Effect of increasing titanium dioxide content on bulk and surface properties of phosphate-based glasses

Structural connectivity and bioactivity in sol-gel silicate glass design

Bioactive glasses (BGs) bond with bone by forming hydroxy carbonate apatite (HCA) upon reaction in physiological fluid, a phenomenon known as bioactivity. BGs structural network connectivity determines their bioactivity. Sol-gel BGs are synthesized through the hydrolysis and condensation of metal alkoxide precursors in the presence of a catalyst, in aqueous environments. Several sol-gel synthesis parameters directly impact BG network connectivity: pH (i.e. acid or basic catalysis), water to alkoxide ratio (Rw), alkoxide type and presence of dopant ions. However, the relationship between bioactivity and these parameters remains surprisingly unexplored. This study highlights the relationship between synthesis pH, Rw, network connectivity and bioactivity in silica-based sol-gel BGs and BGs doped with titanium (Ti) ions (TiBGs), the latter selected for their known ability to enhance network connectivity. BGs and TiBGs are synthesized with various Rw values under acidic and basic conditions, and their bioactivity is assessed in simulated body fluid for 7 days. Increasing Rw decreases network connectivity and increases bioactivity of BGs with high network connectivity, as observed for base-catalyzed BGs and for both acid and base catalyzed TiBGs, but not in BGs with lower connectivity as evidenced in acid-catalyzed BGs. Basic catalysis of TiBGs prevents crystalline TiO2 domain formation, which was instead consistently observed in TiBGs synthesized under acidic catalysis. These findings help the design of BGs for applications where ion release needs to be enhanced even in the presence of dopants that slow down HCA formation, and of BGs with specific properties, e.g. TiO2-containing BGs with potential bactericidal activity. STATEMENT OF SIGNIFICANCE: Bioactive glasses (BGs) bond with bone by dissolving and forming hydroxycarbonate apatite (HCA) on their surface, offering applications in medicine and dentistry. BG's network connectivity influences its dissolution rate, and hence HCA formation. While solution-gelation (sol-gel) is commonly used for BG production, the effect of sol gel synthesis parameters on HCA formation remains unexplored. We studied the relationship between synthesis parameters (water-to-alkoxide ratio (Rw), catalyst, and dopant ions, particularly titanium), BG network connectivity, and HCA formation. We find that increasing Rw with any catalyst enhances HCA formation, particularly in glasses with high network connectivity. This understanding allows tailoring BG synthesis for different applications, e.g. those requiring doping with ions that increase network connectivity and fills a crucial gap in BG literature.

Zinc phosphate glass microspheres promoted mineralization and expression of BMP2 in MC3T3-E1 cells

Degradable phosphate glasses have shown favorable properties for tissue engineering. By changing the composition of the glasses, the degradation rate, and ion release are controllable. Zinc oxide can function as a glass network modifier and has been shown to play a positive role in bone formation. Also, phosphate glasses can easily be processed into microspheres, which can be used as microcarriers. This study aims to develop zinc phosphate glasses microspheres and explore the optimized size and composition for applications in bone tissue engineering. Zinc-titanium-calcium-sodium phosphate glasses with 0, 1, 3, 5, or 10 mol % zinc oxide were prepared and processed into microspheres. The smaller microspheres ranged in size from 50 to 106 μm, while the larger ones ranged from 106 to 150 μm. The characteristics of glasses were examined. The osteoblastic cell line MC3T3-E1 was cultured on the surface of microspheres and the cell viability was examined. To evaluate osteogenic differentiation, Alizarin Red S staining, quantitative reverse transcription polymerase chain reaction, and western blot analysis were performed after 14 days. Different sizes of zinc phosphate glass microspheres were successfully made. The glass microspheres with <10 mol % zinc oxide were able to support the adhesion and proliferation of MC3T3-E1 cell lines. The relative gene expression of BMP2 was significantly upregulated in the smaller glass microspheres containing 3 mol % zinc oxide (26-fold, p < .001) and both sizes of microspheres containing 5 mol % zinc oxide (smaller: 27-fold, p < .001; larger: 35-fold, p < .001). Additionally, cluster formation was observed in glass microspheres after 14 days, and the mineralization of MC3T3-E1 cell lines was promoted. Based on these findings, the glass microspheres containing 3-5 mol % of zinc oxide can promote osteogenic differentiation for MC3T3-E1 cells.

A better roadmap for designing novel bioactive glasses: effective approaches for the development of innovative revolutionary bioglasses for future biomedical applications

The introduction of bioactive glasses (BGs) precipitated a paradigm shift in the medical industry and opened the path for the development of contemporary regenerative medicine driven by biomaterials. This composition can bond to live bone and can induce osteogenesis by the release of physiologically active ions. 45S5 BG products have been transplanted effectively into millions of patients around the world, primarily to repair bone and dental defects. Over the years, many other BG compositions have been introduced as innovative biomaterials for repairing soft tissue and delivering drugs. When research first started, many of the accomplishments that have been made today were unimaginable. It appears that the true capacity of BGs has not yet been realized. Because of this, research involving BGs is extremely fascinating. However, to be successful, it requires interdisciplinary cooperation between physicians, glass chemists, and bioengineers. The present paper gives a picture of the existing clinical uses of BGs and illustrates key difficulties deserving to be faced in the future. The challenges range from the potential for BGs to be used in a wide variety of applications. We have high hopes that this paper will be of use to both novice researchers, who are just beginning their journey into the world of BGs, as well as seasoned scientists, in that it will promote conversation regarding potential additional investigation and lead to the discovery of innovative medical applications for BGs.

Multifunctional bioactive glasses with spontaneous degradation for simultaneous osteosarcoma therapy and bone regeneration

For the treatment of tumor-related bone defects resulting from surgical resection, simultaneous eradication of residual tumor cells and repair of bone defects represent a challenge. To date, photothermal therapy based on photothermal materials is used to remove residual tumor cells under near infrared light. However, most of photothermal materials have no function for bone repair, and even if combined with bioactive materials to enhance osteogenesis, they still cause potential harm to the body due to inability to degrade or poor degradability. Herein, multifunctional bioactive glasses (PGFe5-1100, PGCu5-1100) based on phosphate glass doped with transition metal elements were prepared for photothermal ablation, bone regeneration, and controllable degradation. The glasses exhibited excellent photothermal effect, which was derived from the electron in-band transition after light absorption due to energy level splitting of doped transition metal element and the subsequent electron nonradiative relaxation. The photothermal performance can be controlled by laser power density, element doping content and glass melting temperature. Moreover, the hyperthermia induced by the glasses can effectively kill tumor cells in vitro. In addition, the glasses degraded over time, and the released P, Ca, Na, Fe could promote bone cell proliferation and osteogenic differentiation. Therefore, these results successfully demonstrated that transition metal element-doped phosphate glasses have multifunctional abilities of tumor elimination, bone regeneration, and spontaneous degradation simultaneously with better biosecurity and bioactivity, which is believed to pave the way for the design of novel biomaterials for osteosarcoma treatment.

Antibacterial and Antibiofilm Efficacy of Copper-Doped Phosphate Glass on Pathogenic Bacteria

This study aimed to investigate the antibacterial [minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC)] and antibiofilm activity [log10 colony forming unit/mL (CFU/mL) and biofilm disruption] of copper-doped phosphate glass (CDPG) against Streptococcus oralis, Enterococcus faecalis, Lactobacillus casei, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Methods: the antibacterial activity was determined using microbroth dilution and time-kill assay. The antibiofilm activity was investigated using crystal violet and confocal laser scanning microscopy. Bacteria growing in absence of CDPG were used as controls. Results: the MIC was ≥125 mg of CPDG/mL; the log10 CFU/mL reduction ranged from 2.66–3.14 to 6.23–9.65 after 4 and 24 h respectively. Generally, no growth was observed after 24 h of treatment with CDPG; the MBC was 250 mg/mL for L. casei and S. oralis while 500 mg/mL for the rest of the bacteria. The highest and lowest antibiofilm activity was observed against S. oralis and E. coli respectively. Three patterns of complete biofilm disruption were seen: (i) large areas with E. fecalis and S. oralis, (ii) medium-size pockets with S. aureus and P. aeruginosa, or (iii) small areas with E. coli and L. casei. Conclusion: CDPG can be potentially used as an antibacterial and an antibiofilm agent against oral biofilm-forming bacteria.

Development and Characterization of Phosphate Glass Fibers and Their Application in the Reinforcement of Polyester Matrix Composites

This study focused on the production and characterization of phosphate glass fibers (PGF) for application as composite reinforcement. Phosphate glasses belonging to the system 52P₂O₅24CaO13MgO (11-(X + Y)) K₂OXFe₂O₃YTiO₂ (X:1, 3, 5) and (Y:0.5, 1) were elaborated and converted to phosphate glass fibers. First, their mechanical properties and chemical durability were investigated. Then, the optimized PGF compositions were used afterward as reinforcement for thermosetting composite materials. Polyester matrices reinforced with short phosphate glass fibers (sPGF) up to 20 wt % were manufactured by the contact molding process. The mechanical and morphological properties of different sPGF-reinforced polyester systems were evaluated. The choice between the different phosphate-based glass syntheses (PGFs) was determined by their superior mechanical performance, their interesting chemical durability, and their high level of dispersion in the polyester matrix without any ad sizing as proven by SEM morphological analysis. Moreover, the characterization of mechanical properties revealed that the tensile and flexural moduli of the developed polyester-based composites were improved by increasing the sPGF content in the polymer matrix in perfect agreement with Takayanagi model predictions. The present work thus highlights some promising results to obtain high-quality phosphate glass fiber-reinforced polyester parts which can be transposed to other thermosetting or thermoplastic-based composites for high-value applications.

TiO2 nanoparticles added to dense bovine hydroxyapatite bioceramics increase human osteoblast mineralization activity

OBJECTIVES

This study evaluated the effect of TiO₂ nanoparticles + dense hydroxyapatite (HA) on human osteoblast cells (SAOS-2).

METHODS

Particulate bovine HA powder with or without the addition of either 5 or 8 % TiO₂ (HA, HA/TiO₂Np5 % or HA/TiO₂Np8 %) were pressed into disks (Ø = 12.5 mm; thickness = 1.3 mm) uniaxially (100 MPa) and isostatically (200 MPa/1 min) and sintered at 1300 °C. Y-TZP disks were used as control. The following tests were performed: Scanning Electron Microscopy and Dispersive Energy Spectroscopy (SEM/EDS), Atomic Force Microscopy (AFM), cell viability assay (Alamar Blue-AB) and mineralized matrix deposition (Alizarin Red-AR). AB and AR data were submitted to 2-way ANOVA/Tukey tests and ANOVA/Tukey tests, respectively.

RESULTS

SEM revealed that the surface of HA/TiO₂Np5% resembles DPBHA surface, but also contains smaller granules. HA/TiO₂Np8% characteristics resembles HA/TiO₂Np5% surface, but with irregular topography. Y-TZP showed a typical oxide ceramic surface pattern. EDS revealed Ca, O, and P in all samples. C, O, and Zr appeared in Y-TZP samples. AFM data corroborates SEM analysis. AB test revealed excellent cellular viability for HA/TiO₂Np5% group. AR test showed that all groups containing TiO₂np had more mineralized matrix deposition than all other groups, with statistically differences between HA/TiO₂Np8% and HA cultivated in non-osteogenic medium. Culture in osteogenic medium exhibited much more mineralized matrix deposition by TiO₂np groups.

SIGNIFICANCE

In conclusion, the addition of TiO₂np showed chemical, superficial, and biological changes in the reinforced materials. HA/TiO₂Np5% showed the best results for cell viability and HA/TiO₂Np8% for mineralized matrix deposition.

Bioactive Glasses in Periodontal Regeneration: Existing Strategies and Future Prospects-A Literature Review

The present review deals with bioactive glasses (BGs), a class of biomaterials renowned for their osteoinductive and osteoconductive capabilities, and thus widely used in tissue engineering, i.e., for the repair and replacement of damaged or missing bone. In particular, the paper deals with applications in periodontal regeneration, with a special focus on in vitro, in vivo and clinical studies. The study reviewed eligible publications, identified on the basis of inclusion/exclusion criteria, over a ranged time of fifteen years (from 1 January 2006 to 31 March 2021). While there are many papers dealing with in vitro tests, only a few have reported in vivo (in animal) research, or even clinical trials. Regardless, BGs seem to be an adequate choice as grafts in periodontal regeneration.

Biomimetic Cell-Substrate of Chitosan-Cross-linked Polyaniline Patterning on TiO2 Nanotubes Enables hBM-MSCs to Differentiate the Osteoblast Cell Type

Titanium-based substrates are widely used in orthopedic treatments and hard tissue engineering. However, many of these titanium (Ti) substrates fail to interact properly between the cell-to-implant interface, which can lead to loosening and dislocation from the implant site. As a result, scaffold implant-associated complications and the need for multiple surgeries lead to an increased clinical burden. To address these challenges, we engineered osteoconductive and osteoinductive biosubstrates of chitosan (CS)-cross-linked polyaniline (PANI) nanonets coated on titanium nanotubes (TiO₂NTs) in an attempt to mimic bone tissue's major extracellular matrix. Inspired by the architectural and tunable mechanical properties of such tissue, the TiO₂NTs-PANI@CS-based biofilm conferred strong anticorrosion, the ability to nucleate hydroxyapatite nanoparticles, and excellent biocompatibility with human bone marrow-derived mesenchymal stem cells (hBM-MSCs). An in vitro study showed that the substrate-supported cell activities induced greater cell proliferation and differentiation compared to cell-TiO₂NTs alone. Notably, the bone-related genes (collagen-I, OPN, OCN, and RUNX 2) were highly expressed within TiO₂NTs-PANI@CS over a period of 14 days, indicating greater bone cell differentiation. These findings demonstrate that the in vitro functionality of the cells on the osteoinductive-like platform of TiO₂NTs-PANI@CS improves the efficiency for osteoblastic cell regeneration and that the substrate potentially has utility in bone tissue engineering applications.

Innovative Formulations of Phosphate Glasses as Controlled-Release Fertilizers to Improve Tomato Crop Growth, Yield and Fruit Quality

Three phosphate glass compositions, VF1, VF2, and VF3, containing macro and micronutrients with different [K₂O/(CaO+MgO)] ratio, were formulated to be used as controlled release fertilizers for tomato crop, depending on their chemical durability in water and their propriety with respect to the standards of controlled-release fertilizers. This study investigated the influence of [K₂O/(CaO+MgO)] ratio variation on glass properties. For this, the elaborated glasses have undergone a chemical characterization using inductively coupled plasma atomic emission spectroscopy, a thermal characterization using differential thermal analysis, a physicochemical characterization based on density and molar volume measurements, and a structural characterization using Raman spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. In addition, the chemical durability was determined by measuring the percentage of weight loss and the pH. Results revealed that the glass structure and composition have the mean role in controlling the release of nutrients in water. By increasing [K₂O/(CaO+MgO)] ratio, the dissolution rates of the glasses increased due to the shrinking in the rate of crosslinking between phosphate chains, accompanied with a diminution in transition and crystallization temperatures, and an increase in the molar volume. An agronomic valorization of VF1 and VF2 glass fertilizers, which showed dissolution profiles adequate to the criteria of controlled-release fertilizers, was carried out to evaluate their efficiency on tomato crops. These glass fertilizers improved soil mineral content and tomato performances in comparison to the control and NPK treatments with the distinction of VF2. The results highlight the effectiveness of these smart fertilizers toward their potential large-scale application to improve crop production and quality for high nutritional value foods.

Development and physicochemical characterization of novel porous phosphate glass bone graft substitute and in vitro comparison with xenograft

The process of bone regeneration in bone grafting procedures is greatly influenced by the physicochemical properties of the bone graft substitute. In this study, porous phosphate glass (PPG) morsels were developed and their physicochemical properties such as degradation, crystallinity, organic content, surface topography, particle size and porosity were evaluated using various analytical methods. The in vitro cytotoxicity of the PPG morsels was assessed and the interaction of the PPG morsels with Dental Pulp Stem Cells (DPSCs) was studied by measuring cell proliferation and cell penetration depth. The cell-material interactions between PPG morsels and a commercially available xenograft (XG) were compared. The PPG morsels were observed to be amorphous, biocompatible and highly porous (porosity = 58.45%). From in vitro experiments, PPG morsels were observed to be non-cytotoxic and showed better cell proliferation. The internal surface of PPG was easily accessible to the cells compared to XG.

Porous Phosphate-Based Glass Microspheres Show Biocompatibility, Tissue Infiltration, and Osteogenic Onset in an Ovine Bone Defect Model

Phosphate-based glasses (PBGs) are bioactive and fully degradable materials with tailorable degradation rates. PBGs can be produced as porous microspheres through a single-step process, using changes in their formulation and geometry to produce varying pore sizes and interconnectivity for use in a range of applications, including biomedical use. Calcium phosphate PBGs have recently been proposed as orthobiologics, based on their in vitro cytocompatibility and ion release profile. In this study, porous microspheres made of two PBG formulations either containing TiO₂ (P40Ti) or without (P40) were implanted in vivo in a large animal model of bone defect. The biocompatibility and osteogenic potential of these porous materials were assessed 13 weeks postimplantation in sheep and compared to empty defects and autologous bone grafts used as negative and positive controls. Histological analysis showed marked differences between the two formulations, as lower trabeculae-like interconnection and higher fatty bone marrow content were observed in the faster degrading P40-implanted defects, while the slower degrading P40Ti material promoted dense interconnected tissue. Autologous bone marrow concentrate (BMC) was also incorporated within the P40 and P40Ti microspheres in some defects; however, no significant differences were observed in comparison to microspheres implanted alone. Both formulations induced the formation of a collagen-enriched matrix, from 20 to 40% for P40 and P40Ti2.5 groups, suggesting commitment toward the bone lineage. With the faster degrading P40 formulation, mineralization of the tissue matrix was observed both with and without BMC. Some lymphocyte-like cells and foreign body multinucleated giant cells were observed with P40Ti2.5, suggesting that this more durable formulation might be linked to an inflammatory response. In conclusion, these first in vivo results indicate that PBG microspheres could be useful candidates for bone repair and regenerative medicine strategies and highlight the role of material degradation in the process of tissue formation and maturation.

A parameterised mathematical model to elucidate osteoblast cell growth in a phosphate-glass microcarrier culture

Tissue engineering has the potential to augment bone grafting. Employing microcarriers as cell-expansion vehicles is a promising bottom-up bone tissue engineering strategy. Here we propose a collaborative approach between experimental work and mathematical modelling to develop protocols for growing microcarrier-based engineered constructs of clinically relevant size. Experiments in 96-well plates characterise cell growth with the model human cell line MG-63 using four phosphate glass microcarrier materials. Three of the materials are doped with 5 mol% TiO₂ and contain 0%, 2% or 5% CoO, and the fourth material is doped only with 7% TiO₂ (0% CoO). A mathematical model of cell growth is parameterised by finding material-specific growth coefficients through data-fitting against these experiments. The parameterised mathematical model offers more insight into the material performance by comparing culture outcome against clinically relevant criteria: maximising final cell number starting with the lowest cell number in the shortest time frame. Based on this analysis, material 7% TiO₂ is identified as the most promising.

Assessing behaviour of osteoblastic cells in dynamic culture conditions using titanium-doped phosphate glass microcarriers

Tissue engineering is a promising approach for bone regeneration; yet challenges remain that limit successful translation to patients. It is necessary to understand how real-world manufacturing processes will affect the constituent cells and biomaterials that are needed to create engineered bone. Bioactive phosphate glasses processed into microspheres are an attractive platform for expanding bone-forming cells and also for driving their osteogenic differentiation and maturation. The aim of this study was to assess whether Ti-doped phosphate glass microspheres could support osteoblastic cell responses in dynamic cell culture environments. Dynamic culture conditions were achieved using microwell studies under orbital agitation. Dimensionless parameters such as the Froude number were used to inform the choice of agitation speeds, and the impact on cell proliferation and microunit formation was quantified. We found that phosphate glass microspheres doped with titanium dioxide at both 5 and 7 mol% provided a suitable biomaterial platform for effective culture of MG63 osteoblastic cells and was not cytotoxic. Dynamic culture conditions supported expansion of MG63 cells and both 150 and 300 rpm orbital shake resulted in higher cell yield than static cultures at the end of the culture (day 13). The Froude number analysis provided insight into how the microunit size could be manipulated to enable an appropriate agitation speed to be used, while ensuring buoyancy of the microunits. These small-scale experiments and analyses provide understanding of the impact of fluid flow on cell expansion that will have increasing importance when scaling up to process technologies that can deliver clinical quantities of cell-microsphere units. Such knowledge will enable future engineering of living bone-like material using processing systems such as bioreactors that use mixing and agitation for nutrient transfer, therefore introducing cells to dynamic culture conditions.

Physical properties and biocompatibility effects of doping SiO2 and TiO2 into phosphate-based glass for bone tissue engineering

Phosphate glass is continuing to gain more attention as potential bone substitutes. The ternary (P2O5-CaO-Na2O) is investigated in terms of both physical properties and biocompatibility by doping different percentages of SiO2 and TiO2. Two groups were prepared; the first has different percentages of TiO2 and SiO2, whereas the second group compositions have 5 mol% TiO2 and 5 mol% SiO2 being added to compensate the network-forming oxide P2O5 and the network-modifying oxide CaO. Density, mass loss, pH, DTA, XRD, and cation release experiments were performed to study the physicochemical properties of the compositions, while MG63 and hMS cells were used within in vitro cell culture to study their biocompatibility. Results showed that an increase in TiO2 content correlated with an increase in glass density, decreased mass loss, increased trend of Tg and Tm values, and Na+ and Ca2+ release in group 1. There was no improvement in the MG63 viability or the ability of hMSCs to differentiate into osteoblasts where TiO2 decreased in favour of SiO2. Furthermore, in group 2, 50P2O5–25CaO was less dense than 45P2O5–30CaO, degraded dramatically less, had lower Tg and Tm values and released less Na+ and Ca(2+). The synergistic effect of doping 5 mol% TiO2 and 5 mol% SiO2 increased the MG63 viability in both compositions and was found 45P2O5–30CaO to have promising results in terms of the ability of hMSCs to differentiate into osteoblasts. To conclude, substituting TiO2 in place of SiO2 improved the physical properties and the biocompatibility of (P2O5-CaO-Na2O) glass system, whereas doping 5 mol% SiO2 and 5 mol% TiO2 together in place of P2O5 and CaO had a synergistic effect in controlling their degradation rate and improving their biological responses.

Flame-Spheroidized Phosphate-Based Glass Particles with Improved Characteristics for Applications in Mesenchymal Stem Cell Culture Therapy and Tissue Engineering

The chemical formulation of phosphate-based glasses (PBGs) can be tailored to fit particular end applications such as bone tissue engineering. While most reports to date have evaluated the effect of PBG chemical formulation on bone cells, this study specifically explored the manufacturing process, the changes in physical and chemical properties of PBG particles after flame spheroidization, and subsequent effects on human mesenchymal stem cells (hMSCs), a prime cell type for regenerative medicine applications. Flame spheroidization involves feeding irregular PBG particles (microparticles, MP) into a hot flame, causing them to melt and mold into solid spherical PBG particles (microspheres, MS). The laser diffraction analysis showed an increase in the volume-weighted mean diameter of particles from 48 to 139 μm after spheroidization and also revealed changes in the chemical composition of smaller MS (< 45 μm in size), whereas MS in other size ranges did not show significantly different chemical composition compared to MP. Additionally, some air bubbles were entrapped inside particles during spheroidization, causing a 2% drop in relative density of MS. However, the packing density of MS was 30% higher than that of MP. Culture of hMSCs on the particles showed significant improvement in cell spreading on MS compared to that on MP and nearly 2 times higher cell metabolic activity after 7 days of culture, suggesting that MS provided a more favorable support and geometry for hMSC attachment and growth for tissue engineering.

Effects of Fe2O3 addition and annealing on the mechanical and dissolution properties of MgO-and CaO-containing phosphate glass fibres for bio-applications

This paper investigated the preparation of phosphate glass fibres (PGFs) in the following systems: i) 45P2O5-5B2O3-5Na2O-(29-x)CaO-16MgO-(x)Fe2O3 and ii) 45P2O5-5B2O3-5Na2O-24CaO-(21-x)MgO-(x)Fe2O3 (where x = 5, 8 and 11 mol%) for biomedical applications. Continuous fibres of 23 ± 1 μm diameter were prepared via a meltdraw spinning process. Compositions with higher Fe2O3 content and higher MgO/CaO ratio required higher melting temperature and longer heating time to achieve glass melts for fibre pulling. The effects of Fe2O3 addition and annealing treatment on mechanical properties and degradation behaviours were also investigated. Adding Fe2O3 was found to increase the tensile strength from 523 ± 63 (Ca-Fe5) to 680 ± 75 MPa (Ca-Fe11), improve the tensile modulus from72 ± 4 (Ca-Fe5) to 78 ± 3 GPa (Ca-Fe11) and decrease the degradation rate from 4.0 (Mg-Fe5) to 1.9 × 10−6 kg m−2 s−1 (Mg-Fe11). The annealing process reduced the fibre tensile strength by 46% (Ca-Fe5), increased the modulus by 19.6%(Ca-Fe8) and decreased the degradation rate by 89.5% (Mg-Fe11) in comparison to the corresponding as drawn fibres. Additionally, the annealing process also impeded the formation of precipitate shells and revealed coexistence of the precipitation and the pitting corrosion as fibre degradation behaviours.

Porous calcium phosphate glass microspheres for orthobiologic applications

Orthobiologics is a rapidly advancing field utilising cell-based therapies and biomaterials to enable the body to repair and regenerate musculoskeletal tissues. This paper reports on a cost-effective flame spheroidisation process for production of novel porous glass microspheres from calcium phosphate-based glasses to encapsulate and deliver stem cells. Careful selection of the glass and pore-forming agent, along with a manufacturing method with the required processing window enabled the production of porous glass microspheres via a single-stage manufacturing process. The morphological and physical characterisation revealed porous microspheres with tailored surface and interconnected porosity (up to 76 ± 5%) with average pore size of 55 ± 8 µm and surface areas ranging from 0.34 to 0.9 m² g^-1. Furthermore, simple alteration of the processing parameters produced microspheres with alternate unique morphologies, such as with solid cores and surface porosity only. The tuneable porosity enabled control over their surface area, degradation profiles and hence ion release rates. Furthermore, cytocompatibility of the microspheres was assessed using human mesenchymal stem cells via direct cell culture experiments and analysis confirmed that they had migrated to within the centre of the microspheres. The novel microspheres developed have huge potential for tissue engineering and regenerative medicine applications.

STATEMENT OF SIGNIFICANCE

This manuscript highlights a simple cost-effective one-step process for manufacturing porous calcium phosphate-based glass microspheres with varying control over surface pores and fully interconnected porosity via a flame spheroidisation process. Moreover, a simple alteration of the processing parameters can produce microspheres which have a solid core with surface pores only. The tuneable porosity enabled control over their surface area, degradation profiles and hence ion release rates. The paper also shows that stem cells not only attach and proliferate but more importantly migrate to within the core of the porous microspheres, highlighting applications for bone tissue engineering and regenerative medicine.

Compositional dependency on dissolution rate and cytocompatibility of phosphate-based glasses: Effect of B2O3 and Fe2O3 addition

The unique property of phosphate-based glasses and fibres to be completely dissolved in aqueous media is largely dependent on the glass composition. This article focuses on investigating the effect of replacing Na₂O with 3 and 5 mol% Fe₂O₃ on cytocompatibility, thermal and dissolution properties of P₂O₅–CaO–Na₂O–MgO–B₂O₃ glass system, where P₂O₅ content was fixed at 45 mol%. The effect of increasing Fe₂O₃ from 3 to 5 mol% on P₂O₅–CaO–Na₂O–MgO glasses was also evaluated. The glass transition temperature, onset of crystallisation temperature and liquidus temperature were found to decrease with increasing Fe₂O₃ content and the addition of B₂O₃, while the thermal expansion values were found to decrease. The density of the glasses decreased with increasing Fe₂O₃ content. However, an increase in the density was observed by the addition of 5 mol% B₂O₃. The dissolution properties and mode of bulk glass and fibres were also examined which were found to decrease with increasing B₂O₃ and Fe₂O₃. However, it was found that the dissolution properties of the glasses containing both B₂O₃ and Fe₂O₃ were lower than only Fe₂O₃ containing glasses. The in vitro cell culture studies using human osteoblast like (MG63) cell lines revealed that the glasses containing both B₂O₃ and Fe₂O₃ maintained and showed higher cell viability as compared to the only Fe₂O₃ containing glasses. Glasses containing both B₂O₃ and Fe₂O₃ showed a pronounced effect on the dissolution rate of the glasses, which eventually improved the cytocompatibility properties of the glasses investigated.

Bioactive calcium phosphate-based glasses and ceramics and their biomedical applications: A review

An overview of the formation of calcium phosphate under in vitro environment on the surface of a range of bioactive materials (e.g. from silicate, borate, and phosphate glasses, glass-ceramics, bioceramics to metals) based on recent literature is presented in this review. The mechanism of bone-like calcium phosphate (i.e. hydroxyapatite) formation and the test protocols that are either already in use or currently being investigated for the evaluation of the bioactivity of biomaterials are discussed. This review also highlights the effect of chemical composition and surface charge of materials, types of medium (e.g. simulated body fluid, phosphate-buffered saline and cell culture medium) and test parameters on their bioactivity performance. Finally, a brief summary of the biomedical applications of these newly formed calcium phosphate (either in the form of amorphous or apatite) is presented.

Degradation of zinc containing phosphate-based glass as a material for orthopedic tissue engineering

Phosphate-based glasses have been examined in many studies as a potential biomaterial for bone repair because of its degradation properties, which can be controlled and allow the release of various elements to promote osteogenic tissue growth. However most of these experiments studied either tertiary or quaternary glass systems. This study investigated a qinternary system that included titanium dioxide for degradation rate control and zinc that is considered to have a role in bone formation. Zinc and titanium phosphate glass discs of different compositions were melt synthesized and samples of each composition was tested for different physical, chemical and biological characteristics via density measurement, X-ray diffraction, differential thermal analysis, mass loss, ion release, scanning electron microscopy, biocompatibility studies via live/dead assays at three time points (day 1, 4, and 7). The results showed that the glass was amorphous and that the all thermal variables decreased as zinc oxide amount raised, mass loss as well as ion release increased as zinc oxide increased, and the maximum rise was with ZnO15. The cellular studies showed that all the formulation showed similar cytocompatibility properties with MG63 except ZnO15, which displayed cytotoxic properties and this was confirmed also by the scanning electron microscope images. In conclusion, replacing calcium oxide with zinc oxide in proportion less than 10 % can have a positive effect on bone forming cells.

Titanium phosphate glass microcarriers induce enhanced osteogenic cell proliferation and human mesenchymal stem cell protein expression

In this study, we have developed 50- to 100-µm-sized titanium phosphate glass microcarriers (denoted as Ti5) that show enhanced proliferation of human mesenchymal stem cells and MG63 osteosarcoma cells, as well as enhanced human mesenchymal stem cell expression of bone differentiation markers, in comparison with commercially available glass microspheres at all time points. We also demonstrate that these microcarriers provide superior human mesenchymal stem cell proliferation with conventional Dulbecco’s Modified Eagle medium than with a specially developed commercial stem cell medium. The microcarrier proliferative capacity is revealed by a 24-fold increase in MG63 cell numbers in spinner flask bioreactor studies performed over a 7-day period, versus only a 6-fold increase in control microspheres under the same conditions; the corresponding values of Ti5 and control microspheres under static culture are 8-fold and 7-fold, respectively. The capability of guided osteogenic differentiation is confirmed by ELISAs for bone morphogenetic protein-2 and osteopontin, which reveal significantly greater expression of these markers, especially osteopontin, by human mesenchymal stem cells on the Ti5 microspheres than on the control. Scanning electron microscopy and confocal laser scanning microscopy images reveal favorable MG63 and human mesenchymal stem cell adhesion on the Ti5 microsphere surfaces. Thus, the results demonstrate the suitability of the developed microspheres for use as microcarriers in bone tissue engineering applications.

Development of microspheres for biomedical applications: a review

An overview of microspheres manufactured for use in biomedical applications based on recent literature is presented in this review. Different types of glasses (i.e. silicate, borate, and phosphates), ceramics and polymer-based microspheres (both natural and synthetic) in the form of porous , non-porous and hollow structures that are either already in use or are currently being investigated within the biomedical area are discussed. The advantages of using microspheres in applications such as drug delivery, bone tissue engineering and regeneration, absorption and desorption of substances, kinetic release of the loaded drug components are also presented. This review also reports on the preparation and characterisation methodologies used for the manufacture of these microspheres. Finally, a brief summary of the existing challenges associated with processing these microspheres which requires further research and development are presented.

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.

In vitro bioactivity of titanium-doped bioglass

Previous studies have suggested that incorporating relatively small quantities of titanium dioxide into bioactive glasses may result in an increase in bioactivity and hydroxyapatite formation. The present work therefore investigated the in vitro bioactivity of a titanium doped bioglass and compared the results with 45S5 bioglass. Apatite formation was evaluated for bioglass and Ti-bioglass in the presence and absence of foetal calf serum. Scanning electron microscopy (SEM) images were used to evaluate the surface development and energy dispersive X-ray measurements provided information on the elemental ratios. X-ray diffraction spectra confirmed the presence of apatite formation. Cell viability was assessed for bone marrow stromal cells under direct and indirect contact conditions and cell adhesion was assessed using SEM.

Osteoblastic differentiation under controlled bioactive ion release by silica and titania doped sodium-free calcium phosphate-based glass

Sodium-free phosphate-based glasses (PGs) doped with both SiO2 and TiO2 (50P2O5-40CaO-xSiO2-(10-x)TiO2, where x=10, 7, 5, 3, and 0mol%) were developed and characterised for controlled ion release applications in bone tissue engineering. Substituting SiO2 with TiO2 directly increased PG density and glass transition temperature, indicating a cross-linking effect of Ti on the glass network which was reflected by significantly reduced degradation rates in an aqueous environment. X-ray diffraction confirmed the presence of Ti(P2O7) in crystallised TiO2-containing PGs, and nuclear magnetic resonance showed an increase in Q(1) phosphate species with increasing TiO2 content. Substitution of SiO2 with TiO2 also reduced hydrophilicity and surface energy. In biological assays, MC3T3-E1 pre-osteoblasts effectively adhered to the surface of PG discs and the incorporation of TiO2, and hence higher stability of the PG network, significantly increased cell viability and metabolic activity indicating the biocompatibility of the PGs. Addition of SiO2 increased ionic release from the PG, which stimulated alkaline phosphatase (ALP) activity in MC3T3-E1 cells upon ion exposure. The incorporation of 3mol% TiO2 was required to stabilise the PG network against unfavourable rapid degradation in aqueous environments. However, ALP activity was greatest in PGs doped with 5-7mol% SiO2 due to up-regulation of ionic concentrations. Thus, the properties of PGs can be readily controlled by modifying the extent of Si and Ti doping in order to optimise ion release and osteoblastic differentiation for bone tissue engineering applications.

Antibacterial property expressed by a novel calcium phosphate glass

We have developed a calcium phosphate glass (CPG) doped with Zn(2+) or F(-) or combined Zn(2+) and F(-) ions, which are naturally found in the human body and play a dual role in bone formation and antibacterial activity. Previously, we have demonstrated that this family of CPGs has superior osteoconductive and resorbable properties in vivo. This study aimed to investigate the antibacterial property of CPGs incorporating Zn(2+) and/or F(-) . We used Streptococcus mutans as a model organism because it is one of the major human oral pathogens and an early colonizer, and it has been associated with several oral infections, such as dental caries, periodontitis, and peri-implantitis. CPGs of 0.01 and 0.05 g were incubated with S. mutans for 0, 2, 4, and 6 h. Serial dilutions were plated in triplicate and colony forming units were determined. The antimicrobial effect of CPG incorporating Zn(2+) or F(-) was greater than CPG incorporating both these ions. CPG without doping produced a moderate antimicrobial effect. This family of CPGs, previously shown to promote new bone formation in vivo, is demonstrated to have superior bactericidal properties.

Effect of boron addition on the thermal, degradation, and cytocompatibility properties of phosphate-based glasses

In this study eight different phosphate-based glass compositions were prepared by melt-quenching: four in the (P2O5)45-(CaO)16-(Na2O)15-x -(MgO)24-(B2O3) x system and four in the system (P2O5)50-(CaO)16-(Na2O)10-x -(MgO)24-(B2O3) x , where x = 0,1, 5 and 10 mol%. The effect of B2O3 addition on the thermal properties, density, molar volume, dissolution rates, and cytocompatibility were studied for both glass systems. Addition of B2O3 increased the glass transition (T(g)), crystallisation (T(c)), melting (T(m)), Liquidus (T(L)) and dilatometric softening (T(d)) temperature and molar volume (V(m)). The thermal expansion coefficient (α) and density (ρ) were seen to decrease. An assessment of the thermal stability of the glasses was made in terms of their processing window (crystallisation onset, T(c,ons) minus glass transition temperature, T(g)), and an increase in the processing window was observed with increasing B2O3 content. Degradation studies of the glasses revealed that the rates decreased with increasing B2O3 content and a decrease in degradation rates was also observed as the P2O5 content reduced from 50 to 45 mol%. MG63 osteoblast-like cells cultured in direct contact with the glass samples for 14 days revealed comparative data to the positive control for the cell metabolic activity, proliferation, ALP activity, and morphology for glasses containing up to 5 mol% of B2O3.

Bone formation controlled by biologically relevant inorganic ions: role and controlled delivery from phosphate-based glasses

The role of metal ions in the body and particularly in the formation, regulation and maintenance of bone is only just starting to be unravelled. The role of some ions, such as zinc, is more clearly understood due to its central importance in proteins. However, a whole spectrum of other ions is known to affect bone formation but the exact mechanism is unclear as the effects can be complex, multifactorial and also subtle. Furthermore, a significant number of studies utilise single doses in cell culture medium, whereas the continual, sustained release of an ion may initiate and mediate a completely different response. We have reviewed the role of the most significant ions that are known to play a role in bone formation, namely calcium, zinc, strontium, magnesium, boron, titanium and also phosphate anions as well as copper and its role in angiogenesis, an important process interlinked with osteogenesis. This review will also examine how delivery systems may offer an alternative way of providing sustained release of these ions which may effect and potentiate a more appropriate and rapid tissue response.

Development, characterisation and biocompatibility testing of a cobalt-containing titanium phosphate-based glass for engineering of vascularized hard tissues

There is a continuing need to develop scaffold materials that can promote vascularisation throughout the tissue engineered construct. This study investigated the effect of cobalt oxide (CoO) doped into titanium phosphate glasses on material properties, biocompatibility and vascular endothelial growth factor (VEGF) secretion by osteoblastic MG63 cells. Glasses composed of (P2O5)45(Na2O)20(TiO2)05(CaO)30-x(CoO)x(x=0, 5, 10, and 15 mol%) were fabricated and the effect of Co on physicochemical properties including density, glass transition temperature (Tg), degradation rate, ion release, and pH changes was assessed. The results showed that incorporation of CoO into the glass system produced an increase in density with little change in Tg. It was then confirmed that the pH did not change significantly when CoO was incorporated in the glass, and stayed constant at around 6.5-7.0 throughout the dissolution study period of 336 h. Ion release results followed a specific pattern with increasing amounts of CoO. In general, although incorporation of CoO into a titanium phosphate glass increased its density, other bulk and surface properties of the glass did not show any significant changes. Cell culture studies performed using MG63 cells over a 7-day period indicated that the glasses provide a stable surface for cell attachment and are biocompatible. Furthermore, VEGF secretion was significantly enhanced on all glasses compared with standard tissue culture plastic and Co doping enhanced this effect further. In conclusion, the developed Co-doped glasses are stable and biocompatible and thus offer enhanced potential for engineering vascularized tissue.

Biomedical Applications of Clay

Traditional applications of clay mineral mainly revolved around cosmetics and industrial products, but their scope of application is continuously expanding into pharmaceutics including drug delivery and tissue engineering. The interest in clays amongst the scientific community has increased dramatically in recent years due to its composition and structure which can be easily modified to serve different purposes. Largely due to structural flexibility and its small particle size, clay nanostructure can be modified to tune rheological and mechanical properties, and can entrap moisture to suit a particular application. Additionally, interest in the synthesis of polymer-clay nanocomposites in tissue engineering is growing as it is cheap, easily available, and environmentally-friendly. The structure of clay allows the interclaysion of different biomolecules between the clay layers. These biomolecules can be released in a controlled manner which can be utilised in drug delivery and cosmetic applications.

Titanium phosphate glass microspheres for bone tissue engineering

We have demonstrated the successful production of titanium phosphate glass microspheres in the size range of ∼10-200 μm using an inexpensive, efficient, easily scalable process and assessed their use in bone tissue engineering applications. Glasses of the following compositions were prepared by melt-quench techniques: 0.5P₂O₅-0.4CaO-(0.1-x)Na₂O-xTiO₂, where x=0.03, 0.05 and 0.07 mol fraction (denoted as Ti3, Ti5 and Ti7 respectively). Several characterization studies such as differential thermal analysis, degradation (performed using a novel time lapse imaging technique) and pH and ion release measurements revealed significant densification of the glass structure with increased incorporation of TiO₂ in the glass from 3 to 5 mol.%, although further TiO₂ incorporation up to 7 mol.% did not affect the glass structure to the same extent. Cell culture studies performed using MG63 cells over a 7-day period clearly showed the ability of the microspheres to provide a stable surface for cell attachment, growth and proliferation. Taken together, the results confirm that 5 mol.% TiO₂ glass microspheres, on account of their relative ease of preparation and favourable biocompatibility, are worthy candidates for use as substrate materials in bone tissue engineering applications.

TiO₂-doped phosphate glass microcarriers: a stable bioactive substrate for expansion of adherent mammalian cells

Scalable expansion of cells for regenerative cell therapy or to produce large quantities for high-throughput screening remains a challenge for bioprocess engineers. Laboratory scale cell expansion using t-flasks requires frequent passaging that exposes cells to many poorly defined bioprocess forces that can cause damage or alter their phenotype. Microcarriers offer a potential solution to scalable production, lending themselves to cell culture processes more akin to fermentation, removing the need for frequent passaging throughout the expansion period. One main problem with microcarrier expansion, however, is the difficulty in harvesting cells at the end of the process. Therefore, therapies that rely on cell delivery using biomaterial scaffolds could benefit from a microcarrier expansion system whereby the cells and microcarriers are transplanted together. In the current study, we used bioactive glass microcarriers doped with 5% TiO₂ that display a controlled rate of degradation and conducted experiments to assess biocompatibility and growth of primary fibroblast cells as a model for cell therapy products. We found that the microcarriers are highly biocompatible and facilitate cell growth in a gradual controlled manner. Therefore, even without additional biofunctionalization methods, Ti-doped bioactive glass microcarriers offer potential as a cell expansion platform.

Mixture designs to assess composition–structure–property relationships in SiO2–CaO–ZnO–La2O3–TiO2–MgO–SrO–Na2O glasses: Potential materials for embolization

Embolization with micron-sized particulates is widely applied to treat uterine fibroids. The objective of this work was to develop mixture designs to predict materials composition–structure–property relationships for the SiO2–CaO–ZnO–La2O3–TiO2–MgO–SrO–Na2O glass system and compare its fundamental materials properties (density and cytocompatibility), against a state-of-the-art embolic agent (contour polyvinyl alcohol) to assess the potential of these materials for embolization therapies. The glass structures were evaluated using 29Si MAS NMR to identify chemical shift and line width; the particulate densities were determined using helium pycnometry and the cell viabilities were assessed via MTT assay. 29Si MAS NMR results indicated peak maxima for each glass in the range of −82.3 ppm to −89.9 ppm; associated with Q2 to Q3 units in silicate glasses. All experimental embolic compositions showed enhanced in vitro compatibility in comparison to Contour PVA with the exceptions of ORP9 and ORP11 (containing no TiO2). In this study, optimal compositions for cell viability were obtained for the following compositional ranges: 0.095–0.188 mole fraction ZnO; 0.068–0.159 mole fraction La2O3; 0.545–0.562 mole fraction SiO2 and 0.042–0.050 mole fraction TiO2. To ensure ease of producibility in obtaining good melts, a maximum loading of 0.068 mole fraction La2O3 is required. This is confirmed by the desirability approach, for which the only experimental composition (ORP5) of the materials evaluated was presented as an optimum composition; combining high cell viability with ease of production (0.188 mole fraction ZnO; 0.068 mole fraction La2O3; 0.562 mole fraction SiO2 and 0.042 mole fraction TiO2).

Titanium-containing bioactive phosphate glasses

The use of biomaterials has revolutionized the biomedical field and has received substantial attention in the last two decades. Among the various types of biomaterials, phosphate glasses have generated great interest on account of their remarkable bioactivity and favourable physical properties for various biomedical applications relating to both hard and soft tissue regeneration. This review paper focuses mainly on the development of titanium-containing phosphate-based glasses and presents an overview of the structural and physical properties. The effect of titanium incorporation on the glassy network is to introduce favourable properties. The biocompatibility of these glasses is described along with recent developments in processing methodologies, and the potential of Ti-containing phosphate-based glasses as a bone substitute material is explored.

Mesoporous bioactive glasses: structure characteristics, drug/growth factor delivery and bone regeneration application

The impact of bone diseases and trauma in the whole world has increased significantly in the past decades. Bioactive glasses are regarded as an important bone regeneration material owing to their generally excellent osteoconductivity and osteostimulativity. A new class of bioactive glass, referred to as mesoporous bioglass (MBG), was developed 7 years ago, which possess a highly ordered mesoporous channel structure and a highly specific surface area. The study of MBG for drug/growth factor delivery and bone tissue engineering has grown significantly in the past several years. In this article, we review the recent advances of MBG materials, including the preparation of different forms of MBG, composition-structure relationship, efficient drug/growth factor delivery and bone tissue engineering application. By summarizing our recent research, the interaction of MBG scaffolds with bone-forming cells, the effect of drug/growth factor delivery on proliferation and differentiation of tissue cells and the in vivo osteogenesis of MBG scaffolds are highlighted. The advantages and limitations of MBG for drug delivery and bone tissue engineering have been compared with microsize bioactive glasses and nanosize bioactive glasses. The future perspective of MBG is discussed for bone regeneration application by combining drug delivery with bone tissue engineering and investigating the in vivo osteogenesis mechanism in large animal models.

Phosphate glass fibres and their role in neuronal polarization and axonal growth direction

Phosphate glass fibres with composition 50P(2)O(5)-30CaO-9Na(2)O-3SiO(2)-3MgO-(5-x)K(2)O-xTiO(2)mol.% (x=0, 2.5, 5, respectively coded as TiPS(0), TiPS(2.5) and TiPS(5)) were drawn following the preform drawing approach. A 20-day solubility test in bi-distilled water was carried out on glass fibres with different compositions and diameters ranging between 25 and 82 μm. The results show that the glass composition, the initial fibre diameter and the thermal treatment are the main factors influencing the dissolution kinetics and that the fibres maintain their structural integrity and composition during dissolution. Biological tests were carried out on aligned TiPS(2.5) glass fibres using Neonatal Olfactory Bulb Ensheathing Cell Line (NOBEC) and Dorsal Root Ganglia (DRG) neurons. The fibres showed to be permissive substrates for cell adhesion and proliferation. The aligned configuration of the fibres seemed to provide a directional cue for growing axons of DRG neurons, which showed to sprout and grow long neurites along the fibre axis direction. These promising findings encourages further studies to evaluate the potential use of resorbable glass fibres (e.g.in combination with a nerve guidance tube) for the enhancement of the peripheral nerve healing with the role of supporting and guiding the cells involved in the nerve regeneration.

Effect of phosphate-based glass fibre surface properties on thermally produced poly(lactic acid) matrix composites

Incorporation of soluble bioactive glass fibres into biodegradable polymers is an interesting approach for bone repair and regeneration. However, the glass composition and its surface properties significantly affect the nature of the fibre-matrix interface and composite properties. Herein, the effect of Si and Fe on the surface properties of calcium containing phosphate based glasses (PGs) in the system (50P(2)O(5)-40CaO-(10-x)SiO(2)-xFe(2)O(3), where x = 0, 5 and 10 mol.%) were investigated. Contact angle measurements revealed a higher surface energy, and surface polarity as well as increased hydrophilicity for Si doped PG which may account for the presence of surface hydroxyl groups. Two PG formulations, 50P(2)O(5)-40CaO-10Fe(2)O(3) (Fe10) and 50P(2)O(5)-40CaO-5Fe(2)O(3)-5SiO(2) (Fe5Si5), were melt drawn into fibres and randomly incorporated into poly(lactic acid) (PLA) produced by melt processing. The ageing in deionised water (DW), mechanical property changes in phosphate buffered saline (PBS) and cytocompatibility properties of these composites were investigated. In contrast to Fe10 and as a consequence of the higher surface energy and polarity of Fe5Si5, its incorporation into PLA led to increased inorganic/organic interaction indicated by a reduction in the carbonyl group of the matrix. PLA chain scission was confirmed by a greater reduction in its molecular weight in PLA-Fe5Si5 composites. In DW, the dissolution rate of PLA-Fe5Si5 was significantly higher than that of PLA-Fe10. Dissolution of the glass fibres resulted in the formation of channels within the matrix. Initial flexural strength was significantly increased through PGF incorporation. After PBS ageing, the reduction in mechanical properties was greater for PLA-Fe5Si5 compared to PLA-Fe10. MC3T3-E1 preosteoblasts seeded onto PG discs, PLA and PLA-PGF composites were evaluated for up to 7 days indicating that the materials were generally cytocompatible. In addition, cell alignment along the PGF orientation was observed showing cell preference towards PGF.

In vitro biocompatibility and mechanical performance of titanium doped high calcium oxide metaphosphate-based glasses

This study challenged to produce phosphate-based glasses (PBG) for the treatment of osseous defects. The glasses contained, among other components, 40 mol% CaO and 1–5 mol% TiO₂. The mechanical performance and in vitro biocompatibility using both human osteosarcoma and primary osteoblasts were carried out. Incorporation of TiO₂ into PBG had no significant effect on strength and modulus. These glasses encouraged attachment and maintained high viability of osteosarcoma cells similar to the positive control surface. Cells grown directly (on glasses) or indirectly (in the presence of glass extracts) showed similar proliferation pattern to the positive control cells with no significant effect of TiO₂ detected. Increasing TiO₂ content, however, has a profound effect on cytoskeleton organization and spreading and maturation of primary osteoblasts. It is believed that TiO₂ might have acted as a chemical cue-modulating cells response, and hence the substrates supported maturation/mineralization of the primary osteoblasts.