by Keyword: Composites

Widhe, M, Diez-Escudero, A, Liu, YL, Ringstrom, N, Ginebra, MP, Persson, C, Hedhammar, M, Mestres, G, (2022). Functionalized silk promotes cell migration into calcium phosphate cements by providing macropores and cell adhesion motifs Ceramics International 48, 31449-31460

Calcium phosphate cements (CPCs) are attractive synthetic bone grafts as they possess osteoconductive and osteoinductive properties. Their biomimetic synthesis grants them an intrinsic nano-and microporosity that resembles natural bone and is paramount for biological processes such as protein adhesion, which can later enhance cell adhesion. However, a main limitation of CPCs is the lack of macroporosity, which is crucial to allow cell colonization throughout the scaffold. Moreover, CPCs lack specific motifs to guide cell interactions through their membrane proteins. In this study, we explore a strategy targeting simultaneously both macroporosity and cell binding motifs within CPCs by the use of recombinant silk. A silk protein functionalized with the cell binding motif RGD serves as foaming template of CPCs to achieve biomimetic hydroxyapatite (HA) scaffolds with multiscale porosity. The synergies of RGD-motifs in the silk macroporous template and the biomimetic features of HA are explored for their potential to enhance mesenchymal stem cell adhesion, proliferation, migration and differentiation. Macroporous Silk-HA scaffolds improve initial cell adhesion compared to a macroporous HA in the absence of silk, and importantly, the presence of silk greatly enhances cell migration into the scaffold. Additionally, cell proliferation and osteogenic differentiation are achieved in the scaffolds.

JTD Keywords: Bioceramics, Bone, Bone regeneration, Composites, Degradation, Fabrication, Hydroxyapatite, Hydroxyapatite scaffolds, Injectability, Porosity, Recombinant spider silk, Rgd motifs, Silk, Stem-cells

Sans, J, Arnau, M, Roa, JJ, Turon, P, Alernan, C, (2022). Tailorable Nanoporous Hydroxyapatite Scaffolds for Electrothermal Catalysis Acs Applied Nano Materials 5, 8526-8536

Polarized hydroxyapatite (HAp) scaffolds with customized architecture at the nanoscale have been presented as a green alternative to conventional catalysts used for carbon and dinitrogen fixation. HAp printable inks with controlled nanoporosity and rheological properties have been successfully achieved by incorporating Pluronic hydrogel. Nanoporous scaffolds with good mechanical properties, as demonstrated by means of the nanoindentation technique, have been obtained by a sintering treatment and the posterior thermally induced polarization process. Their catalytic activity has been evaluated by considering three different key reactions (all in the presence of liquid water): (1) the synthesis of amino acids from gas mixtures of N-2, CO2, and CH4; (2) the production of ethanol from gas mixtures of CO2 and CH4; and (3) the synthesis of ammonia from N-2 gas. Comparison of the yields obtained by using nanoporous and nonporous (conventional) polarized HAp catalysts shows that both the nanoporosity and water absorption capacity of the former represent a drawback when the catalytic reaction requires auxiliary coating layers, as for example for the production of amino acids. This is because the surface nanopores achieved by incorporating Pluronic hydrogel are completely hindered by such auxiliary coating layers. On the contrary, the catalytic activity improves drastically for reactions in which the HAp-based scaffolds with enhanced nanoporosity are used as catalysts. More specifically, the carbon fixation from CO2 and CH4 to yield ethanol improves by more than 3000% when compared with nonporous HAp catalyst. Similarly, the synthesis of ammonia by dinitrogen fixation increases by more than 2000%. Therefore, HAp catalysts based on nanoporous scaffolds exhibit an extraordinary potential for scalability and industrial utilization for many chemical reactions, enabling a feasible green chemistry alternative to catalysts based on heavy metals.

JTD Keywords: Amino acids, Amino-acids, Ammonium production, Bone, Carbon fixation, Composites, Constitutive phases, Decarbonization, Dinitrogen, Ditrogen fixation, Elastic-modulus, Electrophotosynthesis, Ethanol production, Hardness, Indentation, Nanoindentation, Pluronic hydrogel, Polarized hydroxyapatite

Zeinali, Reza, del Valle, Luis J., Franco, Lourdes, Yousef, Ibraheem, Rintjema, Jeroen, Alemán, Carlos, Bravo, Fernando, Kleij, Arjan W., Puiggalí, Jordi, (2022). Biobased Terpene Derivatives: Stiff and Biocompatible Compounds to Tune Biodegradability and Properties of Poly(butylene succinate) Polymers 14, 161

Different copolymers incorporating terpene oxide units (e.g., limonene oxide) have been evaluated considering thermal properties, degradability, and biocompatibility. Thus, polycarbonates and polyesters derived from aromatic, monocyclic and bicyclic anhydrides have been considered. Furthermore, ring substitution with myrcene terpene has been evaluated. All polymers were amorphous when evaluated directly from synthesis. However, spherulites could be observed after the slow evaporation of diluted chloroform solutions of polylimonene carbonate, with all isopropene units possessing an R configuration. This feature was surprising considering the reported information that suggested only the racemic polymer was able to crystallize. All polymers were thermally stable and showed a dependence of the maximum degradation rate temperature (from 242 °C to 342 °C) with the type of terpene oxide. The graduation of glass transition temperatures (from 44 °C to 172 °C) was also observed, being higher than those corresponding to the unsubstituted polymers. The chain stiffness of the studied polymers hindered both hydrolytic and enzymatic degradation while a higher rate was detected when an oxidative medium was assayed (e.g., weight losses around 12% after 21 days of exposure). All samples were biocompatible according to the adhesion and proliferation tests performed with fibroblast cells. Hydrophobic and mechanically consistent films (i.e., contact angles between 90° and 110°) were obtained after the evaporation of chloroform from the solutions, having different ratios of the studied biobased polyterpenes and poly(butylene succinate) (PBS). The blend films were comparable in tensile modulus and tensile strength with the pure PBS (e.g., values of 330 MPa and 7 MPa were determined for samples incorporating 30 wt.% of poly(PA-LO), the copolyester derived from limonene oxide and phthalic anhydride. Blends were degradable, biocompatible and appropriate to produce oriented-pore and random-pore scaffolds via a thermally-induced phase separation (TIPS) method and using 1,4-dioxane as solvent. The best results were attained with the blend composed of 70 wt.% PBS and 30 wt.% poly(PA-LO). In summary, the studied biobased terpene derivatives showed promising properties to be used in a blended form for biomedical applications such as scaffolds for tissue engineering.

JTD Keywords: alternating copolymerization, biobased materials, biodegradability, composites, crystallization, cyclohexene oxide, induced phase-separation, limonene oxide, mechanical-properties, polyesters, scaffolds, spherulites, terpene derivatives, thermal properties, thermally-induced phase separation, Acetone, Bio-based, Bio-based materials, Biobased materials, Biocompatibility, Biodegradability, Butenes, Cell culture, Chlorine compounds, Degradation, Evaporation, Glass transition, Limonene oxide, Monoterpenes, Phase separation, Poly (butylenes succinate), Polybutylene succinate, Property, Ring-opening copolymerization, Scaffolds, Spheru-lites, Tensile strength, Terpene derivatives, Thermal properties, Thermally induced phase separation, Thermally-induced phase separation, Thermally?induced phase separation, Thermodynamic properties, Thermogravimetric analysis

Balakrishnan H, Fabregas R, Millan-Solsona R, Fumagalli L, Gomila G, (2021). Spatial Resolution and Capacitive Coupling in the Characterization of Nanowire Nanocomposites by Scanning Dielectric Microscopy Microscopy And Microanalysis 27, 1026-1034

Nanowire-based nanocomposite materials are being developed as transparent and flexible electrodes or as stretchable conductors and dielectrics for biosensing. Here, we theoretically investigate the use of scanning dielectric microscopy (SDM) to characterize these materials in a nondestructive way, with a special focus on the achievable spatial resolution and the possibility of detection of the capacitive coupling between nearby nanowires. Numerical calculations with models involving single and multiple buried nanowires have been performed. We demonstrate that the capacitance gradient spread function of a single buried nanowire consists of a modified Lorenzianan with a cubic decay. We show that the achievable spatial resolution can be determined with good accuracy with the help of this spread function. It is shown that, in general, the spatial resolution worsens when any system parameter decreases the maximum of the nanowire spread function or increases its width, or both. Finally, we show that SDM measurements are also sensitive to the capacitive coupling between nearby nanowires. This latter result is of utmost relevance since the macroscopic electric properties of nanowire nanocomposites largely depend on the electric interaction between nearby nanowires. The present results show that SDM can be a valuable nondestructive subsurface characterization technique for nanowire nanocomposite materials.

JTD Keywords: depth, electrodes, nanocomposites, nanowires, sdm, spatial resolution, subsurface, tomography, Capacitive coupling, Force microscopy, Nanocomposites, Nanowires, Sdm, Spatial resolution, Subsurface

Balakrishnan H, Millan-Solsona R, Checa M, Fabregas R, Fumagalli L, Gomila G, (2021). Depth mapping of metallic nanowire polymer nanocomposites by scanning dielectric microscopy Nanoscale 13, 10116-10126

Polymer nanocomposite materials based on metallic nanowires are widely investigated as transparent and flexible electrodes or as stretchable conductors and dielectrics for biosensing. Here we show that Scanning Dielectric Microscopy (SDM) can map the depth distribution of metallic nanowires within the nanocomposites in a non-destructive way. This is achieved by a quantitative analysis of sub-surface electrostatic force microscopy measurements with finite-element numerical calculations. As an application we determined the three-dimensional spatial distribution of ?50 nm diameter silver nanowires in ?100 nm-250 nm thick gelatin films. The characterization is done both under dry ambient conditions, where gelatin shows a relatively low dielectric constant, ?r ? 5, and under humid ambient conditions, where its dielectric constant increases up to ?r ? 14. The present results show that SDM can be a valuable non-destructive subsurface characterization technique for nanowire-based nanocomposite materials, which can contribute to the optimization of these materials for applications in fields such as wearable electronics, solar cell technologies or printable electronics. © The Royal Society of Chemistry.

JTD Keywords: composite, constant, electrodes, mode, nanostructures, objects, progress, subsurface, tomography, Composite materials, Dielectric materials, Electric force microscopy, Electrostatic force, Force microscopy, Low dielectric constants, Nanocomposites, Numerical calculation, Polymer nanocomposite, Printable electronics, Scanning dielectric microscopy, Silver nanowires, Solar cell technology, Stretchable conductors, Subsurface characterizations, Transparent electrodes, Wearable technology

Zeinali R, Del Valle LJ, Torras J, Puiggalí J, (2021). Recent progress on biodegradable tissue engineering scaffolds prepared by thermally-induced phase separation (Tips) International Journal Of Molecular Sciences 22, 3504

Porous biodegradable scaffolds provide a physical substrate for cells allowing them to attach, proliferate and guide the formation of new tissues. A variety of techniques have been developed to fabricate tissue engineering (TE) scaffolds, among them the most relevant is the thermally-induced phase separation (TIPS). This technique has been widely used in recent years to fabricate three-dimensional (3D) TE scaffolds. Low production cost, simple experimental procedure and easy processability together with the capability to produce highly porous scaffolds with controllable architecture justify the popularity of TIPS. This paper provides a general overview of the TIPS methodology applied for the preparation of 3D porous TE scaffolds. The recent advances in the fabrication of porous scaffolds through this technique, in terms of technology and material selection, have been reviewed. In addition, how properties can be effectively modified to serve as ideal substrates for specific target cells has been specifically addressed. Additionally, examples are offered with re-spect to changes of TIPS procedure parameters, the combination of TIPS with other techniques and innovations in polymer or filler selection.

JTD Keywords: biodegradable polymer, composites, morphology, pore structure, porosity, processing parameters, thermally induced phase separation, Biodegradable polymer, Composites, Morphology, Pore structure, Porosity, Processing parameters, Thermally induced phase separation, Tissue engineering scaffold

Majchrowicz, A., Roguska, A., Krawczy, Lewandowska, M., Martí-Muñoz, J., Engel, E., Castano, O., (2020). In vitro evaluation of degradable electrospun polylactic acid/bioactive calcium phosphate ormoglass scaffolds Archives of Civil and Mechanical Engineering 20, (2), 50

Nowadays, the main limitation for clinical application of scaffolds is considered to be an insufficient vascularization of the implanted platforms and healing tissues. In our studies, we proposed a novel PLA-based hybrid platform with aligned and random fibrous internal structure and incorporated calcium phosphate (CaP) ormoglass nanoparticles (0, 10, 20 and 30 wt%) as an off-the-shelf method for obtaining scaffolds with pro-angiogenic properties. Complex morphological and physicochemical evaluation of PLA–CaP ormoglass composites was performed before and after in vitro degradation test in SBF solution to assess their biological potential. The degradation process of PLA–CaP ormoglass composites was accompanied by numerous CaP-based precipitations with extended topography and cauliflower-like shape which may enhance bonding of the material with the bone tissue and accelerate the regenerative process. Random fiber orientation was preferable for CaP compounds deposition upon in vitro degradation. CaP compounds precipitated firstly for randomly oriented composite nonwovens with 20 and 30 wt% addition of ormoglass. Moreover, the preliminary bioactivity test has shown that BSA adsorbed to PLA–CaP ormoglass composites (both aligned and randomly oriented) with 20 and 30 wt% of ormoglass nanoparticles which was not observed for pure PLA scaffolds.

JTD Keywords: Calcium phosphate ormoglass, Composites, Degradation, Electrospinning, PLA

Won, J. E., Mateos-Timoneda, M. A., Castaño, O., Planell, J. A., Seo, S. J., Lee, E. J., Han, C. M., Kim, H. W., (2015). Fibronectin immobilization on to robotic-dispensed nanobioactive glass/polycaprolactone scaffolds for bone tissue engineering Biotechnology Letters , 37, (4), 935-342

Bioactive nanocomposite scaffolds with cell-adhesive surface have excellent bone regeneration capacities. Fibronectin (FN)-immobilized nanobioactive glass (nBG)/polycaprolactone (PCL) (FN-nBG/PCL) scaffolds with an open pore architecture were generated by a robotic-dispensing technique. The surface immobilization level of FN was significantly higher on the nBG/PCL scaffolds than on the PCL scaffolds, mainly due to the incorporated nBG that provided hydrophilic chemical-linking sites. FN-nBG/PCL scaffolds significantly improved cell responses, including initial anchorage and subsequent cell proliferation. Although further in-depth studies on cell differentiation and the in vivo animal responses are required, bioactive nanocomposite scaffolds with cell-favoring surface are considered to provide promising three-dimensional substrate for bone regeneration.

JTD Keywords: Bone scaffolds, Cell response, Fibronectin, Nanobioactive glass, Nanocomposites, Polycaprolactone, Bone, Cell proliferation, Cells, Cytology, Glass, Nanocomposites, Polycaprolactone, Robotics, Bone scaffolds, Bone tissue engineering, Cell response, Fibronectin, Fibronectin immobilizations, Nano bioactive glass, Nanocomposite scaffolds, Three-dimensional substrates, Scaffolds (biology)

Aguirre, A., Gonzalez, A., Navarro, M., Castano, O., Planell, J. A., Engel, E., (2012). Control of microenvironmental cues with a smart biomaterial composite promotes endothelial progenitor cell angiogenesis European Cells & Materials , 24, 90-106

Smart biomaterials play a key role when aiming at successful tissue repair by means of regenerative medicine approaches, and are expected to contain chemical as well as mechanical cues that will guide the regenerative process. Recent advances in the understanding of stem cell biology and mechanosensing have shed new light onto the importance of the local microenvironment in determining cell fate. Herein we report the biological properties of a bioactive, biodegradable calcium phosphate glass/polylactic acid composite biomaterial that promotes bone marrow-derived endothelial progenitor cell (EPC) mobilisation, differentiation and angiogenesis through the creation of a controlled bone healing-like microenvironment. The angiogenic response is triggered by biochemical and mechanical cues provided by the composite, which activate two synergistic cell signalling pathways: a biochemical one mediated by the calcium-sensing receptor and a mechanosensitive one regulated by non-muscle myosin II contraction. Together, these signals promote a synergistic response by activating EPCs-mediated VEGF and VEGFR-2 synthesis, which in turn promote progenitor cell homing, differentiation and tubulogenesis. These findings highlight the importance of controlling microenvironmental cues for stem/progenitor cell tissue engineering and offer exciting new therapeutical opportunities for biomaterialbased vascularisation approaches and clinical applications.

JTD Keywords: Calcium phosphate glass composite, Smart biomaterial, Endothelial progenitor cell, Angiogenesis, Mechanosensing, Calcium-sensing receptor

Serra, T., Navarro, M., Planell, J. A., (2012). Fabrication and characterization of biodegradable composite scaffolds for tissue engineering Innovative Developments in Virtual and Physical Prototyping 5th International Conference on Advanced Research and Rapid Prototyping (ed. Margarida, T., Ferreira, D.), Taylor & Francis (Leiria, Portugal) VR@P, 67-72

In this study, polylactic acid (PLA) and polyethylene glycol (PEG) were combined with soluble CaP glass particles and processed by rapid prototyping to obtain fully biodegradable structures for Tissue Engineering applications. The obtained 3D biodegradable structures were characterized in terms of their architecture and mechanical properties. The scaffold morphology, internal micro-architecture and mechanical properties were evaluated using Scanning Electron Microscopy (SEM), micro-computed tomography (micro-CT) and mechanical testing, respectively. Well defined structures with pore size of 350-400μm (in the axial view), struts width of approximately 70-80μm, and a porosity ranging between 60-65% were obtained. The combination RP and PLA/PEG/CaP glass turned into promising fully degradable, mechanically stable, bioactive and biocompatible composite scaffolds for TE.

JTD Keywords: Axial view, Biodegradable composites, Composite scaffolds, Glass particles, Mechanically stable, Micro architectures, Micro computed tomography (micro-CT), Poly lactic acid, Scaffold morphology, Tissue engineering applications, Well-defined structures, Bioactive glass, Mechanical properties, Mechanical testing, Polyethylene glycols, Polymer blends, Rapid prototyping, Scaffolds (biology), Scanning electron microscopy, Computerized tomography

Castaño, O., Eltohamy, M., Kim, H. W., (2012). Electrospinning technology in tissue regeneration Nanotechnology in Regenerative Medicine - Methods and Protocols (Methods in Molecular Biology) (ed. Navarro, M., Planell, J. A.), Springer (New York, USA) 811, 127-140

Electrospinning is one of the most versatile and effective tools to produce nanostructured fibers in the biomedical science fields. The nanofibrous structure with diameters from tens to hundreds of nanometers largely mimics the native extracellular matrix (ECM) of many tissues. Thus far, a range of compositions including polymers and ceramics and their composites/hybrids have been successfully applied for generating electrospun nanofibers. Different processing tools in electrospinning set-ups and assemblies are currently developed to tune the morphology and properties of nanofibers. Herein, we demonstrate the electrospinning process and the electrospun biomaterials for specific use in tissue regeneration with some examples, involving different material combinations and fiber morphologies.

JTD Keywords: Ceramic, Composites, Electrospinning, Nanofi bers, Nanostructured fi bers, Polymer, Tissue regeneration

Rajzer, I., Castano, O., Engel, E., Planell, J. A., (2010). Injectable and fast resorbable calcium phosphate cement for body-setting bone grafts Journal of Materials Science-Materials in Medicine , 21, (7), 2049-2056

In this work a calcium phosphate (CPC)/polymer blend was developed with the advantage of being moldable and capable of in situ setting to form calcium deficient hydroxyapatite under physiological conditions in an aqueous environment at body temperature. The CPC paste consists in a mix of R cement, glycerol as a liquid phase carrier and a biodegradable hydrogel such as Polyvinyl alcohol, which acts as a binder. Microstructure and mechanical analysis shows that the CPC blend can be used as an injectable implant for low loaded applications and fast adsorption requirements. The storage for commercial distribution was also evaluated and the properties of the materials obtained do not significantly change during storage at -18A degrees C.

JTD Keywords: Clinical-applications, Composites, Regeneration, Behavior, Scaffold, Repair