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E Fattal

Publications and source records attributed to E Fattal.

At least 55 records · Page 3Linked to original sources
PubMed1998

[New approaches for encapsulation of peptides into poly(lactic/glycolic acid) microspheres].

The aim of the work was to develop small microspheres made from a biodegradable polymer, poly(lactide-co-glycolide), in order to entrap small peptides. Microspheres prepared by a water-in-oil-in-water emulsion solvent evaporation technique displayed a mean diameter below than 10 microns and showed high encapsulation efficiency of a 33 amino acid peptide (V3 BRU). In vitro release kinetics studies showed that such microparticles could be employed for both oral immunization and controlled release. The encapsulation of a seven aminoacid peptide in the same conditions, led to a very low encapsulation efficiency. In order to increase the entrapment efficiency, two strategies were adopted: taking into account the solubility of pBC 264 at different pH, a pH gradient was created to prevent the leakage of the encapsulated peptide into the outer aqueous phase. The inner aqueous phase was maintained at basic pH where the peptide was soluble, while the external aqueous phase was acidic: ovalbumin was added during preparation to stabilize the inner emulsion. These two strategies allowed to increase significantly the encapsulation rate of pBC 264. Nevertheless, the in vitro release kinetics of the peptide were strongly influenced by the presence of ovalbumin which seems to form pores in the microsphere structure (80% of the total peptide content was released after 30 minutes). By contrast, when ovalbumin was replaced by Pluronic F 68 microspheres did not have pores, thus the release profile and the extent of the burst were much smaller. When microspheres were stereotactically implanted in the rat brain, in vivo release profiles were in good agreement with the release observed in vitro. In conclusion, these microspheres are well suited for the slow delivery of neuropeptides in the brain, a feature expected to facilitate the study of long term effects of these compounds.

Animals↗
PubMed1997

Multiple emulsion technology for the design of microspheres containing peptides and oligopeptides.

This paper reviews the preparation and characterization of small poly(lactic-co-glycolic acid) microspheres (mean size lower than 10 µm) containing small peptides and prepared by a water-in-oil-in-water emulsion solvent evaporation technique. These microspheres were shown to encapsulate very efficiently a 33 amino acid peptide (V3 BRU) and in vitro release kinetics studies showed that such microspheres could be employed for both oral vaccination and controlled release. The encapsulation of a seven amino acid peptide (pBC 264) led on the contrary to a very low encapsulation efficiency. In order to increase the encapsulation of pBC 264, two strategies were adopted: (i) taking into account the solubility of pBC 264 at different pH, the inner aqueous phase was maintained at a basic pH where the peptide was soluble, while the external aqueous phase was acidic; (ii) ovalbumin was added to stabilize the inner emulsion. These two strategies allowed us to increase significantly the encapsulation rate of pBC 264. Nevertheless, the in vitro release kinetics of the peptide were strongly influenced by the presence of ovalbumin which seems to form pores in the microsphere structure. By contrast, when ovalbumin was replaced by Pluronic(R) F68, microspheres did not have pores, thus the release profile and the extent of the burst were much smaller. When microspheres were stereotactically implanted in the rat brain, in vivo release profiles were in good agreement with the release observed in vitro. In conclusion, these microspheres are well suited for the slow delivery of neuropeptides in the brain, a feature expected to facilitate the study of long term effects of these compounds.

Journal Article↗
PubMed1997

Evaluation of hepatic antioxidant systems after intravenous administration of polymeric nanoparticles.

We have investigated the modifications of the levels of intracellular markers of the oxidative stress in hepatocytes, after single or repeated injections of poly(isobutyl cyanoacrylate) (PIBCA) and polystyrene (PS) nanoparticles. Nanoparticles were administered intravenously at single doses of 20 and 100 mg kg 1 for 14 days. Levels of reduced (GSH) and oxidized (GSSG) glutathione, superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CT) and the peroxidation of membrane lipids were measured. Single and repeated administration of PIBCA and PS nanoparticles induced a transient depletion of GSH and GSSG levels, a transient inhibition of SOD activity and a slight increase in CT activity. However, GPx activity was not modified and lipid peroxidation was not observed, suggesting that hepatocytes are not strongly affected by these modifications. Since nanoparticles do not distribute in hepatocytes, oxidative species could proceed from hepatic macrophages, activated after nanoparticle phagocytosis. It is unlikely that poly(alkyl cyanoacrylate) degradation products might be responsible for the oxidative attack because non-biodegradable PS nanoparticles induced the same effect. Uptake of polymeric nanoparticles by Kupffer cells in the liver induce modifications in hepatocyte antioxidant systems, probably due to the production of radical oxygen species. However, the depletion in glutathione was not great enough to initiate hepatocyte damage, since no changes in lipid peroxidation and reversible alterations were observed. This is an important factor to be considered in the use of polymeric nanoparticles as drug carriers.

Animals↗
PubMed1997

Protective immunity against Salmonella typhimurium elicited in mice by oral vaccination with phosphorylcholine encapsulated in poly(DL-lactide-co-glycolide) microspheres.

Encapsulation of vaccines in biodegradable microspheres provides excellent mucosal immunogens with a high potential for immunization against bacterial infections. We tested the protective immunity elicited by intragastric vaccination with phosphorylcholine (PC) encapsulated in poly(DL-lactide-co-glycolide) (DL-PLG) microspheres against Salmonella typhimurium in a mouse model of invasive intestinal infection. We chose PC as the antigen because it was found to elicit an immune response after intestinal exposure of mice to PC-bearing S. typhimurium and because anti-PC immunity protects mice against Streptococcus pneumoniae, another PC-bearing microorganism. Mice were primed intragastrically on days 1, 2, and 3 and boosted on days 28, 29, and 30 with PC (280 microg) coupled to porcine thyroglobulin (PC-thyr) encapsulated in DL-PLG microspheres, free PC-thyr, or blank microspheres. A significant rise in anti-PC immunoglobulin A (IgA) titers, as measured by an enzyme-linked immunosorbent assay, was observed in the intestinal secretions after immunization with PC-loaded microspheres, compared to the titers of mice immunized with free PC-thyr or blank microspheres. This antibody response peaked 14 days after the last boost and correlated with a highly significant resistance to oral challenge by S. typhimurium C5 (P < 10(-3)). Control mice were primed intraperitoneally on day 1 with 15 microg of PC in complete Freund's adjuvant and boosted on days 10, 14, and 20 with the same dose without adjuvant but via the same route. In these mice, the levels of anti-PC IgA in intestinal secretions were equivalent to those of the mice intragastrically immunized with PC-loaded microspheres, but protection was significantly weaker, suggesting that either the IgAs were not functional or that other immune mechanisms are important in protection. Taken together, our results highlight the potential of antigen encapsulation in DL-PLG microspheres for eliciting protective immunity against invasive intestinal bacterial diseases and suggest that a similar strategy could be used against diseases caused by other PC-bearing microorganisms.

Administration, Oral↗
PubMed1996

Development of a quantitative polyacrylamide gel electrophoresis analysis using a multichannel radioactivity counter for the evaluation of oligonucleotide-bound drug carrier.

A quantitative polyacrylamide gel electrophoresis (PAGE) analysis using a multichannel radioactivity counter was designed for the evaluation of 33P-labeled antisense oligonucleotide associated with polymeric drug carrier (nanoparticles). The proposed analytical method was first validated. The criteria of specificity, linearity, reliability, detection and quantification limits, and resolution power were determined. Results were compared to those obtained using liquid scintillation counting of crude samples or after solubilization of gel slices. The proposed method gave a better linearity and reliability than liquid scintillation counting of solubilized gel slices. In comparison with the liquid scintillation counting of crude samples, the method presented the advantage of being able to directly separate oligonucleotides differing by only one nucleotide in length. This method was applied for the separation of free oligonucleotides and oligonucleotides bound onto nanoparticles, allowing quantification of the amount of free and bound oligonucleotides without any further separation steps. Thus, because it is easy and rapid, the quantitative PAGE analysis using a multichannel radioactivity counter offers interesting possibilities for the characterization of oligonucleotide nanoparticles.

Cyanoacrylates↗
PubMed1996

Effect of polymeric nanoparticle administration on the clearance activity of the mononuclear phagocyte system in mice.

We investigated the consequences of acute and subacute administration of mice with polyisobutylcyanoacrylate (PIBCA), polyisohexylcyanoacrylate (PIHCA), poly(D,L-lactic) acid (PLA), and polystyrene (PS) nanoparticles on the mononuclear phagocyte system phagocytic function. This was done by measuring the clearance rate of colloidal carbon. Single administration of PIBCA and PIHCA (but not PLA and PS) nanoparticles reduced carbon clearance in both a time- and dose-dependent fashion. Since clearance of preopsonized carbon was normal, it was assumed that PIBCA and PIHCA nanoparticles deplete opsonins specific for carbon recognition. A decrease in plasma fibronectin levels resulting from nanoparticle administration suggested its implication in their removal from blood. However, fibronectin does not seem to be responsible for PIBCA and PIHCA blockade. Phagocytic function was preserved after repeated treatment with nanoparticles, probably as a result of increased Kupffer cell phagocytic activity and the contribution of spleen macrophages. Neither toxicity nor effects due to nanoparticle hepatic accumulation were observed.

Animals↗
PubMed1996

Pharmacokinetics and biodistribution of oligonucleotide adsorbed onto poly(isobutylcyanoacrylate) nanoparticles after intravenous administration in mice.

PURPOSE: The goal of this study was to evaluate the ability of nanoparticles to be used as a targeted delivery system for oligonucleotides. METHODS: Pharmacokinetic and tissue distribution were carried out in mice by measuring radioactivity associated to the model oligothymidylate 33P-pdT16 loaded to poly(isobutylcyanoacryate) (PIBCA) nanoparticles. In addition, we have used a TLC linear analyzer to measure quantitatively on a polyacrylamide gel electrophoresis, the amount of non degraded pdT16. RESULTS: Organ distribution study has shown that nanoparticles deliver 33P-pdT16 specifically to the liver reducing its distribution in the kidney and in the bone marrow. Nanoparticles could partially protect pdT16 against degradation in the plasma and in the liver 5 min after administration, whereas free oligonucleotide was totally degraded at the same time. CONCLUSIONS: Nanoparticles protect oligonucleotides in vivo against degradation and deliver them to the liver.

Adsorption↗
PubMed1996

Slow delivery of the selective cholecystokinin agonist pBC 264 into the rat nucleus accumbens using microspheres.

Neuropeptides have been shown to play a critical role in adaptational processes, probably by long-term modulation of neuronal pathways. It could therefore be interesting to study behavioral changes induced by chronic local stimulation of neuropeptide receptors. With this aim poly(lactide-co-glycolide) microspheres loaded with a highly potent, peptidase-resistant, cholecystokinin (CCK)-B-selective CCK peptidomimetic agonist (pBC 264) were prepared by a water in oil in water emulsion solvent evaporation method and stereotaxically implanted into the anterior part of the rat nucleus accumbens. Two different kinds of loaded polymeric microspheres differing only by the stabilizing agent [ovalbumin (OVA) or Pluronic F 68] added to the inner emulsion were used. The histological and behavioral studies done 24 h and 8 days after implantation of nonloaded microspheres in the nucleus accumbens indicated that the microspheres were well tolerated. The in vivo release of the selective CCK-B agonist pBC 264 (associated with a tracer dose of [3H]pBC 264) from microspheres prepared with OVA was very fast (92% after 6 h), whereas only 26% (88 pmol) of pBC 264 was released from the formulation with Pluronic F 68 after 24 h. Eight days after implantation 36% of pBC 264 had diffused from the microspheres, and 8% (approximately 30 pmol) was still present in the brain concentrated around the site of administration. In all cases the released material was found to correspond to intact pBC 264, thus demonstrating the possibility of obtaining a slow controlled release of peptide in vivo. This method opens up interesting perspectives to study the long-term effects of neuropeptides.

Animals↗
PubMed1996

Evaluation of PLGA microsphere size effect on myotoxicity using the isolated rodent skeletal muscle model.

The present work investigated the magnitude of microsphere-induced acute myotoxicity and determined whether this myotoxicity is related to microsphere size and/or reconstitution solvent. Using a high molecular weight poly(dl-lactide-co-glycolide) copolymer, the myotoxicity of two different size microsphere formulations (3.6 microns and 19 microns) in normal saline or distilled water was quantified using a previously validated isolated rat muscle system. Overall, microspheres were found to be relatively nontoxic compared to known myotoxic agents (e.g., phenytoin) and control muscles. The smaller microspheres were found to be significantly more myotoxic than larger microspheres. Furthermore, the myotoxicity was lower in large microspheres reconstituted with normal saline or normal saline with 0.5% (w/v) carboxymethylcellulose (to prevent aggregation) compared to those reconstituted with distilled water. Smaller microspheres were found to be extremely difficult to inject, due to aggregation, which could not be prevented by the addition of carboxymethylcellulose. This study suggests that larger microspheres are less myotoxic than smaller microspheres.

Animals↗
PubMed1995

Evaluation of liver toxicological effects induced by polyalkylcyanoacrylate nanoparticles.

Intravenous administration of drug-loaded polyalkylcyanoacrylate (PACA) nanoparticles is followed by a rapid uptake by the tissues of the reticuloendothelial system, mainly the liver. Nevertheless, it is so far unknown whether chronic administration of nanoparticles can lead to damage to the liver cells. We have studied the subacute toxicological effects of these drug carriers in a rat in vivo/ex vivo model. Nanoparticles were administered intravenously at a total dose of 200 mg/kg for 14 days (10 individual doses of 20 mg/kg). Hepatocytes were then isolated. Levels of alpha 1-acid glycoprotein secretion increased while albumin secretion decreased in hepatocytes from rats treated with PACA nanoparticles. In addition, glucose production due to the fructose metabolism was lowered. Treated rats induced a temporary increase and hyposialyation of serum alpha 1-acid glycoprotein. These effects were reversible 15 days after the treatment was concluded. Finally, the involvement of Kupffer cells and polymer degradation products was studied in vitro. Modifications of hepatocyte protein synthesis related to the treatments were only observed when direct contact between nanoparticles and hepatocytes existed. Kupffer cells and polymer degradation products did not mediate the hepatocyte response to nanoparticles in vitro. In conclusion, modifications in hepatic function after chronic administration of PACA nanoparticles have been detected by the use of very sensitive models for detecting hepatoxicity. These effects were, however, found to be reversible when the treatment was stopped.

Animals↗
PubMed1995

Stimulation of movement and acrosome reaction of human spermatozoa by PC12 liposomes encapsulating ATP.

The effect of co-incubating human spermatozoa with 8 mmol/L dilauroylphosphatidylcholine (PC12) liposomes containing 6 mmol/L adenosine 5'-triphosphate (LATP) was assessed by CASA and compared to that obtained with blank PC12 liposomes (LB). The aim of this study was to investigate if such treatments can improve sperm movement and sustain sperm motility over time. Significant and similar increases in straight-line velocity and linearity of sperm movement in B2 capacitating medium (both p < 0.01) were obtained with LB and LATP treatments (final concentration: 0.38 mmol/L PC12 and 0.5 mmol/L ATP) while in Tyrode's medium supplemented with 10 mg/mL BSA, these movement parameters were increased significantly only in sperm aliquots treated with LATP. Furthermore, after incubation for 0.5 h in Tyrode's, a bioluminescence assay of intracellular ATP indicated no significant change in ATP concentration for LATP-treated spermatozoa while the ATP content of control and LB-treated spermatozoa decreased significantly during the same period (both p < 0.05). The effect of liposomes on the acrosome reaction was also investigated jointly with CASA. These experiments were performed by fluorescence microscopy, using PSA-FITC and the supravital stain Hoechst 33258. After a precapacitation period of 3 h in BWW medium the spermatozoa were incubated for 1 h with LATP, LB, LB+free ATP and free ATP alone (final concentration 0.5 mmol/L ATP). Under these conditions the percentage of acrosome-reacted spermatozoa was increased similarly after LATP and LB treatments compared to control (respectively from 4.9 to 12%, p < 0.01 and 4.9 to 11.3%, p < 0.05) but the percentage of true acrosome-reacted spermatozoa, and the values for all movement characteristics (except percentage motility) were increased significantly only with LATP treatment. The results indicate the potential of PC12 vesicles for introducing highly hydrophilic compounds into spermatozoa, as well as for modulating membrane structures and functions required for fertilization.

Acrosome↗
PubMed1994

Pore-forming peptides induce rapid phospholipid flip-flop in membranes.

A kinetic model for pore-mediated and perturbation-mediated flip-flop is presented and used to characterize the mechanism of peptide-induced phospholipid flip-flop in bilayers. The model assumes that certain peptides can bind to and aggregate within the membrane. When the aggregate attains a critical size (M peptides), a channel is created that results in a fast flip-flop of phospholipids. In addition, certain peptides induce flip-flop through perturbation of the membrane without forming a pore. Donor phospholipid vesicles with an asymmetrical distribution of the fluorescent phospholipid 1-oleoyl-2-[12-[(7-nitro-1,2,3-benzoxadiazol-4- yl)amino]dodecanoyl]phosphatidylcholine (NBD-PC) were used to measure the extent of flip-flop by quantitating the decrease in fluorescence as the NBD-PC exchanged from the donor vesicles to acceptor vesicles that contained a quencher of the NBD fluorescence. Flip-flop curves generated at lipid/peptide ratios ranging from 30/1 to 300000/1 could be well-simulated by the model. Pore-forming peptides, such as melittin or the synthetic peptide GALA (WEAALAEALAEALAEHLAEALAEALEALAA), induce rapid phospholipid flip-flop with half-times for flip-flop of seconds at low peptide/vesicle ratios. The deduced pore sizes are M = 10 +/- 2 for GALA and M = 2 - 4 for melittin. The synthetic peptide LAGA (WEAALAEAEALALAEHEALALAEAELALAA) can catalyze flip-flop via bilayer perturbation. In contrast, hydrophobic peptides such as gramicidin A and valinomycin intercalate into the membrane, but induce little flip-flop. Modeling of the kinetics of phospholipid translocation supports pore formation as the key factor in accelerating phospholipid flip-flop. Thus, amphipathic segments from membrane proteins may account for non-energy-dependent phospholipid flip-flop in biological membranes.

Amino Acid Sequence↗
PubMed1994

Liposomes, an interesting tool to deliver a bioenergetic substrate (ATP). in vitro and in vivo studies.

Adenosine triphosphate (ATP) was proposed in various medical applications, as a possible bioenergetic substrate. Unfortunately, ATP is very difficult to use at a therapeutic level because of its high sensitivity to enzymatic hydrolysis making this molecule unstable in biological fluids. ATP is also a highly hydrophilic molecule that is unable to cross biological membranes. To try to develop a system able to protect ATP against degradation and to efficiently deliver this bioenergetic substrate, its liposomal encapsulation in multilamellar vesicles was carried out. One of the studies described in this paper deals with the efficiency of liposomal ATP in the treatment of cerebral ischemia. Our results show that encapsulation was able to protect ATP from its degradation by ectonucleotidases and that liposomal ATP was active against experimental brain ischemia. The other study deals with the effect of ATP on the motility and the acrosomal reaction of human spermatozoa. The results show that co-incubating ATP-loaded liposomes with sperm cells was able to induce the process of capacitation in vitro and might therefore be a useful tool in the procedure of in vitro fertilization.

Adenosine Triphosphate↗
PubMed1991

Liposomes and nanoparticles in the treatment of intracellular bacterial infections.

The treatment of infections caused by obligate or facultative intracellular microorganisms is difficult because most of the available antibiotics have either poor intracellular diffusion and retention or reduced activity at the acidic pH of the lysosomes. The need for antibiotics with greater intracellular efficacy led to the development of endocytosable drug carriers, such as liposomes and nanoparticles, which mimic the entry path of the bacteria by penetrating the cells into phagosomes or lysosomes. This Review assesses the potential of liposomes and nanoparticles in the targeted antibiotic therapy of intracellular bacterial infections and diseases and the pharmaceutical advantages and limitations of these submicron delivery systems.

Anti-Bacterial Agents↗
PubMed1991

Liposome-entrapped ampicillin in the treatment of experimental murine listeriosis and salmonellosis.

The tissue distribution of ampicillin entrapped in liposomes was studied in normal noninfected mice and showed that ampicillin concentrated mostly in the liver and spleen. Liposomate ampicillin was significantly more effective than free ampicillin in reducing splenic and hepatic bacterial counts in C57BL/Ka nude mice chronically infected with Listeria monocytogenes EGD. It was also significantly more effective than free ampicillin in reducing mortality in C57BL/6 mice acutely infected with Salmonella typhimurium C5. Comparison of the results with those previously obtained in the same experimental models with the same amounts of ampicillin bound to polyisohexylcyanoacrylate nanoparticles showed that liposomes were more effective than nanoparticles (M. Youssef, E. Fattal, M. J. Alonso, L. Roblot-Treupel, J. Sauzières, C. Tancrède, A. Omnès, P. Couvreur, and A. Andremont, Antimicrob. Agents Chemother. 32:1204-1207, 1988) in targeting ampicillin to the spleen but were less effective than nanoparticles in targeting ampicillin to the liver and reducing mortality in acute salmonellosis.

Ampicillin↗