Direct synthesis of graphitic mesoporous carbon from green phenolic resins exposed to subsequent UV and IR laser irradiations

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Biomimetic nanocrystalline apatite coatings synthesized by Matrix Assisted Pulsed Laser Evaporation for medical applications

tWe report the deposition by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique of biomimeticnanocrystalline apatite coatings on titanium substrates, with potential application in tissue engineering.The targets were prepared from metastable, nanometric, poorly crystalline apatite powders, analogousto mineral bone, synthesized through a biomimetic approach by double decomposition process. For thedeposition of thin films, a KrF* excimer laser source was used (λ = 248 nm, τFWHM ≤ 25 ns). The analy-ses revealed the existence, in synthesized powders, of labile non-apatitic mineral ions, associated withthe formation of a hydrated layer at the surface of the nanocrystals. The thin film analyses showedthat the structural and chemical nature of the nanocrystalline apatite was prevalently preserved. Theperpetuation of the non-apatitic environments was also observed. The study indicated that MAPLE isa suitable technique for the congruent transfer of a delicate material, such as the biomimetic hydratednanohydroxyapatite

Combinatorial MAPLE deposition of antimicrobial orthopedic maps fabricated from chitosan and biomimetic apatite powders

Chitosan/biomimetic apatite thin films were grown in mild conditions of temperature and pressure by Combinatorial Matrix-Assisted Pulsed Laser Evaporation on Ti, Si or glass substrates. Compositional gradients were obtained by simultaneous laser vaporization of the two distinct material targets. A KrF* excimer (λ=248nm, τFWHM=25ns) laser source was used in all experiments. The nature and surface composition of deposited materials and the spatial distribution of constituents were studied by SEM, EDS, AFM, GIXRD, FTIR, micro-Raman, and XPS. The antimicrobial efficiency of the chitosan/biomimetic apatite layers against Staphylococcus aureus and Escherichia coli strains was interrogated by viable cell count assay. The obtained thin films were XRD amorphous and exhibited a morphology characteristic to the laser deposited structures composed of nanometric round shaped grains. The surface roughness has progressively increased with chitosan concentration. FTIR, EDS and XPS analyses indicated that the composition of the BmAp-CHT C-MAPLE composite films gradually modified from pure apatite to chitosan. The bioevaluation tests indicated that S. aureus biofilm is more susceptible to the action of chitosan-rich areas of the films, whilst the E. coli biofilm proved more sensible to areas containing less chitosan. The best compromise should therefore go, in our opinion, to zones with intermediate-to-high chitosan concentration which can assure a large spectrum of antimicrobial protection concomitantly with a significant enhancement of osseointegration, favored by the presence of biomimetic hydroxyapatite

Matrix-Assisted Pulsed Laser Evaporation: A novel approach to design mesoporous carbon films

We report on a fast synthesis method of porous carbon films on solid substrates. Thin carbon microstructures tailored by processing conditions were synthesized for the first time by Matrix-Assisted Pulsed Laser Evaporation. The procedure consists of pulsed laser irradiation of a cryogenic target composed of phloroglucinol/glyoxylic acid organic precursors dissolved in different mixtures of solvents. An excimer UV KrF* pulsed laser was employed inside a vacuum chamber for material expulsion from the target and immobilization on a solid facing collector. By modifying laser energy or target solvents, thin polymeric coatings of hundreds of nanometers with various cross-linking degrees were obtained at room temperature in 10 min only. No drying or thermo-polymerization step is required even for high boiling point solvents such as dymethyl sulfoxide (DMSO). After thermal treatment, mesoporous carbon films exhibiting diverse nano-morphologies and surface areas up to 705 m(2) g(-1) determined by Kr adsorption were then directly obtained onto various collectors. Processing and assembling mechanisms of phenolic resins were investigated and two competing mechanisms, e.g., target absorption of laser wavelength and subsequent molecules transfer/interactions are accounted for the growth of high quality films as highlighted by several techniques. (C) 2017 Elsevier Ltd. All rights reserved

Laser-assisted synthesis of carbon coatings with cobalt oxide nanoparticles embedded in gradient of composition and sizes

International audienceWe report on a new laser-assisted method for the synthesis of composite coatings consisting of cobalt oxide-embedded porous carbon with gradient of composition and sizes. Uniform carbon thin films containing cobalt oxide nanoparticles (CoO NPs) of various concentrations and sizes are obtained by Combinatorial Matrix-Assisted Pulsed Laser Evaporation (C-MAPLE) followed by a post-annealing treatment. Specifically, simultaneous pulsed laser irradiation of two concentric cryogenic targets was applied for gradient thin films assembling on solid substrates. Both targets contained environmentally friendly phloroglucinol/glyoxylic acid organic precursors and a template dissolved in an ethanol-chloroform mixture, whereas one of them enclosed, in addition, cobalt nitrate salt. Due to angular dispersion and crossing of the two vapor plumes during co-deposition process, thin composite polymeric nanocoatings containing Co nitrate salt were obtained. After subsequent thermal annealing treatment of samples at 600 °C, mesoporous carbon films exhibiting CoO NPs gradient distribution were then directly obtained onto the substrates. Carbon matrix formation was supported by EDX analyses and characteristic D, G and 2D bands present in the Raman spectra. Co NPs concentration varied from 3 to 32 wt% on the substrates with a minimum at furthest interaction point of the Co salt containing plume and substrate, while carbon concentration significantly decreased from 91 to 63 wt%. Oxygen amount was relatively constant at about 6 wt% for all coatings. The CoO NPs are homogenously dispersed in the carbon matrix whereas a tendency for aggregation is observed for high loadings. In addition, the CoO NPs size gradient distribution ranged from 3 to 8 nm with the minimum size correlating the minimum concentration

One-pot laser-assisted synthesis of porous carbon with embedded magnetic cobalt nanoparticles

International audienceA novel one-pot laser-assisted approach is reported herein for the synthesis of ordered carbons with embedded cobalt nanoparticles. The process is based on a UV pulsed laser exposure of an ethanolic solution consisting of green carbon precursors, a structure directing agent and a cobalt salt. Very short irradiation times (5 to 30 min) are only required to polymerize and cross-link carbon precursors (i.e. phloroglucinol and glyoxylic acid) independent of a catalyst presence. The influence of three metallic salts (acetate, nitrate and chloride) on the phenolic resin and carbon characteristics (structure, texture and particle size/distribution) was systematically studied. When exposed to UV laser, the metallic salt exhibited a strong influence on the particle size and distribution in the carbon matrix rather than on the textural carbon properties. Using cobalt acetate, very small (3.5 nm) and uniformly dispersed particles were obtained by this simple, fast and green one-pot synthesis approach. An original combined 13C CP-MAS and DP-DEC solid state NMR spectroscopy analysis allowed to determine the structure of phenolic resins as well as the location of the cobalt salt in the resin. Complementarily, the 1H solid-state and relaxation NMR provided unique insights into the rigidity (cross-linking) of the phenolic resin and dispersion of the cobalt salt. The magnetic properties of cobalt nanoparticles were found to be size-dependent: large Co nanoparticles ([similar]50 nm) behave as bulk Co whereas small Co nanoparticles are superparamagnetic

A comparative study of human plasma fibronectin potentialization of the osteogenic activity of BMPs (-2, -6 and -7) onto hydroxyapatite coatings

A comparative study of human plasma fibronectin potentialization of the osteogenic activity of BMPs (-2, -6 and -7) onto hydroxyapatite coating

Synergistic effects of BMP-2, BMP-6 or BMP-7 with human plasma fibronectin onto hydroxyapatite coatings: a comparative study

Voir aussi https://www.ncbi.nlm.nih.gov/pubmed/28434979Design of new osteoinductive biomaterials to reproduce an optimized physiological environment capable of recruiting stem cells and instructing their fate towards the osteoblastic lineage has become a priority in orthopaedic surgery. This work aims at evaluating the bioactivity of BMP combined with human plasma fibronectin (FN/BMP) delivered in solution or coated onto titanium-hydroxyapatite (TiHA) surfaces. Herein, we focus on the comparison of in vitro osteogenic efficacy in mouse C2C12 pre-osteoblasts of three BMP members, namely: BMP-2, BMP-6 and BMP-7. In parallel, we evaluated the molecular binding strength between each BMP with FN using the Surface Plasmon Resonance (SPR) technology. The affinity of BMPs for FN was found totally different and dependent on BMP type. Indeed, the combination of FN with BMP-2 on TiHA surfaces potentiates the burst of gene-mediated osteogenic induction, while it prolongs the osteogenic activity of BMP-6 and surprisingly annihilates the BMP-7 one. These results correlate with FN/BMP affinity for TiHA, since BMP-6>BMP-2>BMP-7. In addition, by analyzing the osteogenic activity in the peri-implant environment, we showed that osteoinductive paracrine effects were significantly decreased upon (FN/BMP-6), as opposed to (FN/BMP-2) coatings. Altogether, our results support the use of FN/BMP-6 to develop a biomimetic microenvironment capable to induce osteogenic activity under physiological conditions, with minimum paracrine signalization. STATEMENT OF SIGNIFICANCE: The originality of our paper relies on the first direct comparison of the in vitro osteogenic potential of three osteogenic BMPs (BMP-2, -6 and -7) combined with native human plasma fibronectin delivered in solution or coated by laser transfer onto titanium hydroxyapatite surfaces. We confirm that BMP association with fibronectin enhances the osteogenic activity of BMP-2, -6 and -7, but with essential discrepancies, depending on the BMP member, and in agreement with the affinity of BMPs for fibronectin. Moreover, we bring elements to explain the origin of the BMP-2 medical life-threatening side-effects by analyzing in vitro paracrine effects. Finally, this work supports the alternative use of FN/BMP-6 to induce osteogenic activity under physiological conditions, with minimum side effects

Composite Drug Delivery System Based on Amorphous Calcium Phosphate–Chitosan: An Efficient Antimicrobial Platform for Extended Release of Tetracycline

One major warning emerging during the first worldwide combat against healthcare-associated infections concerns the key role of the surface in the storage and transfer of the virus. Our study is based on the laser coating of surfaces with an inorganic/organic composite mixture of amorphous calcium phosphate–chitosan–tetracycline that is able to fight against infectious agents, but also capable of preserving its activity for a prolonged time, up to several days. The extended release in simulated fluids of the composite mixture containing the drug (tetracycline) was demonstrated by mass loss and UV–VIS investigations. The drug release profile from our composite coatings proceeds via two stages: an initial burst release (during the first hours), followed by a slower evolution active for the next 72 h, and probably more. Optimized coatings strongly inhibit the growth of tested bacteria (Enterococcus faecalis and Escherichia coli), while the drug incorporation has no impact on the in vitro composite’s cytotoxicity, the coatings proving an excellent biocompatibility sustaining the normal development of MG63 bone-like cells. One may, therefore, consider that the proposed coatings’ composition can open the prospective of a new generation of antimicrobial coatings for implants, but also for nosocomial and other large area contamination prevention