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The combination of poly (vinylidene fluoride) (PVDF) with ionic liquids (ILs) is increasingly being studied for the development of smart materials. Together with the functional response provided by the IL, its incorporation into PVDF allows to nucleate specific electroactive phases of the polymer, depending on the processing conditions. Thus, the isothermal crystallization of PVDF incorporating different contents of the magnetic ionic liquid bis(1-ethyl-3-methylimidazolium) tetrathiocyanatocobaltate ([Emim] 2 [Co(SCN) 4 ]) is reported in this work. Morphological properties of the films were obtained by field emission scanning electronic microscopy (FESEM), and particularly, for the higher contents of IL, segregation was observed through artifacts present on the film surface. This fact has been further confirmed by energy-dispersive x-ray spectroscopy (EDX). The growth of the crystalline phases of PVDF during isothermal crystallization at different temperatures has been analyzed by Fourier transform infrared (FTIR) spectroscopy. Although α, β and γ crystalline phases were present in all samples, their relative percentages varied greatly with the amount of IL present, demonstrating that [Emim] 2 [Co(SCN) 4 ] is a strong inductor of the electroactive (EA) phases of PVDF. By evaluating both FTIR and DSC data, this effect has been ascribed to the higher melting temperatures of the EA structures whose formation is favored at higher crystallization temperatures. The melting temperature (T m) of the β phase is higher than that of the α phase, whereas T m for the γ phase is higher than for α and β phases. Thus, together with the specific functional properties provided by the IL, such as magnetic response and ionic conductivity, the addition of [Emim] 2 [Co(SCN) 4 ] strongly influences PVDF's crystallization kinetics, proving to be a simple and very effective way to nucleate specific phases of PVDF, according also to the specific processing conditions. [Display omitted] • The isothermal crystallization kinetics of PVDF incorporating a magnetic ionic liquid is investigated. • The blends were produced with varying ionic liquid content. • Crystallization kinetics was studied in the temperature range between 128 °C and 160 °C. • Ionic liquid induces nucleation of PVDF in the electroactive β and γ phases. • PVDF crystal growth segregates an amorphous phase rich in IL molecules to the surface of the films. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the viscoelastic properties of a decellularized mesh from the porcine esophagus, prepared by our group, with two commercial acellular tissues derived from porcine small intestine submucosa and bovine pericardium for use in medical devices. The tissues' viscoelastic properties were characterized by creep tests in tension, applying the load in the direction of the fibers or the transverse direction, and also by dynamic-shear mechanical tests between parallel plates or in tension at frequencies between 0.1 and 35 Hz. All the tests were performed in triplicate at a constant temperature of 37 °C immersed in distilled water. The tissues' surface and cross-sectional microstructure were observed by scanning electron microscopy (SEM) to characterize the orientation of the fibers. The matrices of the porcine esophagus present an elastic modulus in the order of 60 MPa when loaded in the longitudinal direction while those of the porcine intestine submucosa and bovine pericardium have an elastic modulus below 5 MPa. Nevertheless, the shear modulus of bovine pericardium nearly triplicates that of the esophageal matrix. The viscoelasticity of decellularized esophageal mucosa is characterized by a fast change in the creep compliance with time. The slope of the creep curve in the double logarithmic plot is twice that of the control samples. These results are consistent with the microstructure observed under electron microscopy regarding the orientation of the fibers that make up the matrices. [ABSTRACT FROM AUTHOR]

• A simple and low-cost method for PFVH/CH microspheres production is presented. • The study with RAW 264.7 showed absence of a cytotoxic response for these materials. • Convincing 3D cell culture was achieved by using Chitosan-based microspheres. • Microspheres are biomimetic 3D environments that can be freely remodeled by MSCs. • Microspheres could be a versatile system for a wide variety of applications. Recent studies have shown the relevance of growing mesenchymal stem cells (MSCs) in three-dimensional environments with respect to the monolayer cell culture on an adherent substrate. In this sense, macroporous scaffolds and hydrogels have been used as three-dimensional (3D) supports. In this work, we explored the culture of MSCs in a 3D environment created by microspheres, prepared with a fumarate-vinyl acetate copolymer and chitosan. In this system, the environment that the cells feel has similarities to that found by the cells encapsulated in a hydrogel, but the cells have the ability to reorganize their environment since the microspheres are mobile. We evaluated their biocompatibility in vitro using RAW 264.7 macrophages and bone marrow mesenchymal stem cells (BMSCs). The results with RAW 264.7 cells showed good cell viability, without evident signs of cytotoxicity. BMSCs not only proliferate, but also rearrange to grow in clusters, thus highlighting the advantages of microspheres as 3D environments. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the effect of platelet factors on the differentiation of mesenchymal stem cells (MSCs) to hyaline cartilage chondrocytes in a three-dimensional environment. MSCs were cultured in a microgel environment with a chondrogenic medium. The microgel consisted of microspheres that combine gelatin and platelet-rich plasma (PRP). The gelatin/PRP microdroplets were produced by emulsion. The gelatin containing the microdroplets was enzymatically gelled, retaining PRP and, just before seeding the cells, platelets were activated by adding calcium chloride so that platelet growth factors were released into the culture media but not before. Platelet activation was analyzed before activation to rule out the possibility that the gelatin cross-linking process itself activated the platelets. The gene expression of characteristic chondrogenic markers and miRNA expression were analyzed in cells cultured in a differentiation medium and significant differences were found between gelation/PRP microgels and those containing only pure gelatin. In summary, the gelatin microspheres effectively encapsulated platelets that secreted and released factors that significantly contributed to cellular chondrogenic differentiation. At the same time, the microgel constituted a 3D medium that provided the cells with adherent surfaces and the possibility of three-dimensional cell–cell contact. [ABSTRACT FROM AUTHOR]

Articular chondrocytes are difficult to grow, as they lose their characteristic phenotype following expansion on standard tissue culture plates. Here, we show that culturing them on surfaces of poly(L-lactic acid) of well-defined microtopography allows expansion and maintenance of characteristic chondrogenic markers. We investigated the dynamics of human chondrocyte dedifferentiation on the different poly(L-lactic acid) microtopographies by the expression of collagen type I, collagen type II and aggrecan at different culture times. When seeded on poly(L-lactic acid), chondrocytes maintained their characteristic hyaline phenotype up to 7days, which allowed to expand the initial cell population approximately six times without cell dedifferentiation. Maintenance of cell phenotype was afterwards correlated to cell adhesion on the different substrates. Chondrocytes adhesion occurs via the α5β1 integrin on poly(L-lactic acid), suggesting cell– fibronectin interactions. However, α2β1 integrin is mainly expressed on the control substrate after 1 day of culture, and the characteristic chondrocytic markers are lost (collagen type II expression is overcome by the synthesis of collagen type I). Expanding chondrocytes on poly(L-lactic acid) might be an effective solution to prevent dedifferentiation and improving the number of cells needed for autologous chondrocyte transplantation. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop micro- or macro-porous substrates of poly(L-lactic acid) (PLLA) for the sustained release of water-soluble proteins. A model protein, bovine serum albumin (BSA), was incorporated into the hydrophobous PLLA matrix by emulsifying an aqueous BSA solution into an organic PLLA solution. The work focused on the effect of the fabrication procedure on substrates' microstructure and protein delivery kinetics. The films were prepared by solvent casting or freeze-extraction, after which the protein release profiles from both matrices were compared. A homogeneous distribution of BSA in the PLLA-films and membranes was obtained. In vitro release of the protein from the freeze-extraction membranes was more significant than the release from the solvent cast films. BSA was found to be released from the freeze-extraction membranes in two stages: an initial fast release followed by a sustained release. The release from the solvent cast films was more moderated and accompanied by the polymer degradation. These materials can find applications in wound healing by local delivery of proteins known to have a positive effect on the regeneration of basal lamina. They can also be used to produce macroporous scaffolds able to deliver growth factors during bone or cartilage regeneration. [ABSTRACT FROM AUTHOR]

The aim of this study is to explore, with an in vivo model, the regeneration of articular cartilage that can be obtained with a strategy that combines the stimulation of the subchondral bone with the implantation of a biomimetic microgel at the site of the cartilage defect. The microgel consists of an agglomerate of two types of microspheres: ones rigid, made of a biodegradable polyester, and the other ones composed of a polymeric network of gelatin and hyaluronic acid that encapsulate platelet-rich plasma (PRP) obtained from circulating autologous blood. A defect of 7 mm in diameter and full depth was performed in the in the articular cartilage at the trochlea of the animal knee, using a minipig model. Microdrilling was performed in the underlying bone and the defect was filled with the microgel in which the platelets it contains were previously activated with calcium chloride. The whole defect containing the microgel was covered with a synthetic membrane to avoid the release of microspheres. The results of the in vivo follow-up of the experiment, the histological analysis and the mechanical measurements of the regenerated tissue 9 months after implantation were compared with those of a group of animals in which only microdrilling was performed and the defect was covered with the membrane and with another group in which a clinical use commercial collagen mesh was implanted. The mean value of the elastic modulus of the newly formed tissue was not significantly different from that of the native tissue in the case of microgel implantation while its content of GAGs, was significantly better than in the other groups. [Display omitted] • Significant improvement of the cartilage regeneration with a microgel. • Combination of rigid synthetic microspheres and others made with biomolecules. • Microgel allows MSCs to invade the defect site and can move during regeneration. • Platelet rich plasma as a source of biochemical cues. • Microdrilling + implant of biomimetic microgel preserves subcondral plate. [ABSTRACT FROM AUTHOR]

Abstract: The thermodynamical properties of water and polymer in a hydrogel are analyzed from experimental equilibrium sorption isotherms at different temperatures in the case of poly(2-hydroxyethyl acrylate). The equations of the thermodynamics of mixtures allow to calculate the specific partial thermodynamical properties of water and polymer in the hydrogel as a function of its water content. Partial volume of water in the gel at low activities is slightly lower than the specific volume of water in the liquid state. The partial enthalpy and entropy differ significantly from those of pure water at the lowest water contents, and tend to those of pure water for activities close to one. The mutual interaction between the gel''s components is discussed through the residual part of the mixing free energy. This function is positive for all gel compositions, suggesting that, on the average, the water–polymer interactions are not stronger than the water–water or polymer–polymer interactions, and that the affinity of water to mix homogeneously with the polymer has a combinatorial origin. The composition dependence of the Flory–Huggins interaction parameter is calculated and explained in terms on the residual free energy. This parameter is compared with the apparent interaction parameter, obtained fitting point by point the experimental sorption isotherm to the Flory–Huggins isotherm. The difference often found between the sorption capacity of an hydrogel when equilibrated in saturated water vapour and in liquid water is discussed. [Copyright &y& Elsevier]

The thermal transitions observed in hydrogels are frequently explained by invoking the existence of different kinds of water such as ‘bound’ and ‘free’ water. However these interpretations are intuitive and do not consider neither the thermodynamics of phase equilibrium nor kinetic aspects. Alternatively, the complicated experimental DSC thermograms have been simply explained in a thermodynamic framework with the help of a transitions diagram where the temperature of the transitions is plotted versus water concentration in the gel. In this work we further support the interpretation of the DSC thermograms on the basis of this diagram by comparing those thermograms with TMA results. The volume changes in the cooling and heating scans can be correlated with the enthalpy changes in the material and can be explained with the transition diagram. [Copyright &y& Elsevier]

In hematological malignancies, leukemias or myelomas, malignant cells present bone marrow (BM) homing, in which the niche contributes to tumor development and drug resistance. BM architecture, cellular and molecular composition and interactions define differential microenvironments that govern cell fate under physiological and pathological conditions and serve as a reference for the native biological landscape to be replicated in engineered platforms attempting to reproduce blood cancer behavior. This review summarizes the different models used to efficiently reproduce certain aspects of BM in vitro; however, they still lack the complexity of this tissue, which is relevant for fundamental aspects such as drug resistance development in multiple myeloma. Extracellular matrix composition, material topography, vascularization, cellular composition or stemness vs. differentiation balance are discussed as variables that could be rationally defined in tissue engineering approaches for achieving more relevant in vitro models. Fully humanized platforms closely resembling natural interactions still remain challenging and the question of to what extent accurate tissue complexity reproduction is essential to reliably predict drug responses is controversial. However, the contributions of these approaches to the fundamental knowledge of non-solid tumor biology, its regulation by niches, and the advance of personalized medicine are unquestionable. [ABSTRACT FROM AUTHOR]

• Freeze-extraction produces electroactive PVDF membranes without skin effects. • Polymer concentration of the starting dissolution modulates membrane porosity. • Substrate porosity affects mesenchymal stem cell adhesion and proliferation. • Cells adhere better to porous membranes but prefers less porous supports to proliferate. Poly(vinylidene fluoride) (PVDF) is a semicrystalline polymer with four crystalline phases, of which the all trans conformation (β-phase) is the one with the largest piezoelectric response and best electroactive properties. This smart material is able to reproduce physiological events such as inherent bone piezoelectricity, making it a perfect candidate to drive the osteogenic differentiation of mesenchymal stem cells (MSCs) towards the osteogenic lineage. The influence of topography on the adhesion, proliferation and maintenance of multipotency of this type of cell is well established and has confirmed that the production of variable porosity substrates is a suitable approach for cell therapy. In this work, novel PVDF microporous membranes in the β-phase were developed by the freeze-extraction technique. Several concentrations of PVDF in N,N-dimethylformamide (10, 15 and 20% w/v) were used to obtain membranes with different grades of porosity in the range of 80–84%. The cell culture supports thus produced were found to possess good crystallinity (66%), β-phase presence (94%) and a microstructure based on spherulite agglomerations with a diameter of spherulite in the order of 1 μm that is higher as the polymer concentration increases. The membranes have good mechanical properties and the storage modulus, with values between 5 and 47 MPa, rises with the polymer content of the starting solution. Porcine bone marrow mesenchymal stem cells (pBM-MSCs) were used to study cell adhesion and proliferation. Regarding cell adhesion at 24 h, the cells preferred the more porous structures and had round focal adhesions with well-developed cytoskeletons, while they had a round morphology on the less porous membranes. The cells preferred the less porous membranes to proliferate, even though the initial morphology at 24 h showed poor adhesion. These findings confirm that the controlled microporosity of β-phase PVDF membranes can be produced by freeze extraction and offer the possibility of modifying the adhesion and proliferation of pBM-MSCs on these substrates. [ABSTRACT FROM AUTHOR]

• Microspheres are flexible biomimetic 3D environments that can be freely remodeled by cells. • Microspheres are a versatile system for a wide variety of cellular analyses. • Cells grown in the microspheres have good proliferation rates. • Cells form aggregates and surround the fibronectin coated microspheres. • Hyaluronic acid coating triggers cell proliferation but hinders cell adhesion. Stem cells reside in niches, specialized microenvironments that sustain and regulate their fate. Extracellular matrix (ECM), paracrine factors or other cells are key niche regulating elements. As the conventional 2D cell culture lacks these elements, it can alter the properties of naïve stem cells. In this work we designed a novel biomimetic microenvironment for cell culture, consisting of magnetic microspheres, prepared with acrylates and acrylic acid copolymers and functionalized with fibronectin or hyaluronic acid as ECM coatings. To characterize cell proliferation and adhesion, porcine mesenchymal stem cells (MSCs) were grown with the different microspheres. The results showed that the 3D environments presented similar proliferation to the 2D culture and that fibronectin allows cell adhesion, while hyaluronic acid hinders it. In the 3D environments, cells reorganize the microspheres to grow in aggregates, highlighting the advantages of microspheres as 3D environments and allowing the cells to adapt the environment to their requirements. [ABSTRACT FROM AUTHOR]

Abstract: Dynamics of multilayer adsorption of macromolecules with different degree of polymerization is studied by coarse‐grained Monte Carlo simulations, focusing on both the interface macromolecule‐surface and chain–chain interaction in and out of equilibrium conditions. The interfacial interaction between the solid flat surface and the macromolecules is modeled by means of a Lennard–Jones potential, and inter‐ and intrachain interactions are simulated using bond angle, bond length, and Lennard–Jones potentials. The results show that local and conformational motions near the glass transition temperature promote configurations with minimal energy, which induce better space efficiency and favor aligned conformations at the interface. In this context, it is also found that restriction of movement, together with the connectivity effect exerted by the partially adsorbed segments, leads to a range of chain lengths that maximizes the molecular groups adsorbed. [ABSTRACT FROM AUTHOR]

Titanium and its alloys are widely used in medical implants because of their excellent properties. However, bacterial infection is a frequent cause of titanium-based implant failure and also compromises its osseointegration. In this study, we report a new simple method of providing titanium surfaces with antibacterial properties by alternating antibacterial chitosan domains with titanium domains in the micrometric scale. Surface microgrooves were etched on pure titanium disks at intervals of 60 μm using a modified 3D printer and were then coated with chitosan antibacterial polysaccharide. The dimensions of the patterned microgrooves made it possible to fix the chitosan domains to the titanium substrate without the need for covalent bonding. These domains were stable after 5 days of immersion in water and reduced the surface contact angle. Preliminary cell adhesion assays demonstrated that MC3T3-E1 pre-osteoblasts preferentially adhered to the titanium regions, while C2C12 myoblasts were uniformly distributed over the whole surface. [ABSTRACT FROM AUTHOR]

The polymer α relaxation process for net-PEA gels swollen with nonpolar p-xylene is studied by employing dielectric relaxation spectroscopy. The results present the in situ monitoring of the dielectric behavior of α relaxation process under p-xylene cold crystallization, isothermal crystallization as well as crystallization from quenching. For the partially crystallized systems, the results exhibit that the amount of p-xylene crystal phase has no remarkable effects on the time scale, being controlled mainly by the amount of the noncrystallized p-xylene (cpx= 0.11-0.15) gel phase. Surprisingly, the stretching exponent βKWW obtains higher values in the isothermal crystallization process as the p-xylene crystallization is in progress and the reorganization of p-xylene through diffusion to crystallites approaches thermodynamic equilibrium. This directly indicates that any α process broadening is originated not solely from the amount of p-xylene crystallites and the induced heterogeneities, but from the presence of remarkable concentration fluctuations close to respective effective glass transition temperature, enhanced for higher solvent contents as well. Finally, the results suggest that the existence of p-xylene crystallites decrease significantly the dielectric strength of α process. The effective medium theory is applied to check whether this recorded reduction originates from the induced spatial heterogeneities (p-xylene crystallites) or from the immobilization in parts of polymer configurations. [ABSTRACT FROM AUTHOR]

Poly(ethyl acrylate) (PEA) induces the formation of biomimetic fibronectin (FN) (nano)networks upon simple adsorption from solutions, a process referred to as material-driven FN fibrillogenesis . The ability of PEA to organize FN has been demonstrated in 2D and 2.5D environments, but not as yet in 3D scaffolds, which incorporate three-dimensionality and chemical crosslinkers that may influence its fibrillogenic potential. In this paper we show for the first time that while three-dimensionality does not interfere with PEA-induced FN fibrillogenesis, crosslinking does, and we determined the maximum amount of crosslinker that can be added to PEA to maintain FN fibrillogenesis. For this, we synthesised 2D substrates with different amounts of crosslinker (1–10% of ethylene glycol dimethacrylate) and studied the role of crosslinking in FN organization using AFM. The glass transition temperature was seen to increase with crosslinking density and, accordingly, polymer segmental mobility was reduced. The organization of FN after adsorption (formation of FN fibrils) and the availability of the FN cell-binding domain were found to be dependent on crosslinking density. Surface mobility was identified as a key parameter for FN supramolecular o r ganization. PEA networks with up to 2% crosslinker organize the FN in a similar way to non-crosslinked PEA. Scaffolds prepared with 2% crosslinker also had FN (nano)networks assembled on their walls, showing PEA’s ability to induce FN fibrillogenesis in 3D environments as long as the amounts of crosslinker is low enough. [ABSTRACT FROM AUTHOR]

The aim of this study is to show that introducing a small fraction of hydrophilic groups into a hydrophobic polyester favor the macrophage activity by accelerating the degradation action in aqueous media. It is also seen that differentiation of MSCs cultured in monolayer towards bone in specific differentiation media is favored in these materials with respect to the corresponding pristine polyesters. Polymer networks based in polycarpolactone or poly( l -lactide) and containing a small fraction of poly(hydroxyethyl acrylate) have been synthesized. Degradation kinetics in vitro was monitored by mass loss and swelling capacity of the polymer network in good solvents, the later as representative of chain cleavage. Hydrolytic and enzymatic degradation is accelerated by the inclusion of poly(hydroxyethyl acrylate) blocks in the network. Macrophages were cultured on the surface of the network films, showing its capacity to erode the material surface but also to accelerate bulk degradation. Bone marrow mesenchymal stem cells were cultured in monolayer on the membranes in osteogenic media, showing an increase of specific markers expression in comparison to pristine polyesters. [ABSTRACT FROM AUTHOR]

ABSTRACT Polymer blend membranes have been obtained consisting of a hydrophilic and a hydrophobic polymers distributed in co-continuous phases. In order to obtain stable membranes in aqueous environments, the hydrophilic phase is formed by a poly(hydrohyethyl acrylate), PHEA, network while the hydrophobic phase is formed by poly(vinylidene fluoride- co-trifluoroethylene) P(VDF-TrFE). To obtain the composites, in a first stage, P(VDF-TrFE) is blended with poly(ethylene oxyde) (PEO), the latter used as sacrificial porogen. P(VDF-TrFE)/PEO blend membranes were prepared by solvent casting at 70°C followed by cooling to room temperature. Then PEO is removed from the membrane by immersion in water obtaining a P(VDF-TrFE) porous membrane. After removing of the PEO polymer, a P(VDF-TrFE) membrane results in which pores are collapsed. Nevertheless the pores reopen when a mixture of hydroxethyl acrylate (HEA) monomer, ethyleneglycol dimethacrylate (as crosslinker) and ethanol (as diluent) is absorbed in the membrane and subsequent polymerization yields hybrid hydrophilic/hydrophobic membranes with controlled porosity. The membranes are thus suitable for lithium-ion battery separator membranes and/or biostable supports for cell culture in biomedical applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 672-679 [ABSTRACT FROM AUTHOR]

ABSTRACT Novel biomaterials are needed for bone tissue repair with improved mechanical performance compared to classical bioceramics. The objective of this work was to characterize a hybrid filler material, which is capable to coat as a thin film porous scaffolds improving their mechanical properties for bone tissue engineering. The hybrid filler material is a blend of chitosan and silica network formed through in situ sol-gel using tetraethylortosilicate and 3-glycidoxypropyltrimethoxysilane (GPTMS) as silica precursors. The hypothesis was that the epoxy ring of GPTMS could react with the amino groups of chitosan in acidic media while it is also reacting the siloxane groups of hydrolyzed silica precursors. The formation of the hybrid organic-inorganic network was assessed by different physical techniques revealing changes in molecular mobility and hydrophilicity upon chemical reaction. Finally, the cytotoxicity of the samples was also evaluated by MTT assay. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1391-1400 [ABSTRACT FROM AUTHOR]

A hydrogel based on interpenetrating polymer networks (IPNs) has been designed to act as a platform in an articular cartilage bioreactor for theex vivotest of scaffolds, simulating the host tissue. Poly(2-hydroxyethyl acrylate) (PHEA) has been mechanically reinforced by its interpenetration with poly(ethyl acrylate). The resulting IPNs are phase separated systems with a porosity that increases with the amount of PHEA. Compression Young's modulus decreases and permeability increases when increasing the PHEA content in the samples, being the IPN with a 79% of PHEA the best candidate to mimic articular cartilage. [ABSTRACT FROM PUBLISHER]

Chitosan-silica porous hybrids were prepared by a novel strategy in order to improve the mechanical properties of chitosan (CHT) in the hydrogel state. The inorganic silica phase was introduced by sol-gel reactions in acidic medium inside the pores of already prepared porous scaffolds. In order to make the scaffolds insoluble in acidic media chitosan was cross-linked by genipin (GEN) with an optimum GEN concentration of 3.2 wt.%. Sol-gel reactions took place with Tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) acting as silica precursors. GPTMS served also as a coupling agent between the free amino groups of chitosan and the silica network. The morphology study of the composite revealed that the silica phase appears as a layer covering the chitosan membrane pore walls. The mechanical properties of the hybrids were characterized by means of compressive stress-strain measurements. By immersion in water the hybrids exhibit an increase in elastic modulus up to two orders of magnitude. [ABSTRACT FROM AUTHOR]

Hybrid porous membranes of polycaprolactone (PCL) and silica were obtained by a two stage procedure. First a porous PCL membrane was produced by freeze extraction technique and then a sol-gel reaction was used to form a uniform silica coating on the pore walls. Sol-gel reaction was performed at low pH with tetraethylorthosilicate (TEOS) as the precursor of silica. In this work we analyze the influence of several clue parameters on the silica film formation and in turn on the properties of the hybrid material. Water:TEOS molar ratio and drying protocol were considered in this study. [ABSTRACT FROM AUTHOR]

Purpose: Due to the attractive properties of poly(L-lactic acid) (PLLA) for tissue engineering, the aim was to determine the growth and differentiation capacity of mesenchymal stromal cells (MSCs) in PLLA scaffolds and their potential use in the treatment of cartilage diseases.Methods: MSCs were cultured in PLLA films and thin porous membranes to study adherence and proliferation. Permeability and porosity were determined for the different scaffolds employed. The optimal conditions for cell seeding were first determined, as well as cell density and distribution inside the PLLA. Scaffolds were then maintained in expansion or chondrogenic differentiation media for 21 days. Apoptosis, proliferation and chondrogenic differentiation was assessed after 21 days in culture by immunohistochemistry. Mechanical characteristics of scaffolds were determined before and after cell seeding.Results: MSCs uniformly adhered to PLLA films as well as to porous membranes. Proliferation was detected only in monolayers of pure PLLA, but was no longer detected after 10 days. Mechanical characterization of PLLA scaffolds showed differences in the apparent compression elastic modulus for the two sizes used. After determining high efficiencies of seeding, the production of extracellular matrix (ECM) was determined and contained aggrecan and collagens type I and X. ECM produced by the cells induced a twofold increase in the apparent elastic modulus of the composite.Conclusions: Biocompatible PLLA scaffolds have been developed that can be efficiently loaded with MSCs. The scaffold supports chondrogenic differentiation and ECM deposition that improves the mechanics of the scaffold. Although this improvement does not met the expectations of a hyaline-like cartilage ECM, in part due to the lack of a mechanical stimulation, their potential use in the treatment of cartilage pathologies encourages to improve the mechanical component. [ABSTRACT FROM AUTHOR]

Abstract: Polycaprolactone (PCL) and chitosan (CHT) are immiscible polymers. However, biodegradable porous scaffolds of both polymers were obtained by combining different techniques based on the synthesis of semi-interpenetrating polymer networks (SemiIPNs) and melt processing. SemiIPNs were prepared through simultaneous precipitation of the polymer blend (PCL/CHT) and subsequent crosslinking of chitosan with tripolyphosphate (weight fractions of CHT up to 30wt.%). High porosity PCL/CHT scaffolds with open pore structure and good interconnectivity were obtained. Mechanical properties, evaluated by dynamic-mechanical analysis, decrease as porosity increases. The physical interactions between functional groups of CHT and carbonyl groups of PCL were assessed by FTIR, the shifting of the main relaxation of PCL towards high temperatures as the fraction of CHT increases as well as the evolution of the thermal properties of the system. [Copyright &y& Elsevier]

Abstract: The conformational changes in poly(ethyl acrylate-co-hydroxyethyl acrylate), P(EA-co-HEA) chains, which constitute a copolymer network hydrogel, induced by the presence of water are investigated by different experimental techniques and compared with the behaviour of the corresponding xerogel. The mechanical relaxation spectrum shows the presence of a new water-induced relaxation, the water content dependence of the glass transition is measured by DSC, and the dielectric relaxation assesses the effect of water for the lower concentrations. Hydrophilic and hydrophobic monomeric units in the P(EA-co-HEA) network are able to aggregate to form two separated (nano)phases in the presence of water due to hydrophobic interaction. Phase separation takes place when the water content of the sample is higher than a critical value estimated as two water molecules per –OH group in the copolymer chain. The existence of the hydrophobic domains is detected by their glass transition being nearly independent on the water content of the sample. Phase separation is also clearly revealed by phase angle measurements in AFM experiments. [Copyright &y& Elsevier]

Abstract: A series of polymer and copolymer networks with varying hydrophilicity and distribution of the hydrophilic groups was synthesized and biologically tested with monolayer culture of human chondrocytes in vitro. Cell viability (MTT), proliferation (BrdU incorporation) and aggrecan expression (PG ELISA) were quantified at 7 and 14 days from seeding. Both assays (MTT and BrdU) showed complementary results that are consistent with positive cellular adhesion on the material. When human chondrocytes were cultured on polymer substrates in which the hydrophilic groups were homogeneously distributed, hydrophobic substrates showed higher values in all the biological parameters analysed. Adhesion, proliferation and viability decreased monotonously with the content of hydrophilic groups in the polymer chain. However poly(ethyl acrylate-co-hydroxyethyl methacrylate) copolymers, in which hydrophilic and hydrophobic nano-domains alternate as phase-separated domains, showed better results than the corresponding homopolymers. [Copyright &y& Elsevier]

The development of three-dimensional environments to mimic the in vivo cellular response is a problem in the building of disease models. This study aimed to synthesize and validate three-dimensional support for culturing monoclonal plasma cells (mPCs) as a disease model for multiple myeloma. The three-dimensional environment is a biomimetic microgel formed by alginate microspheres and produced on a microfluidic device whose surface has been functionalized by a layer-by-layer process with components of the bone marrow's extracellular matrix, which will interact with mPC. As a proof of concept, RPMI 8226 cell line cells were cultured in our 3D culture platform. We proved that hyaluronic acid significantly increased cell proliferation and corroborated its role in inducing resistance to dexamethasone. Despite collagen type I having no effect on proliferation, it generated significant resistance to dexamethasone. Additionally, it was evidenced that both biomolecules were unable to induce resistance to bortezomib. These results validate the functionalized microgels as a 3D culture system that emulates the interaction between tumoral cells and the bone marrow extracellular matrix. This 3D environment could be a valuable culture system to test antitumoral drugs efficiency in multiple myeloma. [ABSTRACT FROM AUTHOR]

• Non-solvent induced phase separation can produce γ-phase porous PVDF membranes. • Elastin-like recombinamers were modified to contain RGD bioactive sequences. • ELRs were deposited on the membranes by layer-by-layer applying click crosslinking. • ELRs coating enhances initial adhesion of MSCs compared to fibronectin adsorption. Bone's inherent piezoelectricity is a key factor in regulating bone growth and mesenchymal stem cells (MSCs) fate towards the osteogenic lineage. The piezoelectric polymer poly(vinylidene) fluoride (PVDF) was thus used to manufacture electroactive membranes by means of non-solvent induced phase separation (NIPS), producing porous membranes with approximately 90% of γ-phase for MSCs culture. The combination of the porous surface and PVDF hydrophobicity hinders cell adhesion and requires a coating to improve cell culture conditions. A layer-by-layer (LbL) method was used to deposit elastin-like recombinamers (ELRs) containing RGD sequences applying click cross-linking chemistry. ELRs potential was confirmed by comparing traditional fibronectin adsorption with ELRs LbL on PVDF electroactive membranes. Porcine bone marrow MSCs preferred ELRs-coated surfaces, which enhanced initial cell adhesion and improved proliferation after 7 days. These findings lead to new possibilities for regenerative therapies in the area of bone tissue engineering, offering the advantages of MSC commitment towards the osteogenic lineage by applying electro-mechanical stimulation on electroactive substrates. [ABSTRACT FROM AUTHOR]

A model for the heterogeneity of local dynamics in polymer and other glass-forming materials is provided here. The fundamental characteristics of the glass transition phenomenology emerge when simulating a condensed matter open cluster that has a strong interaction with its heterogeneous environment. General glass transition features, such as non-exponential structural relaxations, the slowing down of relaxation times with temperature and specific off-equilibrium glassy dynamics can be reproduced by non-Markovian dynamics simulations with the minimum computer resources. Non-Markovian models are shown to be useful tools for obtaining insights into the complex dynamics involved in the glass transition phenomenon, including whether or not there is a need for a growing correlation length or the relationship between the non-exponentiality of structural relaxations and dynamic heterogeneity. [ABSTRACT FROM AUTHOR]

• Membranes made of chitosan-PLGA block copolymer networks that degrade by hydrolysis in 8 weeks. • Membranes that behave as hydrogels in spite of high PLGA content. • The HPUC1 used in combination with bone marrow mononucleated cells are efficient in wound healing in a diabetic rat model. Foot ulcers, a common complication of diabetes, can cause physical incapacity and are derived from several factors, including poor wound healing. New therapeutic strategies are needed to minimize this complication for the sake of patients' health. We therefore developed a new chitosan- polyurethane hydrogel membrane (HPUC) and the test results confirmed that HPUC present low cytotoxicity and improved wound healing when used with mononuclear bone marrow fraction cells in the diabetic rat model. The biodegradable hydrogels were produced in block copolymer networks with a combination of chitosan blocks and biodegradable polyurethane. The membranes were characterized by FTIR, 13C-NMR and thermogravimetry. Swelling and hydrolytic degradation were also evaluated. The non-solubility of the membranes in good solvents and the chemical characterization confirmed that the network structure was formed between the PU and the chitosan through urea/urethane bonds. The findings confirm that the HPUC have interesting properties that make them suitable for wound healing applications. [ABSTRACT FROM AUTHOR]