Publications
285 results found
Sang T, Li S, Ting HK, et al., 2018, Hybrids of silica/poly (caprolactone co-glycidoxypropyl trimethoxysilane) as biomaterials, Chemistry of Materials, Vol: 30, Pages: 3743-3751, ISSN: 0897-4756
Bioactive glasses stimulate bone regeneration but are brittle. Biomaterials are needed that share load with bone, promote bone regeneration and biodegrade at controlled rates. Sol-gel hybrids can achieve this through their intimate inorganic and organic co-networks, depending on the organic polymer used. Polycaprolactone degrades slowly but lacks functional groups for the critical step of covalent coupling to the silica co-network. Here, we synthesised a novel copolymer of caprolactone and glycidoxypropyl trimethoxysilane through one-pot ring opening polymerization (ROP). Hybrids with different organic content were fabricated using such a copolymer for the first time. The copolymer can directly bond to a silica network due its trimethoxysilane groups, which can hydrolyse, leaving silanol groups that undergo polycondensation with silanol groups of the silica network. Number of repeating units of caprolactone and glycidoxypropyl trimethoxysilane functional groups were controlled via ROP. The mechanical properties of the hybrids were tuned by weight percent and the number of repeating units of caprolactone independently, producing a homogeneous material with high strength (64 MPa) and strain to failure (20%) that deformed in a unique linear elastic manner until failure. MC3T3-E1 pre-osteoblast cells adhered to the hybrids. Introducing such a copolymer created a new way to fabricate covalently bonded polycaprolactone/silica hybrids for future bone repair.
Lin S, Jones JR, 2018, The effect of serum proteins on apatite growth for 45S5 Bioglass and common sol-gel derived glass in SBF, Biomedical Glasses, Vol: 4, Pages: 13-20, ISSN: 2299-3932
The inhibitive effects of serum proteins on apatite growth was compared between melt-derived 45S5 Bioglass and sol-gel derived bioactive glass of the 70S30C (70 mol% SiO2, 30 mol% CaO). By using techniques of XRD, TEM and Raman spectroscopy, the transformation of amorphous calcium phosphate to crystalline apatite, and the resulting size and aspect ratio of the crystals, in simulated body fluid (SBF), was seen to decrease in the presence of serum. XRD showed more rapid HA formation on Bioglass particles, compared to that forming on 70S30C particles, however TEM showed similar size and frequency of the needle-like crystals. Phosphate reduction in SBF was similar for Bioglass and 70S30C. Calcium carbonate formation was more likely on the phosphate-free sol-gel glass than on Bioglass.
Vueva Y, Connell L, Chayanun S, et al., 2018, Silica/alginate hybrid biomaterials and assessment of their covalent coupling, Applied Materials Today, Vol: 11, Pages: 1-12, ISSN: 2352-9407
Organic–inorganic hybrid materials composed of co-networks of biodegradable polymer and silica have potential to combine the properties of an elastic organic polymer and inorganic silica. The nanoscale interaction of the co-networks and formation of covalent bonds between them are expected to provide tailored mechanical properties and congruent degradation. Alginate is a natural polymer commonly used in tissue engineering applications due to its good biocompatibility and biodegradability. In this work we present new alginate–silica hybrids prepared through nucleophilic ring opening reaction of 3-glycidoxypropyl trimethoxysilane (GPTMS) by carboxylic groups of alginate and incorporation of this functionalized alginate into the sol–gel process to make a hybrid. The role of the GPTMS is to provide organic/inorganic covalent coupling. The reaction of alginate with GPTMS was followed using NMR, FTIR and ToF-SIMS and the dissolution behaviour, bioactivity and mechanical properties of the resultant alginate–silica hybrid monoliths were evaluated. While mechanical strength was high with values of 110–242 MPa comparable to that of cortical bone, the amount of GPTMS coupling to the alginate was low, with the rest of the GPTMS forming diols or a separate network.
Gholami S, Labbaf S, Houreh AB, et al., 2017, Long term effects of bioactive glass particulates on dental pulp stem cells in vitro, Biomedical Glasses, Vol: 3, Pages: 96-103, ISSN: 2299-3932
Bioactive glasses (BG) are known for their ability to induce bone formation by the action of their dissolution products. Glasses can deliver active ions at a sustained rate, determined by their composition and surface area. Nanoporous sol-gel derived BGs can biodegrade rapidly, which can lead to a detrimental burst release of ions and a pH rise. The addition of phosphate into the glass can buffer the pH during dissolution. Here, dissolution of BG with composition 60 mol% SiO2, 28 mol% CaO and 12 mol% P2O5 at 600 g/ml were investigated. Initially, the dissolution and apatite formation of the BG particulates were examined in simulated body fluid using FTIR and XRD. BG particulates were indirectly exposed to dental pulp stem cells, and the effect of 14 days continuous ion release on human dental pulp stem cells (hDPSC) viability and differentiation was evaluated. Alamar blue assay showed that cell proliferation was not inhibited by the continuous release of Ca, P and soluble silica. In fact, hDPSC in the presence of BG particulate displayed a higher density of mineralized nodules than untreated cells, as assessed by Alizarin red. The results will have a great contribution to the in vivo application of this particular BG.
Naruphontjirakul P, Porter AE, Jones JR, 2017, In vitro osteogenesis by intracellular uptake of strontium containing bioactive glass nanoparticles., Acta Biomaterialia, Vol: 66, Pages: 67-80, ISSN: 1742-7061
Monodispersed strontium containing bioactive glass nanoparticles (Sr-BGNPs) with two compositions were synthesised, through a modified sol-gel Stöber process, wherein silica nanoparticles (SiO2-NPs) were formed prior to incorporation of calcium and strontium, with diameters of 90 ± 10 nm. The osteogenic response of a murine preosteoblast cell line, MC3T3-E1, was investigated in vitro for a nanoparticle concentration of 250 µg/mL with compositions of 87 mol% SiO2, 7 mol% CaO, 6 mol% SrO and 83 mol% SiO2, 3 mol% CaO, 14 mol% SrO. Dissolution studies in minimum essential media (α-MEM) at pH 7.4 and artificial lysosomal fluid (ALF) at pH 4.5 showed that the particles dissolved and that Sr2+ ions were released from Sr-BGNPs in both environments. Both particle compositions and their ionic dissolution products enhanced the alkaline phosphatase (ALP) activity of the cells and calcium deposition. Immunohistochemistry (IHC) staining of Col1a1, osteocalcin (OSC) and osteopontin (OSP) showed that these proteins were expressed in the MC3T3-E1 cells following three weeks of culture. In the basal condition, the late osteogenic differentiation markers, OSC and OSP, were more overtly expressed by cells cultured with Sr-BGNPs with 14 mol% SrO and their ionic release products than in the control condition. Col1a1 expression was only slightly enhanced in the basal condition, but was enhanced further by the osteogenic supplements. These data demonstrate that Sr-BGNPs accelerate mineralisation without osteogenic supplements. Sr-BGNPs were internalised into MC3T3-E1 cells by endocytosis and stimulated osteogenic differentiation of the pre-osteoblast cell line. Sr-BGNPs are likely to be beneficial for bone regeneration and the observed osteogenic effects of these particles can be attributed to their ionic release products. STATEMENT OF SIGNIFICANCE: We report, for the first time, that monodispersed bioactive glass nanoparticles (∼90 nm) are internalised into pre
Ting H-K, Page SJ, Poologasundarampillai G, et al., 2017, Phosphate content affects structure and bioactivity of sol-gel silicate bioactive glasses, INTERNATIONAL JOURNAL OF APPLIED GLASS SCIENCE, Vol: 8, Pages: 372-382, ISSN: 2041-1286
Bioactive glasses can heal bone defects and bond with bone through formation of hydroxyl carbonate apatite (HCA) surface layer. Sol-gel derived bioactive glasses are thought to have potential for improving bone regeneration rates over melt-derived compositions. The 58S sol-gel composition (60 mol% SiO2, 36 mol% CaO, and 4 mol% P2O5) has appeared in commercial products. Here, hydroxyapatite (HA) was found to form within the 58S glass during sol-gel synthesis after thermal stabilization. The preformed HA may lead to rapid release of calcium orthophosphate, or nanocrystals of HA, on exposure to body fluid, rather than the release of separate the calcium and phosphate species. Increasing the P2O5 to CaO ratio in the glass composition reduced preformed HA formation, as observed by XRD and solid-state NMR. Instead, above 12 mol% phosphate, a phosphate glass network (polyphosphate) formed, creating co-networks of phosphate and silica. Nanopore diameter of the glass and rate of HCA layer formation in simulated body fluid (SBF) decreased when the phosphate content increased.
Carta D, Jones JR, Lin S, et al., 2017, Neutron diffraction study of antibacterial bioactive calcium silicate sol-gel glasses containing silver, International Journal of Applied Glass Science, Vol: 8, Pages: 364-371, ISSN: 2041-1286
Bioactive sol-gel calcia-silica glasses can regenerate damaged or diseased bones due to their ability to stimulate bone growth. This capability is related to the formation of a hydroxyapatite layer on the glass surface, which bonds with bone, and the release of soluble silica and calcium ions in the body fluid which accelerates bone growth. The addition of s ilver ions imbues the glass with antibacterial properties due to the release of antibacterial Ag + ion. The antibacterial activity is therefore closely dependent on the dissolution properties of the glasses which in turn are related to their atomic-level structure. Structural characterization of the glasses at the atomic level is therefore essential in order to investigate and control the antibacterial properties of the glass. We have used neutron diffraction to investigate the structure of silver-containing calcia-silica sol-gel bioactive glasses with different Ag 2 O loading (0, 2, 4, 6 mol%). The presence of the silver had little effect on the host glass structure, although some silver metal nanoparticles were present. Results agreed with previous computer simulations.
nommeots-nomm A, lee PD, Jones JR, 2017, Direct ink writing of highly bioactive glasses, Journal of the European Ceramic Society, Vol: 28, Pages: 937-944, ISSN: 0955-2219
Direct ink writing (DIW) or Robocasting, is an additive manufacturing technique that offers the opportunity to create patient specific bioactive glass scaffolds and high strength scaffolds for bone repair. The original 45S5 Bioglass® composition crystallises during sintering and until now, robocast glass scaffolds contained at least 51.9 mol% SiO2 or B2O3 to maintain their amorphous structure. Here, ICIE16 and PSrBG compositions, containing <50 mol% SiO2, giving silicate network connectivity close to that of 45S5, were robocast and compared to 13–93 composition. Results showed Pluronic F-127 can be used as a universal binder regardless of glass reactivity and that particle size distribution affected the ink “printability”. Scaffolds with interconnects of 150 μm (41–43% porosity) had compressive strengths of 32–48 MPa, depending on the glass composition. Robocast scaffolds from these highly reactive bioactive glasses promise greatly improved bone regeneration rates compared with existing bioactive glass scaffolds.
Littmann E, Autefage H, Solanki AN, et al., 2017, Cobalt-containing bioactive glasses reduce humanmesenchymal stem cell chondrogenic differentiation despiteHIF-1α stabilisation, Journal of the European Ceramic Society, Vol: 38, Pages: 877-886, ISSN: 0955-2219
Bioactive glasses (BGs) are excellent delivery systems for the sustained release of therapeutic ions and have been extensively studied in the context of bone tissue engineering. More recently, due to their osteogenic properties and expanding application to soft tissue repair, BGs have been proposed as promising materials for use at the osteochondral interface. Since hypoxia plays a critical role during cartilage formation, we sought to investigate the influence of BGs releasing the hypoxia-mimicking agent cobalt (CoBGs) on human mesenchymal stem cell (hMSC) chondrogenesis, as a novel approach that may guide future osteochondral scaffold design. The CoBG dissolution products significantly increased the level of hypoxia-inducible factor-1 alpha in hMSCs in a cobalt dose-dependent manner. Continued exposure to the cobalt-containing BG extracts significantly reduced hMSC proliferation and metabolic activity, as well as chondrogenic differentiation. Overall, this study demonstrates that prolonged exposure to cobalt warrants careful consideration for cartilage repair applications.
Chung JJ, Sum BST, Li S, et al., 2017, Effect of comonomers on physical properties and cell attachment to silica-methacrylate/acrylate hybrids for bone substitution, Macromolecular Rapid Communications, Vol: 38, Pages: 1-5, ISSN: 1022-1336
Hybrids with a silica network covalently bonded to a polymer are promising materials for bone repair. Previous work on synthesizing methyl methacrylate (MMA) based copolymers by reversible addition‐fragmentation chain transfer (RAFT) polymerization gives high tailorability of mechanical properties since sophisticated polymer structures can be designed. However, more flexible hybrids would be beneficial. Here, n‐butyl methacrylate (BMA) and methyl acrylate (MA) based hybrids are produced. Unlike MMA, BMA and MA hybrids do not show plastic deformation, and BMA hybrid has strain to failure of 33%. Although the new hybrids are more flexible, preosteoblast cells do not adhere on their surfaces, due to higher hydrophobicity and lower stiffness. Comonomer choice is crucial for bone regenerative hybrids.
Boccaccini AR, Fenn M, Jones JR, et al., 2017, Guest editors' preface, JOURNAL OF MATERIALS SCIENCE, Vol: 52, Pages: 8691-8694, ISSN: 0022-2461
Li S, Macon ALB, Jacquemin M, et al., 2017, Sol-gel derived lithium-releasing glass for cartilage regeneration, Journal of Biomaterials Applications, Vol: 32, Pages: 104-113, ISSN: 0885-3282
Wnt-signalling cascadeis one of the crucial pathways involved in the development and homeostasis of cartilage. Influencing this pathway can potentially contribute to improved cartilage repair or regeneration. One key molecular regulator of the Wnt pathway is the glycogen synthase kinase-3 (GSK-3) enzyme, the inhibition of which allows initiation of the signalling pathway. This study aims to utilise a binary SiO2-Li2O sol-gel derived glass for controlled delivery of lithium, a known GSK-3 antagonist. The effect of the dissolution products of the glass on chondrogenic differentiation inanin vitro3-D pellet culture modelis reported. Dissolution productsthat contained5 mM lithium and 3.5 mM silicon, were capable of inducing chondrogenic differentiation and hyaline cartilaginous matrix formation without the presence of growth factors such as TGF-β3. The results suggest that sol-gel derived glass has the potential to be used as a delivery vehicle for therapeutic lithium ions in cartilage regeneration applications.
Macon ALB, Kasuga T, Becer CR, et al., 2017, Silica/methacrylate class II hybrid: telomerisation vs. RAFT polymerisation, Polymer Chemistry, Vol: 8, Pages: 3603-3611, ISSN: 1759-9954
Inorganic–organic co-networks prepared by a sol–gel method are a promising class of materials due to their unique physical and biological properties, especially when covalent bonds are formed between the networks. The polymer structure and composition can have a drastic effect on the synthesis and properties. Here, we compared reversible addition fragmentation chain-transfer (RAFT) with telomerisation (TL), for the synthesis of the polymer, to investigate whether refining the polydispersity of polymethacrylate could lead to better and more tailorable properties. 3-(Methoxysilyl)propyl methacrylate was used as a model and successfully synthesised by RAFT and TL using 2-cyano-2-propyl benzodithioate and thioglycerol as chain transfer agents, respectively. The polydispersity of the polymer had a significant effect on the sol–gel process with an increase in gelation time as the polydispersity decreased. Direct correlation was made between the gelation time and Mz, suggesting that the gelation of hybrids followed the percolation model. However, regarding the properties, it is a tie. No statistical difference in silica release and mechanical properties of the resulting hybrids was observed, regardless of the polydispersity of the polymer.
Nommeots-Nomm A, Labbaf S, Devlin A, et al., 2017, Highly degradable porous melt-derived bioactive glass foam scaffolds for bone regeneration, Acta Biomaterialia, Vol: 57, Pages: 449-461, ISSN: 1878-7568
A challenge in using bioactive melt-derived glass in bone regeneration is to produce scaffolds with interconnected pores while maintaining the amorphous nature of the glass and its associated bioactivity. Here we introduce a method for creating porous melt-derived bioactive glass foam scaffolds with low silica content and report in vitro and preliminary in vivo data. The gel-cast foaming process was adapted, employing temperature controlled gelation of gelatin, rather than the in situ acrylic polymerisation used previously. To form a 3D construct from melt derived glasses, particles must be fused via thermal processing, termed sintering. The original Bioglass® 45S5 composition crystallises upon sintering, altering its bioactivity, due to the temperature difference between the glass transition temperature and the crystallisation onset being small. Here, we optimised and compared scaffolds from three glass compositions, ICIE16, PSrBG and 13–93, which were selected due to their widened sintering windows. Amorphous scaffolds with modal pore interconnect diameters between 100–150 µm and porosities of 75% had compressive strengths of 3.4 ± 0.3 MPa, 8.4 ± 0.8 MPa and 15.3 ± 1.8 MPa, for ICIE16, PSrBG and 13–93 respectively. These porosities and compressive strength values are within the range of cancellous bone, and greater than previously reported foamed scaffolds. Dental pulp stem cells attached to the scaffold surfaces during in vitro culture and were viable. In vivo, the scaffolds were found to regenerate bone in a rabbit model according to X-ray micro tomography imaging.
Mizuno K, Koeda S, Obata A, et al., 2017, Construction of DNAzyme-Encapsulated Fibermats Using the Precursor Network Polymer of Poly(y-glutamate) and 4-Glycidyloxypropyl Trimethoxysilane, Langmuir, Vol: 33, Pages: 4028-4035, ISSN: 1520-5827
Here, we developed functional nucleic acid (FNA)-encapsulated electrospun fibermats. To facilitate stable FNA encapsulation in the γ-PGA/GPTMS fibermats, we used the FNA as an FNA/streptavidin complex, and as a representative FNA, we selected a DNAzyme, the DNA/hemin complex, which is composed of G-quadraplex-forming single-stranded DNA and hemin and exhibits oxidation activity with the aid of a cocatalyst, H2O2. Scanning electron microscopy and Fourier-transform infrared spectroscopy measurements revealed that encapsulation of the DNA/hemin complex (∼1 wt % against the γ-PGA/GPTMS hybrid) in the nanofibers of the γ-PGA/GPTMS fibermats did not affect the structure of the original nanofibers. However, because a unique MW-dependent molecular permeability originated from the 3D network structure of the γ-PGA/GPTMS hybrid, low-MW substrates such as 4-aminoantipyrine, N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3-methylaniline, and luminol were able to reach the encapsulated DNA/hemin complex by permeating to the inside of the nanofibers from an immersion buffer and then underwent catalytic oxidation. Conversely, nucleases, which are proteins featuring high MWs (>5 kDa), could not penetrate the γ-PGA/GPTMS nanofibers, and the encapsulated DNA/hemin complex was therefore effectively protected against nuclease digestion. Thus, encapsulating FNAs on the inside of the nanofibers of fibermats offers clear advantages for the practical application of FNAs in sensors and drugs, particularly for use in the in vivo circumstances.
Chung JJ, Fujita Y, Li S, et al., 2017, Biodegradable inorganic-organic hybrids of methacrylate star polymers for bone regeneration, Acta Biomaterialia, Vol: 54, Pages: 411-418, ISSN: 1878-7568
Hybrids that are molecular scale co-networks of organic and inorganic components are promising biomaterials, improving the brittleness of bioactive glass and the strength of polymers. Methacrylate polymers have high potential as the organic source for hybrids since they can be produced, through controlled polymerization, with sophisticated polymer architectures that can bond to silicate networks. Previous studies showed the mechanical properties of hybrids can be modified by polymer architecture and molar mass (MM). However, biodegradability is critical if hybrids are to be used as tissue engineering scaffolds, since the templates must be remodelled by host tissue. Degradation by-products have to either completely biodegrade or be excreted by the kidneys. Enzyme, or bio-degradation is preferred to hydrolysis by water uptake as it is expected to give a more controlled degradation rate. Here, branched and star shaped poly(methyl methacrylate-co-3-(trimethoxysilyl)propyl methacrylate) (poly(MMA-co-TMSPMA)) were synthesized with disulphide based dimethacrylate (DSDMA) as a biodegradable branching agent. Biodegradability was confirmed by exposing the copolymers to glutathione, a tripeptide which is known to cleave disulphide bonds. Cleaved parts of the star polymer from the hybrid system were detected after 2 weeks of immersion in glutathione solution, and MM was under threshold of kidney filtration. The presence of the branching agent did not reduce the mechanical properties of the hybrids and bone progenitor cells attached on the hybrids in vitro. Incorporation of the DSDMA branching agent has opened more possibilities to design biodegradable methacrylate polymer based hybrids for regenerative medicine.Statement of significanceBioactive glasses can regenerate bone but are brittle. Hybrids can overcome this problem as intimate interactions between glass and polymer creates synergetic properties. Implants have previously been made with synthetic polymers that degrade by
Houreh AB, Labbaf S, Ting H-K, et al., 2017, Influence of calcium and phosphorus release from bioactive glasses on viability and differentiation of dental pulp stem cells, Journal of Materials Science, Vol: 52, Pages: 8928-8941, ISSN: 0022-2461
The release of ions that can significantly contribute toward cellular response is an important characteristic of bioactive glasses (BG). Here, ionic extracts of three different compositions of BG powders in 60 mol% SiO2, x mol% CaO (x = 28, 32 and 36), x mol% P2O5 (x = 12, 8 and 4) compositional system were utilized to study their effect on the viability, differentiation and mineralization of dental pulp stem cells (DPSCs) in vitro. ICP was applied to detect the exact ionic concentrations released from different composition of BG. DPSCs treated with conditioned media from the glass with 4 mol% P2O5 (BGCM1, media containing 44.01 ± 0.6 mg/L Si, 61.72 ± 0.1 mg/L Ca and 7.57 ± 0.01 mg/L P) were more metabolically active compared to conditioned media from the glass with 8 mol% P2O5 (BGCM2, media with 47.36 ± 0.7 mg/L Si, 57.4 ± 0.1 mg/L Ca and 14.54 ± 0.2 mg/L P), at all times tested, but in all cases the process was slower than the control. Cells exposed to media conditioned by the glass with 12 mol% P2O5 (BGCM3, 40.46 ± 0.5 mg/L Si, 61. 85 ± 0.3 mg/L Ca and 28.43 ± 0.3 mg/L P) responded differently, such that cells showed to be more metabolically active than control at day 3, but then similar to or lower than control at higher time points. Differentiation of DPSCs toward osteogenic lineage in the presence of BGCM was assessed by Alizarin red staining. Cells treated with high phosphate BGCM3 displayed a higher density of red mineralized nodules than cells treated with BGCM1 and BGCM2 after 21 days of culture in non-osteogenic medium. BGCM3 was therefore chosen for gene expression studies. Osteogenic differentiation of DPSCs in the presence and/or absence of BGCM3 or osteogenic supplements were studied by RT-PCR. Overall, the results demonstrated that, in the absence of osteogenic supplements, BGCM3 group showed a significantly higher mRNA expression levels for alkaline phosphatase at day 7, osteopontin and
Maçon ALB, Lee S, Poologasundarampillai G, et al., 2017, Synthesis and dissolution behaviour of CaO/SrO-containing sol–gel-derived 58S glasses, Journal of Materials Science, Vol: 52, Pages: 8858-8870, ISSN: 0022-2461
The effect of the substitution of strontium for calcium in the tertiary the SiO2–CaO–P2O5 sol–gel bioactive glass 58S (60SiO2·36CaO·4P2O5, mol%) on its structure and its chemical durability on soaking in simulated body fluids was investigated. 58S was selected as a starting composition, and substitution for calcium was carried out from 0 to 100% with an increment of 25%. A novel phosphate source of diethylphosphatoethyltriethoxysilane, which consists of Si and P connected with ethylene group, was used in this work. XRD and FTIR showed that the gels obtained following drying at 130 °C had a typical sol–gel structure, where a continuous amorphous silica gel network and surface bound mineral salts of Ca(NO3)2 and Sr(NO3)2. Once the gels were heat stabilised to decompose nitrates and incorporate the cations into the network, samples containing Sr formed a strontium silicate crystalline phase. With increasing levels of Sr in the composition, the overall crystallinity of the glass–ceramic increased, while, at the maximum substitution of 100% SrO, macroscopic phase separation was observed, characterised by needle-like crystals of strontium apatite (Sr5(PO4)3OH) and strontium silicate (Sr2SiO4) phases in addition to amorphous regions. Dissolution experiments in Tris-buffered solution showed Sr successfully released into the media even though it existed as a crystalline phase in the glass–ceramic. Further, the glass–ceramics induced nucleation and growth of carbonated hydroxyapatite (HA) on their surface suggesting potential bioactivity of the materials. At higher substitutions (75 and 100% SrO for CaO), HA nucleation was not found to occur this may have been due to low amount of phosphate released from the original glass–ceramic as a result of it being locked up in the strontium apatite phase.
Gardner CL, Jones JR, Scannapieco E, et al., 2017, Numerical Simulation of Star Formation by the Bow Shock of the Centaurus A Jet, ASTROPHYSICAL JOURNAL, Vol: 835, ISSN: 0004-637X
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Zhou P, Wang J, Macon ALB, et al., 2017, Tailoring the delivery of therapeutic ions from bioactive scaffolds while inhibiting their apatite nucleation: a coaxial electrospinning strategy for soft tissue regeneration, RSC Advances, Vol: 7, Pages: 3992-3999, ISSN: 2046-2069
The delivery of therapeutic ions, as a key element for the regeneration of soft tissue, represents a viable alternative to conventional drugs. Primarily designed for the regeneration of hard tissue, degradable bioactive inorganic matrices are a carrier of choice for the delivery of ionic chemical cues. However, they nucleate calcium-phosphate crystal on their surface, which could be undesired for most soft tissue regeneration. Here, a coaxial electrospinning process was engineered, generating core–shell fibres with inorganic particles enclosed within a bio-inert polymeric shell. Silicon doped vaterite (SiV) dispersed in poly(L-lactic acid) was selected as an inorganic composite core and poly(D,L-lactide-co-glycolide) (PLGA) as a shell. By careful selection of the electrospinning parameters, fibres of constant diameter (≈10 μm) with controllable shell thickness (from 1.3 to 4.2 μm) were obtained. The release of calcium and silica followed the Weibull model, showing a purely diffusive release after hydration of the PLGA layer. The rate of release could be controlled with the shell thickness. The nucleation of calcium-phosphate crystals was inhibited. In addition, with the presence of a PLGA shell layer, the mechanical properties of the fibermats were greatly improved with, for instance, an increase of the Young's modulus up to 536% as compared to original composite. These non-woven porous materials are an affordable investigation platform to study the effect of local ionic release onto the surrounding cell metabolism.
Zhou Y, Shi M, Jones JR, et al., 2017, Strategies to direct vascularisation using mesoporous bioactive glass-based biomaterials for bone regeneration, International Materials Reviews, Vol: 62, Pages: 392-414, ISSN: 1743-2804
Blood vessel formation, which encompasses sprouting of capillaries from pre-existing ones (angiogenesis) and the de novo assembly of endothelial progenitor cells to capillaries (vasculogenesis), is vital for biological processes such as organ development, tissue repair and regeneration, and wound healing. The biggest challenge in the regeneration of large bone defects remains the lack of adequate vascularisation within a scaffold/tissue construct to support cell viability and tissue growth. Thus, enhancing the angiogenic potential of biomaterial scaffolds after implantation is pivotal for the success of guided tissue regeneration. Bone is naturally a well vascularised tissue, therefore, for a bone substitute biomaterial to function, a vascular network within the scaffold is a prerequisite. Mesoporous bioactive glasses (MBG) have gained significant attention in the field of bone tissue engineering over the past decade due to their distinct structure and composition. While the ordered mesopores are too small for blood vessel ingrowth, mesopores can increase specific surface area, thus enhancing osteogenesis through controlled ion release and possibly angiogenesis by delivering pro-angiogenic drugs. Engineering the mesoporous structures is a prime example of applying nanotechnology to regenerative medicine. Large macro-pores can be incorporated into mesoporous glasses to produce a highly functional template for tissue regeneration. Various modification strategies for MBG scaffolds have been developed to stimulate angiogenesis, including the addition/delivery of inorganic ionic components, growth factors and drug, manipulation of angiogenic growth factors such as FGF-1 and VEGF, and mimicking hypoxic conditions. This review summarises the application of MBG-based biomaterials for bone regeneration with emphasis given to blood vessel formation.
Connell L, Gabrielli L, Mahony O, et al., 2017, Functionalizing natural polymers with alkoxysilane coupling agents: Reacting 3-glycidoxypropyl trimethoxysilane with poly(γ-glutamic acid) and gelatin., Polymer Chemistry, Vol: 8, Pages: 1095-1103, ISSN: 1759-9962
Hybrid materials, with co-networks of organic and inorganic components, are increasing in popularity due to their tailorable degradation rates and mechanical properties. To increase mechanical stability, particularly in water, covalent bonding must occur between the components. This can be introduced using crosslinking agents such as 3-glycidoxypropyl trimethoxysilane (GPTMS). Attachment of GPTMS to polymers in aqueous conditions is hypothesized to occur by opening of the epoxide ring by nucleophiles on the polymer chain. Despite side reactions that occur between the epoxide ring of GPTMS and water, a range of NMR techniques showed that the carboxylic acid group of poly(γ-glutamic acid) reacted with GPTMS. This result was used to identify the amino acids in gelatin that reacted most rapidly with the GPTMS epoxide ring, confirming that covalent bonding occurred in gelatin–silica hybrid materials.
Liao Z, Sinjab F, Nommeots-Nomm A, et al., 2017, Feasibility of Spatially Offset Raman Spectroscopy for in Vitro and in Vivo Monitoring Mineralization of Bone Tissue Engineering Scaffolds, ANALYTICAL CHEMISTRY, Vol: 89, Pages: 847-853, ISSN: 0003-2700
Fiocco L, Li S, Stevens MM, et al., 2016, Biocompatibility and bioactivity of porous polymer-derived Ca-Mg silicate ceramics., Acta Biomaterialia, Vol: 50, Pages: 56-67, ISSN: 1878-7568
Magnesium is a trace element in the human body, known to have important effects on cell differentiation and the mineralisation of calcified tissues. This study aimed to synthesise highly porous Ca-Mg silicate foamed scaffolds from preceramic polymers, with analysis of their biological response. Akermanite (Ak) and wollastonite-diopside (WD) ceramic foams were obtained from the pyrolysis of a liquid silicone mixed with reactive fillers. The porous structure was obtained by controlled water release from selected fillers (magnesium hydroxide and borax) at 350°C. The homogeneous distribution of open pores, with interconnects of modal diameters of 160-180μm was obtained and maintained after firing at 1100°C. Foams, with porosity exceeding 80%, exhibited compressive strength values of 1-2MPa. In vitro studies were conducted by immersion in SBF for 21days, showing suitable dissolution rates, pH and ionic concentrations. Cytotoxicity analysis performed in accordance with ISO10993-5 and ISO10993-12 standards confirmed excellent biocompatibility of both Ak and WD foams. In addition, MC3T3-E1 cells cultured on the Mg-containing scaffolds demonstrated enhanced osteogenic differentiation and the expression of osteogenic markers including Collagen Type I, Osteopontin and Osteocalcin, in comparison to Mg-free counterparts. The results suggest that the addition of magnesium can further enhance the bioactivity and the potential for bone regeneration applications of Ca-silicate materials. STATEMENTS OF SIGNIFICANCE: Here, we show that the incorporation of Mg in Ca-silicates plays a significant role in the enhancement of the osteogenic differentiation and matrix formation of MC3T3-E1 cells, cultured on polymer-derived highly porous scaffolds. Reduced degradation rates and improved mechanical properties are also observed, compared to Mg-free counterparts, suggesting the great potential of Ca-Mg silicates as bone tissue engineering materials. Excellent biocompatibility of the
Brauer DS, Jones JR, 2016, Special section of papers presented at the larry l. hench memorial symposium on bioactive glasses at the annual meeting of the glass & optical materials division (GOMD) of the American ceramic society, held from 22<sup>nd</sup> to 26<sup>th</sup> may 2016 in madison, Wisconsin, USA, Larry L. Hench Memorial Symposium on Bioactive Glasses at the Annual Meeting of the Glass & Optical Materials Division (GOMD) of the American Ceramic Society, Pages: 49-50
Jones JR, Brauer DS, Hupa L, et al., 2016, Bioglass and bioactive glasses and their impact on healthcare, International Journal of Applied Glass Science, Vol: 7, Pages: 423-434, ISSN: 2041-1294
Glass caused a revolution in healthcare when Bioglass was discovered by Larry Hench. It was the first material to bond with bone, rather than be encapsulated by fibroustissue,launching the field of bioactive ceramics. Bioglass is also biodegradable. Almost 50 years on fromitsdiscovery that revolution continues.Bioactive glasses stimulate more bone regeneration than other bioactive ceramics, which is attributedto their dissolution products stimulating cells at the genetic level.This second discovery has changed the way clinicians, scientists and regulatory bodies think about medical devices and the concept of bioactivity. The original 45S5 Bioglass has only recently found really widespread use in orthopaedics, having regenerated the bones of more than 1.5 million patients. Its full potential is still yet to be fulfilled. Thisarticle takes the reader from Hench’s Bioglass 45S5toits clinical uses and products,before giving examples of non-surgical products that now use Bioglass, from consumer products, such as toothpaste,to cosmetics.Other glasses have also found important healthcare applications, such as borate based glasses that heal chronic wounds. The revolution looks set to continue as new healthcare applications are being found for bioactive glasses, contributing to extending the glass age.
Gardner CL, Jones JR, Hodapp KW, 2016, NUMERICAL SIMULATION OF THE SVS 13 MICROJET AND BOW SHOCK BUBBLE, ASTROPHYSICAL JOURNAL, Vol: 830, ISSN: 0004-637X
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Chung J, Li S, Stevens MM, et al., 2016, Tailoring mechanical properties of sol-gel hybrids for bone regeneration through polymer structure, Chemistry of Materials, Vol: 28, Pages: 6127-6135, ISSN: 1520-5002
Bioglass was the first synthetic biomaterial that formed a chemical bond to bone. Although bioactive glass scaffolds can mimic bone’s porous structure, they are brittle. Sol–gel derived hybrids could overcome this problem because their nanoscale conetworks of silica and organic polymer have the potential to provide unique physical properties and controlled homogeneous biodegradation. Copolymers of methyl methacrylate (MMA) and 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) have been used as an organic source for hybrids to take advantage of their self-hardening property. However, the effect of well-defined poly(MMA-co-TMSPMA) architecture in the hybrid system has not been investigated. Here, linear, randomly branched, and star shaped methacrylate based copolymers were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization method. These copolymers were then used to fabricate hybrids. The 3-D polymer structure had a significant effect on mechanical properties, providing higher strain to failure while maintaining a compressive strength similar to sol–gel glass. Star copolymer–SiO2 hybrids had a modulus of toughness 9.6-fold greater and Young’s modulus 4.5-fold lower than a sol–gel derived bioactive glass. During in vitro cell culture, MC3T3-E1 osteoblast precursor cells adhered on the surface regardless of the polymer structure. Introducing star polymers to inorganic–organic hybrids opens up possibilities for the fine-tuning physical properties of bone scaffold materials.
Maçon ALB, Li S, Chung J, et al., 2016, Ductile silica/methacrylate hybrids for bone regeneration, Journal of Materials Chemistry B, Vol: 4, Pages: 6032-6042, ISSN: 2050-7518
Bioglass® was the first synthetic material capable of bonding with bone without fibrous encapsulation, and fulfils some of the criteria of an ideal synthetic bone graft. However, it is brittle and toughness is required. Here, we investigated hybrids consisting of co-networks of high cross-linking density polymethacrylate and silica (class II hybrid) as a potential new generation of scaffold materials. Poly(3-(methoxysilyl)propyl methacrylate) (pTMSPMA) and tetraethyl orthosilicate (TEOS) were used as sol–gel precursors and hybrids were synthesised with different inorganic to organic ratios (Ih). The hybrids were nanoporous, with a modal pore diameter of 1 nm. At Ih = 50%, the release of silica was controlled by varying the molecular weight of pTMSPMA while retaining a specific surface area above 100 m2 g−1. Strain to failure increased to 14.2%, for Ih = 50% using a polymer of 30 kDa, compared to 4.5% for pure glass. The modulus of toughness (UT) increased from 0.73 (pure glass) to 2.64 GPa. Although, the hybrid synthesised in this report did not contain calcium, pTMSPMA/SiO2 hybrid was found to nucleate bone-like mineral on its surface after 1 week of immersion in simulated body fluid (SBF), whereas pure silica sol–gel glass did not. This increase in apatite forming ability was due to the ion–dipole complexation of calcium with the ester moieties of the polymer that were exposed after release of soluble silica from TEOS. No adverse cytotoxicity for MC3T3-E1 osteoblast-like cells was detected and improved cell attachment was observed, compared to a pure silica gel. pTMSPMA/SiO2 hybrids have potential for the regeneration of hard tissue as they overcome the major drawbacks of pure inorganic substrates while retaining cell attachment.
Macon ALB, Jacquemin M, Page SJ, et al., 2016, Lithium-silicate sol-gel bioactive glass and the effect of lithium precursor on structure-property relationships, Journal of Sol-Gel Science and Technology, Vol: 81, Pages: 84-94, ISSN: 1573-4846
This work reports the synthesis of lithium-silicate glass, containing 10 mol% of Li 22 O by the sol–gel process, intended for the regeneration of cartilage. Lithium citrate and lithium nitrate were selected as lithium precursors. The effects of the lithium precursor on the sol–gel process, and the resulting glass structure, morphology, dissolution behaviour, chondrocyte viability and proliferation, were investigated. When lithium citrate was used, mesoporous glass containing lithium as a network modifier was obtained, whereas the use of lithium nitrate produced relatively dense glass-ceramic with the presence of lithium metasilicate, as shown by X-ray diffraction, 2929 Si and 77 Li MAS NMR and nitrogen sorption data. Nitrate has a better affinity for lithium than citrate, leading to heterogeneous crystallisation from the mesopores, where lithium salts precipitated during drying. Citrate decomposed at a lower temperature, where the crystallisation of lithium-silicate crystal is not thermodynamically favourable. Upon decomposition of the citrate, a solid-state salt metathesis reaction between citrate and silanol occurred, followed by the diffusion of lithium within the structure of the glass. Both glass and glass-ceramic released silica and lithium ions in culture media, but release rate was lower for the glass-ceramic. Both samples did not affect chondrocyte viability and proliferation.
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