Bioinspired Nanofeatured Substrates: Suitable Environment for Bone Regeneration.

Bone mimicking coatings provide a complex microenvironment in which material, through its inherent properties (such as nanostructure and composition), affects the commitment of stem cells into bone lineage and the production of bone tissue regulating factors required for bone healing and regeneration. Herein, a bioactive mineral/biopolymer composite made of calcium phosphate/chitosan and hyaluronic acid (CaP-CHI-HA) was elaborated using a versatile simultaneous spray coating of interacting species. The resulting CaP-CHI-HA coating was mainly constituted of bioactive, carbonated and crystalline hydroxyapatite with 277 ± 98 nm of roughness, 1 μm of thickness, and 2.3 ± 1 GPa of stiffness. After five days of culture, CaP-CHI-HA suggested a synergistic effect of intrinsic biophysical features and biopolymers on stem cell mechanobiology and nuclear organization, leading to the expression of an early osteoblast-like phenotype and the production of bone tissue regulating factors such as osteoprotegerin and vascular endothelial growth factor. More interestingly, amalgamation with biopolymers conferred to the mineral a bacterial antiadhesive property. These significant data shed light on the potential regenerative application of CaP-CHI-HA bioinspired coating in providing a suitable environment for stem cell bone regeneration and an ideal strategy to prevent implant-associated infections.journal article2017 Apr 122017 03 30importe

Harnessing Wharton's jelly stem cell differentiation into bone-like nodule on calcium phosphate substrate without osteoinductive factors.

An important aim of bone regenerative medicine is to design biomaterials with controlled chemical and topographical features to guide stem cell fate towards osteoblasts without addition of specific osteogenic factors. Herein, we find that sprayed bioactive and biocompatible calcium phosphate substrates (CaP) with controlled topography induce, in a well-orchestrated manner, Wharton's jelly stem cells (WJ-SCs) differentiation into osteoblastic lineage without any osteogenic supplements. The resulting WJ-SCs commitment exhibits features of native bone, through the formation of three-dimensional bone-like nodule with osteocyte-like cells embedded into a mineralized type I collagen. To our knowledge, these results present the first observation of a whole differentiation process from stem cell to osteocytes-like on a synthetic material. This suggests a great potential of sprayed CaP and WJ-SCs in bone tissue engineering. These unique features may facilitate the transition from bench to bedside and the development of successful engineered bone.Designing materials to direct stem cell fate has a relevant impact on stem cell biology and provides insights facilitating their clinical application in regenerative medicine. Inspired by natural bone compositions, a friendly automated spray-assisted system was used to build calcium phosphate substrate (CaP). Sprayed biomimetic solutions using mild conditions led to the formation of CaP with controlled physical properties, good bioactivity and biocompatibility. Herein, we show that via optimization of physical properties, CaP substrate induce osteogenic differentiation of Wharton's jelly stem cells (WJ-SCs) without adding osteogenic supplement factors. These results suggest a great potential of sprayed CaP and WJ-SCs in bone tissue engineering and may facilitate the transition from bench to beside and the development of clinically successful engineered bone.journal articleresearch support, non-u.s. gov't2017 022016 11 22importe

Heat dissipation measurements in low stress cyclic loading of metallic materials: from internal friction to micro-plasticity

The present paper deals with a procedure to measure the very small quantities of heat generated during the very first cycles of mechanical loading on metallic specimens. A dedicated procedure is presented to reach the required sensitivity in terms of heat sources with some original features with respect to the present state of the art, assuming that the heat sources are uniformly distributed within the specimen as such low strain levels. Then steel (cold rolled and annealed) and aluminium specimens were tested at two different aspect ratios (R?=0.1 and R?=-1). It was shown that for small stress levels, the heat generated was more or less constant with cycle number. This energy was associated to visco-elastic behaviour (internal friction) and it was shown that the same energy could be measured with the two stress ratios when plotted against strain rate (stress amplitude at constant frequency, here 15 Hz). Then, after a certain stress level, an initial outburst of energy was evidenced over about 10–15 cycles before a constant level was reached again. This was associated to micro-plastic adaptation. This procedure provides an advanced tool to tackle the problem of very early fatigue damage detection and is aimed at providing some physical justification to the procedures of rapid fatigue limit detection by self-heating tests.<br/

Dissipated energy measurements as a marker of microstructural evolution: 316L and DP600

The thermomechanical characteristics and, more specifically, the dissipative behavior of two steels (a DP600 and a 316L stainless steel) have been studied using infrared measurement methods. All dissipated energy measurements have been performed during traction–traction uniaxial tests in the elastic domain. It has been shown that the dissipated energy of these materials is dependent on the material plastic strain and could be used as a non-destructive criterion to monitor the material evolution during loading sequences. Different kinds of loading sequences have been tested, including uniaxial tensile tests, alternative traction–traction loadings and recovery periods to underline specific characteristics of the material

Dissipative energy as an indicator of material microstructural evolution

In this study, the material microstructure evolution has been studied thanks to two indicators: the cumulated plastic strain and the energy dissipation due to internal friction under cyclic loading. An experimental procedure has been designed to underline the variations of the dissipative energy due to cold work on a DP600 specimen. The results showed that the dissipative energy increases with the plastic strain and can be used as an indicator of material microstructural evolution

Serum albumin-alginate coated microsphere : role of the inner gel in binding and release of the KRFK peptide

International audienc

Infusion of docosahexaenoic acid protects against myocardial infarction

International audienc