14 results found
Verdolotti L, Oliviero M, Lavorgna M, et al., 2021, “Aerogel-like” polysiloxane-polyurethane hybrid foams with enhanced mechanical and thermal-insulating properties, Composites Science and Technology, Vol: 213, Pages: 1-9, ISSN: 0266-3538
New organic-inorganic polyurethane-based hybrids with enhanced mechanical properties and thermal insulation properties are reported. Polyurethane-based hybrids are characterized by the intimate interactions of their inorganic and organic co-networks and prepared by sol-gel approach, have exhibited properties exceeding those of polyurethane foams, e.g. enhanced thermal stability, durability and thermal insulating effectiveness. However, mechanical properties have previously been poor. Here, new porous organic-inorganic materials consisting of a polyurethane network modified by in-situ formation of aerogel-like polysiloxane domains, were developed. They exhibit a multiscale-porosity which enhances the insulation, mechanical and thermal properties. The synthesis was performed through a novel stepwise process consisting of: preparation of a siloxane precursor based on methyl-triethoxysilane and tetraethoxysilane; functionalization of traditional polyol for polyurethane foams with 3-(triethoxysilanepropyl)isocyanate as coupling agent; use of suitable catalysts and silicone surfactants; and foaming with methylene-di-isocyanate compound. The siloxane precursors and coupling agent led to formation of “aerogel-like” polysiloxane domains within the walls and struts of the polyurethane foams. The synthesis method enabled increased incorporation of the “aerogel-like” polysiloxane structures into the foams, compared to literature, with 20 wt% SiO2, reducing thermal conductivity of the hybrid foams 30% compared with pristine polyurethane, in addition to significant improvement in thermal stability and mechanical properties.
Riveiro A, Amorim S, Solanki A, et al., 2021, Hyaluronic acid hydrogels reinforced with laser spun bioactive glass micro- and nanofibres doped with lithium, Materials Science and Engineering: C, Vol: 126, Pages: 1-12, ISSN: 0928-4931
The repair of articular cartilage lesions in weight-bearing joints remains as a significant challenge due to the low regenerative capacity of this tissue. Hydrogels are candidates to repair lesions as they have similar properties to cartilage extracellular matrix but they are unable to meet the mechanical and biological requirements for a successful outcome. Here, we reinforce hyaluronic acid (HA) hydrogels with 13-93-lithium bioactive glass micro- and nanofibres produced by laser spinning. The glass fibres are a reinforcement filler and a platform for the delivery of therapeutic lithium-ions. The elastic modulus of the composites is more than three times higher than in HA hydrogels. Modelling of the reinforcement corroborates the experimental results. ATDC5 chondrogenic cells seeded on the composites are viable and more proliferation occurs on the hydrogels containing fibres than in HA hydrogels alone. Furthermore, the chondrogenic behavior on HA constructs with fibres containing lithium is more marked than in hydrogels with no-lithium fibres.
Parkes M, Tallia F, Young G, et al., 2021, Tribological evaluation of a novel hybrid for repair of articular cartilage defects, Materials Science and Engineering C: Materials for Biological Applications, Vol: 119, Pages: 1-10, ISSN: 0928-4931
The friction and wear properties of silica/poly(tetrahydrofuran)/poly(ε-caprolactone) (SiO2/PTHF/PCL-diCOOH) hybrid materials that are proposed as cartilage tissue engineering materials were investigated against living articular cartilage. A testing rig was designed to allow testing against fresh bovine cartilage. The friction force and wear were compared for five compositions of the hybrid biomaterial articulating against freshly harvested bovine cartilage in diluted bovine calf serum. Under a non-migrating contact, the friction force increased and hence shear force applied to the opposing articular cartilage also increased, resulting in minor damage to the cartilage surface. This worse case testing scenario was used to discriminate between material formulations and revealed the increase in friction and damaged area was lowest for the hybrid containing the most silica. Further friction and wear tests on one hybrid formulation with an elastic modulus closest to that of cartilage were then conducted in a custom incubator system. This demonstrated that over a five day period the friction force, cell viability and glucosaminoglycan (GAG) release into the lubricant were similar between a cartilage-cartilage interface and the hybrid-cartilage interface, supporting the use of these materials for cartilage repair. These results demonstrate how tribology testing can play a part in the development of new materials for chondral tissue engineering.
Nelson M, Tallia F, Page SJ, et al., 2021, Electrospun cotton–wool-like silica/gelatin hybrids with covalent coupling, Journal of Sol-Gel Science and Technology, Vol: 97, Pages: 11-26, ISSN: 0928-0707
Inorganic/organic sol–gel hybrids consist of co-networks of inorganic and organic components that can lead to unique properties, compared to conventional composites, especially when there is covalent bonding between the networks. The aim here was to develop new electrospun silica/gelatin sol–gel hybrids, with covalent coupling and unique 3D cotton–wool-like morphology for application as regenerative medicine scaffolds. Covalent coupling is critical for obtaining sustained dissolution of the fibres and we identified the sol–gel synthesis conditions needed for coupling within the electrospun fibres. Under carefully controlled conditions, such as constant humidity, we investigated the effect of the electrospinning process variables of sol viscosity (and aging time) and amount of coupling agent on the 3D morphology of the fibres, their structure (bonding) and dissolution, identifying a detailed optimised protocol for fibre scaffold production.
Li Volsi A, Tallia F, Iqbal H, et al., 2020, Enzyme degradable star polymethacrylate/silica hybrid inks for 3D printing of tissue scaffolds, Materials Advances, Vol: 1, ISSN: 2633-5409
There is unmet clinical need for scaffolds that can share load with the host tissue while biodegrading under the action of enzymes present at the site of implantation. The aim here was to create the first enzyme cleavable inorganic–organic hybrid “inks” that can be 3D printed as scaffolds for bone regeneration. Inorganic–organic hybrids are co-networks of inorganic and organic components. Although previous hybrids performed well under cyclic loads, there was little control over their degradation. Here we synthesised new hybrids able to degrade in response to endogenous tissue specific metallo proteinases (collagenases) that are involved in natural remodeling of bone. Three well-defined star polymers, of the monomer 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) and of methyl methacrylate (MMA), of different architectures were prepared by RAFT polymerisation. The linear arms were connected together at an enzyme degradable core using a collagenase cleavable peptide sequence (GLY-PRO-LEU-GLY-PRO-LYS) modified with dimethacryloyl groups as a crosslinker for RAFT polymerisation. The effect of polymer architecture, i.e. the position of the TMSPMA groups on the polymers, on bonding between networks, mechanical properties, biodegradation rate and 3D printability, via direct ink writing, was investigated for the first time and was proven to be critical for all three properties. Specifically, hybrids made with star polymers with the TMSPMA close to the core exhibited the best mechanical properties, improved printability and a higher degradation rate.
Clark J, Heyraud A, Tavana S, et al., 2020, Exploratory full-field mechanical analysis across the osteochondral tissue– biomaterial interface in an ovine model, Materials, Vol: 13, ISSN: 1996-1944
Osteochondral injuries are increasingly prevalent, yet success in articular cartilage regeneration remains elusive, necessitating the development of new surgical interventions and novel medical devices. As part of device development, animal models are an important milestone in illustrating functionality of novel implants. Inspection of the tissue-biomaterial system is vital to understand and predict load-sharing capacity, fixation mechanics and micromotion, none of which are directly captured by traditional post-mortem techniques. This study aims to characterize the localised mechanics of an ex vivo ovine osteochondral tissue–biomaterial system extracted following six weeks in vivo testing, utilising laboratory micro-computed tomography, in situ loading and digital volume correlation. Herein, the full-field displacement and strain distributions were visualised across the interface of the system components, including newly formed tissue. The results from this exploratory study suggest that implant micromotion in respect to the surrounding tissue could be visualised in 3D across multiple loading steps. The methodology provides a non-destructive means to assess device performance holistically, informing device design to improve osteochondral regeneration strategies.
Clark J, Tavana S, Heyraud A, et al., 2020, Quantifying 3D strain in scaffold implants for regenerative medicine, Materials, Vol: 13, ISSN: 1996-1944
Regenerative medicine solutions require thoughtful design to elicit the intended biological response. This includes the biomechanical stimulus to generate an appropriate strain in the scaffold and surrounding tissue to drive cell lineage to the desired tissue. To provide appropriate strain on a local level, new generations of scaffolds often involve anisotropic spatially graded mechanical properties that cannot be characterised with traditional materials testing equipment. Volumetric examination is possible with three-dimensional (3D) imaging, in situ loading and digital volume correlation (DVC). Micro-CT and DVC were utilised in this study on two sizes of 3D-printed inorganic/organic hybrid scaffolds (n = 2 and n = 4) with a repeating homogenous structure intended for cartilage regeneration. Deformation was observed with a spatial resolution of under 200 µm whilst maintaining displacement random errors of 0.97 µm, strain systematic errors of 0.17% and strain random errors of 0.031%. Digital image correlation (DIC) provided an analysis of the external surfaces whilst DVC enabled localised strain concentrations to be examined throughout the full 3D volume. Strain values derived using DVC correlated well against manually calculated ground-truth measurements (R2 = 0.98, n = 8). The technique ensures the full 3D micro-mechanical environment experienced by cells is intimately considered, enabling future studies to further examine scaffold designs for regenerative medicine.
Li S, Tallia F, Mohammed AA, et al., 2020, Scaffold channel size influences stem cell differentiation pathway in 3-D printed silica hybrid scaffolds for cartilage regeneration, Biomaterials Science, Vol: 8, Pages: 4458-4466, ISSN: 2047-4830
We report that 3-D printed scaffold channel size can direct bone marrow derived stem cell differentiation. Treatment of articular cartilage trauma injuries, such as microfracture surgery, have limited success because durability is limited as fibrocartilage forms. A scaffold-assisted approach, combining microfracture with biomaterials has potential if the scaffold can promote articular cartilage production and share load with cartilage. Here, we investigated human bone marrow derived stromal cell (hBMSC) differentiation in vitro in 3-D printed silica/poly(tetrahydrofuran)/poly(ε-caprolactone) hybrid scaffolds with specific channel sizes. Channel widths of ∼230 μm (210 ± 22 μm mean strut size, 42.4 ± 3.9% porosity) provoked hBMSC differentiation down a chondrogenic path, with collagen Type II matrix prevalent, indicative of hyaline cartilage. When pores were larger (∼500 μm, 229 ± 29 μm mean strut size, 63.8 ± 1.6% porosity) collagen Type I was dominant, indicating fibrocartilage. There was less matrix and voids in smaller channels (∼100 μm, 218 ± 28 μm mean strut size, 31.2 ± 2.9% porosity). Our findings suggest that a 200–250 μm pore channel width, in combination with the surface chemistry and stiffness of the scaffold, is optimal for cell–cell interactions to promote chondrogenic differentiation and enable the chondrocytes to maintain their phenotype.
Autefage H, Allen F, Tang HM, et al., 2019, Multiscale analyses reveal native-like lamellar bone repair and near perfect bone-contact with porous strontium-loaded bioactive glass, Biomaterials, Vol: 209, Pages: 152-162, ISSN: 0142-9612
The efficient healing of critical-sized bone defects using synthetic biomaterial-based strategies is promising but remains challenging as it requires the development of biomaterials that combine a 3D porous architecture and a robust biological activity. Bioactive glasses (BGs) are attractive candidates as they stimulate a biological response that favors osteogenesis and vascularization, but amorphous 3D porous BGs are difficult to produce because conventional compositions crystallize during processing. Here, we rationally designed a porous, strontium-releasing, bioactive glass-based scaffold (pSrBG) whose composition was tailored to deliver strontium and whose properties were optimized to retain an amorphous phase, induce tissue infiltration and encourage bone formation. The hypothesis was that it would allow the repair of a critical-sized defect in an ovine model with newly-formed bone exhibiting physiological matrix composition and structural architecture. Histological and histomorphometric analyses combined with indentation testing showed pSrBG encouraged near perfect bone-to-material contact and the formation of well-organized lamellar bone. Analysis of bone quality by a combination of Raman spectral imaging, small-angle X-ray scattering, X-ray fluorescence and focused ion beam-scanning electron microscopy demonstrated that the repaired tissue was akin to that of normal, healthy bone, and incorporated small amounts of strontium in the newly formed bone mineral. These data show the potential of pSrBG to induce an efficient repair of critical-sized bone defects and establish the importance of thorough multi-scale characterization in assessing biomaterial outcomes in large animal models.
Tallia F, Russo L, Li S, et al., 2018, Bouncing and 3D printable hybrids with self-healing properties, Materials Horizons, Vol: 5, Pages: 849-860, ISSN: 2051-6355
Conventional composites often do not represent true synergy of their constituent materials. This is particularly evident in biomaterial applications where devices must interact with cells, resist cyclic loads and biodegrade safely. Here we propose a new hybrid system, with co-networks of organic and inorganic components, resulting in unprecedented mechanical properties, including “bouncy” elasticity and intrinsic ability to self-heal autonomously. They are also developed as new ‘inks’ that can be directly 3D printed. A hybrid is different from a nanocomposite because the components are indistinguishable from each other at the nanoscale and above. The properties are generated by a novel methodology that combines in situ cationic ring-opening polymerisation with sol–gel, creating silica/poly(tetrahydrofuran)/poly(ε-caprolactone) hybrids with molecular scale interactions and covalent links. Cartilage is notoriously difficult to repair and synthetic biomaterials have yet to mimic it closely. We show that 3D printed hybrid scaffolds with pore channels of ∼200 μm mimic the compressive behaviour of cartilage and provoke chondrocytes to produce markers integral to articular cartilage-like matrix. The synthesis method can be applied to different organic sources, leading to a new class of hybrid materials.
Dadkhah M, Pontiroli L, Fiorilli S, et al., 2017, Preparation and characterisation of an innovative injectable calcium sulphate based bone cement for vertebroplasty application, JOURNAL OF MATERIALS CHEMISTRY B, Vol: 5, Pages: 102-115, ISSN: 2050-750X
Balasubramanian P, Grünewald A, Detsch R, et al., 2016, Ion Release, Hydroxyapatite Conversion, and Cytotoxicity of Boron-containing Bioactive Glass Scaffolds, International Journal of Applied Glass Science, Vol: 7, Pages: 206-215, ISSN: 2041-1286
We report the development and characterization of boron-releasing highly porous three-dimensional bioactive glass (BG) scaffolds fabricated by the foam replica technique. Three types of bioactive glasses with (wt%) 0.2%, 12.5%, 25% B2O3, and related varying SiO2 contents (wt%): 50%, 37.5%, and 25%, were investigated. The well-known 13-93 (silicate) and 13-93B3 (borate) (in wt% - 56.6% B2O3, 5.5% Na2O, 11.1% K2O, 4.6% MgO, 18.5% CaO, 3.7% P2O5) BGs were used as controls to study the influence of the presence of boron on the mechanical properties, surface reactivity, and cytotoxicity of scaffolds. Surface morphology and surface properties of the BG scaffolds were measured. X-ray diffraction (XRD) analyses showed that the scaffolds of all five compositions were amorphous. The scaffolds with 12.5 wt% B2O3 exhibited satisfactory compressive strength in the range of 1-2 MPa. A dissolution study in cell culture medium was carried out, and ion release profiles, and apatite formation of the scaffolds were assessed. The cytotoxicity of the scaffolds was evaluated using a stromal cell line (ST2). Cells were found to attach and spread well on the scaffolds' surfaces. We conclude that borosilicate scaffolds containing 12.5 wt% B2O3 provide the best combination of properties, including relatively high mechanical strength, apatite formation, and cytocompatibility, and thus, they are promising candidates for bone tissue engineering.
Tallia F, Gallo M, Pontiroli L, et al., 2014, Zirconia-containing radiopaque mesoporous bioactive glasses, MATERIALS LETTERS, Vol: 130, Pages: 281-284, ISSN: 0167-577X
Vitale-Brovarone C, Baino F, Tallia F, et al., 2012, Bioactive glass-derived trabecular coating: a smart solution for enhancing osteointegration of prosthetic elements, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, Vol: 23, Pages: 2369-2380, ISSN: 0957-4530
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