VERT Michel
Fonction : DREM
Thème de Recherche: Biopolymères Artificiels
Autre(s) thème(s) de recherche ou rattachement(s) : - cnrs
michel.vert
umontpellier.fr
0467548553 (ou 0411759723)
Bureau: 0, Etg: 2, Bât: I - Site : Faculté de Pharmacie
Domaines de Recherche: - Chimie/Chimie organique
- Chimie/Matériaux
- Sciences du Vivant/Ingénierie biomédicale/Biomatériaux
- Sciences du Vivant/Médecine humaine et pathologie/Chirurgie
- Sciences du Vivant/Médecine humaine et pathologie/Cardiologie et système cardiovasculaire
- Chimie/ou physique
- Physique/Matière Condensée/Science des matériaux
- Chimie/Polymères
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Dernieres productions scientifiques :
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Experimental and Theoretical Studies of Polyanion−Polycation Complexation in Salted Media in the Context of Nonviral Gene Transfection.
Auteur(s): Boustta M., Leclercq L., Vert M., Vasilevskaya Valentina V.
(Article) Publié:
Macromolecules, vol. 47 p.3574-3581 (2014)
Ref HAL: hal-01010383_v1
DOI: 10.1021/ma500447k
Résumé: Positively and negatively charged molecules, endothelia, and cells play important roles in biological salted aqueous media. This work aimed at studying artificial polyelectrolyte complexes in terms of formation and stability in the context of the increasing interest for the use of polyelectrolyte systems in drug delivery or as polyelectrolyte complexes or polyplexes for gene transfection. The effect of salt concentration on model polyelectrolyte complexes was studied both experimentally and from a theoretical viewpoint. The critical salt concentration at which phase separation appeared when multifunctional polyanions, namely poly(Llysine citramide) and poly(L-lysine citramide imide) were mixed with poly(L-lysine) showed that salt concentration, degree of polymerization and charge density conditioned the formation and the stability of corresponding polyelectrolyte complexes. Data agreed well with the trends indicated by the theoretical approach and they are discussed in comparison with the case of nonviral transfection using polyplexes.
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Head-to-Head Comparison of a Drug-Free Early Programmed Dismantling Polylactic Acid Bioresorbable Scaffold and a Metallic Stent in the Porcine Coronary Artery
Auteur(s): Durand Eric, Sharkawi Tahmer, Leclerc Guy, Raveleau Marine, Van Der Leest Machiel, Vert M., Lafont Antoine
(Article) Publié:
Circulation Cardiovascular Interventions, vol. 7 p.70-79 (2014)
Ref HAL: hal-00931053_v1
DOI: 10.1161/CIRCINTERVENTIONS.113.000738
Résumé: We aimed to evaluate a new drug-free fully bioresorbable lactic acid-based scaffold designed to allow early dismantling synchronized with artery wall healing in comparison with a bare metal stent (BMS). Twenty-three BMS (3.0×12 mm) and 36 lactic acid-based bioresorbable scaffolds (BRS, 3.0×11 mm) were implanted in porcine coronary arteries. QCA and optical coherence tomographic analyses were performed immediately after implantation and repeated after 1, 3, and 6 months. Microcomputed tomography was used to detect scaffold dismantling. Polymer degradation was evaluated throughout the study. The primary end-point was late lumen loss, and the secondary end-points were scaffold/stent diameter and acute recoil. Acute recoil was low and comparable between the BRS and the BMS groups (4.6±6.7 versus 4.6±5.1%; P=0.98). BRS outer diameter increased significantly from 1 to 6 months indicating late positive scaffold remodeling (P<0.0001), whereas BMS diameter remained constant (P=0.159). Late lumen loss decreased significantly from 1 to 6 months in the BRS group (P=0.003) without significant difference between BRS and BMS groups at 6 months (P=0.68). Microcomputed tomography identified BRS dismantling starting at 3 months, and weight-average molar masses of scaffold parts were 20% and 14% of their initial values at 3 and 6 months. BRS and BMS have similar 6-month outcomes in porcine coronary arteries. Interestingly, BRS dismantling was detected from 3 months and resulted in late lumen enlargement by increased scaffold diameter at 6 months.
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Complex impedance spectroscopy to investigate degradable chondroitin-poly(amino-serinate) complexes
Auteur(s): Balme Sebastien, Rixte Johan, Boustta M., Vert M., Henn Francois
(Article) Publié:
Polymer Degradation And Stability, vol. 98 p.2161-2167 (2013)
Ref HAL: hal-01241298_v1
DOI: 10.1016/j.polymdegradstab.2013.08.028
Résumé: Sodium chondroitin-4-sulfate and poly(amino-serinate) bromide can interact to form a degradable polyelectrolyte complex. The structure of each polymer and of their complex before and after degradation is investigated by complex impedance spectroscopy. Poly(amino-serinate) bromide and sodium chondroitin-4-sulfate exhibit dc conductivity and dielectric relaxation phenomena in the 102–106 Hz range. On the contrary, no dc conductivity and dielectric relaxation are observed in the polyelectrolyte complex before degradation. After degradation, the released chondroitin-4-sulfate is re-complexed with additional poly(amino-serinate) bromide. Contrary to the original parent complex the restored complex exhibits both dc conductivity and dielectric relaxation phenomena. This difference is assigned to structural defects due to the presence of residual poly(amino-serinate) oligomers which compete with the newly added poly(amino-serinate) to complex the released chondroitin-4-sulfate. This outcome is interpreted assuming the displacement of the low molecular by higher molecular weight chains in contrast to the behavior usually reported for this type of polymeric systems.
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Adjusting a polymer formulation for an optimal bioresorbable stent: a 6-month follow-up study
Auteur(s): Durand Eric, Lemitre Mathilde, Couty Ludovic, Sharkawi Tahmer, Brasselet Camille, Vert M., Lafont Antoine
(Article) Publié:
Eurointervention, vol. 8 p.242-249 (2012)
Ref HAL: hal-00815743_v1
DOI: 10.4244/EIJV8I2A38
Résumé: Aims: To assess the impact of the composition in L- and D- of lactic acid stereo copolymers without drug elution on the in situ behaviour of prototype stents in terms of biomechanics and biocompatibility. Methods and results: PLA50, 75, and 92 stereo-copolymer stents (L/D lactic acid ratio from 1 to 11.5) were processed using the injection moulding facilities of Arterial Remodeling Technologies (Noisy le Roi, France). The resulting 3 mm outer diameter tubes having a diameter at the desired nominal size were laser-cut and crimped on regular angioplasty balloons and chemically sterilised prior to implantation in iliac rabbit arteries. Acute recoil was higher in PLA50 and PLA75 stent-treated arteries than in those with PLA92 stents (17.4 +/- 11.4 vs. 13.5 +/- 7.6 vs. 4.1 +/- 3.8 %, respectively, p=0.001). At one month, in-stent area was higher in PLA92 than in PLA50 and PLA75 stented arteries (5.9 +/- 0.6 vs. 1.6 +/- 1.6 vs. 2.6 +/- 3.2 mm(2), respectively, p<0.001). Re-endothelialisation was complete, and inflammation was mild around the struts, similar among the three stents. Late lumen loss and neointimal area were low and similar in PLA92 stent-treated arteries one and six months after angioplasty (0.2 +/- 0.2 vs. 0.3 +/- 0.2 mm, p=0.60; 0.5 +/- 0.5 vs. 0.5 +/- 0.8 mm(2), p=0.72, respectively). At six months, inflammation decreased compared to one-month follow-up (1.4 +/- 0.5 vs. 0.6 +/- 0.5, p=0.006). Conclusions: A stereo-copolymer composition strongly influences biomechanical properties of PLA bioresorbable stents in agreement with what has been known for a long time from other applications, but not biocompatibility. PLA92 stents appeared as presenting acceptable acute deployment and 6-month favourable outcome in the rabbit model despite the absence of drugs.
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Adsorption of proteins at physiological concentrations on pegylated surfaces and the compatibilizing role of adsorbed albumin with respect to other proteins according to optical waveguide lightmode spectroscopy (OWLS).
Auteur(s): Vert M.
(Article) Publié:
Journal Of Biomaterials Science Polymer Edition, vol. 24 p.1499-1518 (2013)
Ref HAL: hal-01003233_v1
DOI: 10.1080/09205063.2013.772045
Résumé: In literature, contacts between pegylated compounds and blood proteins are generally discussed in terms of excluded volume-related repulsions although adsorption and compatibility have been reported for some of these proteins occasionally. The major problem to investigate the behavior of blood in contact with pegylated surfaces is the complexity of the medium and especially the presence of albumin in large excess. In a model approach, optical waveguide lightmode spectroscopy (OWLS) was used to monitor the fate of albumin, fibrinogen, and γ-globulins at physiological concentrations in pH = 7.4 isotonic HEPES buffer after contact with SiTiO2 chips coated with diblock poly(DL-lactic acid)-block-poly(ethylene oxide)s and triblock poly(DL-lactic acid)-block-poly(ethylene oxide)-block-poly(DL-lactic acid) copolymers. Corresponding homopolymers were used as controls. The three protein systems were investigated separately, as a mixture and when added successively according to different orders of addition. OWLS gave access to the mass and the thickness of adhering protein layers that resist washing with HEPES buffer. Protein depositions were detected regardless of the presence of poly(ethylene glycol) segments on surfaces. Adsorption depended on the protein, on the surface and also on the presence of the other proteins. Unexpectedly any surface coated with a layer of adsorbed albumin prevented deposition of other proteins, including albumin itself. This outstanding finding suggests that it was the presence of albumin adsorbed on a surface, pegylated or not, that made that surface compatible with other proteins. As a consequence, dipping a device to be in contact with the blood of a patient in a solution of albumin could be a very simple means to avoid further protein deposition and maybe platelets adhesion after in vivo implantation.
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