References of "Riva, Raphaël"
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See detailDevice-based controlled local delivery for the treatment of peritoneal pathologies
Riva, Raphaël ULg; Krier, Fabrice; Defrère, Sylvie et al

Poster (2013, August 18)

This contribution aims at reporting the developpment of a controlled drug delivery system (DDS) dedicated to the treatment of intra-peritoneal pathologies, especially endometriosis. At present time ... [more ▼]

This contribution aims at reporting the developpment of a controlled drug delivery system (DDS) dedicated to the treatment of intra-peritoneal pathologies, especially endometriosis. At present time, endometriosis is generally treated by daily oral absorption of drug with the purpose to improve the life quality of patients by the reduction of the pain caused by endometrial lesions. Nevertheless, deleterious side-effects, mainly infertility, are observed as a consequence of the important amount of absorbed active principle. One main advantage of controlled drug delivery devices, e.g. polymer implants, is to maintain sustained drug release over a prolonged period of time thereby eliminating fluctuations in the drug plasma concentration. Moreover, DDS allows a local release of the drug at a specific area, which significantly decreases the active principle concentration in the body and limits side-effects. The peritoneal cavity is a convenient site for the implantation of a DDS against endometriosis because large parts of lesion are localized in this region. At our knowledge, no application of an implant dedicated to the treatment of endometriosis is reported in the literature, whereas the local controlled release of an active principle presents several advantages compared to systemic administration. In this study, anastrozole (2,2’-[5-1H-1,2,4-triazole-1-yl-methyl)-1,3-phenylene]bis(2-methylpropiononitrile)), a well-known aromatase-inhibiting drug, was selected as active molecule. Typically, two non-biodegradable polymers were tested for the elaboration of an anastrozole loaded intra-peritoneal implant, namely polydimethylsiloxane (PDMS) and poly(ethylene-co-vinyl acetate) (EVA). As preliminary research, the ‘in vivo’ biocompatibility of PDMS and EVA in the intra-peritoneal cavity was confirmed by implantation of PDMS and EVA rod-shaped implants in rats. The kinetic of release was determined ‘in vitro’ and confirmed ‘in vivo’. Besides, the efficiency of the implants was improved by the addition of a polymer membrane, which allowed a controlled release of anastrozole over a period of 400 days. [less ▲]

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See detailThermoreversibly cross-linked poly-ε-caprolactones for the elaboration of shape memory materials
Defize, Thomas ULg; Riva, Raphaël ULg; Thomassin, Jean-Michel ULg et al

Poster (2013, April 19)

This contribution aims at reporting a new concept for the preparation of well defined and recyclable PCL- based reversibly cross-linked shape memory polymer by the formation of reversible carbon-carbon ... [more ▼]

This contribution aims at reporting a new concept for the preparation of well defined and recyclable PCL- based reversibly cross-linked shape memory polymer by the formation of reversible carbon-carbon bonds. For this purpose, commercially-available star-shaped PCL precursors were selected and selectively modified at their chain ends either by a diene (furan) or a dienophile (maleimide). PCL-based shape memory materials were prepared by mixing a stoichiometric amount of diene-bearing and maleimide-bearing PCLs at a temperature which favors cycloreversion. The polymer blend is then cured at 65°C (slightly above PCL melting temperature), with the purpose to increase chains mobility and improve the formation of the adducts. The Diels-Alder kinetics has been followed by Raman spectroscopy and the PCL cross-linking was evidenced by both swelling experiments and rheological measurements. The obtained cross-linked PCL was characterized by shape memory properties with excellent fixity and recovery, as determined by cyclic tensile thermomechanical analysis. [less ▲]

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See detailNovel functional degradable block copolymers for the building of reactive micelles
Cajot, Sébastien; Lecomte, Philippe ULg; Jérôme, Christine ULg et al

in Polymer Chemistry (2013), 4(4), 1025-1037

Amphiphilic biocompatible copolymers are promising materials for the elaboration of nanosystems for drug delivery applications. This paper aims at reporting on the synthesis of new functional amphiphilic ... [more ▼]

Amphiphilic biocompatible copolymers are promising materials for the elaboration of nanosystems for drug delivery applications. This paper aims at reporting on the synthesis of new functional amphiphilic copolymers based on biocompatible and bioeliminable blocks. Poly(ethylene oxide) was selected as the hydrophilic block, whereas an aliphatic polyester, i.e. poly(epsilon-caprolactone), or a polycarbonate, i.e. poly(trimethylene carbonate), were chosen as the degradable hydrophobic block. In order to allow a post-functionalization of the micelles core, azide groups were introduced on the hydrophobic segment to provide reactivity towards functional alkyne derivatives by the copper azide-alkyne cycloaddition (CuAAC). For this purpose, a functional lactone, i.e. alpha-chloro-epsilon-caprolactone was introduced during the polymerization of the hydrophobic block before being converted into azide on the preformed copolymer. Such reactivity of the block copolymers and their self-assemblies is of prime interest for drugs or fluorescent dyes grafting, so as for micelles cross-linking. The influence of the azides distribution along the degradable block on the micelles post-functionalization ability has been studied by using alkyne bearing fluorescent dyes as model for drugs. The hydrophilicity of the dye on the micelles post-functionalization efficiency has also been investigated. [less ▲]

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See detailFunctional degradable polymers for advanced drug delivery systems
Cajot, Sébastien; Riva, Raphaël ULg; Jérôme, Christine ULg

Conference (2012, September)

Nowadays, polymer micelles have attracted an increasing interest in pharmaceutical research because they could be used as efficient drug delivery systems. Micelles of amphiphilic block copolymers are ... [more ▼]

Nowadays, polymer micelles have attracted an increasing interest in pharmaceutical research because they could be used as efficient drug delivery systems. Micelles of amphiphilic block copolymers are supramolecular core-shell type assemblies of several tens of nanometers in diameter. In principle, the micelle core is usually constructed with biodegradable hydrophobic polymers such as aliphatic polyesters, e.g. poly(ε-caprolactone) (PCL), which serves as a reservoir for the incorporation of various lipophilic drugs. Water soluble poly(ethylene oxide) (PEO) is most frequently used to build the micelle corona because it is very efficient in preventing protein adsorption at surfaces and in stabilizing micelles in the blood compartment, making particles invisible to the body defense system. Even if micelles get a high stability in aqueous media thanks to their low critical micellar concentration, micelle dissociation is not always preserved when they are injected in the blood compartment. A way to provide the micelle stability during their administration is to cross-link them. Different kinds of cross-linked micelles can be investigated depending on the localization of the cross-linking. Shell cross-linked micelles or nanocage structures with a degradable core have the great advantage to reach drug encapsulation with a high loading rate. However, cross-linking the hydrophilic shell may affect the stealthiness of the carrier. Thus, we have designed reversibly cross-linked micelles by introducing the cross-linking bridges in the hydrophobic segment of the block copolymer, rather than in the hydrophilic one, leading so to more internal cross-linking and thus preserving the mobility of the hydrophilic segment. Three different localizations of the cross-linking has been targeted; (i) loose core cross-linking of a core-corona system, (ii) tight core cross-linking of a core-shell-corona system (the shell and the core being both hydrophobic and the corona hydrophilic) and (iii) tight shell cross-linking of a similar core-shell-corona system. To reach this goal, three types of amphiphilic copolymers have been used bearing pendent azide groups in the hydrophobic segment. These copolymers have been obtained by starting the ring-opening polymerization of ε-CL and a functional CL, either as a mixture or sequentially from a poly(ethylene oxide) macroinitiator leading to the three targeted architectures. The azide groups located along the PCL backbone have then been used to cross-link the micelles by the Huisgens cycloaddition with a bis-alkyne cross-linker. The choice of this cross-linker has also taken into account the requirement to make the cross-linking reversible. For that purpose, disulfide bridges have been selected in order to impart reversibility to the cross-linking by intracellular reduction. Indeed, the marked concentration difference of glutathione between extra- and intra-cellular environments has already been used to trigger drug release by intracellular disulfide bond cleavage. Accordingly, a bis-alkyne disulfide molecule has been chosen as cross-linker. The micellization and cross-linking of these amphiphilic azido macromolecules have been studied. The reversibility of the cross-linking in reductive environment and the cross-linked micelles stealthiness have been tested. [less ▲]

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See detailImplant comprising a core and a tube encasing the core
Donnez, Jacques; Van Langendonkt, Anne; Defrère, Sylvie et al

Patent (2012)

The present invention relates to an implant comprising: - a core material comprising polydimethylsiloxane or at least one hydrogel polymer; - a tube encasing said core material comprising an ethylene ... [more ▼]

The present invention relates to an implant comprising: - a core material comprising polydimethylsiloxane or at least one hydrogel polymer; - a tube encasing said core material comprising an ethylene vinyl acetate polymer or at least one hydrogel polymer; - a sealant for closure of the open ends of said tube comprising polydimethylsiloxane or a mono-, di-, or triacetoxy derivative thereof, or at least one hydrogel polymer; and - at least one active ingredient; wherein said at least one active ingredient is selected from the group comprising celecoxib, sulindac, tamoxifen, oestrogen, oestradiol, ethinyl oestradiol, mestranol, dienogest, norgestrel, levonorgestrel, desogestrel, norgestimate, ethynodiol diacetate, leuprorelin, buserelin, gonrelin, triptorelin, nafarelin, deslorelin, histrelin, and supprelin; and with the proviso that when the sealant is said at least one hydrogelpolymer, the core material comprises polydimethylsiloxane. Furthermore, the invention relates to an implant for use as a medicament. In particular, the invention relates to an implant for use in the treatment of endometriosis. [less ▲]

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See detailImplant comprising a core and a tube encasing the core
Donnez, Jacques; Van Langendonkt, Anne; Defrère, Stéphanie et al

Patent (2012)

The present invention relates to an implant comprising: - a core material comprising polydimethylsiloxane or at least one hydrogel polymer; - a tube encasing said core material comprising an ethylene ... [more ▼]

The present invention relates to an implant comprising: - a core material comprising polydimethylsiloxane or at least one hydrogel polymer; - a tube encasing said core material comprising an ethylene vinyl acetate polymer or at least one hydrogel polymer; - a sealant for closure of the open ends of said tube comprising polydimethylsiloxane or a mono-, di-, or triacetoxy derivative thereof, or at least one hydrogel polymer; and - at least one active ingredient; with the proviso that when the sealant is said at least one hydrogel polymer, the core material comprises polydimethylsiloxane. Furthermore, the invention relates to an implant for use as a medicament. In particular, the invention relates to an implant for use in the treatment of endometriosis. [less ▲]

Detailed reference viewed: 54 (18 ULg)
See detailSynthesis of novel poly(N-vinyl amide)s containing copolymers by cobalt-mediated radical polymerization
Kermagoret, Anthony ULg; Hurtgen, Marie ULg; Liu, Ji ULg et al

Poster (2012, May 10)

Poly(N-vinyl amide)s are found in many applications due to their valued properties including water solubility, biocompatibility, metal-coordination ability, etc. Although N-vinyl amides are easily ... [more ▼]

Poly(N-vinyl amide)s are found in many applications due to their valued properties including water solubility, biocompatibility, metal-coordination ability, etc. Although N-vinyl amides are easily polymerized via radical pathways, their growing radicals are quite reactive due to the lack of stabilizing group, rendering the synthesis of well-defined poly(N-vinyl amide)s challenging. Thus, we explored the organometallic-mediated radical polymerization (OMRP) of a series of N-vinyl amides using bis(acetylacetonato)cobalt(II) as controlling agent in order to develop a platform for the precision synthesis of poly(N-vinyl amide)s. [less ▲]

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See detailCrosslinking of star-shape PCLs through Diels-Alder reactions for the preparation of shape memory polymers
Defize, Thomas ULg; Riva, Raphaël ULg; Thomassin, Jean-Michel ULg et al

Poster (2012, May 10)

Poly(ε-caprolactone) (PCL), a semi-crystalline polymer, is one of the most widely studied polymers for the development of shape memory materials when chemically cross-linked. PCL presents several ... [more ▼]

Poly(ε-caprolactone) (PCL), a semi-crystalline polymer, is one of the most widely studied polymers for the development of shape memory materials when chemically cross-linked. PCL presents several advantages such as a melting transition temperature close to human body temperature, a high biocompatibility and is (bio)degradable. So, this polymer is highly relevant for both biomedical devices such as stents or resorbable suture wires and also for degradable packaging. However, after cross-linking, the material can not be reprocessed, preventing any reuse/recycling of the material. One of the purposes of this work is to find a solution to this major drawback, which would then allow, for example, to reshape packaging films after use or to recycle trimmings remaining after fabrication. Amongst current trends in the design of new polymer and composite materials, the use of organic reactions that are able to create and reversibly disrupt chemical bonds upon an external stimulus (temperature, irradiation,…) is currently gaining more and more attention as it can lead to applications in various areas such as remendable materials, drug delivery systems, stimulus-degrading materials or recyclable materials. This contribution aims at reporting a new concept for the preparation of well defined and recyclable PCL based reversibly cross-linked shape memory polymer by the formation of reversible carbon-carbon bonds. Amongst all the reversible links described in the literature, thermally (4+2) reversible cycloadditions present interesting features such as the creation of robust bonds and well defined reversibility conditions. As an example, the application of furan/maleimide adducts as covalent link, which cycloreversion is largely favored in the range of temperature (90-120°C), is widely reported. For this purpose, commercially-available star-shaped PCL precursors have been selected and selectively modified at their chain ends either by a diene (furan, anthracene) or a dienophile (maleimide). Typically, PCL-based shape memory materials have been prepared by mixing a stoichiometric amount of diene-bearing and maleimide-bearing PCLs in a twin-screw mini-extruder at a temperature which favors cycloreversion. The polymer blend is then cured at 65°C (just above PCL melting temperature), with the purpose to increase chains mobility and improve the formation of the adducts. Cross-linked PCLs were obtained, as evidenced by swelling experiments. The shape memory properties of the materials have been studied by cyclic tensile thermomechanical analysis. The influence of the nature of the Diels-Alder moieties on the cross-linking rate and on the shape memory properties has been studied. Reversibility of the network formation in the case of furan, used as diene, has been assessed by rheology and by recycling experiment. [less ▲]

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See detailTocol modified glycol chitosan for the oral delivery of poorly soluble drugs
Duhem, Nicolas; Rolland, Julien; Riva, Raphaël ULg et al

in International Journal of Pharmaceutics (2012), 423(2), 452-460

The aim of this study was to develop tocol derivatives of chitosan able (i) to self-assemble in the gastrointestinal tract and (ii) to enhance the solubility of poorly soluble drugs. Among the derivatives ... [more ▼]

The aim of this study was to develop tocol derivatives of chitosan able (i) to self-assemble in the gastrointestinal tract and (ii) to enhance the solubility of poorly soluble drugs. Among the derivatives synthesized, tocopherol succinate glycol chitosan (GC-TOS) conjugates spontaneously formed micelles in aqueous solution with a critical micelle concentration of 2 μg mL−1. AFM and TEM analysis showed that spherical micelles were formed. The GC-TOS increased water solubility of 2 model class II drugs. GC-TOS loading efficiency was 2.4% (w/w) for ketoconazole and 0.14% (w/w) for itraconazole, respectively. GC-TOS was non-cytotoxic at concentrations up to 10 mg mL−1. A 3.4-fold increase of the apparent permeation coefficient of ketoconazole across a Caco-2 cell monolayer was demonstrated. Tocol polymer conjugates may be promising vehicles for the oral delivery of poorly soluble drugs. [less ▲]

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See detailMultifunctional poly( ε-caprolactone)-forming networks by Diels–Alder cycloaddition: effect of the adduct on the shape-memory properties
Defize, Thomas ULg; Riva, Raphaël ULg; Jérôme, Christine ULg et al

in Macromolecular Chemistry and Physics (2012), 213(2), 187-197

Star-shaped poly(e-caprolactone)s are functionalized by various dienes (furan and anthracene) and a dienophile (maleimide), and the kinetics of network formation by melt-blending is compared for both ... [more ▼]

Star-shaped poly(e-caprolactone)s are functionalized by various dienes (furan and anthracene) and a dienophile (maleimide), and the kinetics of network formation by melt-blending is compared for both Diels–Alder adducts. When curing at 60 °C, the anthracene–maleimide network forms more rapidly and gives rise to a more crosslinked material than with the furan–maleimide adduct. Shape-memory properties of the networks are compared in terms of Diels–Alder adduct stability. Both materials exhibit excellent fixity and recovery ratios, but the relatively low retro Diels–Alder temperature of the furan–maleimide adduct perturbs the mechanical stability of the network during cyclic tensile testing between 0 and 60 °C, whereas the anthracene–maleimide adduct is shown to be stable up to 150 °C. [less ▲]

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See detail"Click chemistry" to derived antimicrobial polymers
Lecomte, Philippe ULg; Riva, Raphaël ULg; Jérôme, Christine ULg

in Lagaron, José Maria; Ocio Zapata, Maria José; Lopez-Rubio, Amparo (Eds.) Antimicrobial polymers (2012)

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See detailThermo-reversible reactions for the preparation of smart materials: recyclable covalently-crosslinked shape memory polymers
Defize, Thomas ULg; Riva, Raphaël ULg; Thomassin, Jean-Michel ULg et al

in Macromolecular Symposia (2011), 309/310(1), 154-161

[4+2] thermoreversible Diels-Alder cycloaddition has been used to crosslink star-shaped poly(ε-caprolactone) in order to produce networks based on strong carbon-carbon covalent bondings. Depending on the ... [more ▼]

[4+2] thermoreversible Diels-Alder cycloaddition has been used to crosslink star-shaped poly(ε-caprolactone) in order to produce networks based on strong carbon-carbon covalent bondings. Depending on the nature of the Diels-Alder reactants, these bonds can be thermoreversibly broken, allowing re-processing of the polymer matrix. [less ▲]

Detailed reference viewed: 65 (22 ULg)