hazardous contaminant [Cr(VI)] from aqueous matrices

Pollution caused due to discharge of toxic and hazardous chemical contaminants from industrial processes is an issue of major environmental concern. Hexavalent chromium [Cr(VI)] is one such known toxic heavy metal contaminant emanated largely from various industrial processes. Since physical-chemical treatment techniques are beset with several problems, there is an increased attention on the use of waste biomaterials/biomass as sorbents for the elimination of heavy metals from aqueous matrices. The main purpose of this study was to evaluate the effectiveness of some low-cost waste biomaterials such as fruit wastes, agricultural and industrial waste/byproducts, waste parts of photosynthetic plants, aquatic plants and fungal biomass collected from different sources for the biosorption of Cr(VI) from aqueous matrices. Amid the tested biomaterials, wood apple shell (WAS) biomass (Limonia acidissima) was found to be highly efficient biosorbent for Cr(VI) sorption. In majority of biomass, it was observed that biosorption of Cr(VI) took place at acidic pH with optimum pH ranging from 2.0 to 5.0. Loading capacity of WAS biomass (29.37 mg/g) was higher than that of conventional adsorbent activated charcoal (26.56 mg/g), which was used as control. Cr(VI) treated biomass (WAS) was characterized using instrumental techniques such as Scanned Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) confirmed the adsorption of Cr(VI). Boehm titration and FTIR studies were conducted to ascertain the presence of functional groups responsible for Cr(VI) sorption by WAS biomass. The WAS biomass removed Cr(VI) from industrial wastewater with an efficiency of >99.9% thus complying with the statutory limits. Considering the economical aspect, the selected biomass can be viewed as a potential candidate for the elimination of toxic contaminant from wastewater.

Tellurium: A new active element for innovative multifunctional bioactive glasses

Bioactive glasses have been widely investigated for their ability to release ions with therapeutic effect. In this paper, a silica based bioactive glass was doped with a low amount of tellurium dioxide (1 and 5 mol%) to confer antibacterial and antioxidant properties. The obtained glasses were characterized in terms of morphology, composition, structure, characteristic temperatures and in vitro bioactivity. Moreover, comprehensive analyses were carried out to estimate the cytocompatibility, the antibacterial and antioxidant properties of Te-doped glasses. The performed characterizations demonstrated that the Te insertion did not interfere with the amorphous nature of the glass, the substitution of SiO₂ with TeO₂ led to a slight decrease in T_g and a TeO₂ amount higher than 1 mol% can induce a change in the primary crystal field. In vitro bioactivity test demonstrated the Te-doped glass ability to induce the precipitation of hydroxyapatite. Finally, the biological characterization showed a strong antibacterial and antioxidant effects of Te-containing glasses in comparison with the control glass, demonstrating that Te is a promising element to enhance the biological response of biomaterials.

Silica-Based Bioactive Glasses and Their Applications in Hard Tissue Regeneration: A Review

Regenerative medicine is a field that aims to influence and improvise the processes of tissue repair and restoration and to assist the body to heal and recover. In the field of hard tissue regeneration, bio-inert materials are being predominantly used, and there is a necessity to use bioactive materials that can help in better tissue-implant interactions and facilitate the healing and regeneration process. One such bioactive material that is being focused upon and studied extensively in the past few decades is bioactive glass (BG). The original bioactive glass (45S5) is composed of silicon dioxide, sodium dioxide, calcium oxide, and phosphorus pentoxide and is mainly referred to by its commercial name Bioglass. BG is mainly used for bone tissue regeneration due to its osteoconductivity and osteostimulation properties. The bioactivity of BG, however, is highly dependent on the compositional ratio of certain glass-forming system content. The manipulation of content ratio and the element compositional flexibility of BG-forming network developed other types of bioactive glasses with controllable chemical durability and chemical affinity with bone and bioactivity. This review article mainly discusses the basic information about silica-based bioactive glasses, including their composition, processing, and properties, as well as their medical applications such as in bone regeneration, as bone grafts, and as dental implant coatings.

Biomimetic in situ precipitation of calcium phosphate containing silver nanoparticles on zirconia ceramic materials for surface functionalization in terms of antimicrobial and osteoconductive properties

OBJECTIVE

Zirconia is commonly used for manufacturing of dental implants thanks to its excellent mechanical, biological and aesthetic properties. However, its bioinertness inhibits bonding with the surrounding hard tissue and other surface interactions. In our study, we present a method for multifunctionalization of zirconia surface to improve its osseointegration and to minimize the infection risks.

METHODS

For this reason, we introduced antibacterial and bioactive properties to zirconia surfaces by calcium phosphate biomimetic coating. The samples were incubated in vials in horizontal and vertical position in concentrated simulated body fluid (SBF) containing 0.1, 0.5, and 3 g/L of silver nanoparticles (Ag-NPs) and then were tested for their structure, surface properties, cytocompatibility and antibacterial properties.

RESULTS AND SIGNIFICANCE

The results demonstrated that our method is suitable to introduce Ag-NPs at different concentrations into the calcium phosphate layer, i.e. from 0.05-26.6 atom% as shown by EDX. According to the results of CFU-assay these coatings exhibited antibacterial properties against S. aureus and E. coli in correlation with the concentration of Ag-NP. The potential cytotoxicity of the coated samples was determined by AlamarBlue® assay and live/dead staining of MG63 osteoblast-like cells in direct contact and by testing the extracts from the materials. Only samples containing 0.05 atom% Ag-NPs, i.e. incubated in vertical position at SBF with 0.01 g/L Ag-NPs, were found cytocompatible in direct contact with MG63 cells. On the contrary in the indirect tests, the extracts from all the materials were found cytocompatible. This method could allow developing the completely new material group, exhibiting not only one but several biological properties, which can improve osseointegration and minimize infection risks.

Synthesis of Silver Modified Bioactive Glassy Materials with Antibacterial Properties via Facile and Low-Temperature Route

There is an increasing clinical need to develop novel biomaterials that combine regenerative and biocidal properties. In this work, we present the preparation of silver/silica-based glassy bioactive (ABG) compositions via a facile, fast (20 h), and low temperature (80 °C) approach and their characterization. The fabrication process included the synthesis of the bioactive glass (BG) particles followed by the surface modification of the bioactive glass with silver nanoparticles. The microstructural features of ABG samples before and after exposure to simulated body fluid (SBF), as well as their ion release behavior during SBF test were evaluated using infrared spectrometry (FTIR), ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), electron microscopies (TEM and SEM) and optical emission spectroscopy (OES). The antibacterial properties of the experimental compositions were tested against Escherichia coli (E. coli). The results indicated that the prepared ABG materials possess antibacterial activity against E. coli, which is directly correlated with the glass surface modification.

Identification of mesenchymal stromal cell survival responses to antimicrobial silver ion concentrations released from orthopaedic implants

Antimicrobial silver (Ag⁺) coatings on orthopaedic implants may reduce infection rates, but should not be to the detriment of regenerative cell populations, primarily mesenchymal stem/stromal cells (MSCs). We determined intramedullary silver release profiles in vivo, which were used to test relevant Ag⁺ concentrations on MSC function in vitro. We measured a rapid elution of Ag⁺ from intramedullary pins in a rat femoral implantation model, delivering a maximum potential concentration of 7.8 µM, which was below toxic levels determined for MSCs in vitro (EC₅₀, 33 µM). Additionally, we present in vitro data of the reduced colonisation of implants by Staphylococcus aureus. MSCs exposed to Ag⁺ prior to/during osteogenic differentiation were not statistically affected. Notably, at clonal density, the colony-forming capacity of MSCs was significantly reduced in the presence of 10 µM Ag⁺, suggesting that a subpopulation of clonal MSCs was sensitive to Ag⁺ exposure. At a molecular level, surviving colony-forming MSCs treated with Ag⁺ demonstrated a significant upregulation of components of the peroxiredoxin/thioredoxin pathway and processes involved in glutathione metabolism compared to untreated controls. Inhibition of glutathione synthesis using l-buthionine sulfoxamine eliminated MSC clonogenicity in the presence of Ag⁺, which was rescued by exogenous glutathione.

Effect of Al3+ ions substitution in novel zinc phosphate glasses on formation of HAp layer for bone graft applications

Aluminium doped phosphate based bioglasses have potential applications in the field of bone tissue engineering, because of their excellent bioactivity and biocompatibility along with high mechanical strength and controlled dissolution. In the present study, 8ZnO-22Na₂O-(24-x)CaO-46P₂O₅-xAl₂O₃ (where x = 0, 2, 4, 6, 8 and 10 mol%) glass system was synthesized and investigated by means of XRD, FTIR, SEM and EDS before and after immersion in SBF for 3, 7, 14 and 21days, the physic-chemical properties of the samples, including density and microhardness, evaluation of pH and weight loss of glasses in physiological fluid and cell cultural studies like cell viability, cytocompatability and cell proliferation by seeding rMSCs cells on the glass samples in order to throw some light on their structural properties. The results showed that, the density and Vickers hardness found to be increased with the increase in content of alumina due to the slight increase in the number of octahedrally coordinated Al³⁺ ions and stronger ionic cross linkages due to insertion of Al³⁺ ions between phosphate networks. The initial rise in pH and controlled solubility in SBF strongly supports the apatite layer development. The growth of the rMSCs cells on all samples showing good cytocompatability and proliferation up to 6 mol% Al₂O₃ after that decreases slightly with an increase in alumina content due to network forming action of Al³⁺ ions in zinc phosphate based glasses. The results confirmed the suitability of these glasses for clinical trials towards bone repair and regeneration resorbable implants.

Recent advances and future perspectives of sol–gel derived porous bioactive glasses: a review

Sol–gel derived bioactive glasses have been extensively explored as a promising and highly porous scaffold materials for bone tissue regeneration applications owing to their exceptional osteoconductivity, osteostimulation and degradation rates.

Functionalization and Surface Modifications of Bioactive Glasses (BGs): Tailoring of the Biological Response Working on the Outermost Surface Layer

Bioactive glasses (BGs) are routinely being used as potent materials for hard and soft tissue engineering applications; however, improving their biological activities through surface functionalization and modification has been underestimated so far. The surface characteristics of BGs are key factors in determining the success of any implanted BG-based material in vivo since they regulate the affinity and binding of different biological macromolecules and thereby the interactions between cells and the implant. Therefore, a number of strategies using chemical agents (e.g., glutaraldehyde, silanes) and physical methods (e.g., laser treatment) have been evaluated and applied to design properly, tailor, and improve the surface properties of BGs. All these approaches aim at enhancing the biological activities of BGs, including the induction of cell proliferation and subsequent osteogenesis, as well as the inhibition of bacterial growth and adhesion, thereby reducing infection. In this study, we present an overview of the currently used approaches of surface functionalization and modifications of BGs, along with discussing the biological outputs induced by these changes.

Ag modified mesoporous bioactive glass nanoparticles for enhanced antibacterial activity in 3D infected skin model

Bioactive glasses (BG) are versatile materials for various biomedical applications, including bone regeneration and wound healing, due to their bone bonding, antibacterial, osteogenic, and angiogenic properties. In this study, we aimed to enhance the antibacterial activity of SiO₂-CaO mesoporous bioactive glass nanoparticles (MBGN) by incorporating silver (Ag) through a surface modification approach. The modified Ag-containing nanoparticles (Ag-MBGN) maintained spherical shape, mesoporous structure, high dispersity, and apatite-forming ability after the surface functionalization. The antibacterial activity of Ag-MBGN was assessed firstly using a planktonic bacteria model. Moreover, a 3D tissue-engineered infected skin model was used for the first time to evaluate the antibacterial activity of Ag-MBGN at the usage dose of 1 mg/mL. In the planktonic bacteria model, Ag-MBGN exhibited a significant antibacterial effect against both Pseudomonas aeruginosa and Staphylococcus aureus in comparison to non-engineered (Ag-free) MBGN and the blank control. Moreover, Ag-MBGN did not show cytotoxicity towards fibroblasts at the usage dose. However, in the 3D infected skin model, Ag-MBGN only demonstrated antibacterial activity against S. aureus whereas their antibacterial action against P. aeruginosa was inhibited. In conclusion, surface modification by Ag incorporation is a feasible approach to enhance the antibacterial activity of MBGN without significantly impacting their morphology, polydispersity, and apatite-forming ability. The prepared Ag-MBGN are attractive building blocks for the development of 3D antibacterial scaffolds for tissue engineering.

Bioactive Glasses and Glass-Ceramics for Healthcare Applications in Bone Regeneration and Tissue Engineering

The discovery of bioactive glasses (BGs) in the late 1960s by Larry Hench et al. was driven by the need for implant materials with an ability to bond to living tissues, which were intended to replace inert metal and plastic implants that were not well tolerated by the body. Among a number of tested compositions, the one that later became designated by the well-known trademark of 45S5 Bioglass® excelled in its ability to bond to bone and soft tissues. Bonding to living tissues was mediated through the formation of an interfacial bone-like hydroxyapatite layer when the bioglass was put in contact with biological fluids in vivo. This feature represented a remarkable milestone, and has inspired many other investigations aiming at further exploring the in vitro and in vivo performances of this and other related BG compositions. This paradigmatic example of a target-oriented research is certainly one of the most valuable contributions that one can learn from Larry Hench. Such a goal-oriented approach needs to be continuously stimulated, aiming at finding out better performing materials to overcome the limitations of the existing ones, including the 45S5 Bioglass®. Its well-known that its main limitations include: (i) the high pH environment that is created by its high sodium content could turn it cytotoxic; (ii) and the poor sintering ability makes the fabrication of porous three-dimensional (3D) scaffolds difficult. All of these relevant features strongly depend on a number of interrelated factors that need to be well compromised. The selected chemical composition strongly determines the glass structure, the biocompatibility, the degradation rate, and the ease of processing (scaffolds fabrication and sintering). This manuscript presents a first general appraisal of the scientific output in the interrelated areas of bioactive glasses and glass-ceramics, scaffolds, implant coatings, and tissue engineering. Then, it gives an overview of the critical issues that need to be considered when developing bioactive glasses for healthcare applications. The aim is to provide knowledge-based tools towards guiding young researchers in the design of new bioactive glass compositions, taking into account the desired functional properties.

Bioactive Glasses: From Parent 45S5 Composition to Scaffold-Assisted Tissue-Healing Therapies

Nowadays, bioactive glasses (BGs) are mainly used to improve and support the healing process of osseous defects deriving from traumatic events, tumor removal, congenital pathologies, implant revisions, or infections. In the past, several approaches have been proposed in the replacement of extensive bone defects, each one with its own advantages and drawbacks. As a result, the need for synthetic bone grafts is still a remarkable clinical challenge since more than 1 million bone-graft surgical operations are annually performed worldwide. Moreover, recent studies show the effectiveness of BGs in the regeneration of soft tissues, too. Often, surgical criteria do not match the engineering ones and, thus, a compromise is required for getting closer to an ideal outcome in terms of good regeneration, mechanical support, and biocompatibility in contact with living tissues. The aim of the present review is providing a general overview of BGs, with particular reference to their use in clinics over the last decades and the latest synthesis/processing methods. Recent advances in the use of BGs in tissue engineering are outlined, where the use of porous scaffolds is gaining growing importance thanks to the new possibilities given by technological progress extended to both manufacturing processes and functionalization techniques.

New infrared-assisted method for sol-gel derived ZnO:Ag thin films: Structural and bacterial inhibition properties

A new sol-gel method, based on crystallization with Infrared heating, was developed to obtain ZnO:Ag thin films. The common sol, with zinc acetate as precursor and silver nitrate as doping source (1, 3 and 5 % molar), isopropanol and distilled water as solvents and monoethanolamine as stabilizer agent; was modified with Pluronic F127 and diethylene glycol as rheological agents, and with urea as fuel to produce enough energy to the combustion and to promote the crystallization process. Later, Corning glass-substrates were dipped into the sol at a constant speed of 3mms^-1. To provide the necessary energy for obtaining the hexagonal ZnO structure of the coatings during the drying and consolidation process, instead of using the common furnace heat-treatment, the films were heated by means of an infrared (IR) ceramic lamp (800W) for 15, 30, 45, 60 and 180 minutes, and the effect of this annealing method was analyzed. The structural properties were examined by means of X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR), whereas morphology was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The examination revealed a homogeneous distribution of particles with the characteristic pores of pluronic F127, and the coating roughness had an average value of 100nm by AFM. To evaluate the effect on the number of dipping cycles and the IR-treatment on the thickness, ellipsometry results for 1, 3 and 5 deposits were analyzed and showed increments of 780, 945 and 1082nm, respectively. Finally, to test of the antibacterial activity, instead of the common one-microorganism approach, environmental microorganisms that grow with expose of the broth to the ambient conditions were employed (microbial consortium), which is a real environmental condition. The biological test was carried out by kinetic growth inhibition (optical density) of heterotrophic bacteria in culture liquid media under conditions of light, light-dark and darkness, to analyze the effect of light. A significance reduction in growth was obtained for doped coatings with silver in comparison with the control ZnO substrate. Furthermore, the analysis bacteria growth inhibition on a solid surface showed that the films effectively present antibacterial activity. The best result was obtained with ZnO:Ag 1% in light conditions, about 67%, but all the coatings inhibited the bacterial activity.

Structure, dissolution behavior, cytocompatibility, and antibacterial activity of silver-containing calcium phosphate invert glasses

Novel CaO‐P₂O₅‐Nb₂O₅‐Ag₂O invert glasses with substitution Ag₂O for Nb₂O₅ were successfully prepared using a melt‐quenching method. Ag₂O in the glasses act as a network modifier oxide, playing the same role as Na₂O, which breaks the phosphate chains. Analysis of the ultraviolet‐visible absorption spectra of the glasses showed that the glass matrix contained ionic silver species and silver nanoparticles. Approximately 0.05 mM of Nb⁵⁺ ions released from the glasses, which would be expected to stimulate osteoblast differentiation. A glass containing 1 mol % Ag₂O showed a linear increase in the releasing amount of Ag⁺ ions with increasing soaking time, whereas glasses containing 3–5 mol % Ag₂O showed Ag⁺ ion concentrations of around 13 μM at day 3, and then maintained similar values until day 7. When the solution was replaced with fresh solution every 2 days, the Ag⁺ ion dissolution amounts indicated almost constantly 13 μM due to AgCl formation. There were no differences in the numbers of primary osteoblast cells on silver‐free and silver‐containing glasses after cultivation for 1–7 days. The silver‐containing calcium phosphate invert glasses showed cytocompatibility with simultaneous antibacterial activity to Escherichia coli and Staphylococcus aureus. © 2017 The Authors. Journal of Biomedical Materials Research Part A published by Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3127–3135, 2017.

Structural Characterization and Antifungal Studies of Zinc-Doped Hydroxyapatite Coatings

The present study is focused on the synthesis, characterization and antifungal evaluation of zinc-doped hydroxyapatite (Zn:HAp) coatings. The Zn:HAp coatings were deposited on a pure Si (Zn:HAp_Si) and Ti (Zn:HAp_Ti) substrate by a sol-gel dip coating method using a zinc-doped hydroxyapatite nanogel. The nature of the crystal phase was determined by X-ray diffraction (XRD). The crystalline phase of the prepared Zn:HAp composite was assigned to hexagonal hydroxyapatite in the P63/m space group. The colloidal properties of the resulting Zn:HAp (xZn = 0.1) nanogel were analyzed by Dynamic Light Scattering (DLS) and zeta potential. Scanning Electron Microscopy (SEM) was used to investigate the morphology of the zinc-doped hydroxyapatite (Zn:HAp) nanogel composite and Zn:HAp coatings. The elements Ca, P, O and Zn were found in the Zn:HAp composite. According to the EDX results, the degree of Zn substitution in the structure of Zn:HAp composite was 1.67 wt%. Moreover, the antifungal activity of Zn:HAp_Si and Zn:HAp_Ti against Candida albicans (C. albicans) was evaluated. A decrease in the number of surviving cells was not observed under dark conditions, whereas under daylight and UV light illumination a major decrease in the number of surviving cells was observed.

Preparation and characterization of hemoglobin-silver composites as biocompatible antiseptics

Microbial contamination has been a major challenge in a wide variety of fields such as biomedical and biomaterial applications. The development of biomaterials that possess excellent antibacterial ability and biocompatibility is of great importance to enhance the service life of biomaterials. In this study, the main protein component of red blood cells, hemoglobin (Hb), was employed to prepare Ag-Hb nanocomposites as novel biocompatible antiseptics. The formation of Ag-Hb nanocomposites on the titanium substrate are confirmed by field-emission scanning electron microscopy, Fourier transformed infrared spectroscopic, contact angles, and inductively coupled plasma atomic emission spectrometry analysis. The Ag-Hb titanium shows potent antibacterial ability against planktonic bacteria in the suspension and ability to prevent bacterial adhesion. Moreover, the Ag-Hb titanium shows excellent biocompatibility, which supports healthy osteoblast cellular activity and osteoblast differentiation. The results indicate that the Ag-Hb nanocomposites can be potentially useful for the fabrication of biomaterials for long-term applications.

Synthesis of Monodispersed Ag-Doped Bioactive Glass Nanoparticles via Surface Modification

Monodispersed spherical Ag-doped bioactive glass nanoparticles (Ag-BGNs) were synthesized by a modified Stöber method combined with surface modification. The surface modification was carried out at 25, 60, and 80 °C, respectively, to investigate the influence of processing temperature on particle properties. Energy-dispersive X-ray spectroscopy (EDS) results indicated that higher temperatures facilitate the incorporation of Ag. Hydroxyapatite (HA) formation on Ag-BGNs was detected upon immersion of the particles in simulated body fluid for 7 days, which indicated that Ag-BGNs maintained high bioactivity after surface modification. The conducted antibacterial assay confirmed that Ag-BGNs had an antibacterial effect on E. coli. The above results thereby suggest that surface modification is an effective way to incorporate Ag into BGNs and that the modified BGNs can remain monodispersed as well as exhibit bioactivity and antibacterial capability for biomedical applications.

In situ plasma fabrication of ceramic-like structure on polymeric implant with enhanced surface hardness, cytocompatibility and antibacterial capability

Polymeric materials are commonly found in orthopedic implants due to their unique mechanical properties and biocompatibility but the poor surface hardness and bacterial infection hamper many biomedical applications. In this study, a ceramic-like surface structure doped with silver is produced by successive plasma implantation of silicon (Si) and silver (Ag) into the polyamine 66 (PA66) substrate. Not only the surface hardness and elastic modulus are greatly enhanced due to the partial surface carbonization and the ceramic-like structure produced by the reaction between energetic Si and the carbon chain of PA66, but also the antibacterial activity is improved because of the combined effects rendered by Ag and SiC structure. Furthermore, the modified materials which exhibit good cytocompatibility upregulate bone-related genes and proteins expressions of the contacted bone mesenchymal stem cells (BMSCs). For the first time, it explores out that BMSCs osteogenesis on the antibacterial ceramic-like structure is mediated via the iNOS and nNOS signal pathways. The results reveal that in situ plasma fabrication of an antibacterial ceramic-like structure can endow PA66 with excellent surface hardness, cytocompatibility, as well as antibacterial capability.

Antibacterial and bioactive composite bone cements containing surface silver-doped glass particles

A bioactive silica-based glass powder (SBA2) was doped with silver (Ag(+)) ions by means of an ion-exchange process. Scanning electron microscopy (SEM), energy dispersion spectrometry (EDS) and x-ray diffraction (XRD) evidenced that the glass powder was enriched with Ag(+) ions. However, a small amount of Ag2CO3 precipitated with increased Ag concentrations in the exchange solution. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of Ag-SBA2 towards Staphylococcus aureus were also evaluated and were respectively 0.05 mg ml(-1) and 0.2 mg ml(-1). Subsequently, Ag-SBA2 glass was used as filler (30%wt) in a commercial formulation of bone cement (Simplex(™) P) in order to impart both antibacterial and bioactive properties. The composite bone cement was investigated in terms of morphology (using SEM) and composition (using EDS); the glass powder was well dispersed and exposed on the cement surface. Bioactivity tests in simulated body fluid (SBF) evidenced the precipitation of hydroxyapatite on sample surfaces. Composite cement demonstrated antibacterial properties and a compressive strength comparable to the commercial formulation.

Investigating the effect of silver coating on the solubility, antibacterial properties, and cytocompatibility of glass microspheres

Silver (Ag) coatings have been incorporated into many medical materials due to its ability to eradicate harmful microbes. In this study, glass microspheres (SiO2–Na2O–CaO–Al2O3) were synthesized and employed as substrates to investigate the effect Ag coating has on glass solubility and the subsequent biological effects. Initially, glasses were amorphous with a glass transition point (Tg) of 605℃ and microspheres were spherical with a mean particle diameter of 120 µm (±27). The Ag coating was determined to be crystalline in nature and its presence was confirmed using scanning electron microscopy and X-ray photoelectron spectroscopy. Ion release determined that Ag-coated ( Ag-S) microspheres increased the Na+ release rate but slightly reduced the Ca2+ and Si4+ release compared to an uncoated control ( UC-S). Additionally, the Ag-S reduced the pH to just above neutral (7.3–8.5) compared to the UC-S (7.7–9.1). Antibacterial testing determined significant reductions in planktonic Escherichia coli ( p = 0.000), Staphylococcus epidermidis ( p = 0.000) and Staphylococcus aureus ( p = 0.000) growth as a function of the presence of Ag and with respect to maturation (1, 7, and 30 days). Testing for toxicity levels using L929 Fibroblasts determined higher cell viability for the Ag-S at lower concentrations (5 µg/ml); in addition, no significant reduction in cell viability was observed with higher concentrations (15, 30 µg/ml).

Physics and chemistry of antimicrobial behavior of ion-exchanged silver in glass

The results of a comprehensive study involving the antimicrobial activity in a silver ion-exchanged glass are presented. The study includes the glass composition, the method of incorporating silver into the glass, the effective concentration of the silver available at the glass surface, and the effect of the ambient environment. A quantitative kinetic model that includes the above factors in predicting the antimicrobial activity is proposed. Finally, experimental data demonstrating antibacterial activity against Staphylococcus aureus with correlation to the predicted model is shown.

Bioactive glasses beyond bone and teeth: emerging applications in contact with soft tissues

The applications of bioactive glasses (BGs) have to a great extent been related to the replacement, regeneration and repair of hard tissues, such as bone and teeth, and there is an extensive bibliography documenting the role of BGs as bone replacement materials and in bone tissue engineering applications. Interestingly, many of the biochemical reactions arising from the contact of BGs with bodily fluids, in particular the local increase in concentration of various ions at the glass-tissue interface, are also relevant to mechanisms involved in soft tissue regeneration. An increasing number of studies report on the application of BGs in contact with soft tissues, aiming at exploiting the well-known bioactive properties of BGs in soft tissue regeneration and wound healing. This review focuses on research, sometimes involving preliminary in vitro studies but also in vivo evidence, that demonstrates the suitability of BGs in contact with tissues outside the skeletal system, which includes studies investigating vascularization, wound healing and cardiac, lung, nerve, gastrointestinal, urinary tract and laryngeal tissue repair using BGs in various forms of particulates, fibers and nanoparticles with and without polymer components. Potentially active mechanisms of interaction of BGs and soft tissues based on the surface bioreactivity of BGs and on biomechanical stimuli affecting the soft tissue-BG collagenous bonding are discussed based on results in the literature.

Synthesis of new antibacterial composite coating for titanium based on highly ordered nanoporous silica and silver nanoparticles

Infection is the most common factor that leads to dental titanium implant failure. Antibacterial implant surfaces based on nano-scale modifications of the titanium appear as an attractive strategy for control of peri-implantitis. In the present work, the preparation and antibacterial properties of a novel composite coating for titanium based on nanoporous silica and silver nanoparticles are presented. Starch-capped silver nanoparticles (AgNPs) were synthesized and then incorporated into sol-gel based solution system. The AgNP-doped nanoporous silica coatings were prepared on titanium surface using a combined sol-gel and evaporation-induced self-assembly (EISA) method. The coating nanostructure was characterized by XRD, SEM-EDX, and HR-TEM. Antibacterial activity was evaluated against Aggregatibacter actinomycetemcomitans, a representative pathogen of dental peri-implantitis. Colony-forming units (CFUs) were counted within the biofilm and at the planktonic state. Biofilm development was quantified using crystal violet staining and viability of adherent bacteria was confirmed with the Live/Dead fluorescence assay. Silica-based composite coating containing AgNPs (AgNP/NSC) was prepared on titanium surface by direct incorporation of AgNP suspension into the sol-gel system. The self-assembly technique enabled the spontaneous formation of a highly ordered nanoporosity in the coating structure, which is a desired property for osseointegration aspects of titanium implant surface. AgNP/NSC coating produces a strong antibacterial effect on titanium surface by not only killing the adherent bacteria but also reducing the extent of biofilm formation. Biofilm survival is reduced by more than 70% on the AgNP/NSC-modified titanium surface, compared to the control. This antibacterial effect was verified for up to 7 days of incubation. The long-term antibacterial activity exhibited by the nanostructured AgNP/NSC-titanium surface against A. actinomycetemcomitans suggests that this type of nano-scale surface modification is a promissory strategy to control infections associated with dental implant rehabilitation.

Bioceramics in ophthalmology

The benefits of ceramics in biomedical applications have been universally appreciated as they exhibit an extraordinarily broad set of physico-chemical, mechanical and biological properties which can be properly tailored by acting on their composition, porosity and surface texture to increase their versatility and suitability for targeted healthcare applications. Bioceramics have traditionally been used for the repair of hard tissues, such as bone and teeth, mainly due to their suitable strength for load-bearing applications, wear resistance (especially alumina, zirconia and composites thereof) and, in some cases, bone-bonding ability (calcium orthophosphates and bioactive glasses). Bioceramics have been also applied in other medical areas, like ophthalmic surgery; although their use in such a context has been scientifically documented since the late 1700s, the potential and importance of ceramic ocular implants still seem to be underestimated and an exhaustive, critical assessment is currently lacking in the relevant literature. The present review aims to fill this gap by giving a comprehensive picture of the ceramic-based materials and implants that are currently used in ophthalmology and pointing out the strengths and weaknesses of the existing devices. A prospect for future research is also provided, highlighting the potential of new, smart bioceramics able to carry specific added values which could have a significant impact on the treatment of ocular diseases.

Calcium and zinc containing bactericidal glass coatings for biomedical metallic substrates

The present work presents new bactericidal coatings, based on two families of non-toxic, antimicrobial glasses belonging to B₂O₃–SiO₂–Na₂O–ZnO and SiO₂–Na₂O–Al₂O₃–CaO–B₂O₃ systems. Free of cracking, single layer direct coatings on different biomedical metallic substrates (titanium alloy, Nb, Ta, and stainless steel) have been developed. Thermal expansion mismatch was adjusted by changing glass composition of the glass type, as well as the firing atmosphere (air or Ar) according to the biomedical metallic substrates. Formation of bubbles in some of the glassy coatings has been rationalized considering the reactions that take place at the different metal/coating interfaces. All the obtained coatings were proven to be strongly antibacterial versusEscherichia coli (>4 log).

Review: emerging developments in the use of bioactive glasses for treating infected prosthetic joints

Bacterial contamination of implanted orthopedic prostheses is a serious complication that requires prolonged systemic antibiotic therapy, major surgery to remove infected implants, bone reconstruction, and considerable morbidity. Local delivery of high doses of antibiotics using poly(methyl methacrylate) (PMMA) cement as the carrier, along with systemic antibiotics, is the standard treatment. However, PMMA is not biodegradable, and it can present a surface on which secondary bacterial infection can occur. PMMA spacers used to treat deep implant infections must be removed after resolution of the infection. Alternative carrier materials for antibiotics that could also restore deficient bone are therefore of interest. In this article, the development of bioactive glass-based materials as a delivery system for antibiotics is reviewed. Bioactive glass is osteoconductive, converts to hydroxyapatite, and heals to hard and soft tissues in vivo. Consequently, bioactive glass-based carriers can provide the combined functions of controlled local antibiotic delivery and bone restoration. Recently-developed borate bioactive glasses are of particular interest since they have controllable degradation rates coupled with desirable properties related to osteogenesis and angiogenesis. Such glasses have the potential for providing a new class of biomaterials, as substitutes for PMMA, in the treatment of deep bone infections.

Biomaterials for orbital implants and ocular prostheses: overview and future prospects

The removal of an eye is one of the most difficult and dramatic decisions that a surgeon must consider in case of severe trauma or life-threatening diseases to the patient. The philosophy behind the design of orbital implants has evolved significantly over the last 60 years, and the use of ever more appropriate biomaterials has successfully reduced the complication rate and improved the patient's clinical outcomes and satisfaction. This review provides a comprehensive picture of the main advances that have been made in the development of innovative biomaterials for orbital implants and ocular prostheses. Specifically, the advantages, limitations and performance of the existing devices are examined and critically compared, and the potential of new, smart and suitable biomaterials are described and discussed in detail to outline a forecast for future research directions.

Long-lasting in vivo and in vitro antibacterial ability of nanostructured titania coating incorporated with silver nanoparticles

Although titanium (Ti) implants are widely used clinically, implant-associated bacterial infection is still one of the most serious complications in orthopedic surgery. Long-term antibacterial properties and the ability to inhibit biofilm formation are highly desirable to prevent implant associated infection. In this study, a controllable amount of silver (Ag) nanoparticles was incorporated into titanium oxide; or titanium, nanotubes (TiO₂ -NTs). The reliable release and long-term antibacterial function of Ag, in vivo and in vitro, and influence normal bone-implant integration from the Ag released from Ag-incorporated NTs in vivo have been studied to make them useable in clinical practice. In the current study, TiO₂ -NTs loaded with Ag (NT-Ag) exhibited strong antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA, ATCC43300) in vitro for 30 days, and the ability to penetrate the protein layer well. In addition, X-ray examination and 2-[(18)F]-fiuoro-2-deoxy-D-glucose positron emission tomography indicates that NT-Ag show extremely long antibacterial activity in vivo in a rat model. Furthermore, histomorphometric analysis demonstrated that satisfactory bio-integration can be expected. Our results indicate that NT-Ag has both simultaneous antimicrobial and excellent bio-integration properties, make it a promising therapeutic material for orthopedic application.

Silver coated bioactive glass particles for wound healing applications

Bioactive glass particles (0.42SiO(2)-0.15CaO-0.23Na(2)O-0.20ZnO) of varying size (<90 μm and 425-850 μm) were synthesized and coated with silver (Ag) to produce Ag coated particles (PAg). These were compared against the uncoated analogous particles (Pcon.). Surface area analysis determined that Ag coating of the glass particles resulted in increased the surface area from 2.90 to 9.12 m(2)/g (90 μm) and 1.09-7.71 m(2)/g (425-850 μm). Scanning electron microscopy determined that the Ag coating remained at the surface and there was little diffusion through the bulk. Antibacterial (Escherichia coli--13 mm and Staphylococcus epidermidis--12 mm) and antifungal testing (Candida albicans--7.7 mm) determined that small Ag-coated glass particles exhibited the largest inhibition zones compared to uncoated particles. pH analysis determined an overall higher pH consider in the smaller particles, where after 24 h the large uncoated and Ag coated particles were 8.27 and 8.74 respectively, while the smaller uncoated and Ag coated particles attained pH values of 9.63 and 9.35 respectively.