The effect of composition on ion release from Ca-Sr-Na-Zn-Si glass bone grafts

Co-doping of iron and copper ions in nanosized bioactive glass by reactive laser fragmentation in liquids

Bioactive glass (BG) is a frequently used biomaterial applicable in bone tissue engineering and known to be particularly effective when applied in nanoscopic dimensions. In this work, we employed the scalable reactive laser fragmentation in liquids method to produce nanosized 45S5 BG in the presence of light-absorbing Fe and Cu ions. Here, the function of the ions was twofold: (i) increasing the light absorption and thus causing a significant increase in laser fragmentation efficiency by a factor of 100 and (ii) doping the BG with bioactive metal ions up to 4 wt%. Our findings reveal an effective downsizing of the BG from micrometer-sized educts into nanoparticles having average diameters of <50 nm. This goes along with successful element-specific incorporation of the metal ions into the BG, inducing co-doping of Fe and Cu ions as verified by energy-dispersive X-ray spectroscopy (EDX). In this context, the overall amorphous structure is retained, as evidenced by X-ray powder diffraction (XRD). We further demonstrate that the level of doping for both elements can be adjusted by changing the BG/ion concentration ratio during laser fragmentation. Consecutive ion release experiments using inductively-coupled plasma mass spectrometry (ICP-MS) were conducted to assess the potential bioactivity of the doped nanoscopic BG samples, and cell culture experiments using MG-63 osteoblast-like cells demonstrated their cytocompatibility. The elegant method of in situ co-doping of Fe and Cu ions during BG nanosizing may provide functionality-advanced biomaterials for future studies on angiogenesis or bone regeneration, particularly as the level of doping may be adjusted by ion concentrations and ion type in solution.

A novel and injectable strontium-containing hydroxyapatite bone cement for bone substitution: A systematic evaluation

Reconstruction of bone defects is still a challenge. In this study, we developed and systematically evaluated a novel injectable strontium-containing hydroxyapatite (Sr-HA) bone cement in which Sr-HA powder included 5% Sr and was mixed with a setting liquid that included 5% potassium citrate. This Sr-HA cement was mainly composed of HA and α-tricalcium phosphate (TCP) and exhibited favorable injectability (100%), setting times (the initial setting time was 240 s and the final setting time was 420 s), compressive strength (73.4 MPa), maximal load and maximum bending stress, and excellent radiopacity. In addition, the Sr-HA cement also had excellent biocompatibility that exhibited low cytotoxicity for cell proliferation and no obvious disturbing effect on the osteogenic differentiation of periodontal ligament stem cells (DLSCs) and dental pulp stem cells (DPSCs). However, the Sr-HA cement could slightly promote the osteogenic differentiation of MC3T3 cells, which also implied that it would promote osseointegration between the cement and surrounding bone but would not obviously disturb the biological behavior of DLSCs and DPSCs. An in vivo study further confirmed that Sr-HA cement exhibited favorable osseointegration with the maxilla and tibia. All these findings implied that the novel Sr-HA cement was a suitable bone substitution for bone defects.

Calcium sulfate-containing glass polyalkenoate cement for revision total knee arthroplasty fixation

Poly(methyl methacrylate) (PMMA) bone cement is used as a minor void filler in revision total knee arthroplasty (rTKA). The application of PMMA is indicated only for peripheral bone defects with less than 5 mm depth and that cover less than 50% of the bone surface. Treating bone defects with PMMA results in complications as a result of volumetric shrinkage, bone necrosis, and aseptic loosening. These concerns have driven the development of alternative bone cements. We report here on novel modified glass polyalkenoate cements (mGPCs) containing 1, 5 and 15 wt% calcium sulfate (CaSO₄ ) and how the modified cements' properties compare to those of PMMA used in rTKA. CaSO₄ is incorporated into the mGPC to improve both osteoconductivity and bioresorbability. The results confirm that the incorporation of CaSO₄ into mGPCs decreases the setting time and increases release of therapeutic ions such as Ca²⁺ and Zn²⁺ over 30 days of maturation in deionized (DI) water. Moreover, the compressive strength for 5 and 15 wt% CaSO₄ addition increased to over 30 MPa after 30 day maturation. Although the overall initial compressive strength of the mGPC (~ 30 MPa) is less than PMMA (~ 95 MPa), the compressive strength of mGPC is closer to that of cancellous bone (~ 1.2-7.8 MPa). CaSO₄ addition did not affect biaxial flexural strength. Fourier transform infrared analysis indicated no cross-linking between CaSO₄ and the GPC after 30 days. in vivo tests are required to determine the effects the modified GPCs as alternative on PMMA in rTKA.

Component effects of bioactive glass on corrosion resistance and in vitro biological properties of apatite-matrix coatings

BACKGROUND

Surface modification of metallic implants is critical for improving the clinical performance of the dental and orthopedic devices. Bioactive glasses exhibit different levels of cellular function and physicochemical behavior; however, there have been few previous studies on the effect of constituents of the bioactive glasses on the in vitro osteogenic activity and corrosion resistance of apatite-based coatings.

OBJECTIVE

The objective of this work was to investigate the effect of SiO2, CaO, Na2O, and P2O5 on plasma-sprayed apatite coatings on Ti alloy substrates for tailoring the properties of implants making them suitable for clinical applications.

METHODS

The corrosion potential and corrosion current of various coatings in simulated body fluid (SBF) were examined. MG63 cell proliferation, differentiation, and mineralization of plasma-sprayed apatite-matrix coatings were evaluated.

RESULTS

The SiO2 and CaO-containing HA (HSC) coating had a higher corrosion potential than the other three coatings, while SiO2-containing HA (HS) coating displayed the highest corrosion current among all coatings. The effect of the oxides on cell functions followed the order SiO2 > CaO > P2O5 > Na2O in terms of cell attachment, proliferation, differentiation, and mineralization.

CONCLUSIONS

The flexibility in oxide doping may allow for the tunable biological properties and corrosion-resistant ability of the apatite coatings.

Multiple and Promising Applications of Strontium (Sr)-Containing Bioactive Glasses in Bone Tissue Engineering

Improving and accelerating bone repair still are partially unmet needs in bone regenerative therapies. In this regard, strontium (Sr)-containing bioactive glasses (BGs) are highly-promising materials to tackle this challenge. The positive impacts of Sr on the osteogenesis makes it routinely used in the form of strontium ranelate (SR) in the clinical setting, especially for patients suffering from osteoporosis. Therefore, a large number of silicate-, borate-, and phosphate-based BGs doped with Sr and produced in different shapes have been developed and characterized, in order to be used in the most advanced therapeutic strategies designed for the management of bone defects and injuries. Although the influence of Sr incorporation in the glass is debated regarding the obtained physicochemical and mechanical properties, the biological improvements have been found to be substantial both in vitro and in vivo. In the present study, we provide a comprehensive overview of Sr-containing glasses along with the current state of their clinical use. For this purpose, different types of Sr-doped BG systems are described, including composites, coatings and porous scaffolds, and their applications are discussed in the light of existing experimental data along with the significant challenges ahead.

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.

Strontium-releasing fluorapatite glass-ceramics: Crystallization behavior, microstructure, and solubility

The purpose of this work was to investigate the effect of strontium partial replacement for calcium on the crystallization behavior, microstructure and solubility of fluorapatite glass-ceramics. Four glass compositions were prepared with increasing amounts of strontium partially replacing calcium. The crystallization behavior was analyzed by differential scanning calorimetry and X-ray diffraction (XRD). The microstructure was investigated by scanning electron microscopy. The chemical solubility was quantified according to ISO standard 10993-14. The amount of strontium released in solution after incubation in TRIS-HCl or citric acid buffer was measured by atomic absorption spectroscopy. XRD analyses revealed that partially substituted strontium-fluorapatite and strontium-åkermanite crystallized after strontium additions. The lattice cell volume of both phases increased linearly with the amount of strontium in the composition. Strontium additions led to a reduction in crystal size and an increase in crystal number density. The chemical solubility and amount of strontium released in solution increased linearly with the amount of strontium present in the composition in both TRIS-HCl and citric acid buffers. Total amounts of strontium released reached a maximum of 547 ± 80 ppm in TRIS-HCl and 1252 ± 290 ppm in citric acid buffer for the glass composition with the highest amount of strontium. For all strontium-containing compositions, the amount released in TRIS-HCl continued to increase between 70 and 120 h, indicating sustained release rather than burst release. © 2017 Wiley Periodicals, Inc. J Biomater Res Part B: 106B: 1421-1430, 2018.

Novel bioglasses for bone tissue repair and regeneration: Effect of glass design on sintering ability, ion release and biocompatibility

Eight novel silicate, phosphate and borate glass compositions (coded as NCLx, where x = 1 to 8), containing different oxides (i.e. MgO, MnO2, Al2O3, CaF2, Fe2O3, ZnO, CuO, Cr2O3) were designed and evaluated alongside apatite-wollastonite (used as comparison material), as potential biomaterials for bone tissue repair and regeneration. Glass frits of all the formulations were processed to have particle sizes under 53 μm, with their morphology and dimensions subsequently investigated by scanning electron microscopy (SEM). In order to establish the nature of the raw glass powders, X-ray diffraction (XRD) analysis was also performed. The sintering ability of the novel materials was determined by using hot stage microscopy (HSM). Ionic release potential was assessed by inductively coupled plasma optical emission spectroscopy (ICP-OES). Finally, the cytotoxic effect of the novel glass powders was evaluated for different glass concentrations via a colorimetric assay, on which basis three formulations are considered promising biomaterials.

Effect of strontium substitution on the cytocompatibility and 3-D scaffold structure for the xSrO-(10-x) MgO-60SiO2-20CaO-10 P2O5 (2 ≤ x ≤ 8) sol-gel glasses

In the present study, novel glasses xSrO-(10-x) MgO-60SiO₂-20CaO-10 P₂O₅ (2 ≤ x ≤ 8, in steps of 2) are synthesized via sol-gel method. The current work focusses on the evaluation of mechanical, physical and biocompatible properties for sol-gel glasses. The pore size and surface area of these glasses were studied using BET analysis. The structural aspect of the glasses/glass ceramics was studied by XRD and Raman spectroscopy. The cytotoxicity assays were conducted for MG63 human osteosarcoma cell line. Furthermore, the as prepared glasses were used for the fabrication of 3-D porous scaffolds via polymer replication method. The loaded green bodies have been sintered at 700, 800 and 900 °C and were kept for 6 h to densify the glass network. The effect of sintering temperature on the structure and properties of as prepared scaffolds were analyzed via scanning electron microscopy (SEM) and porosity calculations.

Fabrication of Zn-Sr-doped laser-spinning glass nanofibers with antibacterial properties

The morphology and dimensions of bioactive materials are essential attributes to promote tissue culture. Bioactive materials with nanofibrous structure have excellent potential to be used as bone-defect fillers, since they mimic the collagen in the extracellular matrix. On the other hand, bioactive glasses with applications in regenerative medicine may present antibacterial properties, which depend on glass composition, concentration and the microorganisms tested. Likewise, their morphology may influence their antibacterial activity too. In the present work, the laser-spinning technique was used to produce bioactive glass nanofibers of two different compositions: 45S5 Bioglass® and ICIE16M, bioactive glass doped with zinc and strontium. Their antibacterial activity against Staphylococcus aureus was tested by culturing them in dynamic conditions. Bacterial growth index profiles during the first days of experiment can be explained by the variations in the pH values of the media. The bactericidal effect of the doped nanofibers at longer times is justified by the release of zinc and strontium ions. Cytotoxicity was analyzed by means of cell viability tests performed with BALB/3T3 cell line.

Antibacterial and osteo-stimulatory effects of a borate-based glass series doped with strontium ions

This work considered the effect of both increasing additions of Strontium (Sr²⁺) and incubation time on solubility and both antibacterial and osteo-stimulatory effects of a series of glasses based on the B₂O₃-P₂O₅-CaCO₃-Na₂CO₃-TiO₂-SrCO₃ series. The amorphous nature of all the glasses was confirmed by X-ray diffraction. Discs of each glass were immersed in de-ionized water for 1, 7 and 30 days, and the water extracts were used for ion release profiles, pH measurements and cytotoxicity testing. Atomic absorption spectroscopy was employed to detect the release of Na⁺, Ca²⁺ and Sr²⁺ ions from the glasses with respect to maturation, which indicated that the addition of Sr²⁺ retarded solubility of the glass series. This effect was also confirmed by weight loss analysis through comparing the initial weight of glass discs before and after periods of incubation. The incorporation of Sr²⁺ in the glasses did not influence the pH of the water extracts when the glasses were stored for up to 30 days. Cytotoxicity testing with an osteoblastic cell line (MC3T3-E1) indicated that glasses with the higher (20 mol% and 25 mol%) Sr²⁺ incorporation promoted proliferation of osteoblast cells, while the glasses with lower Sr²⁺ contents inhibited cell growth. The glass series, except for Ly-B5 (which contained the highest Sr²⁺ incorporation; 25 mol%), were bacteriostatic against S. aureus in the short term (1-7 days) as a result of the dissolution products released.

Review and the state of the art: Sol-gel and melt quenched bioactive glasses for tissue engineering

Biomaterial development is currently the most active research area in the field of biomedical engineering. The bioglasses possess immense potential for being the ideal biomaterials due to their high adaptiveness to the biological environment as well as tunable properties. Bioglasses like 45S5 has shown great clinical success over the past 10 years. The bioglasses like 45S5 were prepared using melt-quenching techniques but recently porous bioactive glasses have been derived through sol-gel process. The synthesis route exhibits marked effect on the specific surface area, as well as degradability of the material. This article is an attempt to provide state of the art of the sol-gel and melt quenched bioactive bioglasses for tissue regeneration. Fabrication routes for bioglasses suitable for bone tissue engineering are highlighted and the effect of these fabrication techniques on the porosity, pore-volume, mechanical properties, cytocompatibilty and especially apatite layer formation on the surface of bioglasses is analyzed in detail. Drug delivery capability of bioglasses is addressed shortly along with the bioactivity of mesoporous glasses. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1248-1275, 2016.

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.

Calcium polyphosphate as an additive to zinc-silicate glass ionomer cements

Aluminum-free glass ionomer cements (GICs) are under development for orthopedic applications, but are limited by their insufficient handling properties. Here, the addition of calcium polyphosphate (CPP) was investigated as an additive to an experimental zinc-silicate glass ionomer cement. A 50% maximum increase in working time was observed with CPP addition, though this was not clinically significant due to the short working times of the starting zinc-silicate GIC. Surprisingly, CPP also improved the mechanical properties, especially the tensile strength which increased by ∼33% after 30 days in TRIS buffer solution upon CPP addition up to 37.5 wt%. This strengthening may have been due to the formation of ionic crosslinks between the polyphosphate chains and polyacrylic acid. Thus, CPP is a potential additive to future GIC compositions as it has been shown to improve handling and mechanical properties. In addition, CPP may stimulate new bone growth and provide the ability for drug delivery, which are desirable modifications for an orthopedic cement.

Role of glass structure in defining the chemical dissolution behavior, bioactivity and antioxidant properties of zinc and strontium co-doped alkali-free phosphosilicate glasses

We investigated the structure-property relationships in a series of alkali-free phosphosilicate glass compositions co-doped with Zn(2+) and Sr(2+). The emphasis was laid on understanding the structural role of Sr(2+) and Zn(2+) co-doping on the chemical dissolution behavior of glasses and its impact on their in vitro bioactivity. The structure of glasses was studied using molecular dynamics simulations in combination with solid state nuclear magnetic resonance spectroscopy. The relevant structural properties are then linked to the observed degradation behavior, in vitro bioactivity, osteoblast proliferation and oxidative stress levels. The apatite-forming ability of glasses has been investigated by X-ray diffraction, infrared spectroscopy and scanning electron microscopy-energy-dispersive spectroscopy after immersion of glass powders/bulk in simulated body fluid (SBF) for time durations varying between 1h and 14 days, while their chemical degradation has been studied in Tris-HCl in accordance with ISO 10993-14. All the glasses exhibit hydroxyapatite formation on their surface within 1-3h of their immersion in SBF. The cellular responses were observed in vitro on bulk glass samples using human osteosarcoma MG63 cell line. The dose-dependent cytoprotective effect of glasses with respect to the concentration of zinc and strontium released from the glasses is also discussed.

Bioactivity and cytotoxicity of glass and glass-ceramics based on the 3CaO·P₂O₅--SiO₂--MgO system

The mechanical strength of bioactive glasses can be improved by controlled crystallization, turning its use as bulk bone implants viable. However, crystallization may affect the bioactivity of the material. The aim of this study was to develop glass-ceramics of the nominal composition (wt%) 52.75(3CaO·P₂O₅)-30SiO₂-17.25MgO, with different crystallized fractions and to evaluate their in vitro cytotoxicity and bioactivity. Specimens were heat-treated at 700, 775 and 975 °C, for 4 h. The major crystalline phase identified was whitlockite, an Mg-substituted tricalcium phosphate. The evaluation of the cytotoxicity was carried out by the neutral red uptake methodology. Ionic exchanges with the simulated body fluid SBF-K9 acellular solution during the in vitro bioactivity tests highlight the differences in terms of chemical reactivity between the glass and the glass-ceramics. The effect of crystallinity on the rates of hydroxycarbonate apatite (HCA) formation was followed by Fourier transformed infrared spectroscopy. Although all glass-ceramics can be considered bioactive, the glass-ceramic heat-treated at 775 °C (V775-4) presented the most interesting result, because the onset for HCA formation is at about 24 h and after 7 days the HCA layer dominates completely the spectrum. This occurs probably due to the presence of the whitlockite phase (3(Ca,Mg)O·P₂O₅). All samples were considered not cytotoxic.

An evaluation of the processing conditions, structure, and properties (biaxial flexural strength and antibacterial efficacy) of sintered strontium–zinc–silicate glass ceramics

The use of artificial bone grafts has increased in order to satisfy a growing demand for bone replacement materials. Initial mechanical stability of synthetic bone grafts is very advantageous for certain clinical applications. Coupled with the advantage of mechanical strength, a material with inherent antibacterial properties would be very beneficial. A series of strontium-doped zinc silicate (Ca–Sr–Na–Zn–Si) glass ceramics have been characterized in terms of their crystalline structure, biaxial flexural strength and antibacterial efficacy based on the identification of optimum sintering conditions. All three glass ceramics, namely, BT110, BT111, and BT112 were found to be fully crystalline, with BT111 and BT112 comprising of biocompatible crystalline phases. The biaxial flexural strengths of the three glass ceramics ranged from 70 to 149 MPa and were shown to be superior to those of clinically established ceramics in dry conditions and following incubation in simulated physiological conditions. The bacteriostatic effect for each glass ceramic was also established, where BT112 showed an inhibitory effect against three of the most common bacteria found at implantation sites, namely, Enterococcus faecalis, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. The results of the evaluation suggest that the materials studied offer advantages over current clinical materials and indicate the potential suitability of the glass ceramics as therapeutic bone grafts.

Metallic ions as therapeutic agents in tissue engineering scaffolds: an overview of their biological applications and strategies for new developments

This article provides an overview on the application of metallic ions in the fields of regenerative medicine and tissue engineering, focusing on their therapeutic applications and the need to design strategies for controlling the release of loaded ions from biomaterial scaffolds. A detailed summary of relevant metallic ions with potential use in tissue engineering approaches is presented. Remaining challenges in the field and directions for future research efforts with focus on the key variables needed to be taken into account when considering the controlled release of metallic ions in tissue engineering therapeutics are also highlighted.

Influence of strontium on structure, sintering and biodegradation behaviour of CaO-MgO-SrO-SiO(2)-P(2)O(5)-CaF(2) glasses

The present study investigates the influence of SrO on structure, apatite-forming ability, physico-chemical degradation and sintering behaviour of melt-quenched bioactive glasses with the composition (mol.%): (36.07 - x) CaO-xSrO-19.24MgO-5.61P(2)O(5)-38.49SiO(2)-0.59CaF(2), where x varies between 0 and 10. The detailed structural analysis of the glasses is made by infrared spectroscopy and magic angle spinning-nuclear magnetic resonance spectroscopy. Silicon is predominantly present as Q(2) (Si) species, while phosphorus is found as orthophosphate in all the investigated glasses. The apatite-forming ability of glasses is investigated by immersion of glass powders in simulated body fluid for time durations varying between 1 h and 7 days. While increasing the Sr(2+)/Ca(2+) ratio in the glasses does not affect their structure significantly, their apatite-forming ability is decreased considerably. Further, physico-chemical degradation of glasses is studied in accordance with ISO 10993-14 "Biological evaluation of medical devices - Part 14: Identification and quantification of degradation products from ceramics" in Tris-HCl and citric acid buffer, and the possible implications of the ion release profiles from the glasses in different solutions are discussed. The addition of strontium to the glasses leads to a sevenfold decrease in chemical degradation of glasses in Tris-HCl. The sintering of glass powders renders glass ceramics (GCs) with varying degrees of crystallinity and good flexural strength (98-131 MPa), where the mechanical properties depend on the nature and amount of crystalline phases present in the GCs.

Preliminary evaluation of therapeutic ion release from Sr-doped zinc-silicate glass ceramics

Bioactive and degradable porous bioceramics play an important role in many clinical situations. Porosity is essential to the performance of a material that is proposed to be used as an implantable osseous scaffold. Scaffolds provide a three dimensional support and template to osseous integration and vascularization. Combining the porosity of a scaffold with the ability of the scaffold material to deliver therapeutic ions to the site of implantation goes some way towards developing an ideal bone graft. A series of strontium-doped zinc silicate (Ca-Sr-Na-Zn-Si) glass ceramics scaffoldswere developed, whose porosity was measured to be between 93% and 96%, which is advantageous in terms of osseous integration and vascularization. The levels of Zn2+ and Sr2+ detected as a result of degradation of the crystalline phases were found to be 1.4–600 parts per million (ppm) and 0–583 ppm, respectively. The levels detected correlate well with the levels of Sr2+ and Zn2+ions typically associated with clinical benefits, including antibacterial efficacy, osteoblastic differentiation and impaired osteoclastic resorption.

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

Several inorganic materials such as special compositions of silicate glasses, glass-ceramics and calcium phosphates have been shown to be bioactive and resorbable and to exhibit appropriate mechanical properties which make them suitable for bone tissue engineering applications. However, the exact mechanism of interaction between the ionic dissolution products of such inorganic materials and human cells are not fully understood, which has prompted considerable research work in the biomaterials community during the last decade. This review comprehensively covers literature reports which have investigated specifically the effect of dissolution products of silicate bioactive glasses and glass-ceramics in relation to osteogenesis and angiogenesis. Particularly, recent advances made in fabricating dense biomaterials and scaffolds doped with trace elements (e.g. Zn, Sr, Mg, and Cu) and investigations on the effect of these elements on the scaffold biological performance are summarized and discussed in detail. Clearly, the biological response to artificial materials depends on many parameters such as chemical composition, topography, porosity and grain size. This review, however, focuses only on the ion release kinetics of the materials and the specific effect of the released ionic dissolution products on human cell behaviour, providing also a scope for future investigations and identifying specific research needs to advance the field. The biological performance of pure and doped silicate glasses, phosphate based glasses with novel specific compositions as well as several other silicate based compounds are discussed in detail. Cells investigated in the reviewed articles include human osteoblastic and osteoclastic cells as well as endothelial cells and stem cells.

The effect of ionic dissolution products of Ca-Sr-Na-Zn-Si bioactive glass on in vitro cytocompatibility

Many commercial bone grafts cannot regenerate healthy bone in place of diseased bone. Bioactive glasses have received much attention in this regard due to the ability of their ionic dissolution products to promote cell proliferation, cell differentiation and activate gene expression. Through the incorporation of certain ions, bioactive glasses can become therapeutic for specific pathological situations. Calcium-strontium-sodium-zinc-silicate glass bone grafts have been shown to release therapeutic levels of zinc and strontium, however the in vitro compatibility of these materials is yet to be reported. In this study, the in vitro cytocompatibility of three different calcium-strontium-sodium-zinc-silicate glasses was examined as a function of their ion release profiles, using Novabone® bioglass as a commercial comparison. Experimental compositions were shown to release Si(4+) ranging from 1 to 81 ppm over 30 days; comparable or enhanced release in comparison to Novabone. The maximum Ca(2+) release detected for experimental compositions was 9.1 ppm, below that reported to stimulate osteoblasts. Sr(2+) release was within known therapeutic ranges, and Zn(2+) release ranged from 0.5 to 1.4 ppm, below reported cytotoxic levels. All examined glass compositions show equivalent or enhanced in vitro compatibility in comparison to Novabone. Cells exposed to BT112 ionic products showed enhanced cell viabilities indicating cell proliferation was induced. The ion release profiles suggest this effect was due to a synergistic interaction between certain combinations and concentrations of ions. Overall, results indicate that the calcium-strontium-sodium-zinc-silicate glass compositions show equivalent or even enhanced in vitro compatibility compared to Novabone®.