Hybrid composites of silica glass fibre/nano-hydroxyapatite/polylactic acid for medical application

Fibre reinforced composites (FRC) have shown great potential for the application of internal bone fixation due to mechanical properties that are similar to those of human cortical bones. Ternary composites of silica glass fibres, nano-hydroxyapatite (n-HA) and polylactic acid (PLA) were prepared by compression moulding and their mechanical properties were characterized in this study. With the volumetric content of glass fibre remained constantly at 30% and the volume fraction of n-HA increased from 0% to 5%, the flexural strengths of composites decreased from 625.68 MPa to 206.55 MPa, whereas a gradual increment of flexural modulus from 11.01 to 14.08 GPa were observed at the same time. Within a 28-day degradation period, the flexural strengths decreased by 30%, while no obvious trend of modulus variation was found. The flexural properties of all composites prepared in this study were all found to be close to the reported flexural properties. On the other hand, as more n-HA were incorporated, the water absorption percentages increased, whereas negligible mass loss were recorded. SEM images revealed that the impregnation of fibre mats was poor as loose fibres were observed, which shall be solved in future research to further improve the mechanical properties as well as endurance against degradation. © 2017 International Committee on Composite Materials. All rights reserved

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

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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

© The Author(s) 2014. 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-B2O2 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 45 P2O5-16CaO-5Na2OP-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

Novel bioresorbable textile composites for medical applications

Currently, phosphate glass fibre (PGF) reinforced composites are a potential solution for bone repairing due to sufficient mechanical properties and full bioresorbability. In this study, a small inkle-type loom for hand weaving facilitated the production of PGF in textile form. These PGF textiles, along with unidirectional (UD) fibre mats made from the same batch of yarns, were utilised to manufacture fully resorbable textile composites (T-C) and 0°/90° lay-up UD fibre reinforced composites (0/90-C). Retention of flexural properties and weight loss of the composites were evaluated during degradation in phosphate buffered saline (PBS) at 37°C for 28 days. The initial flexural strength values that were observed for the T-C and 0/90-C composites were ∼;176 MPa and ∼;137 MPa, whilst the modulus values were 8.6 GPa and 6.9 GPa, respectively. The higher flexural strength and modulus values for the T-C when compared to those of 0/90-C were attributed to the textile weaving manually, resulting in a biased fabric with a higher density of fibres in the warp direction. ∼;20% flexural strength and ∼;25% flexural modulus were maintained for all composites at the 28 day interval. For this study, the textile achievement will be the significant milestone on the research of bioresorbable PGFs reinforced composite in medical application, and important step on the industrial direction of bioresorbable medical device. © 2017 International Committee on Composite Materials. All rights reserved

Mechanical, degradation and cytocompatibility properties of magnesium coated phosphate glass fibre reinforced polycaprolactone composites

Retention of mechanical properties of phosphate glass fibre reinforced degradable polyesters such as polycaprolactone and polylactic acid in aqueous media has been shown to be strongly influenced by the integrity of the fibre/polymer interface. A previous study utilising ‘single fibre’ fragmentation tests found that coating with magnesium improved the fibre and matrix interfacial shear strength. Therefore, the aim of this study was to investigate the effects of a magnesium coating on the manufacture and characterisation of a random chopped fibre reinforced polycaprolactone composite. Short chopped strand non-woven phosphate glass fibre mats were sputter coated with degradable magnesium to manufacture phosphate glass fibre/polycaprolactone composites. The degradation behaviour (water uptake, mass loss and pH change of the media) of these polycaprolactone composites as well as of pure polycaprolactone was investigated in phosphate buffered saline. The Mg coated fibre reinforced composites revealed less water uptake and mass loss during degradation compared to the non-coated composites. The cations released were also explored and a lower ion release profile for all three cations investigated (namely Na+, Mg2+ and Ca2+) was seen for the Mg coated composite samples. An increase of 17% in tensile strength and 47% in tensile modulus was obtained for the Mg coated composite samples. Both flexural and tensile properties were investigated and a higher retention of mechanical properties was obtained for the Mg coated fibre reinforced composite samples up to 10 days immersion in PBS. Cytocompatibility study showed both composite samples (coated and non-coated) had good cytocompatibility with human osteosarcoma cell line

Structural, thermal and dissolution properties of MgO- and CaO-containing borophosphate glasses: effect of Fe2O3 addition

This paper investigated manufacture of high-durability phosphate glass fibres for biomedical applications. Five different borophosphate glass formulations in the systems of 45P2O5–5B2O3–5Na2O–(29 − x)CaO–16MgO–(x)Fe2O3 and 45P2O5–5B2O3–5Na2O–24CaO–(21 − x)MgO–(x)Fe2O3 where x = 5, 8 and 11 mol% were produced via melt quenching. The compositions and amorphous nature of the glasses were confirmed by ICP-MS and XRD, respectively. FTIR results indicated depolymerisation of the phosphate chains with a decrease in Q2 units with increasing Fe2O3 content. DSC analyses showed an increase in Tg by ~5 °C with an increment of 3 mol% in Fe2O3 content. The thermal properties were also used to calculate processing window (i.e. Tc,ons—Tg) and another parameter, Kgl, to determine the suitability for fibre drawing directly from melt, which equals (Tc,ons—Tg)/(Tl—Tc,ons). The degradation study conducted in PBS solution at 37 °C showed a decrease of 25–47% in degradation rate with increasing Fe2O3 content. This confirmed that the chemical durability of the glasses had increased, which was suggested to be due to Fe2O3 addition. Furthermore, the density measured via Archimedes method revealed a linear increase with increasing Fe2O3 content

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Accelerated Evolution of the Prdm9 Speciation Gene across Diverse Metazoan Taxa

The onset of prezygotic and postzygotic barriers to gene flow between populations is a hallmark of speciation. One of the earliest postzygotic isolating barriers to arise between incipient species is the sterility of the heterogametic sex in interspecies' hybrids. Four genes that underlie hybrid sterility have been identified in animals: Odysseus, JYalpha, and Overdrive in Drosophila and Prdm9 (Meisetz) in mice. Mouse Prdm9 encodes a protein with a KRAB motif, a histone methyltransferase domain and several zinc fingers. The difference of a single zinc finger distinguishes Prdm9 alleles that cause hybrid sterility from those that do not. We find that concerted evolution and positive selection have rapidly altered the number and sequence of Prdm9 zinc fingers across 13 rodent genomes. The patterns of positive selection in Prdm9 zinc fingers imply that rapid evolution has acted on the interface between the Prdm9 protein and the DNA sequences to which it binds. Similar patterns are apparent for Prdm9 zinc fingers for diverse metazoans, including primates. Indeed, allelic variation at the DNA–binding positions of human PRDM9 zinc fingers show significant association with decreased risk of infertility. Prdm9 thus plays a role in determining male sterility both between species (mouse) and within species (human). The recurrent episodes of positive selection acting on Prdm9 suggest that the DNA sequences to which it binds must also be evolving rapidly. Our findings do not identify the nature of the underlying DNA sequences, but argue against the proposed role of Prdm9 as an essential transcription factor in mouse meiosis. We propose a hypothetical model in which incompatibilities between Prdm9-binding specificity and satellite DNAs provide the molecular basis for Prdm9-mediated hybrid sterility. We suggest that Prdm9 should be investigated as a candidate gene in other instances of hybrid sterility in metazoans

Stroke genetics informs drug discovery and risk prediction across ancestries

Previous genome-wide association studies (GWASs) of stroke — the second leading cause of death worldwide — were conducted predominantly in populations of European ancestry1,2. Here, in cross-ancestry GWAS meta-analyses of 110,182 patients who have had a stroke (five ancestries, 33% non-European) and 1,503,898 control individuals, we identify association signals for stroke and its subtypes at 89 (61 new) independent loci: 60 in primary inverse-variance-weighted analyses and 29 in secondary meta-regression and multitrait analyses. On the basis of internal cross-ancestry validation and an independent follow-up in 89,084 additional cases of stroke (30% non-European) and 1,013,843 control individuals, 87% of the primary stroke risk loci and 60% of the secondary stroke risk loci were replicated (P < 0.05). Effect sizes were highly correlated across ancestries. Cross-ancestry fine-mapping, in silico mutagenesis analysis3, and transcriptome-wide and proteome-wide association analyses revealed putative causal genes (such as SH3PXD2A and FURIN) and variants (such as at GRK5 and NOS3). Using a three-pronged approach4, we provide genetic evidence for putative drug effects, highlighting F11, KLKB1, PROC, GP1BA, LAMC2 and VCAM1 as possible targets, with drugs already under investigation for stroke for F11 and PROC. A polygenic score integrating cross-ancestry and ancestry-specific stroke GWASs with vascular-risk factor GWASs (integrative polygenic scores) strongly predicted ischaemic stroke in populations of European, East Asian and African ancestry5. Stroke genetic risk scores were predictive of ischaemic stroke independent of clinical risk factors in 52,600 clinical-trial participants with cardiometabolic disease. Our results provide insights to inform biology, reveal potential drug targets and derive genetic risk prediction tools across ancestries

Structure, thermal properties, dissolution behaviour and biomedical applications of phosphate glasses and fibres: a review

For the last few decades, there has been a growing interest in using glasses for biomedical applications. Bioactive glasses are a group of surface reactive glasses which can initiate a range of biological responses by releasing ions into the local environment. Silicate, borate and phosphate glasses are known to show good bioactive characteristics and could be potentially used as favourable templates for bone-tissue formation. Phosphate glasses are unique group of materials that offer great potential for hard and soft tissue engineering over other types of bioactive glasses due to their fully resorbable characteristics, with some formulations possessing chemical composition similar to the mineral phase of natural bone. Moreover, these phosphate glasses can be prepared as fibres which could be used for soft tissue engineering and as fibrous reinforcement for resorbable polymers such as poly-(lactic acid) for fracture fixation applications. This review details some of the properties of phosphate glasses, such as thermal, viscosity/temperature, dissolution and biocompatibility of and how different factors can effectively alter these properties. The effect of the addition of different modifier oxides on the structure in terms of chain length is included. This review also reports on the manufacturing process, mechanical properties and biomedical application of phosphate glass fibres. A brief comparison between three different types of bioactive glasses has also been presented in this review. The main aim of this review is to present the factors affecting the properties of phosphate glasses and glass fibres and how these may be exploited in the design of a biomaterial