References of "Riva, Raphaël"
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See detailRecyclable shape-memory materials based on photo or thermo-reversible crosslinking
Defize, Thomas ULg; Riva, Raphaël ULg; Wauters, Céline et al

Poster (2014, November 11)

Shape memory polymers (SMPs) are remarkable materials able to switch from a stressed deformed state (temporary shape) to their initial relaxed state (permanent shape) by the application of a stimulus ... [more ▼]

Shape memory polymers (SMPs) are remarkable materials able to switch from a stressed deformed state (temporary shape) to their initial relaxed state (permanent shape) by the application of a stimulus, such as heat or light. Typically, the shape memory property is generally observed for chemically or physically cross-linked polymers that exhibit an elastomeric behavior above a phase transition, e.g. glass or melting transition. Cross-linked semi-crystalline poly(ε-caprolactone) (PCL) is already widely studied for the development of SMPs. However, the tensile strength of standard PCL-based SMPs remains quite low, limiting their use in some applications. A convenient way to enhance the strength of SMPs relies on the introduction of nanofillers, such as silica nanoparticles, leading to an enhancement of mechanical strength. Moreover, silica nanoparticles can be advantageously used as multifunctional crosslinking nodes, with the purpose to increase the cross-linking density of the material. As most of SMPs are irreversibly cross-linked material, their reprocessing is impossible preventing any recycling. Thereby, reversible reactions, allowing the formation/cleavage of the network, raise tremendous interest in macromolecular engineering. Recently, a reversibly cross-linked 4-arm star-shaped PCL-based SMP was prepared using the Diels-Alder (DA) reaction between furan and maleimide moieties, well-known to create reversible bonds. This shape memory material demonstrated to be implementable, and so recyclable, and was characterized by excellent fixity and recovery before and after recycling experiments. However, the relatively low retro-DA temperature of the furan- maleimide adducts led to an inelastic deformation during shape memory tensile cycles. In order to get rid of this drawback, two alternative approaches were investigated. Firstly, the substitution of the DA reaction by a photo-reversible reaction, typically the photo- induced (2+2) cycloaddition of coumarins, was proposed to crosslink the PCL matrix. The second approach is based on the use of surface functionalized silica nanoparticles as crosslinking nodes with the purpose to increase the crosslinking density of the material. The network formation and cleavage were studied by solid-state NMR and rheology.4 The resulting shape memory materials were characterized by excellent one-way and two-way shape memory properties as demonstrated by dynamical mechanical analysis. [less ▲]

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See detailSmart cross-linked polymer micelles for drug delivery
Riva, Raphaël ULg; Vanslambrouck, Stéphanie ULg; Ergül, Zeynep ULg et al

Conference (2014, November 11)

Nowadays, polymer crosslinking is widely used in industry to improve or to impart new properties to existing polymer material. In the pharmaceutical field, polymer crosslinking is of great interest for ... [more ▼]

Nowadays, polymer crosslinking is widely used in industry to improve or to impart new properties to existing polymer material. In the pharmaceutical field, polymer crosslinking is of great interest for the elaboration of drug delivery devices, mostly hydrogels. Nevertheless, crosslinking is also very useful in nanovectorization of active principle. Indeed, each day, new drugs are synthesized and available on the market but in too many cases, the high hydrophobicity of some drugs makes them useless because of the absence of an appropriated administration method. The encapsulation of the drug into a nanocarrier, typically in the hydrophobic core of a polymer micelle, allows a significant increase of the drugs concentration in water in addition to the protection of the active principle against degradation. However, polymer micelles suffer of the main drawback to not be stable, leading to a premature release of the drug, when the concentration falls down the critical micellar concentration (CMC), which it is rapidly observed after intravenous injection. In order to get rid of the CMC, crosslinking of the micelle core is the most proposed strategy. Nevertheless, the crosslinking of the micelle core may have a non-negligible effect on the drug loading but mainly on the drug release due to the sequestration of the drug in the network. Over the last years, our lab investigated several strategies for the crosslinking of the micelle core made of amphiphilic and biocompatible block copolymers generally by UV radiation in order to fulfill the increasingly stringent requirements of biomedical applications. These strategies are very helpful to prepare injectable nanosized cross-linked particles loaded with an active particle. For some systems, the effect of the crosslinking rate on the drug loading and the drug release was evaluated using a model drug. As the crosslinking may interfere with the drug release after internalization of the carrier into the cell, a reversible crosslinking of the micelle core was proposed. Typically, the introduction of disulfide bond as inter-chain links allowed to delay the drug release by diffusion whereas into the cell, the reduction of the disulfide bridges into corresponding thiol led to the fast disassemble of the micelle and the specific release of the drug into cytoplasm. [less ▲]

Detailed reference viewed: 172 (10 ULg)
See detailAmphiphilic copolymers containing polyphosphates for drug delivery applications
Vanslambrouck, Stéphanie ULg; Clément, Benoit; Riva, Raphaël ULg et al

Poster (2014, September 19)

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See detailMicellization of PEO-b-polyphosphate for drug delivery applications
Vanslambrouck, Stéphanie ULg; Clément, Benoit; Riva, Raphaël ULg et al

Conference (2014, July 11)

Detailed reference viewed: 35 (12 ULg)
See detailStructure-morphology relationship of polyphosphate containing polymer micelles
Vanslambrouck, Stéphanie ULg; Clément, Benoit; Riva, Raphaël ULg et al

Conference (2014, June 18)

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See detailSynthesis of a glucosamine labeled amphiphilic polymer for drug delivery application
Riva, Raphaël ULg; Boyère, Cédric; Debuigne, Antoine ULg et al

Poster (2014, May 27)

Detailed reference viewed: 54 (6 ULg)
See detailComprehensive study of chemically cross-linked PCLs presenting one-way and two-way shape memory properties
Defize, Thomas ULg; Riva, Raphaël ULg; Thomassin, Jean-Michel ULg et al

Poster (2014, May 26)

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. 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. 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 at which DA cycloaddition is largely disfavored, followed by the curing of the blend above the melting temperature to improve the kinetic of DA adduct formation. The shape memory properties of the materials have been studied by cyclic tensile thermomechanical analysis. As cross-linked PCLs are knowned to exhibit one-way and two-way shape memory properties, a comprehensive study of the shape memory of these materials has been carried out. Unfortunately, creep from shape memory cycle to cycle was observed in DMA for the furan/maleimide sample, certainly due to the reversibility of the adduct. In order to limit this creep effect, the substitution of the furan/maleimide adduct by a more stable adduct is required. The anthracene/maleimide system was tested because this adduct is more stable under stress than the furan/maleimide one. This contribution aims at reporting a complete study of one-way and two-way shape memory properties of the PCL cross-linked by anthracene/maleimide adduct. The shape memory properties of this material have been assessed by DMA and DSC experiments. [less ▲]

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See detailMetal-free synthesis of a glucosamine labeled amphiphilic polymer for drug delivery applications
Riva, Raphaël ULg; Boyère, Cécric; Debuigne, Antoine ULg et al

Poster (2014, May 19)

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See detailDrug delivery systems based on PEO-b-polyphosphate copolymers
Vanslambrouck, Stéphanie ULg; Clément, Benoit; Riva, Raphaël ULg et al

Poster (2014, May)

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See detailElaboration of drug nanocarriers based on a glucosamine labeled amphiphilic polymer
Boyère, Cédric; Duhem, N; Debuigne, Antoine ULg et al

in Polymer Chemistry (2014), 5(8), 3030-3037

A new functional polymer micelle with high loading efficiency of a poorly soluble drug was made of biocompatible and/or biosourced compounds, i.e. cholesterol-poly(ethylene glycol)-glucosamine (Chol-PEG ... [more ▼]

A new functional polymer micelle with high loading efficiency of a poorly soluble drug was made of biocompatible and/or biosourced compounds, i.e. cholesterol-poly(ethylene glycol)-glucosamine (Chol-PEG-GlcNH2). A synthesis strategy combining enzymatic and metal-free click chemistry was developed in order to meet the increasingly stringent requirements of biomedical applications. After the self-assembly of the Chol-PEG-GlcNH2 amphiphilic polymer in water, the presence of glucosamine at the micelle surface confers an active targeting moiety to the nanocarriers whereas protonation of the peripheral primary amine delay their aggregation. The complete characterization of this novel functional amphiphilic bioconjugate is presented as well as its aqueous solution behaviour and encapsulation efficiency using ketoconazole as a model hydrophobic drug. [less ▲]

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See detailChitosan nanoparticles for siRNA delivery: Optimizing formulation to increase stability and efficiency
Ragelle, Héloïse; Riva, Raphaël ULg; Vandermeulen, G. et al

in Journal of Controlled Release (2014), 176

This study aims at developing chitosan-based nanoparticles suitable for an intravenous administration of small interfering RNA (siRNA) able to achieve (i) high gene silencing without cytotoxicity and (ii ... [more ▼]

This study aims at developing chitosan-based nanoparticles suitable for an intravenous administration of small interfering RNA (siRNA) able to achieve (i) high gene silencing without cytotoxicity and (ii) stability in biological media including blood. Therefore, the influence of chitosan/tripolyphosphate ratio, chitosan physicochemical properties, PEGylation of chitosan as well as the addition of an endosomal disrupting agent and a negatively charged polymer was assessed. The gene silencing activity and cytotoxicity were evaluated on B16 melanoma cells expressing luciferase. We monitored the integrity and the size behavior of siRNA nanoparticles in human plasma using fluorescence fluctuation spectroscopy and single particle tracking respectively. The presence of PEGylated chitosan and poly(ethylene imine) was essential for high levels of gene silencing in vitro. Chitosan nanoparticles immediately released siRNA in plasma while the inclusion of hyaluronic acid and high amount of poly(ethylene glycol) in the formulation improved the stability of the particles. The developed formulations of PEGylated chitosan-based nanoparticles that achieve high gene silencing in vitro, low cytotoxicity and high stability in plasma could be promising for intravenous delivery of siRNA. [less ▲]

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See detailDevice-based controlled local delivery of anastrozol into peritoneal cavity: in vitro and in vivo evaluation
Krier, Fabrice ULg; Riva, Raphaël ULg; Defrère, Sylvie et al

in Journal of Drug Delivery Science and Technology [=JDDST] (2014), 24(2), 198-204

Local treatment using drug loaded implants allows decreasing seric concentrations of the active ingredient with the purpose of limiting side effects and reaching perfect observance. Nowadays, some ... [more ▼]

Local treatment using drug loaded implants allows decreasing seric concentrations of the active ingredient with the purpose of limiting side effects and reaching perfect observance. Nowadays, some diseases are already treated with implants, but generally, by subcutaneous or intra vaginal implantation. In this work, a new implant device dedicated to the intra-peritoneal cavity was developed. For this purpose, a core-membrane polymer implant was selected. We propose an original method to determine the most appropriate membrane to control the release based on the use of Franz cells. The ability of the implant to release a constant quantity of an active ingredient will be assessed by testing implants in vitro. Finally, intra peritoneal cavity and subcutaneous in vivo implantation has been achieved in order to confirm the controlled and local release of the active ingredient. [less ▲]

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See detailChitosan: a versatile platform for pharmaceutical applications
Riva, Raphaël ULg; Jérôme, Christine ULg

in Material Matters: Chemistry Driving Performance (2014), 9(3), 95-98

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See detailReversibly cross-linked polymer micelle as smart drug dellivery device
Lecomte, Philippe ULg; Riva, Raphaël ULg; Cajot, Sébastien et al

Conference (2013, November 20)

Detailed reference viewed: 23 (8 ULg)
See detailDrug delivery systems based on amphiphilic polyphosphate-copolymers
Vanslambrouck, Stéphanie ULg; Clement, Benoît ULg; Riva, Raphaël ULg et al

Poster (2013, September 18)

Thanks to their biocompatibility, biodegradability and their structure similar to natural biomacromoleculesn such as nucleic acids, polyphosphates (PPhos) are of prime interest as biomaterials. In ... [more ▼]

Thanks to their biocompatibility, biodegradability and their structure similar to natural biomacromoleculesn such as nucleic acids, polyphosphates (PPhos) are of prime interest as biomaterials. In contrast to poly--caprolactone and polylactides, PPhos properties and functionality are easily tuned via the nature of the pendant group of the starting cyclic monomer. For example, by varying the length of the alkyl chain the hydrophobicity of the PPhos can be adjusted. In this work, an efficient organo-catalytic system was developed to synthesize a series of amphiphilic diblock copolymers, i.e. poly(ethylene oxide)-b-polyphosphate (PEO-b-PPhos) by ring-opening polymerization of cyclic phosphates. This novel approach prevents metallic residues to polute the final product, and which is highly desirable when biomedical applications are foreseen. For drug delivery application, the micellization of these novel diblock copolymers in aqueous media was investigated, as well as, encapsulation of an hydrophobic drug. Data on, the influence of the polyphosphate nature of the polymer on drug loading will be presented. [less ▲]

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See detailTailor made amphiphilic copolymers for the design of smart drug delivery systems
Riva, Raphaël ULg; Cajot, Sébastien; Jérôme, Christine ULg

Conference (2013, August 21)

Detailed reference viewed: 42 (6 ULg)
See detailShape-memory materials based on thermoreversibly cross-linked poly-ε-caprolactones
Defize, Thomas ULg; Riva, Raphaël ULg; Thomassin, Jean-Michel ULg et al

Poster (2013, August 19)

Shape memory polymers (SMPs) are materials that are able to change their shape from a temporary shape to a permanent one by application of a stimulus such as heat or light. SMPs are usually chemically or ... [more ▼]

Shape memory polymers (SMPs) are materials that are able to change their shape from a temporary shape to a permanent one by application of a stimulus such as heat or light. SMPs are usually chemically or physically crosslinked materials that exhibit an elastomeric behaviour above a glass or melting transition temperature. Poly(ε-caprolactone) (PCL) is one of the most widely studied polymers for the development of SMPs. PCL presents several advantages such as a melting transition temperature close to human body temperature, a high biocompatibility, is (bio)degradable and potentially biosourced. So, this polymer is highly relevant for both degradable packaging and also for biomedical devices such as resorbable suture wires or stents. However, after crosslinking, the material can not be reprocessed, preventing any reuse/recycling. The main purpose of this work is to provide a solution to this major drawback, which would then enable, for example, to reshape packaging films after use or to reprocess trimmings remaining after production. Amongst current trends in the design of new polymer and composite materials, organic reactions that are able to create and reversibly disrupt chemical bonds upon an external stimulus (temperature, irradiation,…) are currently gaining more and more attention in macromolecular engineering and are used in various areas such as remendable materials, drug delivery systems, stimulus-degrading materials or recyclable materials. Amongst all the reversible links described in the literature, thermally (4+2) reversible cycloadditions present interesting properties 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. This contribution aims at reporting a new concept for the preparation of well defined and recyclable PCL based reversibly cross-linked SMPs by the formation of reversible carbon-carbon bonds. For this purpose, commercially-available linear and multi-arm star shaped PCL precursors have been selected and selectively functionalized 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 architecture of the PCL precursors as well as 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 ▲]

Detailed reference viewed: 6 (2 ULg)