References of "Regibeau, Nicolas"
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Peer Reviewed
See detailOptimization of hydroxyapatite synthesis via sol-gel process for bone reconstruction application
Tilkin, Rémi ULiege; Regibeau, Nicolas ULiege; Grandfils, Christian ULiege et al

Poster (2017, September 07)

During the past few years, tissue engineering has become one of the most promising techniques to maintain, improve, or reconstruct human tissue, even complete human organs. This solution is frequently ... [more ▼]

During the past few years, tissue engineering has become one of the most promising techniques to maintain, improve, or reconstruct human tissue, even complete human organs. This solution is frequently based on the realization of temporary porous matrices, also called "scaffolds". Scaffolds are highly porous matrices notably designed to structure the development of cells, but also to guarantee the function of the implant during the regeneration process. Several materials have been proposed for the conception of scaffold. These have to meet strict criteria regarding biocompatibility, degradability, mechanical and surface properties. As a result of their biomimetism, bioceramics, like hydroxyapatite (Ca5(PO4)3(OH)), have been widely developed during the past few years for bone reconstruction. The aim of this study is the optimization of the synthesis of hydroxyapatite by sol-gel process to be used in the conception of scaffold for bone reconstruction application. In this optic, powder obtained from two synthesis processes (wet precipitation and sol-gel process) were compared with commercial hydroxyapatite. For wet precipitation process, calcium nitrate and phosphoric acid were used as reagent. For sol-gel process, calcium acetate was used as the source of calcium and triethylphosphate as the source of phosphate. Reagents were mixed and the solution was aged. The powder was then dried and sintered. Finally, particles were washed in HCl to remove CaO and then dried. Those new materials were characterized, particularly in terms of chemical composition (XRD, FTIR), crystallinity (XRD), morphology (SEM, TEM), size (TEM, DLS) and Ca/P ratio (EDX). [less ▲]

Detailed reference viewed: 23 (1 ULiège)
Peer Reviewed
See detailEffect of surface modification of polylactides on fibroblasts L-929 and osteoblasts MG-63
Tilkin, Rémi ULiege; Regibeau, Nicolas ULiege; Lambert, Stéphanie ULiege et al

Conference (2017, July 12)

During the past few years, tissue engineering has become one of the most promising techniques to maintain, improve, or reconstruct human tissue, even complete human organs. This solution is frequently ... [more ▼]

During the past few years, tissue engineering has become one of the most promising techniques to maintain, improve, or reconstruct human tissue, even complete human organs. This solution is frequently based on the realization of temporary porous matrices, also called "scaffolds", design as model and structure for the development of cells. Surface properties of those biomaterials are some determinant criteria for cell adhesion and proliferation. The scope of this work is the study of adhesion and proliferation of fibroblasts L-929 and osteoblasts MG-63 on untreated, hydrolyzed or aminolyzed polylactides. First, these substrates are developed: poly-L,D-lactide (PDLLA) powder is pressed into disks. The surface of disks was chemically modified by hydrolysis and aminolysis surface treatments. Surface modifications were based on previous studies. [1,2] The hydrolysis process is carried out by immersing PDLLA disks in 2 M NaOH for 20 min at room temperature (24°C) under constant agitation. The aminolysis process is performed by placing PDLLA disks in 15 % ethylenediamine in isopropanol for 5 min at room temperature (24°C) under constant agitation. Substrates are characterized by optical microscopy, Scanning Electron Microscopy and water contact angle. Finally, cell adhesion, proliferation, and viability on these substrates are assessed by cell counting and MTT assay after 1, 4, and 8 days of cell culture. Results from surface characterization show an increase of roughness for hydrolyzed polylactide. Regarding water contact angle measurements, values are smaller on treated substrates even though the difference with untreated substrates appears smaller than expected in the literature. [1,2] Cell counting and MTT assay show an increase of cell proliferation and cell viability for treated polylactide substrates in the case of fibroblasts and a decrease of cell proliferation for aminolyzed polylactide substrates in the case of osteoblasts. In conclusions, this work highlights the different effects of surface modification on fibroblasts and osteoblasts viability. References : [1]. Wang YQ, Cai JY. Enhanced cell affinity of poly(L-lactic acid) modified by base hydrolysis: wettability and surface roughness at nanometer scale. Current Applied Physics 2007, 7(S1):e108–e111. [2]. Lin Y, Chrzanowski W, Knowles J, Bishop A, Bismarck A. Functionalized poly(D,L-lactide) for pulmonary epithelial cell culture. Advanced Engineering Materials 2010, 12(4): B101–B112. [less ▲]

Detailed reference viewed: 45 (8 ULiège)
Peer Reviewed
See detailReactive extrusion of pharmaceutical grade PLLA
Regibeau, Nicolas ULiege; Tilkin, Rémi ULiege; Grandfils, Christian ULiege et al

Poster (2017)

During the 20th century, degradable aliphatic polyesters have undergone fast and dynamic developments. Nowadays, these materials can be found in several areas of human activities. Originally there have ... [more ▼]

During the 20th century, degradable aliphatic polyesters have undergone fast and dynamic developments. Nowadays, these materials can be found in several areas of human activities. Originally there have been first designed for the pharmaceutical and medical fields, in particular in surgery and for drug delivery systems. In these domains, polymers are synthesized according to a batch procedure due to the low capacity needed. This work is dedicated to the optimization of a continuous synthesis of pharmaceutical grade polyesters (e.g. poly-L-lactide, PLLA) by reactive extrusion using a twin screws extruder. This equipment presents several advantages compared to batch reactor such as: absence of solvent, high degree of mixing, easiness of scale-up, and rapid continuous synthesis. PLLA synthesis by reactive extrusion has been performed adopting a co-rotating twin-screws extruder (diameter=11 mm and L/D ratio=40). A highly active catalyst must be used to reach the target conversion due to the limited residence time. Tin octoate, approved by US Food and Drugs Administration, has been used alone as catalyst considering a catalyst / monomer molar ratio of 1/5000. A polyethylene glycol has been adopted as initiator. 1H.NMR and size exclusion chromatography (SEC) have been adopted to monitor the conversion rate of the monomer and to analyse the mean molecular weights and the corresponding polydispersity. Static mechanical tests have also carried out to assess the influence of residual monomer within the polymer. Our optimization study has highlighted that the main challenging aspects were the control of the reaction atmosphere and of the residence time. In the first case, even presence in trace water can competitively initiate the polymerization, but also promote hydrolysis. In order to reach a high monomer conversion (≥ 99 %), the residence time has to be well controlled and extended. This latter parameter is particularly affected by the screw configuration and the use of the protic initiator. In particular, the screw configuration was based on previous studies dedicated to the synthesis of polyesters by reactive extrusion [1, 2]. After synthesis, post-processing step was realized in order to reduce the monomer residue. Once optimized we have succeeded to reach in a reproducible way high molecular weight PLLA (typically in a range of 50 to 100 KDa) with a high monomer conversion (>96 %) on a time scale of some minutes. Post-polymerization has successfully decreased the residual monomer below 1%. In conclusion, this work provides a continuous and robust process to synthesize pharmaceutical grade PLLA by reactive extrusion. References : [less ▲]

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