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Biomedical subjects

F Boury

Publications and source records attributed to F Boury.

At least 19 recordsLinked to original sources
PubMed2005

Interactions between hen egg-white lysozyme, PEG2,000, and PLA50 at the air-water interface.

In this paper, we compared the efficiency of polymer films, made of a poly(ethylene glycol) (PEG2,000)/poly(d,l-lactide) (PLA50) mixture, or a PEG2,000-PLA50 copolymer, to prevent adsorption of a model protein, the hen egg-white lysozyme (HEWL), at the air-water interface. This was achieved by analyzing the surface pressure/surface area curves, and the X-ray reflectivity data of the polymer films spread on a Langmuir trough, obtained in absence or in presence of the protein. For both the mixture and the copolymer, the amount of protein adsorbed at the air-water interface decreases when the density of the polymer surface coverage increases. It was shown that even in a condensed state, the polymer film made by the mixture can not totally prevent HEWL molecules to adsorb and penetrate the polymer mixed film, but however, protein molecules would not be directly exposed to the more hydrophobic phase, i.e. the air phase. It was also shown that the configuration adopted by the copolymer at the interface in its condensed state would prevent adsorption of HEWL molecules for several hours; this would be due in particular to the presence of PEG segments in the interfacial film.

Adsorption↗
PubMed2004

Plant protein-polysaccharide interactions in solutions: application of soft particle analysis and light scattering measurements.

The soft particle analysis theory was applied to plant proteins and polysaccharides in solution, to determine the charge density of these polymers and the depth of the layer accessible by counterions according to pH conditions. In addition to the macromolecule shape characterized by light scattering measurements, these properties are also correlated with the optimum coacervation condition, so as to establish the prevalent plant protein-polysaccharide interactions governing the coacervate formation. Globulin was found to be highly charged and spherically shaped. The best coacervation condition was obtained at the pH value, which corresponds to the protein conformation with a dense and compact accessible layer. On the contrary, for the alpha gliadin, bearing a lower charge, a more extended conformation seems to be more favourable. For the plant proteins studied, the coacervation seems to be controlled by the structure of the counter polyanion used: from our model, it turns out that the rod-like structure of arabic gum observed at acidic pH allows the interaction with plant proteins to form coacervates, contrary to the highly charged and spherical structure of alginate.

Carbohydrate Conformation↗
PubMed2003

Spectroscopic studies on poly(ethylene glycol)-lysozyme interactions.

In the present paper, different spectroscopic methods were applied to evaluate conformational changes of hen egg-white lysozyme (HEWL) in various solvents and in the presence of poly(ethylene glycol) (PEG). In citrate (0.007M, pH=6), or in Tris (0.1M, pH=7.4), no conformational change of the protein was measured across the range of concentrations tested. In addition, HEWL in ultra-pure water revealed no irreversible conformational change and no activity loss, at least at low concentrations (< or =0.2mg/ml). Whereas PEG can induce a reorganization of water molecules, no change of the secondary and tertiary protein conformations was observed in the presence of PEG. In addition, in the presence of PEG of various molecular weights, no change of enzymatic activity of the HEWL was observed across the range of concentrations tested.

Circular Dichroism↗
PubMed2003

Interfacial properties of adsorbed films made of a PEG2000 and PLA50 mixture or a copolymer at the dichloromethane-water interface.

Adsorption kinetics of films of poly(ethylene glycol) (PEG2000) studied by the dynamic pendant drop method showed that PEG2000 was more tensioactive at the dichloromethane (DCM)-water interface than at the air-water interface. When initially solubilized into DCM, PEG2000 segments would form an adsorbed layer with hydrophobic segments buried into the polymer chains turned toward the organic phase. Compression of this layer, accompanied by viscoelastic effects, led to expulsion of some hydrophilic tails toward the water phase. When initially dissolved in water, adsorption of PEG2000 segments led to an elastic PEG2000 layer organized on both sides of the interface. Results showed that when the PEG2000-PLA50 (poly(D,L-lactide)) copolymer film was adsorbed at the DCM-water interface, it resulted in a mixed layer exclusively turned toward DCM and its rheological properties were governed by PLA50. When adsorption at the DCM-water interface resulted from a physical mixture of PEG2000 and PLA50, rheological properties of the film were influenced by the initial localization of PEG2000 in the bulk phases. In the case of a mixed film formed by the adsorption of PLA50 from DCM and PEG2000 from water, results showed that PEG2000 segments totally pushed those of PLA50 away from the interface and exclusively influenced the behavior of the mixed film.

Kinetics↗
PubMed2002

Influence of some formulation parameters on lysozyme adsorption and on its stability in solution.

According to our results concerning the behavior of lysozyme at interfaces, its secondary structure and its enzymatic activity, successful protein encapsulation would need to maintain a pH value far from the enzyme isoelectric point value during the formulation to reduce, in particular, the adsorption of lysozyme molecules at the created interfaces. Moreover, buffers or salt solution must be used in order to keep intact the native secondary conformation of lysozyme, and preserve its enzymatic activity.

Adsorption↗
PubMed2001

Interfacial properties of amiodarone: the stabilizing effect of phosphate anions.

Amiodarone, a drug used in heart therapy, is poorly soluble in water at room temperature, but forms transparent phases much more concentrated than the critical micellar concentration (CMC), when crystals are heated (above 60 degrees C) in presence of water and cooled down to room temperature. These pseudosolutions were supposed to be made of a complex system of micelles. In order to better understand the effects of pH and ion species on the supramolecular organization of amiodarone, interfacial pressure measurements were performed at the air/water interface on a Langmuir trough. Monolayers spread from chloroformic solutions over non bufferered subphases were insoluble at basic pH (NaOH, pH 10) but soluble at acidic pH (HCl, pH 4). However, a higher ionic strength obtained by adding NaCl (0.15 N) or NaH(2)PO(4) (0.15 N) to the subphase stopped the amiodarone solubilization. On an acidic phosphate subphase (NaH(2)PO(4), pH 4.4, 0.15 N), abnormally high surface pressures (>1 mN/m) were measured for high molecular areas (80-200 Å(2)/molecule) suggesting a supramolecular organization of the surface film. Insoluble monolayers were also obtained when the amiodarone supramolecular pseudosolution was spread on neutral (NaH(2)PO(4), pH 6.25, 0.15 N) or acidic (NaH(2)PO(4), pH 4.4, 0.15 N) subphases. However, a great instability on basic subphase (phosphate buffer pH 8.8) indicated the breakage of the supramolecular structure during spreading. These results are discussed taking into account the amiodarone state of ionization and the electrostatic interactions with counterions. Combining the use of phosphate counterions and that of acidic pH opens new perspectives in the optimization of amiodarone intravenous formulations.

Journal Article↗
PubMed1999

Structural Properties of Asymmetric Mixed-Chain Phosphatidylethanolamine Films.

By use of Langmuir isotherms and atomic force microscopy (AFM) experiments, we compare the structural properties of an asymmetric 1-palmitoyl-2-oleoyl-glycero-3-phosphoethanolamine (PE 181/160) film sampled at 21 degrees C on mica plates with those of a film composed of a mixture of the related saturated phospholipid (PE 160/160) and unsaturated phospholipid (PE 181/181). From PE 181/160, the Pi-A curve obtained presents a plateau (35 mN/m) where AFM images allowed us to determine a nucleation process, which governs the growth of condensed domains. This surface transition is interpreted as reflecting hydrophobic interactions mainly between the alkyl chains of the molecules. Moreover Pi-A curves of a mixture (v/v) of the two related saturated and unsaturated phospholipids (PE 160/160 and PE 181/181) show a "double plateau" (50 and 54 mN/m) and we have characterized a partial surface demixing at every surface pressure. Finally we show that only PE 181/160 is able to form bilayers above the collapse pressure. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Why does PEG 400 co-encapsulation improve NGF stability and release from PLGA biodegradable microspheres?

PURPOSE: The aim of this work was to understand the mechanism by which co-encapsulated PEG 400 improved the stability of NGF and allowed a continuous release from PLGA 37.5/25 microspheres. METHODS: Microparticles were prepared according to the double emulsion method. PEG 400 was added with NGF in the internal aqueous phase (PEG/PLGA ratio 1/1 and 1.8/1). Its effect was investigated through interfacial tension studies. Protein stability was assessed by ELISA. RESULTS: A novel application of PEG in protein stabilization during encapsulation was evidenced by adsorption kinetics studies. PEG 400 limited the penetration of NGF in the interfacial film of the primary emulsion. Consequently, it stabilized the NGF by reducing the contact with the organic phase. In addition, it avoided the NGF release profile to level off by limiting the irreversible NGF anchorage in the polymer layers. On the other hand, the amount of active NGF released in the early stages was increased. During microparticle preparation, NaCl could be added in the external aqueous phase to modify the structure of microparticles. This allowed to reduce the initial release rate without affecting the protein stability always encountered in the absence of PEG. CONCLUSIONS: PEG 400 appeared of major interest to achieve a continuous delivery of NGF over seven weeks from biodegradable microparticles prepared by the double emulsion technique.

Biodegradation, Environmental↗
PubMed1999

Direct qualitative and quantitative characterization of a radiosensitizer, 5-iodo-2'-deoxyuridine within biodegradable polymeric microspheres by FT-Raman spectroscopy.

Non-destructive qualitative and quantitative characterization of a radiosensitizer, 5-iodo-2'-deoxyuridine (IdUrd), incorporated within injectable microspheres of a biodegradable polymer, poly(D,L-lactide-co-glycolide) (PLGA), was performed using Fourier transform (FT) Raman spectroscopy. Raman spectra of IdUrd, free and entrapped in microspheres, were recorded under fluorescence-free conditions, described and assigned. For the Raman bands of the PLGA microspheres, assignments with preferential localization of the corresponding vibrations at lactic or glycolic units were proposed. No evidence for drug-polymer interactions in microspheres was found. This allowed the FT-Raman spectra to be used for the quantification of the IdUrd content in the samples. For the microspheres with IdUrd loadings varying from 2 to 27% of the total weight, the methodology used provided good reproducibility and precision (1%). Within the sensitivity of the technique, samples exposed to sterilization doses (27 kGy) of gamma-radiation did not exhibit marked changes in the drug structure.

Humans↗
PubMed1998

NGF release from poly(D,L-lactide-co-glycolide) microspheres. Effect of some formulation parameters on encapsulated NGF stability.

Poly(d,l-lactide-co-glycolide) (PLGA 37.5/25 and 25/50) biodegradable microparticles, which allow the locally delivery of a precise amount of a drug by stereotactic injection in the brain, were prepared by a W/O/W emulsion solvent evaporation/extraction method which had been previously optimized. The aim of this work was to study the influence of two formulation parameters (the presence of NaCl in the dispersing phase and the type of PLGA) on the NGF release profiles and NGF stability during microencapsulation. A honey-comb-like structure characterized the internal morphology of the microspheres. The initial burst was attributed to the rapid penetration of the release medium inside the matrix through a network of pores and to the desorption of weakly adsorbed protein from the surface of the internal cavities. The non-release fraction of the encapsulated protein observed after twelve weeks of incubation was accounted for firstly by the adsorption of the released protein on the degrading microparticles and secondly by the entanglement of the encapsulated protein in the polymer chains. The use of sodium chloride in the dispersing phase of the double emulsion markedly reduced the burst effect by making the microparticle morphology more compact. Unfortunately, it induced in parallel a pronounced NGF denaturation. Finally, it appeared that microparticles made from a hydrophilic uncapped PLGA 37.5/25 in the absence of salt, allowed the release of intact NGF at least during the first 24 h as determined by both ELISA and a PC12 cell-based bioassay.

Animals↗
PubMed1997

Surface characterization of poly(alpha-hydroxy acid) microspheres prepared by a solvent evaporation/extraction process.

This work constitutes the first attempt to characterize the wettability of poly(alpha-hydroxy acid) (PAHA) microspheres in situ, prepared according to a complex process involving emulsification, solvent evaporation, washing and freeze-drying. The analysis of the flotation profile of the microspheres has allowed us to determine both advancing and receding contact angles at the microsphere/air/water interface and furnished information on the organization of poly(vinyl alcohol) (PVA) and bovine serum albumin (BSA) at the surface of the PAHA coating. By the comparison of contact angles measured from model surfaces obtained by sampling pure PAHA, PVA, BSA and mixed PVA/PAHA monolayers on glass and poly(methyl methacrylate) (PMMA) substrates, it was concluded that the emulsifier (PVA or BSA) was strongly anchored to the surfaces of the microspheres. The use of BSA to formulate the microspheres from a single oil-in-water emulsion led to dry particles having a hydrophobic surface. The unfolding of the hydrophilic segments of the BSA embedded at the surface of the microspheres, following immersion in water, increased the wettability of the microspheres by water. The same qualitative results were obtained when PVA was used to stabilize single emulsions. On the other hand, microspheres formulated from a double water-in-oil-in-water emulsion displayed no modifications of their wettability when immersed in water. This can be explained by the absence of mobility of the hydrophilic segments of the emulsifier which are blocked in the surface or at the subsurface of the polymer matrix.

Biocompatible Materials↗
PubMed1987

Production and characterization of monoclonal antibodies showing a different spectrum of reactivity to human breast tissue.

We have generated three hybridoma-producing monoclonal antibodies (MAs) that show a different spectrum of reactivity to human mammary tissues. Two of these antibodies, 1F10B4 and 1F10G2, recognize a cytoplasmic determinant highly expressed in most of the primary and metastatic breast carcinomas studied, and weakly (or not at all) in normal breast and nonbreast tissues. 3C6F9 detected a surface determinant common to both normal and neoplastic mammary epithelium. Five hundred hybridomas were obtained from the fusion of NS-1 myeloma cells with spleen cells of mice hyperimmunized with the well-characterized human breast carcinoma cell line BT-20. After the initial screenings and clonings, three monoclonal antibodies (1F10B4, 1F10G2, and 3C6F9) showing a restricted range of reactivity were selected for further investigation. These three antibodies recognized a panel of neoplastic mammary cell lines; however, the degree of reactivity could not be correlated to any of the various characteristics of these epithelial cell lines. Moreover, immunofluorescence analysis of acetone-fixed cryostat section showed that 1F10B4 and 1F10G2 recognize the vast majority of the 37 primary and metastatic breast cancers tested, binding strongly to 47% and 67% of them respectively. Only one of the primary carcinomas was not recognized by 1F10B4. On the other hand, these two MAs reacted weakly or not at all with normal breast and nonbreast tissues showing only few focal reactivities with the luminal pole of some ducts of the breast; very weak staining in renal tubular epithelial cells, in few keratinocytes and epithelial cells lining some sebaceous glands in the skin; and a moderate staining in biliary ducts of the liver. All mesenchymal structures including smooth and striated muscle tissues, lymph nodes, and connective tissue were negative. On the other hand, 3C6F9 recognized a more limited number of human mammary tumors and reacted with normal ductal epithelium in the breast and with nonbreast tissues. Because of their wide spectrum of reactivity with breast cancer cells and restricted recognition of normal mammary tissues, their cytoplasmic localization, and their heterogeneous distribution within a single neoplasm, 1F10B4 and 1F10G2 are now being used to characterize antigenic phenotypes of tumor-associated antigens in retrospective studies performed on conventional formalin-fixed, paraffin-embedded human mammary carcinomas.

Animals↗
PubMed1984

Adriamycin and adriamycin-DNA nephrotoxicity in rats.

The early nephrotoxicity of free and DNA-bound adriamycin (ADR) was compared in left nephrectomized rats. Free ADR induced progressive renal failure within 3 weeks, in association with renal changes characterized by severe tubular distention and vacuolization of podocytes in glomeruli. On the contrary, renal function remained normal and renal lesions were discrete in animals treated with ADR bound to DNA. Thus, the binding of ADR to DNA seems to reduce the early nephrotoxicity of free ADR.

Acute Kidney Injury↗
PubMed1983

Comparative toxicity of adriamycin and adriamycin-DNA in rats.

Adriamycin (ADR) can be linked to DNA without loss of its antitumoral activity while reducing the acute toxicity of free ADR (Deprez--DeCampeneere et al., 1979, 1980). However, the potential chronic toxic effects of both forms of ADR are poorly documented. For such a study, it is necessary to establish the sequence of treatment allowing the administration of a sufficient amount of drugs to induce chronic toxicity and a schedule leading to prolonged survival of animals. In this study, 24 Lewis rats were injected twice a week during four weeks with either free or DNA-linked ADR, and three dose levels were tested: 4, 2 and 1 mg/kg. Our results indicated that the total cumulative dose of ADR should not exceed 8 mg/kg over one month, if prolonged survival is desired. The binding of ADR to DNA seemed also to reduce the acute toxic effects induced by free ADR, in rats. However, such a beneficial effect was not observed when the chronic nephrotoxicity was considered since characteristic renal lesions were observed in all long-term survivors, whatever the dose and the form of ADR received.

Animals↗
PubMed1981

Effectiveness of the adriamycin-DNA complex in kidney allograft immunosuppression.

The chemotherapeutic effectiveness of the lysosomotropic Adriamycin-DNA complex has been demonstrated experimentally. This study evaluated the immunosuppressive activity of the complex on renal allografts in rats of the Buffalo-Lewis strain. Six rats receiving no treatment served as a control. Five rats received DNA along (at a dose equivalent to that in the complex), seven received the Adriamycin-DNA complex (molar ratio of DNA mononucleotide to Adriamycin, 20:1) and five were given free Adriamycin. Adriamycin, free or linked to DNA, was injected as follows: 2 mg/kg on days 2, 6 and 9 and 1 mg/kg on day 13 after transplantation. The Adriamycin-DNA complex prevented renal allograft rejection in the early postoperative period, by delaying for more than a week, the increase in serum creatinine levels in animals receiving transplants. Histologic examination of renal grafts in these rats confirmed the reduced severity of acute cellular rejection. There was also functional and morphologic evidence of reduced toxicity of Adriamycin when linked to DNA. The beneficial effect of such a drug should be attributed to its lysosomotropic mechanism of activity.

Animals↗
PubMedDate not supplied

Rheological interfacial properties of plant protein-arabic gum coacervates at the oil-water interface.

This study concerns the interfacial properties of the plant proteins-arabic gum coacervates, which are involved in encapsulation processes based on complex coacervation. The results make it possible to deduce the prerequisite characteristics of the protein, which are involved in the coacervate interfacial properties. The influence of pH and concentration on protein interfacial properties was also studied so as to enable us to predict the best conditions to achieve encapsulation. It has been established that, to obtain a good encapsulation yield, the coacervate must show high surface-active properties and its adsorption on the oil droplets must be favored compared to the free protein adsorption. On the other hand, mechanical properties of the interfacial film made of the coacervate, appear to be a key parameter, as reflected by the dilational viscoelasticity measurements. When compared to the properties of the proteins films, an increase of the rigidity of the interfacial film was shown with the coacervates. It was also observed that viscoelastic properties of the coacervate film were strongly reduced, as well as the associated relaxation times. In acidic conditions, the coacervates containing alpha-gliadin are characterized by an interfacial viscoelastic behavior. This behavior reflects the softness of the interfacial film. This viscoelasticity allows also the formation of a continuous layer around the oil droplets to be encapsulated. Drop tensiometry is shown to be a method that could allow the most adapted protein to be selected and the conditions of the coacervation process to be optimized with regard to concentration and pH.

Adsorption↗