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Blends of polycaprolactone (PCL) and chitosan (CHT) were prepared by casting from the mixture of solutions of both components in suitable solvents. PCL, and CHT, form phase separated blends with improved mechanical properties and increased water sorption ability with respect to pure PCL. The morphology of the system was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and confocal microscopy. Dispersed domains of CHT in the semicrystalline PCL matrix were found in samples with less than 20% CHT but cocontinuous phase morphologies are found in blends with 20% or more CHT. This feature was corroborated by the temperature dependence of the elastic modulus measured by dynamic mechanical properties as a function of temperature. It was observed that for those blends above 20 wt% CHT, the mechanical stability of the system was kept even after melting of the PCL phase. Primary human chondrocytes were cultured on the different substrates. Cell morphology was studied by SEM and the viability and proliferation was investigated by the colorimetric MTT assay. Different protein conformations were found by AFM on CHT and PCL samples which were related to the biological performance of the substrates. Hydrophilicty of the material is not directly related to the biological response and the sample with 20 wt% CHT shows better results than the other blends with respect to chondrocyte viability and proliferation. However, the results obtained in the blends are worse than in pure PCL. It seems to be correlated with the surface energy of the different blends rather than hydrophilicity. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [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]

• 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]

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]