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Biomedical subjects

Patrick Couvreur

Publications and source records attributed to Patrick Couvreur.

At least 37 records · Page 2Linked to original sources
PubMed2005

Protein driven patterning of self-assembled cubosomic nanostructures: long oriented nanoridges.

Self-assembly lipid/protein cubosomic nanostructures are generated at high hydration level (dispersion of 5% lipid only) and examined by freeze-fracture electron microscopy (FF-EM) and synchrotron X-ray diffraction (XRD). The fracture surface of the three-dimensional (3D) soft-matter membranous assembly reveals starlike nanopatterns of oriented 100-nm-long cubosomic nanoridges with lateral periodicity defined by their 21-nm diameters. The average water channel radius in these liquid crystalline cubosomic nanoarchitectures, determined by high-resolution FF-EM and XRD, is 18.0 Angstrom. The protein-directed fragmentation of a diamond-type lipid cubic phase at high hydration can induce 3D patterns of oriented nanoporous building blocks, which are a unique example of tertiary organization of functionalized fluid lipid/water interfaces.

Chemistry, Physical↗
PubMed2005

Phospholipid hydrolysis in a pharmaceutical emulsion assessed by physicochemical parameters and a new analytical method.

The aim of this work was to develop a simple high-performance liquid chromatography (HPLC) technique with evaporative light scattering detection (ELSD) for the separation and quantification of the major phospholipid (PL) and lysophospholipid (LPL) classes contained in a pharmaceutical phospholipid-based emulsion. In the established method, phosphatidylcholine (PC), phosphatidylethanolamine (PE), sphingomyeline (SM), lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine (LPE) were separated with a PVA-Sil stationary phase and a binary gradient from pure chloroform to methanol:water (94:6 v/v) at 3.4%/min. The ELSD detection was enhanced using 0.1% triethylamine and formic acid in each gradient mobile phases. Factors such as stationary phase and ELSD drift tube temperature were optimized, concluding in optimal temperatures of 25 degrees C for separation and 50 degrees C for evaporation. This HPLC-ELSD method was then applied to a PL-emulsion exposed to autoclaving and accelerated thermal conditions at 50 degrees C. Hydrolysis of PC and PE followed first-order kinetics, representing only 45% of the total lipid mass after 3 months. The chemical stability was correlated to commonly measured formulation physical and physico-chemical parameters such as droplet size, emulsion pH and zeta-potential.

Chemistry Techniques, Analytical↗
PubMed2005

Increase of doxorubicin sensitivity by doxorubicin-loading into nanoparticles for hepatocellular carcinoma cells in vitro and in vivo.

BACKGROUND/AIMS: Hepatocellular carcinoma (HCC) is known to be chemoresistant to anticancer drugs due to the multidrug resistant (MDR) transporters expression. Here, we compared in vitro and in vivo the anti-tumor efficacy of doxorubicin-loaded polyisohexylcyanoacrylate nanoparticles (PIHCA-Dox) versus free doxorubicin (Dox). These nanoparticles are known to overcome the MDR phenotype. METHODS: We first determined in vitro the 50% inhibition concentration (IC(50)) of these drugs on different human hepatoma cell lines. Secondly, the efficacy of the drugs in vivo was determined on the X/myc transgenic murine model of HCC by histological counting of apoptotic tumorous hepatocytes and by TUNEL labeling. We characterized by semi-quantitative RT-PCR the MDR-related gene (mdr1, mdr3, mrp1) expression pattern in this model. RESULTS: In vitro, IC(50) was reduced with PIHCA-Dox versus Dox for Huh7 (1.7-fold reduction; P<0.001), HepaRG (4.5-fold reduction; P<0.01), HepG2 (1.5-fold reduction; P<0.001), and HepG2.2.15 (1.5-fold reduction; P=0.059). In vivo, HCC in transgenic mice overexpressed the mdr1 and mdr3 genes and the antitumor drugs efficacy was greatly enhanced after injection of PIHCA-Dox (9.0+/-5.0%; n=15) versus Dox (4.6+/-3.3%; n=13; P=0.01) for apoptotic bodies count. CONCLUSIONS: These promising data showing a higher anti-tumor efficacy on HCC of PIHCA-Dox versus Dox, warrant further studies in both animals and humans.

Animals↗
PubMed2005

In vivo potentialities of EWS-Fli-1 targeted antisense oligonucleotides-nanospheres complexes.

The EWS/FLI-1 fusion gene, resulting from a t(11;22) translocation, plays a key role in the pathogenesis of Ewing sarcoma. Previously, we have shown that antisense oligonucleotides designed against EWS-Fli-1 inhibited tumor growth in nude mice provided they were delivered intratumorally by nanocapsules or by CTAB-coated nanospheres. In this study, we have used two types of nanospheres (designated as type 1 and type 2 nanospheres) stabilized with chitosan for both intratumoral and systemic administration of oligonucleotides. Inhibition of the tumor growth in vivo was found to be dependent on the carrier type as well as on antisense oligonucleotide modification. Indeed, whereas both types of nanospheres were efficient in reducing tumor growth after intratumoral injection, we have obtained only with type 2 nanospheres an antitumoral effect after intravenous injection in a preliminary experiment. Additionally, the anticancer efficacy of a localized modification of the EWS-Fli-1 phosphodiester/phosphorothioate chimeric antisense oligonucleotide was demonstrated. In cell culture the oligonucleotides inhibit cell growth by their antisense activity. Further investigations are needed in vivo to learn the mechanism of action of the complexes.

Animals↗
PubMed2005

Metallic colloid nanotechnology, applications in diagnosis and therapeutics.

In recent years the fields of medicine and biology assist to an ever-growing innovation related to the development of nanotechnologies. In the pharmaceutical domain, for example, liposomes, polymer based micro and nanoparticles have been subjects of intense research and development during the last three decades. In this scenario metallic particles, which use was already suggested in the first half of the '80, are now experiencing a real renaissance. In the field of diagnosis, magnetic resonance imaging is one of the first and up to now the most developed application of metallic particles. But beside this application, a very new generation of biosensors based on the optical properties of colloidal gold and fluorescent nanocrystals, called quantum dots seems to be ready to be implemented in diagnosis and medical imaging. Concerning therapeutic applications, the potentialities of metal nanoparticles to help fulfilling the need of time and space controlled release of drugs has been intuited for a long time. Nowadays, magnetically guided carriers or thermal responsive matrices, in which drug release is triggered by the heating of metal nanoparticles, are effective examples of their application in drug delivery, while more recently efforts to develop metallic nanoobjects to be used as vectors of nucleic acids for vaccination and transfection have been multiplied. In the future, one of the most interesting challenges is certainly the use of metallic nanoparticles for an innovating, effective and selective physical treatment of solid tumors via targeted intracellular hyperthermia.

Animals↗
PubMed2004

Negative preclinical results with stealth nanospheres-encapsulated Doxorubicin in an orthotopic murine brain tumor model.

Previous results have shown that PEG-coated poly(hexadecylcyanoacrylate) (PEG-PHDCA) nanospheres displayed a significant accumulation within an orthotopic 9L gliosarcoma model, after i.v. administration to rats. Hence, the aim of the present study was to evaluate in the same model the pre-clinical efficacy of this carrier when loaded with Doxorubicin, an anticancer drug which poorly distributes in the CNS. Free and nanospheres-encapsulated Doxorubicin were administered with a multiple dose treatment. Their maximum tolerated dose (MTD) and increase in life span were respectively assessed in healthy and intracranially 9L-bearing rats. A comparative biodistribution study of Doxorubicin-loaded and unloaded PEG-PHDCA nanospheres was also performed in the tumor-bearing group. The results showed that the cumulative MTD of nanoparticulate doxorubicin was 1.5 times higher than this of free Doxorubicin. Nevertheless, encapsulated Doxorubicin was unable to elicit a better therapeutic response in the 9L gliosarcoma. Biodistribution study revealed that the Doxorubicin-loaded nanospheres accumulated to a 2.5-fold lesser extent in the 9L tumor as compared to the unloaded nanospheres and that they were mainly localized in the lungs and the spleen. Such a typical profile indicated aggregation with plasma proteins as a consequence of the positive surface charge of these loaded particles; this ionic interaction resulting from drug encapsulation was mainly responsible for 9L treatment failure.

Animals↗
PubMed2004

"Smart" delivery of antisense oligonucleotides by anionic pH-sensitive liposomes.

Antisense oligonucleotides are molecules that are able to inhibit gene expression being, therefore, potentially active for the treatment of viral infections cancer or inflammatory diseases. However, because of their poor stability in biological medium and their weak intracellular penetration, "smart" delivery systems such as anionic pH-sensitive liposomes were designed. Most known liposome formulations contain a specific phospholipid, phosphatidylethanolamine (PE), which undergoes a transition from lamellar to inverted micelles structures at low pH and allow fusion of liposomal and endosomal membranes and by consequence destabilization of the endosomes. Therefore, liposomes made of PE are able to release their contents in response to acidic pH within the endosomal system while remaining stable in plasma thus improving the cytoplasmic delivery of oligonucleotides after endocytosis. This review illustrates the advantages of this approach for the delivery of antisense oligonucleotides.

Animals↗
PubMed2004

Intraocular injection of tamoxifen-loaded nanoparticles: a new treatment of experimental autoimmune uveoretinitis.

In this study, we tested the efficiency of an intravitreal injection of tamoxifen, a non-steroidal estrogen receptor modulator, in retinal soluble antigen (S-Ag)-induced experimental autoimmune uveoretinitis (EAU). To increase the bioavailability of tamoxifen, we incorporated tamoxifen into polyethylene glycol (PEG)-coated nanoparticles (NP-PEG-TAM). The localization of the nanoparticles within the eye was investigated using fluorescent-labeled PEG-coated nanoparticles after injection into the vitreous cavity of rats with EAU. Some nanoparticles were distributed extracellularly throughout the ocular tissues, others were concentrated in resident ocular cells and in infiltrating macrophages. Whereas the injection of free tamoxifen did not alter the course of EAU, injection of NP-PEG-TAM performed 1-2 days before the expected onset of the disease in controls resulted in significant inhibition of EAU. NP-PEG-TAM injection significantly reduced EAU compared to injection of NP-PEG-TAM with 17beta-estradiol (E2), suggesting that tamoxifen is acting as a partial antagonist to E2. Diminished infiltration by MHC class II(+) inflammatory cells and low expression of TNF-alpha, IL-1beta, and RANTES mRNA were noted in eyes of NP-PEG-TAM-treated rats. Intravitreal injection of NP-PEG-TAM decreased S-Ag lymphocyte proliferation, IFN-gamma production by inguinal lymph node cells, and specific delayed-type hypersensitivity indicative of a reduced Th1-type response. It increased the anti-S-Ag IgG1 isotype indicating an antibody class switch to Th2 response. These data suggest that NP-PEG-TAM inhibition of EAU could result from a form of immune deviation. Tamoxifen-loaded nanoparticles may represent a new option for the treatment of experimental uveitis.

Animals↗
PubMed2004

Heparin coated poly(alkylcyanoacrylate) nanoparticles coupled to hemoglobin: a new oxygen carrier.

A new generation of drug delivery systems based on heparin-poly(isobutylcyanoacrylate) copolymers has been developed to carry hemoglobin. These copolymers spontaneously form, in water, nanoparticles with a ciliated surface of heparin. These nanoparticles maintain the heparin antithrombotic properties and inhibit complement activation. One ml of nanoparticle suspension can be loaded with up to 2.1mg of hemoglobin, which preserves its ligand binding capacity. This work constitutes the first demonstration of hemoglobin loaded on nanoparticle surface, rather than being encapsulated. With a size of 100 nm, these drug delivery systems make suitable tools in the treatment of thrombosis oxygen deprived pathologies.

Adult↗
PubMed2004

Extensive surface studies help to analyse zeta potential data: the case of cationic emulsions.

The present study is aimed to characterize the electrostatic parameters of oil in water emulsion droplets composed of MCT (medium chain triglycerides), PL (phospholipids) and Poloxamer and containing increasing concentrations of the cationic lipid oleylamine (OA), in Hepes 20 mM pH 7.4. The initial zeta-potential data suggesting saturation of the droplet surface at high OA concentrations were completed by supplementary analysis: the distribution of the oleylamine within the droplet was determined by reacting the amino groups with the hydrophilic TNBS (trinitrobenzenesulfonic acid), the method being initially standardised with vesicles. In addition, surface potential and pH at the droplet surface were monitored by the pH-sensitive fluorophore 4-heptadecyl-7-hydroxycoumarin. Our results demonstrate that almost all the OA is localised and fully ionised at the droplet surface for all concentrations and that the observed plateau in the zeta-potential values obeys the Gouy-Chapman theory of ion condensation. It is also shown that the slipping plane separation as estimated by the Eversole-Boardman equation is higher that the expected values of 0.2 nm as a result of the relative position of the fluorophore and the outer boundary of the lipid interface thickness and the Poloxamer anchored at the interface only plays a minor role.

Amines↗
PubMed2004

Polysaccharide-decorated nanoparticles.

Surface modified colloidal carriers such as nanoparticles are able to modulate the biodistribution of the loaded drug when given intravenously, but also to control the absorption of drugs administered by other routes. This review presents the different strategies to coat the surface of polymeric as well as inorganic nanoparticles with polysaccharides. Various physicochemical and biological methods have been described to demonstrate such surface modification. The medical applications, mainly in imaging cancer, of polysaccharide-coated nanoparticles are presented, including their abilities to increase the blood circulation time and to target specific tumoral tissues. It has been shown that these coatings allow also to improve drug absorption via nasal or ocular pathways, due the mucoadhesive and/or permeability enhancer properties of the polysaccharides. Finally, the ability of polysaccharide-coated nanoparticles to deliver DNA or oligonucleotides will be discussed.

Animals↗
PubMed2004

Molecular reactivity of busulfan through its experimental electrostatic properties in the solid state.

PURPOSE: In the route of developing novel liquid phase formulations based on the encapsulation of busulfan into liposomes in nontoxic solvents, drug crystallization inevitably occurs. In order to better understand the reactivity of busulfan, the characterization of its molecular properties was therefore considered as a key point. Also, preliminary attempts to prevent crystallization using cyclodextrins were explored. METHODS: An accurate single-crystal high-resolution X-ray diffraction experiment at 100 K has been carried out. The experimental electron density of busulfan was refined using a multipole model. Busulfan/beta-cyclodextrin coprecipitates were analyzed by powder X-ray diffraction and 1H-NMR spectroscopy. RESULTS: The electrostatic properties of busulfan and the methylsulfonate fragment dipole moment (3.2 D) were determined. The polar moieties play a key role in the crystallization of busulfan, which presents a nucleophilic region surrounding the sulfonate part, whereas the carbon chain displays an electrophilic character. This highlights the subtle busulfan/beta-cyclodextrin association. CONCLUSIONS: Busulfan electrostatic properties were used to quantify its chemical reactivity. This explains the difficulty to formulate busulfan into liposomes due to a strong polar character of the methylsulfonate terminal groups. The complexation with cyclodextrins deserves to be further investigated to allow the formulation of busulfan in nontoxic solvents.

Busulfan↗
PubMed2004

Cationic vectors in ocular drug delivery.

Despite extensive research in the field, the major problem in the ocular drug delivery domain still is rapid precorneal drug loss and poor corneal permeability. One of the approaches recently developed is the drug incorporation into cationic submicronic vectors which exploit the negative charges present at the corneal surface for increased residence time and penetration. This review will focus on the formulation of three main representative cationic colloids developed for ophthalmic delivery: liposomes, emulsions and nanoparticles (NP). Parameters such as choice of the vector type and size, nature of the cationic molecule, pH and ionic strength of the external phase and characteristics of the encapsulated drug will be discussed with accent on the relevance of the positive charge.

Animals↗
PubMed2003

A computationally derived structural model of doxorubicin interacting with oligomeric polyalkylcyanoacrylate in nanoparticles.

We report a molecular simulation study of doxorubicin interacting within a frame of n-butyl polycyanoacrylate, one of the most commonly encountered polymers in the production of nanoparticles. Emphasis is put on the tetrameric, hexameric and octameric oligomers (PACA's). Log P was calculated for all interacting species. Molecular dynamics along with energy minimization processes (molecular mechanics MM2, semi-empirical quantum mechanics PM3) were employed to probe the conformational behavior of doxorubicin and polyalkylcyanoacrylate both as isolated species and interacting with each other. A docked structure of protonated doxorubicin with two octamers of n-butyl polycyanoacrylate is described. Among the main stability factors of the assembly was the charge-dipole interaction representing a stabilizing contribution of -33 kcal/mol. The mechanism of aggregation and desegregation (doxorubicin release) can be summarized as follows: oligomeric PACA's are lipophilic entities that scavenge amphiphilic doxorubicin already during the polymerization process by extraction of the protonated species from the aqueous environment to the increasingly lipophilic phase of the growing PACA's. The establishment of hydrogen bonds between the ammonium N-H function and the cyano groups is noteworthy. The cohesion in PACA nanoparticle comes therefore from a blend of dipole-charge interaction, H bonds, and hydrophobic forces,

Cyanoacrylates↗
PubMed2003

Poly(alkylcyanoacrylates) as biodegradable materials for biomedical applications.

This review considers the use of poly(alkylcyanoacrylates) (PACAs) as biomedical materials. We first present the different aspects of the polymerization of alkylcyanoacrylate monomers and briefly discuss their applications as skin adhesives, surgical glues and embolitic materials. An extensive review of the developments and applications of PACAs as nanoparticles for the delivery of drugs is then given. The methods of preparation of the nanoparticles are presented and considerations concerning the degradation, in vivo distribution, toxicity and cytotoxicity of the nanoparticles are discussed. The different therapeutic applications are presented according to the route of administration of the nanoparticles and include the most recent developments in the field.

Absorbable Implants↗
PubMed2003

Study of emulsion stabilization by graft copolymers using the optical analyzer Turbiscan.

Oil-in-water nanoemulsions were prepared using a series of synthetic graft copolymers with a backbone of dextran (DEX) and a number of side chains of poly-epsilon-caprolactone (PCL). In this paper, we focus on the o/w emulsion stabilizing abilities of these novel PCL-DEX copolymers, using a recently developed optical analyzer (Turbiscan). The main advantage of Turbiscan is to detect the destabilization phenomena in non-diluted emulsion, much earlier than the naked eye's operator, especially in the case of an opaque and concentrated system. This study shows that PCL-DEX copolymers successfully stabilized ethyl acetate-in-water emulsions, even in the absence of additional surfactants, whereas they were not efficient in stabilizing methylene chloride-in-water emulsions which coalesced fast and irreversibly. The ethyl acetate-in-water emulsion stabilizing ability of PCL-DEX seemed to be related to the localization of their blocks with regard to the oil-water interface.

Acetates↗