A review of the biological response to ionic dissolution products from bioactive glasses and glass-ceramics

The osteogenic response of mesenchymal stromal cells to strontium-substituted bioactive glasses

Bioactive glasses are known to stimulate bone healing, and the incorporation of strontium has the potential to increase their potency. In this study, calcium oxide in the 45S5 bioactive glass composition was partially (50%, Sr50) or fully (100%, Sr100) substituted with strontium oxide on a molar basis. The effects of the substitution on bioactive glass properties were studied, including density, solubility, and in vitro cytotoxicity. Stimulation of osteogenic differentiation was investigated using mesenchymal stromal cells obtained from rat bone marrow. Strontium substitution resulted in altered physical properties including increased solubility. Statistically significant reductions in cell viability were observed with the addition of bioactive glass powders to culture medium. Specifically, addition of ≥ 13.3 mg/ml of 45S5 bioactive glass or Sr50, or ≥ 6.7 mg/ml of Sr100, resulted in significant inhibition. Real‐time PCR analyses detected the upregulation of genes associated with osteoblastic differentiation in the presence of all bioactive glass compositions. Some genes, including Alpl and Bglap, were further stimulated in the presence of Sr50 and Sr100. It was concluded that strontium‐substituted bioactive glasses promoted osteogenesis in a differentiating bone cell culture model and, therefore, have considerable potential for use as improved bioactive glasses for bone tissue regeneration. © 2015 The Authors. Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons Ltd.

Sol-gel synthesis and in vitro bioactivity of copper and zinc-doped silicate bioactive glasses and glass-ceramics

Metal doping of bioactive glasses based on ternary 60SiO2-36CaO-4P2O5 (58S) and quaternary 60SiO2-25CaO-11Na2O-4P2O5 (NaBG) mol% compositions synthesized using a sol-gel process was analyzed. In particular, the effect of incorporating 1, 5 and 10 mol% of CuO and ZnO (replacing equivalent quantities of CaO) on the texture, in vitro bioactivity, and cytocompatibility of these materials was evaluated. Our results showed that the addition of metal ions can modulate the textural property of the matrix and its crystal structure. Regarding the bioactivity, after soaking in simulated body fluid (SBF) undoped 58S and NaBG glasses developed an apatite surface layer that was reduced in the doped glasses depending on the type of metal and its concentration with Zn displaying the largest inhibitions. Both the ion release from samples and the ion adsorption from the medium depended on the type of matrix with 58S glasses showing the highest values. Pure NaBG glass was more cytocompatible to osteoblast-like cells (SaOS-2) than pure 58S glass as tested by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. The incorporation of metal ions decreased the cytocompatibility of the glasses depending on their concentration and on the glass matrix doped. Our results show that by changing the glass composition and by adding Cu or Zn, bioactive materials with different textures, bioactivity and cytocompatibility can be synthesized.

Understanding the composition-structure-bioactivity relationships in diopside (CaO·MgO·2SiO₂)-tricalcium phosphate (3CaO·P₂O₅) glass system

The present work is an amalgamation of computation and experimental approach to gain an insight into composition-structure-bioactivity relationships of alkali-free bioactive glasses in the CaO-MgO-SiO2-P2O5 system. The glasses have been designed in the diopside (CaO·MgO·2SiO2; Di)-tricalcium phosphate (3CaO·P2O5; TCP) binary join by varying the Di/TCP ratio. The melt-quenched glasses have been investigated for their structure by molecular dynamic (MD) simulations as well as by nuclear magnetic resonance spectroscopy (NMR). In all the investigated glasses silicate and phosphate components are dominated by Q(2) (Si) and Q(0) (P) species, respectively. The apatite forming ability of the glasses was investigated using X-ray diffraction (XRD), infrared spectroscopy after immersion of glass powders in simulated body fluid (SBF) for time durations varying between 1 h and 14 days, while their chemical degradation has been studied in Tris-HCl in accordance with ISO 10993-14. All the investigated glasses showed good bioactivity without any substantial variation. A significant statistical increase in metabolic activity of human mesenchymal stem cells (hMSCs) when compared to the control was observed for Di-60 and Di-70 glass compositions under both basal and osteogenic conditions.

Characterization and biocompatibility of a fibrous glassy scaffold

Bioactive glasses (BGs) are known for their ability to bond to living bone and cartilage. In general, they are readily available in powder and monolithic forms, which are not ideal for the optimal filling of bone defects with irregular shapes. In this context, the development of BG-based scaffolds containing flexible fibres is a relevant approach to improve the performance of BGs. This study is aimed at characterizing a new, highly porous, fibrous glassy scaffold and evaluating its in vitro and in vivo biocompatibility. The developed scaffolds were characterized in terms of porosity, mineralization and morphological features. Additionally, fibroblast and osteoblast cells were seeded in contact with extracts of the scaffolds to assess cell proliferation and genotoxicity after 24, 72 and 144 h. Finally, scaffolds were placed subcutaneously in rats for 15, 30 and 60 days. The scaffolds presented interconnected porous structures, and the precursor bioglass could mineralize a hydroxyapatite (HCA) layer in simulated body fluid (SBF) after only 12 h. The biomaterial elicited increased fibroblast and osteoblast cell proliferation, and no DNA damage was observed. The in vivo experiment showed degradation of the biomaterial over time, with soft tissue ingrowth into the degraded area and the presence of multinucleated giant cells around the implant. At day 60, the scaffolds were almost completely degraded and an organized granulation tissue filled the area. The results highlight the potential of this fibrous, glassy material for bone regeneration, due to its bioactive properties, non-cytotoxicity and biocompatibility. Future investigations should focus on translating these findings to orthotopic applications. Copyright © 2015 John Wiley & Sons, Ltd.

In-situ hybridization of calcium silicate and hydroxyapatite-gelatin nanocomposites enhances physical property and in vitro osteogenesis

Low mechanical strengths and inadequate bioactive material-tissue interactions of current synthetic materials limit their clinical applications in bone regeneration. Here, we demonstrate gelatin modified siloxane-calcium silicate (GEMOSIL-CS), a nanocomposite made of gelatinous hydroxyapatite with in situ pozzolanic formation of calcium silicate (CS) interacting among gelatin, silica and Calcium Hydroxide (Ca(OH)2). It is shown the formation of CS matrices, which chemically bonds to the gelatinous hydroxyapatite, provided hygroscopic reinforcement mechanism and promoted both in vitro and in vivo osteogenic properties of GEMOSIL-CS. The formation of CS was identified by Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction. The interfacial bindings within nanocomposites were studied by FTIR and thermogravimetric analysis. Both gelatin and CS have been found critical to the structure integrity and mechanical strengths (93 MPa in compressive strength and 58.9 MPa in biaxial strength). The GEMOSIL-CS was biocompatible and osteoconductive as result of type I collagen secretion and mineralized nodule formation from MC3T3 osteoblasts. SEM and TEM indicated the secretion of collagen fibers and mineral particles as the evidence of mineralization in the early stage of osteogenic differentiation. In vivo bone formation capability was performed by implanting GEMOSIL-CS into rat calvarial defects for 12 weeks and the result showed comparable new bone formation between GEMOSIL-CS group (20%) and the control (20.19%). The major advantage of GEMOSIL-CS composites is in situ self-hardening in ambient or aqueous environment at room temperature providing a simple, fast and cheap method to produce porous scaffolds.

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.

Investigating the influence of Na+ and Sr2+ on the structure and solubility of SiO2-TiO2-CaO-Na2O/SrO bioactive glass

This study was conducted to determine the influence that network modifiers, sodium (Na+) and strontium (Sr2+), have on the solubility of a SiO2-TiO2-CaO-Na2O/SrO bioactive glass. Glass characterization determined each composition had a similar structure, i.e. bridging to non-bridging oxygen ratio determined by X-ray photoelectron spectroscopy. Magic angle spinning nuclear magnetic resonance (MAS-NMR) confirmed structural similarities as each glass presented spectral shifts between -84 and -85 ppm. Differential thermal analysis and hardness testing revealed higher glass transition temperatures (Tg 591-760 °C) and hardness values (2.4-6.1 GPa) for the Sr2+ containing glasses. Additionally the Sr2+ (~250 mg/L) containing glasses displayed much lower ion release rates than the Na+ (~1,200 mg/L) containing glass analogues. With the reduction in ion release there was an associated reduction in solution pH. Cytotoxicity and cell adhesion studies were conducted using MC3T3 Osteoblasts. Each glass did not significantly reduce cell numbers and osteoblasts were found to adhere to each glass surface.

The future of bioactive ceramics

Two important worldwide needs must be satisfied in the future; (1) treatment of the deteriorating health of an aging population and, (2) decreasing healthcare costs to meet the needs of an increased population. The ethical and economic dilemma is how to achieve equality in quality of care while at the same time decreasing cost of care for an ever-expanding number of people. The limited lifetime of prosthetic devices made from first-generation nearly inert biomaterials requires new approaches to meet these two large needs. This paper advises an expanded emphasis on: (1) regeneration of tissues and (2) prevention of tissue deterioration to meet this growing need. Innovative use of bioactive ceramics with genetic control of in situ tissue responses offers the potential to achieve both tissue regeneration and prevention. Clinical success of use of bioactive glass for bone regeneration is evidence that this concept works. Likewise the use of micron sized bioactive glass powders in a dentifrice for re-mineralization of teeth provides evidence that prevention of tissue deterioration is also possible. This opinion paper outlines clinical needs that could be met by innovative use of bioactive glasses and ceramics in the near future; including: regeneration of skeletal tissues that is patient specific and genetic based, load-bearing bioactive glass-ceramics for skeletal and ligament and tendon repair, repair and regeneration of soft tissues, and rapid low-cost analysis of human cell-biomaterial interactions leading to patient specific diagnoses and treatments using molecularly tailored bioceramics.

Characterization of Y2O3 and CeO2 doped SiO2-SrO-Na2O glasses

The structural effects of yttrium (Y) and cerium (Ce) are investigated when substituted for sodium (Na) in a 0.52SiO2–0.24SrO–(0.24−x)Na2O–xMO (where x = 0.08; MO = Y2O3 and CeO2) glass series. Network connectivity (NC) was calculated assuming both Y and Ce can act as a network modifier (NC = 2.2) or as a network former (NC up to 2.9). Thermal analysis showed an increase in glass transition temperature (Tg) with increasing Y and Ce content, Y causing the greater increase from the control (Con) at 493∘C to 8 mol% Y (HY) at 660∘C. Vickers hardness (HV) was not significantly different between glasses. 29Si Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR) did not show peak shift with addition of Y, however Ce produced peak broadening and a negative shift in ppm. The addition of 4 mol% Ce in the YCe and LCe glasses shifted the peak from Con at −81.3 ppm to −82.8 ppm and −82.7 ppm respectively; while the HCe glass produced a much broader peak and a shift to −84.8 ppm. High resolution X-ray Photoelectron Spectroscopy for the O 1s spectral line showed the ratio of bridging (BO) to non-bridging oxygens (NBO), BO:NBO,was altered,where Con had a ratio of 0.7, HY decreased to 0.4 and HCe to 0.5.

Zinc-containing bioactive glasses for bone regeneration, dental and orthopedic applications

Zinc is a vital and beneficial trace element found in the human body. Though found in small proportions, zinc performs a variety of functions in relation to the immune system, cell division, fertility and the body growth and maintenance. In particular, zinc is proven to be a necessary element for the formation, mineralization, development and maintenance of healthy bones. Considering this attractive attributes of zinc, recent research has widely focused on using zinc along with silicate-based bioactive glasses for bone tissue engineering applications. This paper reviews relevant literature discussing the significance of zinc in the human body, along with its ability to enhance antibacterial effects, bioactivity and distinct physical, structural and mechanical properties of bioactive glasses. In this context, even if the present analysis is not meant to be exhaustive and only representative studies are discussed, literature results confirm that it is essential to understand the properties of zinc-containing bioactive glasses with respect to their in vitro biological behavior, possible cytotoxic effects and degradation characteristics to be able to effectively apply these glasses in bone regeneration strategies. Topics attracting increasing research efforts in this field are elaborated in detail in this review, including a summary of the structural, physical, biological and mechanical properties of zinc-containing bioactive glasses. This paper also presents an overview of the various applications in which zinc-containing bioactive glasses are considered for use as bone tissue scaffolds, bone filling granules, bioactive coatings and bone cements, and advances and remaining challenges are highlighted.

On the Collagen Mineralization. A Review

Collagen mineralization (CM) is a challenging process that has received a lot of attention in the past years. Among the reasons for this interest, the key role is the importance of collagen and hydroxyapatite in natural bone, as major constituents. Different protocols of mineralization have been developed, specially using simulated body fluid (SBF) and many methods have been used to characterize the systems obtained, starting with methods of determining the mineral content (XRD, FTIR, Raman, High-Resolution Spectral Ultrasound Imaging), continuing with imaging methods (AFM, TEM, SEM, Fluorescence Microscopy), thermal analysis (DSC and TGA), evaluation of the mechanical and biological properties, including statistical methods and molecular modeling. In spite of the great number of studies regarding collagen mineralization, its mechanism, both in vivo and in vitro, is not completely understood. Some of the methods used in vitro and investigation methods are reviewed here.

Combining collagen and bioactive glasses for bone tissue engineering: a review

Collagen (COL), the most abundant protein in mammals, offers a wide range of attractive properties for biomedical applications which are the result of its biocompatibility and high affinity to water. However, due to the relative low mechanical properties of COL its applications are still limited. To tackle this disadvantage of COL, especially in the field of bone tissue engineering, COL can be combined with bioactive inorganic materials in a variety of composite systems. One of such systems is the collagen-bioactive glass (COL-BG) composite family, which is the theme of this Review. BG fillers can increase compressive strength and stiffness of COL-based structures. This article reviews the relevant literature published in the last 15 years discussing the fabrication of a variety of COL-BG composites. In vitro cell studies have demonstrated the osteogenic, odontogenic, and angiogenic potential of these composite systems, which has been confirmed by stimulating specific biochemical indicators of relevant cells. Bony integration and connective tissue vessel formation have also been studied by implantation of the composites in vivo. Areas of future research in the field of COL-BG systems, based on current challenges, and gaps in knowledge are highlighted.

Influence of textural properties on biomineralization behavior of mesoporous bioactive glasses

A new method of calcination for the sol-gel derived bioactive glass sample has been developed to produce superior textural and bioactive properties. Based on this method, mesoporous 67.4 SiO

Composition and Modifications of Dental Implant Surfaces

Since Brånemark discovered the favorable effects of titanium in bone healing in 1965, titanium has emerged as the gold standard bulk material for present-time dental implantology. In the course of years researchers aimed for improvement of the implants performance in bone even at compromised implant sites and multiple factors were investigated influencing osseointegration. This review summarizes and clarifies the four factors that are currently recognized being relevant to influence the tissue-implant contact ratio: bulk materials and coatings, topography, surface energy, and biofunctionalization. The macrodesigns of bulk materials (e.g., titanium, zirconium, stainless steel, tantalum, and magnesium) provide the mechanical stability and their influence on bone cells can be additionally improved by surface treatment with various materials (calcium phosphates, strontium, bioglasses, diamond-like carbon, and diamond). Surface topography can be modified via different techniques to increase the bone-implant contact, for example, plasma-spraying, grit-blasting, acid-etching, and microarc oxidation. Surface energy (e.g., wettability and polarity) showed a strong effect on cell behavior and cell adhesion. Functionalization with bioactive molecules (via physisorption, covalent binding, or carrier systems) targets enhanced osseointegration. Despite the satisfying clinical results of presently used dental implant materials, further research on innovative implant surfaces is inevitable to pursuit perfection in soft and hard tissue performance.

Preparation and Characterization of Low Temperature Heat-Treated 45S5 Bioactive Glass-Ceramic Analogues

The 45S5 Bioglassr and its sintered bioactive glass-ceramic (BGC) have been widely investigated as bone implants, mainly for its ability to bond to hard tissues. However, high temperature treatment is not enough to improve its poor mechanical properties, but compromise its biologically relevant performances. The innovative BGC compositions based on the thermally treated 45S5 Bioglassr were developed by decreasing the P2O5 quantity and adding B2O3 (0-6%) into the Na2O–2CaO–3SiO2- based bioactive glasses (BG). The thermally treated BGCs were fully characterized from the microstructural and mechanical points of view and compared to each other. Their bioactivity and bio-dissolutionwere established by means of in vitro soaking tests. The new B2O3-added 45S5 BG analogues, named NCS-xB, can be transformed to crystalline phase (Na2Ca2Si3O9)-based BGCs of high compactness and bioactivity at a relatively low temperature heat treatment (≤ 900ºC), since their bioactivity is preserved. Our experimental results suggest that the new 45S5 BGC analogues with optimized composition exhibit improved micro- structural and mechanical properties, and are beneficial for making specific products such as porous scaffolds or composites for bone defect repair.

Bioactive polymethylmethacrylate bone cement modified with combinations of phosphate group-containing monomers and calcium acetate

Bone cement from polymethylmethacrylate powder and methylmethacrylate liquid has been successfully demonstrated as artificial material to anchor joint replacements in bone. However, it lacks the capability to bond directly to bone, so long-term implantation leads to an increased risk of loosening. Bioactive materials show better performance in fixation to bone, and the chemical bonding depends on bone-like apatite formation. This is triggered by surface reactions with body fluid. For these reactions, superficial functional groups like silanol (Si-OH) are ideal sites to induce apatite nucleation and the release of Ca(2+) ions accelerates the apatite growth. Therefore, incorporation of materials containing these key components may provide the cement with apatite-forming ability. In this study, phosphoric acid 2-hydroxyethyl methacrylate ester or bis[2-(methacryloyloxy)ethyl] phosphate supplying a phosphate group (PO4H2) was added into methylmethacrylate liquid, while calcium acetate as a source of Ca(2+) ions was mixed into polymethylmethacrylate powder. The influences of the combinations on the setting time and compressive strength were also investigated. Apatite was formed on the cements modified with 30 mass% of phosphoric acid 2-hydroxyethyl methacrylate ester or bis[2-(methacryloyloxy)ethyl] phosphate. The induction period was shortened with increased amounts of Ca(CH3COO)2. The setting time could be controlled by the Ca(CH3COO)2/monomer mass ratio. Faster setting was achieved at a ratio close to the mixing ratio of the powder/liquid (2:1), and both increases and decreases in the amount of Ca(CH3COO)2 prolonged the setting time based on this ratio. The highest compressive strength was 88.8 ± 2.6 MPa, higher than the lowest limit of ISO 5833 but was lower than that of the simulated body fluid-soaked reference. The increase of additives caused the decline in compressive strength. In view of balancing apatite formation and clinical standard, bis[2-(methacryloyloxy)ethyl] phosphate is more suitable as an additive, and the optimal modification is a combination of 30 mass% of bis[2-(methacryloyloxy)ethyl] phosphate and 20 mass% of Ca(CH3COO)2.

Mesoporous bioactive glasses: Relevance of their porous structure compared to that of classical bioglasses

In the last decade, the development of third generation bioceramics for Bone Tissue Regeneration has experienced significant progress with the emergence of a new generation of nanostructured materials named mesoporous bioactive glasses (MBG). This new generation of materials, also known as “templated glasses”, presents chemical compositions similar to those of conventional bioactive sol–gel glasses and the added value of an ordered mesopore arrangement. This article shows an indepth comparative study of the ordered porous structures of MBGs compared to conventional glasses (melt and solgel) andhowthese properties influence the bioactivity process. Moreover, the possibility to tailor the textural and structural properties of these nanostructured materials by an exhaustive control of the different synthesis parameters is also discussed. A brief overview regarding the possibility of using these materials as controlled drug delivery systems and as starting materials for the fabrication of 3D scaffolds for bone tissue regeneration is also given.

The bifunctional regulation of interconnected Zn-incorporated ZrO2 nanoarrays in antibiosis and osteogenesis

Bifunctional regulation in antibiosis and osteogenesis is obtained using well-organized Zn-incorporated ZrO₂ nanoarrays with interconnected internal space.

Development of silica grafted poly(1,8-octanediol-co-citrates) hybrid elastomers with highly tunable mechanical properties and biocompatibility

By a facile polymerization, we synthesized a series of silica grafted poly (1,8-octanediol-co-citrate) (SPOC) hybrid elastomers with highly tunable physicochemical properties and bioactivities.

Nanoporous structured carbon nanofiber–bioactive glass composites for skeletal tissue regeneration

Bioactive glass (BG) decorated nanoporous composite carbon nanofibers (PCNF–BG) were prepared for the purpose of obtaining effective substrates for skeletal tissue regeneration.

A highly bioactive and biodegradable poly(glycerol sebacate)–silica glass hybrid elastomer with tailored mechanical properties for bone tissue regeneration

A highly bioactive and biodegradable PGS–Silica bioactive glass hybrid elastomer with tailored mechanical properties was developed for bone tissue regeneration application.

Novel Co-akermanite (Ca2CoSi2O7) bioceramics with the activity to stimulate osteogenesis and angiogenesis

Both osteogenesis and angiogenesis of bioactive materials play the vital role in the regeneration of large skeletal defects.

Porous and strong three-dimensional carbon nanotube coated ceramic scaffolds for tissue engineering

A method to coat high-quality uniform coatings of carbon nanotubes throughout 3D porous structures is developed. Testing of their physical and biological properties demonstrate their potential for application in tissue engineering.

Bidirectional regulation of zinc embedded titania nanorods: antibiosis and osteoblastic cell growth

A bifunctional regulation in antibiosis and osteoblastic cell growth is achieved by well-organized TiO₂–Zn nanoarrays.

Electrophoretic deposition of mesoporous bioactive glass on glass-ceramic foam scaffolds for bone tissue engineering

In this work, the coating of 3-D foam-like glass-ceramic scaffolds with a bioactive mesoporous glass (MBG) was investigated. The starting scaffolds, based on a non-commercial silicate glass, were fabricated by the polymer sponge replica technique followed by sintering; then, electrophoretic deposition (EPD) was applied to deposit a MBG layer on the scaffold struts. EPD was also compared with other techniques (dipping and direct in situ gelation) and it was shown to lead to the most promising results. The scaffold pore structure was maintained after the MBG coating by EPD, as assessed by SEM and micro-CT. In vitro bioactivity of the scaffolds was assessed by immersion in simulated body fluid and subsequent evaluation of hydroxyapatite (HA) formation. The deposition of a MBG coating can be a smart strategy to impart bioactive properties to the scaffold, allowing the formation of nano-structured HA agglomerates within 48 h from immersion, which does not occur on uncoated scaffold surfaces. The mechanical properties of the scaffold do not vary after the EPD (compressive strength ~19 MPa, fracture energy ~1.2 × 10(6) J m(-3)) and suggest the suitability of the prepared highly bioactive constructs as bone tissue engineering implants for load-bearing applications.

Atomic-scale models of early-stage alkali depletion and SiO2-rich gel formation in bioactive glasses

Molecular dynamics simulations of Na⁺/H⁺-exchanged 45S5 Bioglass® reveal the co-existence of bonded and non-bonded hydroxyls, suggesting a direct mechanism for forming a silica-rich gel structure upon the initial ion exchange.

Preparation, physicochemical properties and in vitro bioactivity of hierarchically porous bioactive glass scaffolds

Bioactive glass scaffolds with macropores (300–500 μm), midpores (20 nm to 2 μm) and mesopores (around 5 nm) were prepared using P123, yeast cells and polyurethane sponges as templates.

Dendrimer templated bioactive glass-ceramic nanovehicle for gene delivery applications

Herein, multifunctional nanocrystalline microporous 45S5 bioglass particles were synthesized using poly(amidoamine) dendrimer generation 3 as a template and evaluated for gene delivery applications.

Angiogenic effects of ionic dissolution products released from a boron-doped 45S5 bioactive glass

In regenerative medicine of vascularized tissues, there is a great interest in the use of biomaterials that are able to stimulate angiogenesis, a process necessary for rapid revascularization to allow the transport and exchange of oxygen, nutrients, growth factors and cells that take part in tissue repair and/or regeneration. An increasing number of publications have shown that bioactive glasses stimulate angiogenesis. Because it has been established that boron (B) may play a role in angiogenesis, the aim of this study was to assess the in vivo angiogenic effects of the ionic dissolution products that from a bioactive glass (BG) in the 45S5 system doped with 2 wt% B₂O₃ (45S5.2B). The pro-angiogenic capacity of 45S5.2B BG was assessed on the vasculature of the embryonic quail chorioallantoic membrane (CAM). Ionic dissolution products from 45S5.2B BG increased angiogenesis. This is quantitatively evidenced by the greater expression of integrin α_vβ₃ and higher vascular density in the embryonic quail CAM. The response observed at 2 and 5 days post-treatment was equivalent to that achieved by applying 10 µg mL^-1 of basic fibroblast growth factor. These results show that the ionic dissolution products released from the bioactive glass 45S5.2B stimulate angiogenesis in vivo. The effects observed are attributed to the presence the ionic dissolution products, which contained 160 ± 10 µM borate.

Bioactive copper-doped glass scaffolds can stimulate endothelial cells in co-culture in combination with mesenchymal stem cells

Bioactive glass (BG) scaffolds are being investigated for bone tissue engineering applications because of their osteoconductive and angiogenic nature. However, to increase the in vivo performance of the scaffold, including enhancing the angiogenetic growth into the scaffolds, some researchers use different modifications of the scaffold including addition of inorganic ionic components to the basic BG composition. In this study, we investigated the in vitro biocompatibility and bioactivity of Cu2+-doped BG derived scaffolds in either BMSC (bone-marrow derived mesenchymal stem cells)-only culture or co-culture of BMSC and human dermal microvascular endothelial cells (HDMEC). In BMSC-only culture, cells were seeded either directly on the scaffolds (3D or direct culture) or were exposed to ionic dissolution products of the BG scaffolds, kept in permeable cell culture inserts (2D or indirect culture). Though we did not observe any direct osteoinduction of BMSCs by alkaline phosphatase (ALP) assay or by PCR, there was increased vascular endothelial growth factor (VEGF) expression, observed by PCR and ELISA assays. Additionally, the scaffolds showed no toxicity to BMSCs and there were healthy live cells found throughout the scaffold. To analyze further the reasons behind the increased VEGF expression and to exploit the benefits of the finding, we used the indirect method with HDMECs in culture plastic and Cu2+-doped BG scaffolds with or without BMSCs in cell culture inserts. There was clear observation of increased endothelial markers by both FACS analysis and acetylated LDL (acLDL) uptake assay. Only in presence of Cu2+-doped BG scaffolds with BMSCs, a high VEGF secretion was demonstrated by ELISA; and typical tubular structures were observed in culture plastics. We conclude that Cu2+-doped BG scaffolds release Cu2+, which in turn act on BMSCs to secrete VEGF. This result is of significance for the application of BG scaffolds in bone tissue engineering approaches.

Polymer nanocarriers for dentin adhesion

To obtain more durable adhesion to dentin, and to protect collagen fibrils of the dentin matrix from degradation, calcium- and phosphate-releasing particles have been incorporated into the dental adhesive procedure. The aim of the present study was to incorporate zinc-loaded polymeric nanocarriers into a dental adhesive system to facilitate inhibition of matrix metalloproteinases (MMPs)-mediated collagen degradation and to provide calcium ions for mineral deposition within the resin-dentin bonded interface. PolymP- N : Active nanoparticles (nanoMyP) were zinc-loaded through 30-minute ZnCl2 immersion and tested for bioactivity by means of 7 days' immersion in simulated body fluid solution (the Kokubo test). Zinc-loading and calcium phosphate depositions were examined by scanning and transmission electron microscopy, elemental analysis, and x-ray diffraction. Nanoparticles in ethanol solution infiltrated into phosphoric-acid-etched human dentin and Single Bond (3M/ESPE) were applied to determine whether the nanoparticles interfered with bonding. Debonded sticks were analyzed by scanning electron microscopy. A metalloproteinase collagen degradation assay was also performed in resin-infiltrated dentin with and without nanoparticles, measuring C-terminal telopeptide of type I collagen (ICTP) concentration in supernatants, after 4 wk of immersion in artificial saliva. Numerical data were analyzed by analysis of variance (ANOVA) and Student-Newman-Keuls multiple comparisons tests (p < .05). Nanoparticles were effectively zinc-loaded and were shown to have a chelating effect, retaining calcium regardless of zinc incorporation. Nanoparticles failed to infiltrate demineralized intertubular dentin and remained on top of the hybrid layer, without altering bond strength. Calcium and phosphorus were found covering nanoparticles at the hybrid layer, after 24 h. Nanoparticle application in etched dentin also reduced MMP-mediated collagen degradation. Tested nanoparticles may be incorporated into dental adhesive systems to provide the appropriate environment in which dentin MMP collagen degradation is inhibited and mineral growth can occur.

Composition-structure-properties relationship of strontium borate glasses for medical applications

We have synthesized TiO2 doped strontium borate glasses, 70B2O3-(30-x)SrO-xTiO2 and 70B2 O3 -20SrO(10-x)Na2 O-xTiO2 . The composition dependence of glass structure, density, thermal properties, durability, and cytotoxicity of degradation products was studied. Digesting the glass in mineral acid and detecting the concentrations of various ions using an ICP provided the actual compositions that were 5-8% deviated from the theoretical values. The structure was investigated by means of (11)B magic angle spinning (MAS) NMR spectroscopy. DSC analyses provided the thermal properties and the degradation rates were measured by measuring the weight loss of glass disc-samples in phosphate buffered saline at 37°C in vitro. Finally, the MTT assay was used to analyze the cytotoxicity of the degradation products. The structural analysis revealed that replacing TiO2 for SrO or Na2 O increased the BO3/BO4 ratio suggesting the network-forming role of TiO2 . Thermal properties, density, and degradation rates also followed the structural changes. Varying SrO content predominantly controlled the degradation rates, which in turn controlled the ion release kinetics. A reasonable control (2-25% mass loss in 21 days) over mass loss was achieved in current study. Even though, very high concentrations (up to 5500 ppm B, and 1200 ppm Sr) of ions were released from the ternary glass compositions that saturated the degradation media in 7 days, the degradation products from ternary glass system was found noncytotoxic. However, quaternary glasses demonstrated negative affect on cell viability due to very high (7000 ppm) Na ion concentration. All the glasses investigated in current study are deemed fast degrading with further control over degradation rates, release kinetics desirable.

PCL/chitosan/Zn-doped nHA electrospun nanocomposite scaffold promotes adipose derived stem cells adhesion and proliferation

Chitosan (Ch), and poly(ɛ-caprolactone) (PCL), widely used as biomaterials with desirable properties for tissue engineering applications, were both blended with zinc-doped hydroxyapatite nanoparticles(nZnHA) and electrospun into nanofibrous scaffolds using formic acid/acetic acid. The rationale behind this study was to demonstrate that presence of small quantities of Zn(2+) ions doped in HA nanoparticles can improve biocompatibility of PCL/Ch blends. SEM observation revealed that average fiber diameter was increased from about 136 nm for a PCL/Ch blend, to around 210 nm for PCL/Ch/nZnHA nanocomposite. PCL/Ch/nZnHA scaffolds offered higher elastic modulus (about 3-fold) and tensile strength (nearly 1.5-fold) than the corresponding PCL/Ch scaffolds. In-vitro biocompatibility studies using human adipose derived stem cells (hAD-MSCs), demonstrated that the presence of only 5 wt% nZnHA in PCL/Ch/nZnHA nanocomposites enhanced hAD-MSCs' attachment compared to PCL/Ch and PCL/Ch/nHA. Finally, hAD-MSCs proliferation occurred at significantly higher rates of 1.5, 1.3 and 1.2 times on PCL/Ch/nZnHA scaffold compared to PCL, PCL/Ch and PCL/Ch/nHA, respectively.

Toughening and functionalization of bioactive ceramic and glass bone scaffolds by biopolymer coatings and infiltration: a review of the last 5 years

Inorganic scaffolds with high interconnected porosity based on bioactive glasses and ceramics are prime candidates for applications in bone tissue engineering. These materials however exhibit relatively low fracture strength and high brittleness. A simple and effective approach to improve the toughness is to combine the basic scaffold structure with polymer coatings or through the formation of interpenetrating polymer-bioactive ceramic microstructures. The polymeric phase can additionally serve as a carrier for growth factors and therapeutic drugs, thus adding biological functionalities. The present paper reviews the state-of-the art in the field of polymer coated and infiltrated bioactive inorganic scaffolds. Based on the notable combination of bioactivity, improved mechanical properties and drug or growth factor delivery capability, this scaffold type is a candidate for bone and osteochondral regeneration strategies. Remaining challenges for the improvement of the materials are discussed and opportunities to broaden the application potential of this scaffold type are also highlighted.

Injectable dopamine-modified poly(ethylene glycol) nanocomposite hydrogel with enhanced adhesive property and bioactivity

A synthetic mimic of mussel adhesive protein, dopamine-modified four-armed poly(ethylene glycol) (PEG-D4), was combined with a synthetic nanosilicate, Laponite (Na(0.7+)(Mg5.5Li0.3Si8)O20(OH)4)(0.7-)), to form an injectable naoncomposite tissue adhesive hydrogel. Incorporation of up to 2 wt % Laponite significantly reduced the cure time while enhancing the bulk mechanical and adhesive properties of the adhesive due to strong interfacial binding between dopamine and Laponite. The addition of Laponite did not alter the degradation rate and cytocompatibility of PEG-D4 adhesive. On the basis of subcutaneous implantation in rat, PEG-D4 nanocomposite hydrogels elicited minimal inflammatory response and exhibited an enhanced level of cellular infiltration as compared to Laponite-free samples. The addition of Laponite is potentially a simple and effective method for promoting bioactivity in a bioinert, synthetic PEG-based adhesive while simultaneously enhancing its mechanical and adhesive properties.

Zoledronate and ion-releasing resins impair dentin collagen degradation

This study analyzed the amounts of solubilized telopeptides cross-linked carboxyterminal telopeptide of type I collagen (ICTP) and C-terminal crosslinked telopeptide of type I collagen (CTX) derived from matrix-metalloproteinases (MMPs) and cysteine cathepsins (CTPs) subsequent to application of a filler-free (Res.A) or an ion-releasing resin (Res.B) to ethylenediaminetetraacetic acid (EDTA)-demineralized dentin with or without zoledronate-containing primer (Zol-primer) pre-treatment. The chemical modification induced following treatments and artificial saliva (AS) storage was also analyzed through attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Totally EDTA-demineralized specimens were infiltrated with Res.A or Res.B with or without Zol-primer pre-treatment, light-cured, and immersed in AS for up to 4 wk. ICTP release was reduced following infiltration with Res.B and further reduced when Res.B was used with Zol-primer; remarkable phosphate mineral uptake was attained after AS storage. CTX release was increased in Res.A- and Res.B-treated dentin. However, when Zol-primer was used with Res.A, the CTX release fell significantly compared to the other tested resin-infiltration methods. In conclusion, zoledronate offers an additional inhibitory effect to the ion-releasing resins in MMP-mediated collagen degradation. However, Zol-primer induces a modest reduction in CTX release only when used with resin-based systems containing no ion-releasing fillers.

Bone marrow stromal cells on a three-dimensional bioactive fiber mesh undergo osteogenic differentiation in the absence of osteogenic media supplements: the effect of silanol groups

Osteogenic differentiation is a tightly regulated process dependent on the stimuli provided by the micro-environment. Silicon-substituted materials are known to have an influence on the osteogenic phenotype of undifferentiated and bone-derived cells. This study aims to investigate the bioactivity profile as well as the mechanical properties of a blend of starch and poly-caprolactone (SPCL) polymeric fiber mesh scaffolds functionalized with silanol (Si-OH) groups as key features for bone tissue engineering strategies. The scaffolds were made from SPCL by a wet spinning technique. A calcium silicate solution was used as a non-solvent to develop an in situ functionalization with Si-OH groups in a single-step approach. We also explored the relevance of silicon incorporated in SPCL-Si scaffolds to the in vitro osteogenic process of goat bone marrow stromal cells (gBMSCs) with and without osteogenic supplements in the culture medium. We hypothesized that SPCL-Si scaffolds could act as physical and chemical millieus to induce per se the osteogenic differentiation of gBMSCs. Results show that osteogenic differentiation of gBMSCs and the production of a mineralized extracellular matrix on bioactive SPCL-Si scaffolds occur for up to 2weeks, even in the absence of osteogenic supplements in the culture medium. The omission of media supplements to induce osteogenic differentiation is a promising feature towards simplified and cost-effective cell culturing procedures of a potential bioengineered product, and concomitant translation into the clinical field. Thus, the present work demonstrates that SPCL-Si scaffolds and their intrinsic properties sustain gBMSC osteogenic features in vitro, even in the absence of osteogenic supplements to the culture medium, and show great potential for bone regeneration strategies.

Development of Novel Mesoporous Silica-Based Bioactive Glass Scaffolds with Drug Delivery Capabilities

Novel silica-based bioactive glasses were successfully prepared by the sol-gel method. The optimized glass composition for fabrication of the scaffolds was (in mol.%) 60% SiO2 – 30% CaO - 5% Na2O - 5% P2O5 (60S30C5N5P). This composition was confirmed to develop a thick hydroxycarbonate apatite (HCA) layer in Simulated Body Fluid (SBF) after 7 days, as revealed by Fourier Transform Infrared Spectroscopy (FTIR), indicating the bioactive character of the scaffolds. The mesoporous nature of the glass structure allows the load of tetracycline and a sustained release of the drug in PBS during 7 days was measured.

Scaffold-based regeneration of skeletal tissues to meet clinical challenges

The management and reconstruction of damaged or diseased skeletal tissues have remained a significant global healthcare challenge. The limited efficacy of conventional treatment strategies for large bone, cartilage and osteochondral defects has inspired the development of scaffold-based tissue engineering solutions, with the aim of achieving complete biological and functional restoration of the affected tissue in the presence of a supporting matrix. Nevertheless, significant regulatory hurdles have rendered the clinical translation of novel scaffold designs to be an inefficient process, mainly due to the difficulties of arriving at a simple, reproducible and effective solution that does not rely on the incorporation of cells and/or bioactive molecules. In the context of the current clinical situation and recent research advances, this review will discuss scaffold-based strategies for the regeneration of skeletal tissues, with focus on the contribution of bioactive ceramic scaffolds and silk fibroin, and combinations thereof, towards the development of clinically viable solutions.