Recent advances in the synthesis of aliphatic polyesters by ring-opening polymerization

in Advanced Drug Delivery Reviews (2008), 60(9), 1056-1076

Advanced drug delivery systems rely on the availability of biocompatible materials. Moreover, biodegradability is highly desirable in the design of those systems. Consequently, aliphatic polyesters appear ... [more ▼]

Advanced drug delivery systems rely on the availability of biocompatible materials. Moreover, biodegradability is highly desirable in the design of those systems. Consequently, aliphatic polyesters appear as a class of promising materials since they combine both properties. Nevertheless, their use in practical biomedical systems relies on clinical approval which not only depends on the material itself but also on its reproducible synthesis with the absence of residual toxics. The first sections of this review aim at reporting on the evolution of the initiators/catalytic systems and of the synthesis conditions (particularly the use of supercritical CO2 as polymerization medium) in order to produce aliphatic polyesters with controlled macromolecular parameters by still "greener" ways. In addition, the further development of delivery systems also depends on the synthesis of materials exhibiting novel properties, such as amphiphilicity or pH-sensitivity that are emerging from the active research in macromolecular engineering. Functionalizing aliphatic polyesters is quite tedious due to their sensitivity towards hydrolytic degradation. The last section of this review is discussing several strategies to obtain functional (co)polyesters of various architectures providing them with novel properties. [less ▲]

Surface coating of hydrogel intraocular lenses toward resistance to posterior capsular opacification

Conference (2008, May 23)

Modification of AFM probes with polymers: biosensors and actuators

Poster (2008, May 22)

Key role of metal-coordination in cobalt mediated radical polymerization

Poster (2008, May 22)

Superhydrophobic surfaces by electrospinning of polymer mixtures

Poster (2008, May 22)

Hydrophobic surfaces have found great interest in environment resist coating, antifouling marine structures and low friction devices whereas superhydrophobic materials, with contact angle higher than 150° ... [more ▼]

Hydrophobic surfaces have found great interest in environment resist coating, antifouling marine structures and low friction devices whereas superhydrophobic materials, with contact angle higher than 150°, are of special interest in self-cleaning surfaces and stain resistant textiles. (Super)hydrophobicity is a key property that depends on both the surface chemistry and surface roughness. Numerous methods were reported for the preparation of superhydrophobic surfaces by either increasing the surface roughness of an inherently hydrophobic material or decreasing the surface free energy of a rough surface by post-treatment. For instance, controlled crystallization, lithography , etching were reported in the literature for the production of such surfaces. Nevertheless, all these techniques suffer from some drawback such as high cost, time consuming and expensive processes. As an alternative approach, electrospinning was proposed for the production of superhydrophobic surfaces with controlled roughness, morphology and/or porosity. For instance, Acatay et Al. reported on the preparation of electrospun fibers starting from a poly(AN-co-TMI)/fluorolink-D mixture followed by the annealing of these material in order to enable the reorientation of the perfluorinated groups to the solid-air interface. Rutledge et al. described the preparation of superhydrophobic surfaces by combining electrospinning of PCL and initiated chemical vapor deposition of perfluoroalkyl ethyl methacrylate. Allcock et al. prepared superhydrophibic nanofibers by electrospinning of an organic-soluble poly[bis(2,2,2-trifluoroethoxy)phosphazene]. In order to simplify the experimental protocols described in the literature on the preparation of superhydrophobic surfaces and decrease the cost related to the use of pure fluoropolymers, electrospinning of homopolymer/semifluorinated diblock copolymer mixture, i.e. a polyisobornylacrylate/poly(isobornyl acrylate-b-heptadecafluorodecyl acrylate) mixture, onto aluminum plates is proposed in this study. In practice, a diblock copolymer based on 1H,1H,2H,2H heptadecafluorodecyl acrylate and isobornyl acrylate was prepared by RAFT polymerization. In a second step, electrospinning of PIBA/PAC8-b-PIBA mixtures of different compositions was investigated. At high fluorine content ([PIBA]/[PAC8-b-PIBA] = 50/50), the electrospun mats show high surface roughness (microparticles of undefined morphologies) and a superhydrophic character. By decreasing the fluorine content, the morphology of the films changed from particles to beaded fibers (([PIBA]/[PAC8-b-PIBA] = 70/30) or fibers (([PIBA]/[PAC8-b-PIBA] = 85/15), which is consistent with an increase of the solution viscosity, but the surfaces still demonstrate or tend to superhydrophobicity. [less ▲]

Gd(III)-DOTA conjugate with furtive targeting copolymer poly(AMPEO-co-HEA) by click chemistry for magnetic resonance imaging

Poster (2008, May 22)

Extrusion foaming of poly(styrene-co-acrylonitrile) using supercritical carbon dioxide

Conference (2008, May 05)

New pH-sensitive flower micelles for potential tumour targeting

Poster (2008, April 16)

Contribution of "click chemistry" to the synthesis of antimicrobial aliphatic copolyester

in Polymer (2008), 49(8), 2023-2028

A straightforward strategy is proposed to impart antimicrobial properties to biodegradable poly(oxepan-2-one) (poly(epsilon-caprolactone) or PCL), which is based on the grafting of pendant ammonium salts ... [more ▼]

A straightforward strategy is proposed to impart antimicrobial properties to biodegradable poly(oxepan-2-one) (poly(epsilon-caprolactone) or PCL), which is based on the grafting of pendant ammonium salts by "click" chemistry. First, statistical copolymerization of 3-chlorooxepan-2-one (alpha-chloro-epsilon-caprolactone or alpha Cl epsilon CL) with oxepan-2-one (epsilon-caprolactone or epsilon CL) was initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP). In a second step, pendant chlorides were converted into azides by reaction with sodium azide (NaN3). Finally, quaternary ammonium containing alkynes were quantitatively added to the pendant azide groups of PCL by the copper-catalyzed Huisgen's 1,3-dipolar cycloaddition, which is a typical "click" reaction. An alternative two-step strategy based on the cycloaddition of the amine containing alkyne onto the pendant azides, followed by quaternization turned out to be less efficient. The antimicrobial activity was analyzed by the "shaking flask method" in the presence of Escherichia coli [less ▲]

Unsuccessful Induction of Endometriosis in Female Rhesus Macaques (Macaca mulatta).

in Gynecologic & Obstetric Investigation (2008), 66(2), 84-90

Background/Aims: The aim of this study was to induce endometriosis in female rhesus macaques (Macaca mulatta) for research purposes. Methods: Three female monkeys from 4 to 4.5 years of age underwent ... [more ▼]

Background/Aims: The aim of this study was to induce endometriosis in female rhesus macaques (Macaca mulatta) for research purposes. Methods: Three female monkeys from 4 to 4.5 years of age underwent three consecutive attempts at endometriosis induction over an 8-month period: (i) the first attempt involved intravaginal sampling of endometrial tissue and transplantation into the intrapelvic cavity; (ii) the second entailed surgical removal of endometrium after hysterotomy and intra-abdominal placement, and (iii) the third used endometrial mucosa obtained by scraping the uterus after hysterectomy, placed in a surgical pouch created in the retrovesical space (Retzius). In each case, the pelvic cavity was closely inspected after 7, 9, and 6 weeks respectively for the presence of endometriotic lesions, and peritoneal biopsies were performed. Results: Neither macroscopic observation nor histological analysis revealed any endometriotic lesions. Conclusion: This failure to induce endometriosis in female rhesus macaques suggests that this species is not the most efficient experimental model among primates to investigate endometriosis development or treatment. [less ▲]