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Stimuli responsive materials are found in a broad range of applications, from energy harvesters to biomolecular sensors. Here, we report the production of poly (L-lactic acid) (PLLA) thin films that exhibit a mechanical stress responsive behaviour. By simply applying a mechanical stress through an AFM tip, a local electrical polarization was generated and measured by Kelvin Probe Force Microscopy. We showed that the magnitude of the stress generated electrical polarization can be manipulated by varying the thickness or crystallization state of the PLLA thin films. Besides exhibiting a mechanical stress-response behaviour with potential for energy harvesting and sensor applications, we show by AFM that these platforms react to mechanical forces with physiological relevance: interaction forces as low as a cell sheet migrating over a substrate or larger ones as the fluid induced stresses in bone tissue. In living tissues, as most mechanical stimuli are transduced as strain gradients for the anatomical structures, these mechanically responsive substrates can be used as ex vivo platforms to study the protein and cells response over a large range of electrical stimuli amplitude. As a proof of concept, selective adsorption of a human fibronectin was demonstrated by local patterning of the stimuli responsive PLLA films. Bioelectricity is inherent to the formation and repair of living tissues and electrical stimulation has been recognized for promoting regeneration. Given the proven beneficial effects of electric fields and the absence of a suitable method of stimulation, there is a clinical need for smart substrates, which can generate a polarization (charges) to promote tissue regeneration without the need of external devices. In this work, we report the fabrication of poly(L-lactic) acid platforms that exhibit a mechanical stress responsive behaviour when subjected to physiologically relevant forces. This behaviour can be tailored by varying the thickness or crystallization state of the PLLA films. We further demonstrate the biofunctionality of such platforms by exploiting the mechanically-induced charge for adhesion protein adsorption. [Display omitted] [ABSTRACT FROM AUTHOR]

Tissue engineering is evolving towards the production of smart platforms exhibiting stimulatory cues to guide tissue regeneration. This work explores the benefits of electrical polarization to produce more efficient neural tissue engineering platforms. Poly ( l -lactic) acid (PLLA)-based scaffolds were prepared as solvent cast films and electrospun aligned nanofibers, and electrically polarized by an in-lab built corona poling device. The characterization of the platforms by thermally stimulated depolarization currents reveals a polarization of 60 × 10 −10 C cm −2 that is stable on poled electrospun nanofibers for up to 6 months. Further in vitro studies using neuroblastoma cells reveals that platforms’ polarization potentiates Retinoic Acid-induced neuronal differentiation. Additionally, in differentiating embryonic cortical neurons, poled aligned nanofibers further increased neurite outgrowth by 30% (+70 μm) over non-poled aligned nanofibers, and by 50% (+100 μm) over control conditions. Therefore, the synergy of topographical cues and electrical polarization of poled aligned nanofibers places them as promising biocompatible and bioactive platforms for neural tissue regeneration. Given their long lasting induced polarization, these PLLA poled nanofibrous scaffolds can be envisaged as therapeutic devices of long shelf life for neural repair applications. [ABSTRACT FROM AUTHOR]

Abstract: The use of functional materials, such as ferroelectrics, as platforms for tissue growth in situ or ex situ, is new and holds great promise. But the usage of materials in any bioapplication requires information on biocompatibility and desirably on bioactive behavior when bone tissue engineering is envisaged. Both requirements are currently unknown for many ferroelectrics. Herein the bioactivity of LiNbO3 and LiTaO3 is reported. The formation of apatite-like structures on the surface of LiNbO3 and LiTaO3 powders after immersion in simulated body fluid (SBF) for different soaking periods indicates their bioactive potential. The mechanism of apatite formation is suggested. In addition, the significant release of lithium ions from the ferroelectric powders in the very first minutes of soaking in SBF is examined and ways to overcome this likely hurdle addressed. [Copyright &y& Elsevier]

The implementation of processed magnetic materials onto thermoplastics can be an approach for practical use of brittle intermetallic materials on device development with the advantage of enlarging the range of applications. In this paper, we present the evaluation on the effect of blending magnetocaloric Gd 5 Si 2.4 Ge 1.6 3.4 μm particles with in different weight fractions onto a flexible, transparent and non-magnetic poly(methyl methacrylate) (PMMA). A close to homogeneous grain distribution along the polymer surface were achieved by using a simple solvent casting method for their magnetocaloric properties studies. From XRD analysis, it was found a unit cell volume shrinkage by increasing the powder concentration followed by a reduction on the amount of secondary monoclinic phase as a result of interfacial interactions. As a consequence, a weakening of secondary phases effect on the composite magnetocaloric behavior is observed as a result of the effective hydrostatic pressure from the difference between thermal expansions of matrix and filler. Unlabelled Image • Particle size reduction of Gd 5 Si 2.4 Ge 1.6 bulk to 3.4 μm increases the detection on the amount of distorted monoclinic phase. • The solvent casting technique allows a close to homogeneous dispersion of the micropowder along the composite volume. • Inclusion of the micropowder into the thermoplastic converts the monoclinic phase into an orthorhombic-I phase. • PMMA matrix works as a pressure cell for the micropowder leading to a reduction on the magnetocaloric response of the monoclinic phase. [ABSTRACT FROM AUTHOR]