Biomedical subjects

Elias Fattal

Publications and source records attributed to Elias Fattal.

At least 19 recordsLinked to original sources

PubMed2006

Encapsulation of dexamethasone into biodegradable polymeric nanoparticles.

The present paper concerns both the optimization of dexamethasone (DXM) entrapment and its release from biodegradable poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles prepared by the solvent evaporation process. Since the addition of DXM induced the formation of drug crystals beside the nanoparticle suspension, the influence of several parameters on DXM encapsulation was investigated such as the type of organic solvent and polymer, the DXM initial mass, the evaporation rate of the solvent, the continuous phase saturation and the incorporation of a lipid in the polymer. Nanoparticle size and zeta potential were not modified in the presence of DXM and were respectively around 230 nm and -4 mV. The highest drug loading was obtained using 100 mg PLGA 75:25 in a mixture of acetone-dichloromethane 1:1 (v:v) and 10 mg of DXM. The drug was completely released from this optimized formulation after 4 h of incubation at 37 degrees C. Neither the evaporation rate of the organic solvent, nor the aqueous phase saturation with salt or the incorporation of 1mg 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) within the nanoparticles modified the encapsulation efficiency. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) demonstrated that the drug was molecularly dispersed within the nanoparticles whereas the non-encapsulated DXM crystallized. These results demonstrate the feasibility of encapsulating dexamethasone and its subsequent delivery.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2006

Ocular delivery of nucleic acids: antisense oligonucleotides, aptamers and siRNA.

Nucleic acids have gained a lot of interest for the treatment of ocular diseases. The first to enter in clinic has been Vitravene an antisense oligonucleotide for the treatment of cytomegalovirus (CMV) infection and more recently, research on aptamers have led to the marketing of anti-vascular endothelial growth factor (VEGF) inhibitor (Macugen) for the treatment of age-related macular degeneration (AMD). The siRNAs appear very promising as they are very potent inhibitors of protein expression. Despite their potential, nucleic acids therapeutic targets of nucleic acid-based drugs are mainly located in the posterior segment of the eye requiring invasive administration which can be harmful if repeated. Their intracellular penetration in some cases needs to be enhanced. This is the reason why adequate delivery systems were designed either to insure cellular penetration, protection against degradation or to allow long-term delivery. A combination of both effects was also developed for an implantable system. In conclusion, the intraocular administration of nucleic acids offers interesting perspectives for the treatment of ocular diseases.

Animals↗

PubMed2006

Predicting plutonium decorporation efficacy after intravenous administration of DTPA formulations: Study of pharmacokinetic-pharmacodynamic relationships in rats.

PURPOSE: The objectives of this study were: 1) to assess the relationship between plutonium decorporation (increased excretion and reduced retention in main organs of deposition) induced by intravenous liposome formulations of the chelating agent diethylene triamine pentaacetic acid (DTPA) and its pharmacokinetics, and 2) to model the renal excretion of plutonium after treatment with liposome-encapsulated DTPA in order to predict its efficacy and to optimise treatment schedules. MATERIALS AND METHODS: Pharmacokinetic parameters from plasma or urinary data (days 0-16 sample collections) were modelled versus decorporation efficacy, and best correlations were selected for their goodness of fit. RESULTS: The plutonium decorporation enhancement by DTPA liposomal formulations was well described by logistic models and the best correlation was observed with the area under the DTPA concentration curve of each formulation. The plutonium urinary excretion rates decreased mono-exponentially as a function of time after a single dose and the proposed model allowed a simple determination of the elimination half-life of the Pu-DTPA complex, a reasonably good approximation of the long-term efficacy of the treatments from truncated urinary data. CONCLUSIONS: Both liposomal formulations of chelating agents and pharmacokinetic approaches to plutonium decorporation should be helpful in optimising treatment protocols.

Animals↗

PubMed2006

Improved antitumoral properties of pure antiestrogen RU 58668-loaded liposomes in multiple myeloma.

In most of multiple myeloma (MM) cells, the "pure" antiestrogen (AE) RU 58668 (RU) induced either a G1-arrest (LP-1, OPM-2, NCI-H929, U266 cells) or apoptosis (RPMI 8226 cells). In RPMI 8226 cells, RU activates a caspase-dependent cell death pathway leading to the release of cytochrome c, the decrease of the essential MM survival factor Mcl-1, the cleavage of Bid and the activation of caspases-3 and -8. Incorporation of RU in pegylated cholesterol-containing liposomes allowed a controlled RU release, improving its anti-proliferative and apoptotic effects in cells. In RPMI 8226 xenografts, i.v. injected RU-liposomes but not free RU, exhibited antitumor activity. In vivo, RU-liposomes triggered the mitochondrial death pathway, concomitantly with a down-regulation of Mcl-1 and Bid cleavage. The decrease of CD34 immunoreactivity indicated a reduction of angiogenesis. The decrease of VEGF secretion in vitro supported a direct effect of RU on angiogenesis. These pro-apoptotic and antiangiogenic effects were explained by a prolonged exposure to the drug and to the endocytosis capacity of liposomes which might increase RU uptake and bypass a membrane export of free RU. Thus, these combined enhanced activities of RU-liposomes support that such a delivery of an AE may constitute a strategy of benefit for MM treatment.

Animals↗

PubMed2006

Evaluation of critical formulation parameters influencing the bioactivity of beta-lactamases entrapped in pectin beads.

The bioactivity of beta-lactamases upon entrapment in calcium-pectinate beads was evaluated. Non-amidated (NAP) and amidated pectin (AP) beads were prepared according to the ionotropic gelation method using calcium chloride (CaCl(2)) as gelling agent, washed and dried at 37 degrees C in an oven for 2h. Both enzyme activity and protein content were determined as well as bead calcium content. NAP allowed a better encapsulation of the protein than AP. Increasing both CaCl(2) concentration and bead residence time in the gelation medium led to a significant loss of beta-lactamase activity. The drying process of beads also lowered the enzyme activity. Moreover, bead calcium content increased as the CaCl(2) concentration augmented. Being very hygroscopic, the excess of CaCl(2) correlates with an increase of moisture content in beads that affects enzyme activity. After elimination of free calcium from beads, it was shown that a small amount is needed to form the Ca-pectinate network and that the activity of beta-lactamases is preserved in these conditions. Therefore, the bioactivity of encapsulated beta-lactamases in pectin beads mainly depends on formulation parameters such as pectin type, CaCl(2) concentration, washing and drying processes.

Calcium↗

PubMed2006

Efficacy of siRNA nanocapsules targeted against the EWS-Fli1 oncogene in Ewing sarcoma.

The EWS-Fli1 fusion gene encodes for a chimeric oncogenic transcription factor considered to be the cause of the Ewing sarcoma. The efficiency of small interfering RNAs (siRNAs) targeted toward the EWS-Fli1 transcript (at the junction point type 1) was studied, free or encapsulated into recently developed polyisobutylcyanoacrylate aqueous core nanocapsules. Because this mRNA sequence is only present in cancer cells, it therefore constituted a relevant target. Studies of the intracellular penetration by confocal microscopy in NIH/3T3 EWS-Fli1 cells showed that nanocapsules improved the intracellular penetration of siRNA with mainly a cytoplasmic localization. These biodegradable siRNA-loaded nanocapsules were then tested in vivo on a mice xenografted EWS-Fli1-expressing tumor; they were found to trigger a dose-dependant inhibition of tumor growth after intratumoral injection. A specific inhibition of EWS-Fli1 was observed, too. These findings now open new prospects for the treatment of experimental cancers with junction oncogenes.

Animals↗

PubMed2006

Oligonucleotide-polyethylenimine complexes targeting retinal cells: structural analysis and application to anti-TGFbeta-2 therapy.

PURPOSE: The aim of this study was to characterize oligonucleotide-polyethylenimine (ODN/PEI) complex preparation for potential transfection of retinal cells in vitro and in vivo. METHODS: The effect of medium preparation [HEPES-buffered saline (HBS), water] on particle size and morphology was evaluated. Cultured Lewis rat retinal Müller glial (RMG) cells were transfected using fluorescein isothiocyanate (FITC)-ODN/PEI complexes specifically directed at transforming growth factor beta (TGFbeta)-2. Efficacy of transfection was evaluated using confocal microscopy, and regulation of gene expression was assayed using quantitative real-time RT-PCR and ELISA assay. One, 24, and 72 h after injection of FITC-ODN/PEI complexes into the vitreous of rat eyes, their distribution was analyzed on eye sections. RESULTS: Complexes prepared in HBS were smaller than complexes prepared in pure water and presented a core-shell structure. These particles showed a high cellular internalization efficacy, along with a significant and specific down-regulation of TGFbeta-2 expression and production in RMG cells, correlating with specific inhibition of cell growth at 72 h. In vivo, complexes efficiently transfect retinal cells and follow a transretinal migration at 24 h. After 72 h, ODN seems to preferentially target RMG cells without inducing any detectable toxicity. CONCLUSIONS: Specific down-regulation of TGFbeta-2 expression using ODN/PEI complexes may have potential interest for the treatment of retinal diseases associated with glial proliferation.

Animals↗

PubMed2006

Sustained release of nanosized complexes of polyethylenimine and anti-TGF-beta 2 oligonucleotide improves the outcome of glaucoma surgery.

The purpose of this study was to design microspheres combining sustained delivery and enhanced intracellular penetration for ocular administration of antisense oligonucleotides. Nanosized complexes of antisense TGF-beta2 phosphorothioate oligonucleotides (PS-ODN) with polyethylenimine (PEI), and naked PS-ODN were encapsulated into poly(lactide-co-glycolide) microspheres prepared by the double-emulsion solvent evaporation method. The PS-ODN was introduced either naked or complexed in the inner aqueous phase of the first emulsion. We observed a marked influence of microsphere composition on porosity, size distribution and PS-ODN encapsulation efficiency. Mainly, the presence of PEI induced the formation of large pores observed onto microsphere surface. Introduction of NaCl in the outer aqueous phase increased the encapsulation efficiency and reduced microsphere porosity. In vitro release kinetic of PS-ODN was also investigated. Clearly, the higher the porosity, the faster was the release and the higher was the burst effect. Using an analytical solution of Fick's second law of diffusion, it was shown that the early phase of PS-ODN and PS-ODN-PEI complex release was primarily controlled by pure diffusion, irrespectively of the type of microsphere. Finally, microspheres containing antisense TGF-beta2 nanosized complexes were shown, after subconjunctival administration to rabbit, to significantly increase intracellular penetration of ODN in conjunctival cells and subsequently to improve bleb survival in a rabbit experimental model of filtering surgery. These results open up interesting prospective for the local controlled delivery of genetic material into the eye.

Animals↗

PubMed2006

Antisense oligonucleotide nanocapsules efficiently inhibit EWS-Fli1 expression in a Ewing's sarcoma model.

The cytogenetic abnormality of Ewing's sarcoma is related to the presence of a balanced t(11;22) translocation expressing the EWS-Fli1 chimeric fusion protein. Oligonucleotides (ODNs) are specific compounds that inhibit gene expression at the transcriptional level. They possess a poor bioavailability and are degraded by nucleases very rapidly. Therefore, there is a strong need for the development of ODN drug delivery systems. In the present study, polyisobutylcyanoacrylate nanocapsules entrapping ODNs in their aqueous core were prepared, with high encapsulation yield (99%). Previous studies have demonstrated that such complexes were able to inhibit tumor growth in mice. Nevertheless, no information was available about their mode of action at the cellular level. The aim of this study was to investigate the efficacy of these ODN nanocapsules on cultured tumor cells. We found that nanocapsules were capable of protecting ODN against degradation. Using confocal microscopy, we observed that cell uptake and nuclear accumulation of ODNs were importantly enhanced when ODNs were associated with these nanocapsules. Consequently, a specific cellular growth inhibition and suppression of EWSFli1 fusion gene expression was noticed. In conclusion, it was demonstrated that nanocapsules as nonviral vectors show great potential for the delivery of ODNs to cells.

Animals↗

PubMed2005

Sustained delivery of growth factors from methylidene malonate 2.1.2-based polymers.

The incorporation of growth factors into new methylidene malonate 2.1.2-based biocompatible polymeric blends of oligomers and polymers to improve their stability and controlled release was investigated. Five growth factors were used in this study: FGF2, PDGF, TGF-beta, NGF and GM-CSF. Formulation in poly(methylidene malonate 2.1.2) blends was achieved by a four-step optimized process, using different oligomers/polymers ratios. Once dried, formulations could be subsequently stored at 4 or 20 degrees C or immediately subjected to degradation in conditioned cell culture medium. Toxicity of blends and their degradation products were evaluated in several cell lines with MTT. Bioactivity and biospecificity of the formulated growth factors were investigated using MTT and immunohistochemical staining. Combined ELISA and crystal violet colorimetric assays were performed to analyze growth factors release. Limited toxicities were observed for unloaded poly(methylidene malonate 2.1.2) blends. Once optimized, growth factors formulations did not reveal lower bioactivities or loss of biospecificity. Moreover, a sustained release over a 21-day period with more than 90% of preserved bioactivity was reached. To conclude, dual growth factor delivery was made possible by the mean of poly(methylidene malonate 2.1.2) blends. These studies demonstrate the ability of methylidene malonate 2.1.2-based polymeric blends for the delivery of growth factors.

Animals↗

PubMed2005

Pharmacokinetics of DTPA entrapped in conventional and long-circulating liposomes of different size for plutonium decorporation.

The aim of the present study was to develop an efficient DTPA liposome formulation designed for plutonium decorporation. DTPA was encapsulated in conventional (CL) and polyethylene glycol-coated stealth liposomes (SL) prepared by extrusion followed by the freeze-thawing method and sizing from around 100 to 800 nm. DTPA encapsulation percentages were approximately 30% in CL of any size but dropped from 48% to 7% as the diameter of SL was reduced. The pharmacokinetics of [(14)C]-DTPA encapsulated in large and small vesicles was evaluated in rats after a single intravenous administration. Both liposomal composition and size reduction had a significant impact on pharmacokinetic parameters, inducing a marked increased in exposure of the body to DTPA and its delayed excretion. DTPA distribution was moderate in liver but enhanced in spleen and bone and was dose-dependent, especially when SL of 100 nm were given. In conclusion, small and stealth(R) vesicles have interesting properties in delivering DTPA to contaminated tissues.

Animals↗

PubMed2005

Cellular fate of oligonucleotides when delivered by nanocapsules of poly(isobutylcyanoacrylate).

Dual-labeled phosphorothioate oligonucleotides were encapsulated in the internal aqueous core of poly(isobutylcyanoacrylate) nanocapsules with high yields. Intracellular distribution of naked and encapsulated oligomers was assessed on cultured vascular smooth muscle cells using cell fractionation and confocal microscopy methods. The results showed that cell uptake and more interestingly, nuclear accumulation of oligonucleotides were importantly enhanced when the oligonucleotides were associated to the nanocapsules as compared to the naked oligomers. These results suggested an efficient capacity of this polymeric carrier to deliver its payload to the cytosol and nucleus of smooth muscle cells.

Animals↗

PubMed2005

Role of gut macrophages in mice orally contaminated with scrapie or BSE.

While there is a growing consensus on the understanding of the propagation pathways after oral infection of transmissible spongiform encephalopathy (TSE) agents and even if the central role of follicular dendritic cells is identified, little is known about the key players in the first steps of the infection and about the site of the disease development. We investigated the role of gut macrophages, which are capable of capturing aggregates of the prion protein. PLGA particles containing clodronate were designed in order to be orally administered and to target Peyer's patches for inducing gut-associated macrophages suicide in mice. Mice were subsequently infected with scrapie or BSE by the oral route. It was found that the efficacy of macrophage suppression in the Peyer's patches correlated well with an earlier appearance of PrPres in these formations and with a higher amount of PrPres at a later stage of the infection. Thus, the capture of infectious particles that have crossed the epithelial gut barrier and their elimination by macrophages seems to be a key event to restrict the amount of agent initiating the infection.

Animals↗

PubMed2005

Cyclodextrin-mediated drug release from liposomes dispersed within a bioadhesive gel.

PURPOSE: The aim of the present study was to design a new mucosal drug delivery system composed of liposomes dispersed within a bioadhesive hydrogel containing methyl-beta-cyclodextrin (Me(beta)CD) for controlled drug release. METHODS: A hydrophilic model molecule, inulin, was encapsulated within positively charged and PEG-ylated liposomes and its release was measured in the presence of Me(beta)CD after vesicle dispersion within the bioadhesive Carbopol 974P gel. Freeze-fracture electron microscopy (FFEM) was used to follow liposome morphological changes when dispersed within the hydrogel. Liposome-Me(beta)CD interactions were investigated by turbidity monitoring during continuous addition of Me(beta)CD to liposomes and by FFEM. RESULTS: Inulin diffusion within the gel was influenced by Carbopol 974P concentration since no gel erosion occurred. When dispersed within the gel, positively charged liposomes displayed a higher stability than PEG-ylated vesicles. In the presence of Me(beta)CD, higher amounts of free inulin were released from liposomes, especially in Carbopol-free system. Me(beta)CD appeared to diffuse towards lipid vesicles and permeabilized their bilayer allowing inulin leakage. Indeed, freeze-fracture experiments and liposome turbidity monitoring have shown that Me(beta)CD behaved as a detergent behavior, resulting in lipid vesicle solubilization. CONCLUSION: is able to mediate, within a bioadhesive hydrogel, the release of a liposome-encapsulated molecule allowing further application of this delivery system for mucosal administration.

Acrylic Resins↗

PubMed2005

Innovative drug delivery nanosystems improve the anti-tumor activity in vitro and in vivo of anti-estrogens in human breast cancer and multiple myeloma.

Anticancer drug efficiency is governed by its bioavailability. In order to increase this parameter, we synthesized several injectable and biodegradable systems based on incorporation of anti-estrogens (AEs) in nanoparticles (NPs) and liposomes were synthesized. Both nanospheres (NS) and nanocapsules (NCs, polymers with an oily core in which AEs were solubilized) incorporated high amounts of 4-hydroxy-tamoxifen (4-HT) or RU 58668 (RU). Physico-chemical and biological parameters of these delivery systems, and coupling of polyethylene-glycol chains on the NP surface revealed to enhance the anti-tumoral activity of trapped AEs in a breast cancer MCF-7 cell xenograft model and to induce apoptosis. These features correlated with an augmentation of p21(Waf-1/Cip1) and of p27(Kip1) and a concomitant decrease of cyclin D1 and E in tumor extracts. Liposomes containing various ratios of lipids enhanced the apoptotic activity of RU in several multiple myeloma (MM) cell lines tested by flow cytometry. MM cell lines expressed both estrogen receptor alpha and beta subtypes except Karpas 620. Karpas 620 cells which did not respond to AEs became responsive following ER cDNA transfection. A new MM xenograft model was generated after s.c. injection of RPMI 8226 cells in nude mice. RU-loaded liposomes, administered i.v. in this model, at a dose of 12mgRU/kg/week, induced the arrest of tumor growth contrary to free RU or to empty liposomes. Thus, the drug delivery of anti-estrogens enhances their ability to arrest the growth of tumors which express estrogen receptors and are of particular interest for estrogen-dependent breast cancer treatment. In addition it represents a new potent therapeutic approach for multiple myeloma.

Apoptosis↗

PubMed2005

Evaluation of buccal methyl-beta-cyclodextrin toxicity on human oral epithelial cell culture model.

Cyclodextrins, especially methylated beta-cyclodextrins offer several advantages for drug delivery which include improved drug solubilization, protection against physicochemical and enzymatic degradation, as well as a potential for absorption improvement. However, little or no data are available for their use as drug penetration enhancer via the buccal route. This study focuses on the toxicity of randomly methylated beta-cyclodextrin (RAMEB) on buccal mucosa using a reconstituted human oral epithelium model composed of TR 146 cells. Toxicity of RAMEB on TR 146 cells was evaluated by measuring cell viability (MTT assay) and membrane damages followed by LDH release after single and repeated exposures to RAMEB solutions. Inflammatory effects of RAMEB are also considered by measuring expression of interleukin-1alpha and are supported by histological examination. The present results indicate that 10% RAMEB results in cytotoxic and inflammatory effects depending on time exposure, whereas 2% and 5% RAMEB do not induce tissue damages even after 5 days of repeated exposures. Therefore, the highly water-soluble RAMEB is thought to be a safe candidate as an excipient for buccal mucosal drug delivery.

Cell Survival↗

PubMed2005

Poly (lactide-co-glycolide) particles of different physicochemical properties and their uptake by peyer's patches in mice.

Nano-and microparticles of poly(lactide-co-glycolide) (PLGA) were formulated using poly(vinyl alcohol) (PVA) or hydrophobically modified hydroxyethylcellulose (HMHEC) or polyethyleneimine (PEI) as stabilizers. The uptake by murine Peyer's patches (PPs) and the binding to Peyer's patches-free tissue (PPFT) of these particles was investigated using fluorescence microscopy providing qualitative information about the tissue distribution of particles. Observations of intestinal cryo-sections showed significant discrimination in the uptake by PP of nano-and microparticles. The uptake by PPs of PLGA-PVA and PLGA-HMHEC nano-and microparticles, of negative and neutral zeta potential, respectively, was comparable, whereas a smaller number was observed in the case of nano-and microparticles of PLGA-PEI, positively charged. Moreover, particle uptake by PPs appeared to be strongly size-dependent. The number of particles of mean diameter around 0.3 and 1 microm observed in PPs was much greater than that of particles of diameter average close to 3 microm. However, in all cases, particles were found in the PPFT for at least 48 h. In conclusion, regarding the tissue samples we have observed, it appeared that the uptake of particles by PPs and binding to PPFT could be influenced by the physicochemical properties of the particles but this may not have been true at all sites of the intestine and may differ between animals.

Administration, Oral↗

PubMed2005

In vitro and in vivo evaluation of pectin beads for the colon delivery of beta-lactamases.

The aim of the present study was to provide a "proof of concept" of colon delivery of beta-lactamases by pectin beads aiming to degrade residual beta-lactam antibiotics, in order to prevent the emergence of resistant bacterial strains. Pectin beads were prepared according to ionotropic gelation method using CaCl2 as a gelling agent. Particles were then washed and soaked in polyethylenimine (PEI). Coating beads with PEI considerably improved their stability in simulated intestinal medium. In vitro studies showed that beta-lactamases were released from pectin beads in colonic medium due to the action of pectinolytic enzymes. When ampicillin was added to this medium, the release of beta-lactamases induced, as expected, the antibiotic inactivation. Finally, after oral administration of loaded-beads to CD1 mice, beta-lactamases were retrieved in high concentrations in faeces. Observation by SEM of beads extracted from mice intestinal tracts concluded the core degradation of beads without any modification of the PEI coating layer. This study demonstrates that a multiparticulate system with suitable characteristics for site-specific colonic delivery can be prepared. This system could be used to target beta-lactamases to the colon in order to hydrolyse antibiotic residues during treatment and prevent their impact on colonic microflora.

Animals↗