Tailoring Pyro-and Orthophosphate Species to Enhance Stem Cell Adhesion to Phosphate Glasses.

Phosphate-based glasses (PBGs) offer significant therapeutic potential due to their bioactivity, controllable compositions, and degradation rates. Several PBGs have already demonstrated their ability to support direct cell growth and in vivo cytocompatibility for bone repair applications. This study investigated development of PBG formulations with pyro- and orthophosphate species within the glass system (40 - x)P2O5·(16 + x)CaO·20Na2O·24MgO (x = 0, 5, 10 mol%) and their effect on stem cell adhesion properties. Substitution of phosphate for calcium revealed a gradual transition within the glass structure from Q2 to Q0 phosphate species. Human mesenchymal stem cells were cultured directly onto discs made from three PBG compositions. Analysis of cells seeded onto the discs revealed that PBG with higher concentration of pyro- and orthophosphate content (61% Q1 and 39% Q0) supported a 4.3-fold increase in adhered cells compared to glasses with metaphosphate connectivity (49% Q2 and 51% Q1). This study highlights that tuning the composition of PBGs to possess pyro- and orthophosphate species only, enables the possibility to control cell adhesion performance. PBGs with superior cell adhesion profiles represent ideal candidates for biomedical applications, where cell recruitment and support for tissue ingrowth are of critical importance for orthopaedic interventions.

Effect of cellulose nanowhiskers on surface morphology, mechanical properties, and cell adhesion of melt-drawn polylactic Acid fibers.

Polylactic acid (PLA) fibers were produced with an average diameter of 11.2 (± 0.9) µm via a melt-drawing process. The surface of the PLA fibers was coated with blends of cellulose nanowhiskers (CNWs) (65 to 95 wt %) and polyvinyl acetate (PVAc). The CNWs bound to the smooth PLA fiber surface imparted roughness, with the degree of roughness depending on the coating blend used. The fiber tensile modulus increased 45% to 7 GPa after coating with 75 wt % CNWs compared with the uncoated PLA fibers, and a significant increase in the fiber moisture absorption properties at different humidity levels was also determined. Cytocompatibility studies using NIH-3T3 mouse fibroblast cells cultured onto CNWs-coated PLA surface revealed improved cell adhesion compared with the PLA control, making this CNW surface treatment applicable for biomedical and tissue engineering applications. Initial studies also showed complete cell coverage within 2 days.

The Use of Microspheres for Cancer Embolization Therapy: Recent Advancements and Prospective.

Embolization therapy involving biomaterials has improved the therapeutic strategy for most liver cancer treatments. Developing biomaterials as embolic agents has significantly improved patients' survival rates. Various embolic agents are present in liquid agents, foam, particulates, and particles. Some of the most applied embolic agents are microparticles, such as microspheres (3D micrometer-sized spherical particles). Microspheres with added functionalities are currently being developed for effective therapeutic embolization. Their excellent properties of high surface area and capacity for being loaded with radionuclides and alternate active or therapeutic agents provide an additional advantage to overcome limitations from traditional cancer treatments. Microspheres (non-radioactive and radioactive) have been widely used and explored for localized cancer treatment. Non-radioactive microspheres exhibit improved clinical performance as drug delivery vehicles in chemotherapy due to their controlled and sustained drug release to the target site. They offer better flow properties and are beneficial for the ease of delivery via injection procedures. In addition, radioactive microspheres have also been exploited for use as an embolic platform in internal radiotherapy as an alternative to cancer treatment. This short review summarizes the progressive development of non-radioactive and radioactive embolic microspheres, emphasizing material characteristics. The use of embolic microspheres for various modalities of therapeutic arterial embolization and their impact on therapeutic performance are also discussed.

L-DOPA coating improved phosphate glass fibre strength and fibre/matrix interface.

The levodopa (L-DOPA) has been reported as a promising adhesive for various materials. In this study, we utilized L-DOPA as an interfacial agent for phosphate glass fibre/polycaprolactone (PGF/PCL) composites, with the aim to enhance the interfacial properties between the fibres and polymer matrix. The PGFs were dip-coated in varying concentrations of L-DOPA solution ranging between 5 and 40 g L-1. The fibre strength and interfacial shear strength (IFSS) of the composites were measured via a single fibre tensile test and single fibre fragmentation test, respectively. It was found that the L-DOPA agent (at conc. 10 g L-1) significantly improved the IFSS of the composites up to 27%. Also, the L-DOPA coating (at conc. 40 g L-1) significantly increased the glass fibre strength up to 18%. As a result, an optimum coating level could be tailored depending on application and whether fibre strength or IFSS was of greater importance. In addition, SEM and TGA analyses were used to detect and quantify the coating agents. FTIR and XPS further confirmed presence of the coating and indicated the zwitterionic crystals of L-DOPA and the formation of a melanin-like polymer layer. The spectroscopy data also evidenced that both catechol and amine groups contributed to the interaction between the L-DOPA and the PGF surface.

Developing Echogenic Materials as Catheters for Use with Ultrasound.

Patients with peripherally inserted central catheters (PICCs) are routinely discharged with the catheters in place. These patients experience complications due to undetected thrombosis or accidental dislodgement, with tracking through limited X-ray imaging. Developing catheters with the capability to be tracked without the need for X-ray imaging would greatly benefit these patients by decreasing patient stress, reducing time to diagnosis, and increasing nursing home capabilities. This study reports on the incorporation of echogenic microspheres into catheters to produce bulk echogenic effects for developments in the field of real-time ultrasound tracking of polymeric medical devices. The impact on elastic modulus, ultrasound contrast, and cytocompatibility of the polymer was analyzed when incorporating up to 10 wt % glass microspheres. Up to this loading level, the elastic modulus was found to remain constant. However, at 10 wt %, extrusion defects due to agglomeration, air bubbles, and shearing were numerous and deemed detrimental to ultrasound imaging. Successful, defect-free samples were produced with 5 wt % microsphere loading and when embedded in a soft tissue phantom revealed a significant increase in the signal-to-noise ratio as compared to the polymer alone. Preliminary results have shown a successful increase in polymer's echogenic properties, without undermining its mechanical and cytocompatibility properties.

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.

Processing and characterization of phosphate glass fiber/polylactic acid commingled yarn composites for commercial production.

This study investigated the production of phosphate glass fiber/polylactic acid (PGF/PLA) commingled yarns, textiles and composites for biomedical applications. The PGF volume contents of the composites investigated were 25% and 40%. Plain weave textiles with yarn counts of 10 warp/cm and 6 weft/cm were produced using a commercial weaving machine. An orthogonal array design (OAD) was employed as a statistical method to investigate the effects of compression molding parameters (processing temperature, preheating time, compression time, and pressure) on flexural strength and porosity of PGF/PLA textile composites. Processing temperature showed the most significant effect in achieving maximum laminate flexural strength and molecular weight of PLA. Processing models were developed using regression techniques to predict the laminate flexural strength and the molecular weight of PLA. Composites with fiber contents of 25 and 40 vol% produced using optimized processing conditions identified by the processing models, provided flexural strengths of 236 MPa and 293 MPa, respectively.

Long-Term Culture of Stem Cells on Phosphate-Based Glass Microspheres: Synergistic Role of Chemical Formulation and 3D Architecture.

Phosphate-based glasses (PBGs) are biomaterials that degrade under physiological conditions and can be modified to release various ions depending on end applications. This study utilized slow-degrading (P45:45P2O5-16CaO-24MgO-11Na2O-4Fe2O3, mol %) and comparatively faster degrading (P40:40P2O5-16CaO-24MgO-20Na2O, mol %) PBG microspheres with or without porosity, to evaluate the combined effect of chemical formulation and geometry on human mesenchymal stem cells (MSCs), a clinically relevant cell source for orthopedic applications. Scanning electron microscopy showed 2, 46, and 29% of P45 bulk (P45-B), P40 bulk (P40-B), and P40 porous (P40-P) microspheres, respectively, that had cracks or peeling off surfaces after 42 days of incubation in culture medium. Cytotoxicity assessment showed that glass debris released into the culture medium may interact with cells and affect their survival. Direct-contact cell experiments up to 42 days showed that P45-B microspheres did not sustain viable long-term cell cultures and did not facilitate extracellular matrix formation. On the other hand, P40-B microspheres enhanced alkaline phosphatase activity, calcium deposition, and collagen and osteocalcin production in MSCs. Introduction of porosity in P40 glass further enhanced these parameters and proliferation at later time points. The small pore windows (<5 µm wide) and interconnection (<10 µm wide) may have allowed limited cell penetration into the porous structures. P40-B and P40-P have potential for bone repair and reinforcement therapy based on their chemical formulation and porous geometry.

Formulating injectable pastes of porous calcium phosphate glass microspheres for bone regeneration applications.

Current trends in regenerative medicine treatments for bone repair applications focus on cell-based therapies. These aim to deliver the treatment via a minimally invasive injection to reduce patient trauma and to improve efficacy. This paper describes the injectability of porous calcium phosphate glass microspheres to be used for bone repair based on their formulation, rheology and flow behavior. The use of excipients (xanthan gum, methyl cellulose and carboxyl methyl cellulose) were investigated to improve flow performance. Based on our results, the flow characteristics of the glass microsphere pastes vary according to particle size, surface area, and solid to liquid ratio, as well as the concentration of viscosity modifiers used. The optimal flow characteristics of calcium phosphate glass microsphere pastes was found to contain 40 mg/mL of xanthan gum which increased viscosity whilst providing elastic properties (∼29,000 Pa) at shear rates that mirror the injection process and the resting period post injection, preventing the glass microspheres from both damage and dispersion. It was established that a base formulation must contain 1 g of glass microspheres (60-125 µm in size) per 1 mL of cell culture media, or 0.48 g of glass microspheres of sizes between 125 and 200 µm. Furthermore, the glass microsphere formulations with xanthan gum were readily injectable via a syringe-needle system (3-20 mL, 18G and 14G needles), and have the potential to be utilized as a cell (or other biologics) delivery vehicle for bone regeneration applications.

Phosphate glass fibers facilitate proliferation and osteogenesis through Runx2 transcription in murine osteoblastic cells.

Cell-material interactions and compatibility are important aspects of bioactive materials for bone tissue engineering. Phosphate glass fiber (PGF) is an attractive inorganic filler with fibrous structure and tunable composition, which has been widely investigated as a bioactive filler for bone repair applications. However, the interaction of osteoblasts with PGFs has not been widely investigated to elucidate the osteogenic mechanism of PGFs. In this study, different concentrations of short PGFs with interlaced oriented topography were cocultured with MC3T3-E1 cells for different periods, and the synergistic effects of fiber topography and ionic product of PGFs on osteoblast responses including cell adhesion, spreading, proliferation, and osteogenic differentiation were investigated. It was found that osteoblasts were more prone to adhere on PGFs through Vinculin protein, leading to enhanced cell proliferation with polygonal cell shape and spreading cellular actin filaments. In addition, osteoblasts incubated on PGF meshes showed enhanced alkaline phosphatase activity, extracellular matrix mineralization, and increased expression of osteogenesis-related marker genes, which could be attributed to the Wnt/ß-catenin/Runx2 signaling pathway. This study elucidated the possible mechanism of PGF on triggering specific osteoblast behavior, which would be highly beneficial for designing PGF-based bone graft substitutes with excellent osteogenic functions.

Production and characterisation of novel phosphate glass fibre yarns, textiles, and textile composites for biomedical applications.

This work presents manufacturing, processing and characterisation of the phosphate glass fibre (PGF) products for biomedical applications, including multifilament PGF strands, yarns and textiles, and PGF textile composites. The multifilament production of PGF strands was achieved using a 50-nozzle bushing. PGF yarns, with a linear density of 87 tex, a twist angle of 14° and a tensile strength of 0.29 N/tex, were produced by combining 8 fibre strands using the ring-spinning method. PGF textiles, with a width of 15 mm and a thickness of 0.36 mm, were prepared using an inkle loom. The maximum flexural strength and modulus of unidirectional (UD) composites with a fibre volume fraction of ~17% were 262 ±â€¯11 MPa and 10.4 ±â€¯0.2 GPa, respectively. PGF textile composites with a fibre volume fraction of ~21% exhibited mechanical properties of 176 ±â€¯13 MPa for flexural strength and 8.6 ±â€¯0.6 GPa for flexural modulus. Despite the UD and textile composites having almost an equivalent amount of fibres in the 0 direction, the crimp of the yarns was found to contribute to the significantly lower flexural properties of the textile composites in comparison with the unidirectional (UD) composites. Additionally, the processing conditions such as processing temperature and time were found to have a strong effect on the mechanical properties of the resultant composite products. The number-average molecular weight of PLA was also found to reduce by 13% and 19% after the production of PLA films and PLA plates, respectively, in comparison with the as-received PLA pellets.

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.

Role of geometrical cues in bone marrow-derived mesenchymal stem cell survival, growth and osteogenic differentiation.

Mesenchymal stem cells play a vital role in bone formation process by differentiating into osteoblasts, in a tissue that offers not a flat but a discontinuous three-dimensional (3D) topography in vivo. In order to understand how geometry may be affecting mesenchymal stem cells, this study explored the influence of 3D geometry on mesenchymal stem cell-fate by comparing cell growth, viability and osteogenic potential using monolayer (two-dimensional, 2D) with microsphere (3D) culture systems normalised to surface area. The results suggested lower cell viability and reduced cell growth in 3D. Alkaline phosphatase activity was higher in 3D; however, both collagen and mineral deposition appeared significantly lower in 3D, even after osteogenic supplementation. Also, there were signs of patchy mineralisation in 3D with or without osteogenic supplementation as early as day 7. These results suggest that the convex surfaces on microspheres and inter-particulate porosity may have led to variable cell morphology and fate within the 3D culture. This study provides deeper insights into geometrical regulation of mesenchymal stem cell responses applicable for bone tissue engineering.

Electric Field-Assisted Orientation of Short Phosphate Glass Fibers on Stainless Steel for Biomedical Applications.

Structural and compositional modifications of metallic implant surfaces are being actively investigated to achieve improved bone-to-implant bonding. In this study, a strategy to modify bulk metallic surfaces by electrophoretic deposition (EPD) of short phosphate glass fibers (sPGF) is presented. Random and aligned orientation of sPGF embedded in a poly(acrylic acid) matrix is achieved by vertical and horizontal EPD, respectively. The influence of EPD parameters on the degree of alignment is investigated to pave the way for the fabrication of highly aligned sPGF structures in large areas. Importantly, the oriented sPGF structure in the coating, owing to the synergistic effects of bioactive composition and fiber orientation, plays an important role in directional cell migration and enhanced proliferation. Moreover, gene expression of MC3T3-E1 cells cultured with different concentrations of sPGF is thoroughly assessed to elucidate the potential stimulating effect of sPGF on osteogenic differentiation. This study represents an innovative exploitation of EPD to develop textured surfaces by orientation of fibers in the macroscale, which shows great potential for directional functionalization of metallic implants.

Cytocompatibility, mechanical and dissolution properties of high strength boron and iron oxide phosphate glass fibre reinforced bioresorbable composites.

In this study, Polylactic acid (PLA)/phosphate glass fibres (PGF) composites were prepared by compression moulding. Fibres produced from phosphate based glasses P2O5-CaO-MgO-Na2O (P45B0), P2O5-CaO-MgO-Na2O-B2O3 (P45B5), P2O5-CaO-MgO-Na2O-Fe2O3 (P45Fe3) and P2O5-CaO-MgO-Na2O-B2O3-Fe2O3 (P45B5Fe3) were used to reinforce the bioresorbable polymer PLA. Fibre mechanical properties and degradation rate were investigated, along with the mechanical properties, degradation and cytocompatibility of the composites. Retention of the mechanical properties of the composites was evaluated during degradation in PBS at 37°C for four weeks. The fibre volume fraction in the composite varied from 19 to 23%. The flexural strength values (ranging from 131 to 184MPa) and modulus values (ranging from 9.95 to 12.29GPa) obtained for the composites matched those of cortical bone. The highest flexural strength (184MPa) and modulus (12.29GPa) were observed for the P45B5Fe3 composite. After 28 days of immersion in PBS at 37°C, ~35% of the strength profile was maintained for P45B0 and P45B5 composites, while for P45Fe3 and P45B5Fe3 composites ~40% of the initial strength was maintained. However, the overall wet mass change of P45Fe3 and P45B5Fe3 remained significantly lower than that of the P45B0 and P45B5 composites. The pH profile also revealed that the P45B0 and P45B5 composites degraded quicker, correlating well with the degradation profile. From SEM analysis, it could be seen that after 28 days of degradation, the fibres in the fractured surface of P45B5Fe3 composites remain fairly intact as compared to the other formulations. The in vitro cell culture studies using MG63 cell lines revealed both P45Fe3 and P45B5Fe3 composites maintained and showed higher cell viability as compared to the P45B0 and P45B5 composites. This was attributed to the slower degradation rate of the fibres in P45Fe3 and P45B5Fe3 composites as compared with the fibres in P45B0 and P45B5 composites.

In-situ polymerisation of fully bioresorbable polycaprolactone/phosphate glass fibre composites: In vitro degradation and mechanical properties.

Fully bioresorbable composites have been investigated in order to replace metal implant plates used for hard tissue repair. Retention of the composite mechanical properties within a physiological environment has been shown to be significantly affected due to loss of the integrity of the fibre/matrix interface. This study investigated phosphate based glass fibre (PGF) reinforced polycaprolactone (PCL) composites with 20%, 35% and 50% fibre volume fractions (Vf) manufactured via an in-situ polymerisation (ISP) process and a conventional laminate stacking (LS) followed by compression moulding. Reinforcing efficiency between the LS and ISP manufacturing process was compared, and the ISP composites revealed significant improvements in mechanical properties when compared to LS composites. The degradation profiles and mechanical properties were monitored in phosphate buffered saline (PBS) at 37°C for 28 days. ISP composites revealed significantly less media uptake and mass loss (p<0.001) throughout the degradation period. The initial flexural properties of ISP composites were substantially higher (p<0.0001) than those of the LS composites, which showed that the ISP manufacturing process provided a significantly enhanced reinforcement effect than the LS process. During the degradation study, statistically higher flexural property retention profiles were also seen for the ISP composites compared to LS composites. SEM micrographs of fracture surfaces for the LS composites revealed dry fibre bundles and poor fibre dispersion with polymer rich zones, which indicated poor interfacial bonding, distribution and adhesion. In contrast, evenly distributed fibres without dry fibre bundles or polymer rich zones, were clearly observed for the ISP composite samples, which showed that a superior fibre/matrix interface was achieved with highly improved adhesion.

In vitro degradation and mechanical properties of PLA-PCL copolymer unit cell scaffolds generated by two-photon polymerization.

The manufacture of 3D scaffolds with specific controlled porous architecture, defined microstructure and an adjustable degradation profile was achieved using two-photon polymerization (TPP) with a size of 2 × 4 × 2 mm(3). Scaffolds made from poly(D,L-lactide-co-ɛ-caprolactone) copolymer with varying lactic acid (LA) and ɛ -caprolactone (CL) ratios (LC16:4, 18:2 and 9:1) were generated via ring-opening-polymerization and photoactivation. The reactivity was quantified using photo-DSC, yielding a double bond conversion ranging from 70% to 90%. The pore sizes for all LC scaffolds were see 300 µm and throat sizes varied from 152 to 177 µm. In vitro degradation was conducted at different temperatures; 37, 50 and 65 °C. Change in compressive properties immersed at 37 °C over time was also measured. Variations in thermal, degradation and mechanical properties of the LC scaffolds were related to the LA/CL ratio. Scaffold LC16:4 showed significantly lower glass transition temperature (T g) (4.8 °C) in comparison with the LC 18:2 and 9:1 (see 32 °C). Rates of mass loss for the LC16:4 scaffolds at all temperatures were significantly lower than that for LC18:2 and 9:1. The degradation activation energies for scaffold materials ranged from 82.7 to 94.9 kJ mol(-1). A prediction for degradation time was applied through a correlation between long-term degradation studies at 37 °C and short-term studies at elevated temperatures (50 and 65 °C) using the half-life of mass loss (Time (M1/2)) parameter. However, the initial compressive moduli for LC18:2 and 9:1 scaffolds were 7 to 14 times higher than LC16:4 (see 0.27) which was suggested to be due to its higher CL content (20%). All scaffolds showed a gradual loss in their compressive strength and modulus over time as a result of progressive mass loss over time. The manufacturing process utilized and the scaffolds produced have potential for use in tissue engineering and regenerative medicine applications.

Magnesium coated phosphate glass fibers for unidirectional reinforcement of polycaprolactone composites.

Bioresorbable composites have shown much potential for bone repair applications, as they have the ability to degrade completely over time and their degradation and mechanical properties can be tailored to suit the end application. In this study, phosphate glass fiber (from the system 45% P2 O5-16% CaO-24% MgO-11% Na2 O-4% Fe2 O3 (given in mol%)) were used to reinforce polycaprolactone (PCL) with approximately 20% fiber volume fraction. The glass fiber surfaces were coated with magnesium (Mg) through magnetron sputtering to improve the fiber-matrix interfacial properties. The Mg coating provided a rough fiber surface (roughness (Ra) of about 44nm). Both noncoated and Mg-coated fiber-reinforced composites were assessed. The water uptake and mass loss properties for the composites were assessed in phosphate-buffered saline (PBS) at 37°C for up to 28 days, and ion release profiles were also investigated in both water and PBS media. Inhibition of media influx was observed for the Mg-coated composites. The composite mechanical properties were characterized on the basis of both tensile and flexural tests and their retention in PBS media at 37°C was also investigated. A higher retention of the mechanical properties was observed for the Mg-coated composites over the 28 days degradation period.

Effect of boron oxide addition on fibre drawing, mechanical properties and dissolution behaviour of phosphate-based glass fibres with fixed 40, 45 and 50 mol% P2O5.

Previous studies investigating manufacture of phosphate-based glass fibres from glasses fixed with P2O5 content less than 50 mol% showed that continuous manufacture without breakage was very difficult. In this study, nine phosphate-based glass formulations from the system P2O5-CaO-Na2O-MgO-B2O3 were prepared with P2O5 contents fixed at 40, 45 and 50 mol%, where Na2O was replaced by 5 and 10 mol% B2O3 and MgO and CaO were fixed to 24 and 16 mol%, respectively. The effect of B2O3 addition on the fibre drawing, fibre mechanical properties and dissolution behaviour was investigated. It was found that addition of 5 and 10 mol% B2O3 enabled successful drawing of continuous fibres from glasses with phosphate (P2O5) contents fixed at 40, 45 and 50 mol%. The mechanical properties of the fibres were found to significantly increase with increasing B2O3 content. The highest tensile strength (1200 ± 130 MPa) was recorded for 45P2O5-16CaO-5Na2O-24MgO-10B2O3 glass fibres. The fibres were annealed, and a comparison of the mechanical properties and mode of degradation of annealed and non-annealed fibres were investigated. A decrease in tensile strength and an increase in tensile modulus were observed for the annealed fibres. An assessment of the change in mechanical properties of both the annealed and non-annealed fibres was performed in phosphate-buffered saline (PBS) at 37℃ for 28 and 60 days, respectively. Initial loss of mechanical properties due to annealing was found to be recovered with degradation. The B2O3-containing glass fibres were found to degrade at a much slower rate as compared to the non-B2O3-containing fibres. Both annealed and non-annealed fibres exhibited a peeling effect of the fibre's outer layer during degradation.

Effects of adding resorbable phosphate glass fibres and PLA to calcium phosphate bone cements.

BACKGROUND: Calcium phosphate cements (CPCs), due to their biocompatibility and degradation properties, are being widely investigated as a replacement to more commonly used polymethylmethacrylate (PMMA) for vertebroplasty. CPCs have shown the potential to be replaced by host bone tissue during the healing/remodelling process. However, brittleness and comparatively low strength restrict the use of CPC in load-bearing applications. Although porous CPC can integrate with bone over time, slow degradation profiles and poor interconnectivity between pores restricts osseointegration to the top layer of CPC only. METHODS: Polylactic acid (PLA) and phosphate glass fibres (PGFs) were incorporated in a CPC matrix to overcome the problem of inherent brittleness and limited osseointegration. RESULTS: Incorporation of PLA and PGFs within CPC was successful in achieving a much less brittle CPC matrix without affecting the mechanical properties of CPC. The area under the stress-strain curve showed that the total energy to failure of the CPC hybrid was significantly greater than that of the CPC control. CONCLUSIONS: The methodology adopted here to add PLA within the CPC matrix may also allow for incorporation of PLA cross-linked biochemicals. Micrographic studies revealed that it was possible to confer control over pore size, shape and interconnectivity without negatively affecting the mechanical properties of the cement. This tailorable porosity could potentially lead to better osseointegration within CPC.