Sol-gel Bioactive Glasses Research Articles

Microwave-assisted fabrication of nanostructured borate bioactive glass and its bioactivity.

Sol-gel bioactive glass with nanocrystalline structures has demonstrated enhanced bioactivity and acceptance by the surrounding bone tissue. In particular, borate bioactive glasses exhibit higher reactivity and apatite formation under the simulated in vitro and in vivo conditions. This study presents a microwave-assisted synthesis of borate bioactive glass (58S) and an understanding of its structural and in vitro bioactivity. By this synthesis method, the nanocrystalline structures formed within the amorphous matrix will regulate the degradation rate of the glass network during apatite formation. The calcinated borate bioactive glass features a nanorod crystalline hydroxyapatite structure embedded in the amorphous borate glass network. The formation of apatite on the surface of borate bioactive glass within 6 hours of immersion in simulated body fluid confirms the material's enhanced bioactivity and reactivity. Anti-oxidant studies, cell viability, and alkaline phosphate activity further corroborate the bioactivity of borate bioactive glass. In summary, this study highlights the significant potential of microwave-synthesized borate bioactive glass for a wide range of bone tissue engineering applications.

In Ukrainian

The aim of the work is the synthesis of nanodispersed phosphors based on lanthanum fluoride and phosphate, activated by terbium (LaF3:Tb3+ and LaРО4:Tb3+, respectively), promising for use in photodynamic therapy and optopharmacology, the study of their structural properties and luminescence spectra when excited by ultraviolet and X-ray radiation, as well as the possibility of their use in the composition of nanocomposites with magnetically sensitive nanosized Fe3O4 carriers and bioactive glass 60S. Nanocrystalline lanthanum fluoride and phosphate of hexagonal syngonium were synthesized, activated with terbium. The structural properties, chemical activity and biocompatibility of the surface, UV and X-ray luminescence spectra of the synthesized crystals were studied. The possibility of their use in the composition of nanocomposites with magnetically sensitive nanosized drug carriers and bioactive sol-gel glass is shown. The acid-base nature of the surface active centers of LaF3 and LaF3:Tb3+ NPs has been revealed. The proportions of negatively a––, positively a+ charged and neutral a0 active centers were calculated in the range of pH 2.4 – 12.7. The identified active surface centers can be represented by acidic (La3+) and basic (F-) Lewis centers, as well as basic Brønsted centers (OH- groups). The obtained data can be useful in optimizing the conditions of adsorption immobilization from a physiological solution of molecules of photosensitive substances (sensitizers) on the surface of phosphors based on lanthanum fluoride. Ensembles of particles of magnetically sensitive Fe3O4/LaF3:Tb3+ NCs of core-shell type were synthesized. The conditions of synthesis of NCs did not significantly change the magnetic properties of their cores – the initial single-domain Fe3O4 NPs. Composites of bioglass 60S with nanodispersed crystalline LaF3:Tb3+ and LaPO4:Tb3+ in the dry state and in distilled water medium demonstrated the presence of luminescence when excited by UV and X-ray radiation. The given data indicate the prospects of research of nanodispersed phosphors based on lanthanum fluoride and phosphate, their composites with magnetically sensitive nanosized carriers and bioactive glass, for use in optopharmacology and photodynamic therapy of tumor diseases, in particular, localized in organs of skull and bone tissues. In addition, research results can be useful for technical applications, in particular, in the creation of fluorescent detectors of high-energy electromagnetic radiation, development of photo- and optoelectronic devices, etc.

Design of sol-gel bioactive glasses: Towards tailored architecture and ion-supply for bone tissue regeneration

This paper reports the synthesis of borosilicate bioactive glasses nanoparticles containing ions of interest (calcium, strontium or silver ions) for the purpose of bone tissue regeneration using a modified Stöber method and their shaping by robocasting to produce macroporous grid-like architectures with controlled interconnected porosity. Main focus is on the design of a paste formulation, the optimization of the robocasting process to produce 3D scaffolds and ion release from the sintered scaffold in solution. Pastes were developed (40 vol% powder loading), characterized, and extruded layer-by-layer to form three-dimensional scaffolds with a grid-like macrostructure (400 μm diameter of the rods). After drying under controlled atmosphere, scaffolds were sintered. The sintering study revealed that the addition of silver reduced the densification point of the borosilicate glass. After immersion in a buffer solution, ionic release (Si, B and Sr) of the sintered scaffold was evaluated, and compared with the synthetized powder. The shaping process did not affect Sr dissolution. This controllable ion-release behavior of the scaffolds are promising for their therapeutic application.

The effect of copper addition on strontium-containing silicate-based sol-gel bioactive glass for tissue regeneration

Previous studies on bioactive glasses (BGs) have reported the therapeutic potential of either strontium (Sr2+) or copper (Cu2+) ions as dopants. This study incorporates both dopants into a novel BG composition for soft tissue attachment. The X-ray diffraction (XRD) patterns showed the presence of multiple crystalline phases, including copper oxide (CuO). Thermal analysis revealed the glass transition temperatures (Tg) ranged from 543 to 561 °C and decreased as Cu2+ concentrations increased. Raman spectroscopy showed the glass structure contained predominantly Q2 and Q3 species, while particle size and surface area were between 1.1–2.5 µm and 8–15 m2/g, respectively. No Cu2+ ions were released from the glass structure after 1000 h of incubation in deionized (DI) water. Agar diffusion testing against S. aureus found that each glass possessed antibacterial properties, with 4 mol% containing Cu-BG presenting the most significant inhibition zones at 3.1 ± 0.1 mm over the 7-day incubation time.

Nanostructured sol-gel bioactive glass 60S: In vitro study of bioactivity and antibacterial properties in combination with vancomycin

Nanostructured samples of bioactive glass 60S (BG 60S) with a composition (mol %) of 60% SiO2, 36% CaO, 4% P2O5 were synthesized by the sol-gel method in this research. The bioactivity of the synthesized material was evaluated by in vitro assays. The dynamics of the formation of hydroxyapatite (HA), contributing to the formation of effective bonds with bones and soft tissues during immersion in a simulated body fluid (SBF Kokubo), was evaluated using FTIR, XRD, and SEM-EDX. Changes of the specific surface values, particle size and zeta potential for soaked samples in SBF were also investigated. Determination of the antibacterial activity of BG 60S/vancomycin composites was carried out on test cultures of gram-positive microorganisms being one of the most frequent etiological factors of infectious complications in injuries – Staphylococcus aureus. The effectiveness of the release of the antibiotic was confirmed by determining the zone of inhibition of the test culture using the modified Kirby–Bauer disk diffusion method. It is shown that BG 60S/vancomycin composites are characterized by the preservation of antibacterial properties of vancomycin with its prolonged release, and osteoconductive properties, which are inherent in bioactive sol-gel glass and are promising for practical use in the surgical treatment of bone diseases. Based on the foundings, it is possible to suggest a positive effect of the joint application of BG 60S and vancomycin as part of composites with an effective combination of the functions of bone tissue restoration, treatment and prevention of postoperative infectious complications.

On the structure of Ag-containing sol-gel bioactive glasses: A surface crystal growth of metallic silver removes its network modifier role in the glass structure

Ag-containing bioactive glasses (Ag-BG) have been extensively studied as a bactericidal biomaterial, produced mainly by the sol-gel method over the last decades. According to the literature, sol-gel-derived Ag-BG may show metallic or ionic silver species in the glass structure. However, most of these works lack detailed information about how the addition of silver affects the glass network. In this study, we systematically produced sol-gel derived 58S glasses containing different quantities of Ag2O (1, 5, and 10 wt%), yielding glasses with different proportions of silver species (Ag0 or Ag+1). Results from X-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) evidenced the progressive formation of silver crystals due to the addition of silver in the glass structure. 29Si and 31P nuclear magnetic resonance and photoelectronic X-ray spectroscopies evidenced a glass depolymerization caused by Ag1+ addition in the glass structure. On the other hand, the presence of silver crystals (Ag0) removes the network modifier role of silver, yielding glasses with higher network connectivity. A possible mechanism to explain the formation of silver crystals was proposed based on surface nucleation and growth. Finally, we suggest understanding Ag1+ or Ag0 formation as a solution to design glasses with tuned bactericidal properties.

Influence of Mesoporous Bioactive Glass Particles Doped with Cu and Mg on the Microstructure and Properties of Zein-Based Coatings Obtained by Electrophoretic Deposition

Cu- and Mg-doped mesoporous sol-gel bioactive glasses (MSGG) were developed and their microstructure was investigated. Selected biological tests were also performed to assess their suitability for the functionalization of polymer zein coatings. The electrophoretic deposition (EPD) conditions to obtain composite coatings on Ti-13Nb-13Zr substrates were determined. The coatings with excellent adhesion to the substrates were macroscopically uniform, exhibiting open porosity and high roughness. The surfaces of the samples coated with MSGG/zein coatings became more hydrophilic than the titanium alloy substrates. However, with increase of the volume fraction of glass particles in the coatings, the contact angle increased. The coated alloy showed enhanced resistance to electrochemical corrosion in Ringer’s solution. The chemical composition of the glass used in the coating affected the parameters of wettability and resistance to electrochemical corrosion. Both coating types showed an increase in the antibacterial properties against Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria compared to pure zein. However, no significant differences were observed after a 24 h-long test.

Borosilicate sol–gel bioactive glasses and the effect of borate content on structure-property relationships

AbstractBorate-doped silicate glasses with chemical compositions of (70 − x)SiO2–xB2O3–30CaO (x = 0, 5, 15, and 25, in mol%) were synthesized using the sol–gel method, intended to be used in tissue regeneration. The effects of borate content on the glass surface morphology, chemical structure, ion dissolution behavior, and fibroblast compatibility were investigated. 11B magic angle spinning-solid state nuclear magnetic resonance and Fourier transform infrared spectra demonstrated that borate, in the glasses, possessed both three- and four-coordinated structures. From nitrogen sorption, the specific surface area of the glasses decreased with increased borate content and calcination temperature, from 600 °C to 700 °C. In the case of glasses undergoing calcination at 700 °C, silicate and calcium ion released in a Tris–HCl buffer solution (pH = 7.4) at the early stage of the immersion test decreased as borate content increased. The decrease in surface area caused by stabilizing at 700 °C due to the effect of increasing borate concentration controlled the ion dissolution behavior of the glasses. The proliferation ability of fibroblasts cultured with the dissolution products of the glasses were improved as borate content increased in the glass composition. Graphical Abstract

Mesoporous Bioactive Nanoparticles for Bone Tissue Applications.

Research in nanomaterials with applications in bone regeneration therapies has experienced a very significant advance with the development of bioactive mesoporous nanoparticles (MBNPs). These nanomaterials consist of small spherical particles that exhibit chemical properties and porous structures that stimulate bone tissue regeneration, since they have a composition similar to that of conventional sol-gel bioactive glasses and high specific surface area and porosity values. The rational design of mesoporosity and their ability to incorporate drugs make MBNPs an excellent tool for the treatment of bone defects, as well as the pathologies that cause them, such as osteoporosis, bone cancer, and infection, among others. Moreover, the small size of MBNPs allows them to penetrate inside the cells, provoking specific cellular responses that conventional bone grafts cannot perform. In this review, different aspects of MBNPs are comprehensively collected and discussed, including synthesis strategies, behavior as drug delivery systems, incorporation of therapeutic ions, formation of composites, specific cellular response and, finally, in vivo studies that have been performed to date.

Combined sol–gel bioactive glass and β-tricalcium phosphate for potential dental tissue engineering: a preliminary study

Combined sol–gel bioactive glass and β-tricalcium phosphate for potential dental tissue engineering: a preliminary study

In English

The purpose of the work is the synthesis of samples of X-ray luminescent nanodispersed lanthanum phosphate activated with terbium (LaРО4:Tb3+), the study of their structural properties and luminescence spectra when excited by ultraviolet and X-ray radiation, as well as determination of the possibility of their use in nanocomposites with bioactive glass and colloidal nanosystems. Samples of nanocrystalline lanthanum phosphate were synthesized composed of LaPO4·0.5H2O, of hexagonal syngonium, activated with terbium, their structural properties, luminescence spectra were studied upon excitation by UV and X-ray radiation, a possibility was shown to use them in nanocomposites with bioactive sol-gel glass and aqueous colloidal systems. Composites of 60S bioglass with nanodispersed crystalline LaPO4:Tb3+ in the dry state and in distilled water medium demonstrated the presence of luminescence when excited by UV and X-ray radiation. The given data indicate the perspective of nanodispersed phosphors based on lanthanum phosphate, their composites with bioactive sol-gel glass in colloidal systems, for use in optopharmacology and photodynamic therapy of diseases localized in bone tissues. In addition, the results of research can be useful for technical applications, in particular, in the creation of luminescent detectors of high-energy electromagnetic radiation, development of photo- and optoelectronic devices, etc.

Electrospinning of cotton-like fibers based on cerium-doped sol–gel bioactive glass

In this study, Ce-doped calcium silicate-based bioactive glass sols were electrospun under well-defined parameters and heat-treated to obtain cotton-like fibrous structures. The 3D structures comprised long and entangled fibers with interconnected pores, and the successful incorporation of Ce was confirmed by EDX analysis. The fibers were highly hydrophilic and demonstrated in vitro bioactivity after immersion in simulated body fluid. The fibers were non-cytotoxic toward keratinocytes and did not inhibit the wound closure process, which was characterized in vitro.

Electrophoretic deposition, microstructure and selected properties of nanocrystalline SnO2/Sr enriched bioactive glass/chitosan composite coatings on titanium

The presented study aimed to develop composite chitosan-based coatings with the addition of bioactive sol-gel glass enriched with Sr and potentially antimicrobial SnO2 nanoparticles on titanium substrates by cathodic electrophoretic deposition (EPD). The effect of suspension's chemical composition and pH level on their stability were investigated and adjusted to obtain macroscopically homogenous coatings. The electrosteric mechanism was responsible for coatings deposition. The dense coatings with excellent adhesion to the titanium and a well-developed surface including agglomerates of sol-gel glass and SnO2 particles were developed. It was shown that the roughness of the coatings was higher than for the underlying Ti substrate. All coatings demonstrated moderate wettability, 40 % higher in contact with water and 66 % higher in contact with non-polar liquid than for the pure Ti substrate. The surface free energy of the uncoated Ti substrates was about 32 % lower compared to the coated titanium. Furthermore, it was demonstrated that composite coatings containing SnO2 NPs, improve the electrochemical corrosion resistance of Ti substrates in Ringer's solution. Owing to the high adhesion strength of coatings, their morphology, wettability, and high corrosion resistance, they appear to be noteworthy in the future development of bioactive enhanced titanium surfaces with antibacterial properties.

A perfect pair: Niobium- and gallium-doped ceramic biomaterial enabled by coupled synthesis method with potential application for bone regeneration and cancer-targeted therapy

In this work, we report the synthesis and characterization of sol-gel bioactive glasses containing niobium (Nb) and gallium (Ga), a multifunctional glass that synergistically combines the respective effects of these species in potentiating bone repair and regeneration, concomitantly with a bone cancer targeted therapy. We found that the entry of Ga3+ into the vitreous network promotes an increase in the network connectivity, contributing to an increase in the degree of polymerization of the glass, since part of the calcium ions that behave as network modifying agents were replaced by gallium ions that act as network formers, and hence a replacement of part of the Si-O−…Ca2+…−O-Si by Si-O-Ga-O-Si bonds. Such results confirmed an increase in bridging oxygen bond density associated with a decrease in the number of bonds per unit volume of the glass due to the expansion of the glassy network. Furthermore, the incorporation of Ga2O3 at the expense of CaO in the composition of SNb3Ga3 decreased the ionicity of the chemical bonds. The study of pH variation revealed that the presence of Ga decreases the solubility of the glass influenced by a reduction in non-bridging oxygens (NBOs) concentration, which in turn is associated with an increase in glass network connectivity.

Corrosion and Metal Release Investigation of a Porous Biomedical Vitallium Alloy Coated with 58S Sol-Gel Bioactive Glass

Corrosion and Metal Release Investigation of a Porous Biomedical Vitallium Alloy Coated with 58S Sol-Gel Bioactive Glass

Unveiling the mechanism of the triethyl phosphate hydrolysis reaction in the synthesis of the sol-gel-derived 58S bioactive glass

The sol-gel method is one of the most used methods due to its outstanding capacity to obtain alkaline-earth phosphosilicate bioactive glass with high bioactivity. This efficient synthesis method involves several stages constituted by intermediate chemical reactions, which are governed by mechanisms and kinetic parameters that lead to the formation of the precursor gel of the vitreous matrix. Although the sol-gel method has been widely used for the preparation of materials, some steps are still not completely understood and that affect the final properties of the synthesized materials. For instance, the hydrolysis reaction of triethyl phosphate (TEP) which, similarly to tetraethyl orthosilicate (TEOS), is assumed to be complete in the stage of formation of the precursor gel of the glass matrix. Furthermore, the SN2-type mechanism for the hydrolysis of TEP is widely assumed. However, the absence of studies that support these presumptions fully justifies the use of theoretical methods to gain information about the hydrolysis of TEP within the sol-gel synthesis of 58S bioactive glass. Density functional theory (DFT) and molecular dynamics (MD) simulations were used to study the reaction mechanisms and kinetic behavior of TEP hydrolysis. Our results show that the TEP hydrolysis reaction is very slow in its three stages, occurring not only via the SN2 mechanism with configuration inversion (SN2–I), as is commonly reported in the literature, but also via SN2 with configuration retention (SN2–R). Furthermore, it was found that the hydrolysis reaction via SN2–I occurs with faster kinetics than SN2–R. This behavior was observed for the three stages of TEP hydrolysis, both in protonated and non-protonated solutions. Based on our findings on the mechanisms and kinetics of triethyl phosphate hydrolysis reactions, a simple chemical model for the formation of calcium pyrophosphate crystalline domains in 58S sol-gel bioactive glass was proposed. In our model, TEOS undergoes rapid hydrolysis, followed by immediate condensation leading to the formation of three-dimensional silica gels, that permeate non-hydrolyzed TEP molecules due to their slow kinetic rate. This mismatch between the reactions of precursor alkoxides in acidic medium, results in a strong tendency in the formation of a glassy microstructure with low structural homogeneity characterized by crystalline domains of calcium pyrophosphate permeated by a silica-rich glass matrix.

Chemical Compounds Released from Specific Osteoinductive Bioactive Materials Stimulate Human Bone Marrow Mesenchymal Stem Cell Migration.

In this work, a poly(L-lactide-co-glycolide) (PLGA)-based composite was enriched with one of the following sol-gel bioactive glasses (SBG) at 50 wt.%: A1—40 mol% SiO2, 60 mol% CaO, CaO/SiO2 ratio of 1.50; S1—80 mol% SiO2, 20 mol% CaO, CaO/SiO2 ratio of 0.25; A2—40 mol% SiO2, 54 mol% CaO, 6 mol% P2O5, CaO/SiO2 ratio of 1.35; S2—80 mol% SiO2,16 mol% CaO, 4 mol% P2O5, CaO/SiO2 ratio of 0.20. The composites and PLGA control sheets were then soaked for 24 h in culture media, and the obtained condition media (CM) were used to treat human bone marrow stromal cells (hBMSCs) for 72 h. All CMs from the composites increased ERK 1/2 activity vs. the control PLGA CM. However, expressions of cell migration-related c-Fos, osteopontin, matrix metalloproteinase-2, C-X-C chemokine receptor type 4, vascular endothelial growth factor, and bone morphogenetic protein 2 were significantly increased only in cells treated with the CM from the A1/PLGA composite. This CM also significantly increased the rate of human BMSC migration but did not affect cell metabolic activity. These results indicate important biological markers that are upregulated by products released from the bioactive composites of a specific chemical composition, which may eventually prompt osteoprogenitor cells to colonize the bioactive material and accelerate the process of tissue regeneration.

Silver-doped calcium silicate sol-gel glasses with a cotton-wool-like structure for wound healing

Skin has excellent capacity to regenerate, however, in the event of a large injury or burn skin grafts are required to aid wound healing. The regenerative capacity further declines with increasing age and can be further exacerbated with bacterial infection leading to a chronic wound. Engineered skin substitutes can be used to provide a temporary template for the damaged tissue, to prevent/combat bacterial infection and promote healing. In this study, the sol-gel process and electrospinning were combined to fabricate 3D cotton-wool-like sol-gel bioactive glass fibers that mimic the fibrous architecture of skin extracellular matrix (ECM) and deliver metal ions for antibacterial (silver) and therapeutic (calcium and silica species) actions for successful healing of wounds. This study investigated the effects of synthesis and process parameters, in particular sintering temperature on the fiber morphology, the incorporation and distribution of silver and the degradation rate of fibers. Silver nitrate was found to decompose into silver nanoparticles within the glass fibers upon calcination. Furthermore, with increasing calcination temperature the nanoparticles increased in size from 3 nm at 600 °C to ~25 nm at 800 °C. The antibacterial ability of the Ag-doped glass fibers decreased as a function of the glass calcination temperature. The degradation products from the Ag-doped 3D non-woven sol-gel glass fibers were also found to promote fibroblast proliferation thus demonstrating their potential for use in skin regeneration.

Synthesis and characterization of sol-gel bioactive glass nanoparticles doped with boron and copper

In this work the sol-gel synthesis of bioactive glass nanoparticles containing both boron and copper oxides is reported for the first time in the literature. Two acid/base co-catalysed methods were compared. The obtained glasses have been characterized in terms of morphology, composition, particle surface area, phase analysis and bioactivity in acellular simulated body fluids. The almost spherical nanoparticles (<100 nm diameter) obtained are characterized by a certain degree of aggregation and have compositions, which are coherent with the theoretical ones. Each glass revealed the ability to promote the growth of hydroxyapatite on its surface during soaking in simulated body fluid, thus we can assume that the addition of boron and copper did not negatively affect the bioactivity of the sol-gel derived glasses. Future investigations will be devoted to biological characterizations for cytotoxicity, antibacterial properties and pro-angiogenetic abilities.

Engineered nanostructures within sol-gel bioactive glass for enhanced bioactivity and modulated drug delivery.

The engineering of nanocrystalline phase in amorphous oxide materials such as bioactive glass is emerging as a new area of great technological and scientific interest in the field of biomaterials. This study reports for the first time the infusion of apatite nanocrystals in sol-gel-derived bioactive glass using P123 as the structure-directing agent. The synthesis of a multicomponent 80SiO2-15CaO-5P2O5 bioactive glass material having a hierarchically ordered mesoporous structure with uniformly grown nanocrystals of apatite was achieved through a sono-assisted surfactant-templated sol-gel method. The bulk crystallographic analysis together with microstructural characterizations shows that the nanocrystalline apatite domains are uniformly dispersed as well as embedded along the mesopores. These nanocrystalline domains were found to influence the textural properties. In addition, macroscopic evidence for higher signs of bonelike matrix formation was observed by the biomineralization study in simulated body fluids. Osteostimulatory effects of these glass samples were evident by cultures in a osteogenic and non-osteogenic mediums with human osteosarcoma cells and a higher osteopromotive potential was authenticated by the alkaline phosphatase activity and alizarin red staining. Further, this study shows a new strategy to prolong the drug release period on account of the nanocrystalline phase and hierarchically positioned mesopores, thus making it a better drug delivery matrix as well.