Biomedical subjects

Madeleine Besnard

Publications and source records attributed to Madeleine Besnard.

11 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

Interaction between miltefosine and amphotericin B: consequences for their activities towards intestinal epithelial cells and Leishmania donovani promastigotes in vitro.

The aim of this study was to evaluate the potential of a combination of two antileishmanial drugs, miltefosine (HePC) and amphotericin B (AMB), when administered by the oral route. Caco-2 cell monolayers were used as a validated in vitro model of the intestinal barrier and Leishmania donovani promastigotes as a model for evaluating the effect of the drug combination. Spectroscopic measurements demonstrated that HePC and AMB associate, leading to the formation of mixed aggregates in which AMB is solubilized as monomers. The incubation of the association of HePC and AMB with Caco-2 cell monolayers, at a concentration higher than 5 microM, led to (i) a reduction of the HePC-induced paracellular permeability enhancement in Caco-2 cell monolayers, (ii) an inhibition of the uptake of both drugs, and (iii) a decrease in the transepithelial transport of both drugs, suggesting that a pharmacokinetic antagonism between HePC and AMB could occur after their oral administration. However, the combination did not exhibit any antagonism or synergy in its antileishmanial activity. These results demonstrated a strong physicochemical interaction between HePC and AMB, depending on the concentration of each, which could have important consequences for their biological activities, if they are administered together.

Amphotericin B↗

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↗

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↗

PubMed2004

Synchrotron FT-IR microscopic study of chemical enhancers in transdermal drug delivery: example of fatty acids.

This article illustrates the analysis by synchrotron infrared microscopy of skin treated with penetration enhancers. Pig skin was treated with two fatty acids commonly employed as penetration enhancers, palmitic (C16) and myristic (C14) acids, in propylene glycol (PG). The use of perdeuterated fatty acid chains enabled the penetrating molecules to be perfectly distinguished from the endogenous lipids due to the difference between C-D and C-H stretching modes. Palmitic acid was detected in the stratum corneum (SC), a particularly alkyl-rich region, whereas myristic acid penetrates deeper into the epidermis. Similar experiments with lead and calcium soaps were also performed, but no detectable signal was observed, indicating a much weaker penetration. Additionally, the C-D2 stretching frequency provides information about the conformational order of the penetrating molecules inside the skin. The results indicate that fatty chains are in an ordered state. The improved spatial resolution allows the determination of both chemical composition and distribution in the different layers, from the SC to the dermis.

Adjuvants, Pharmaceutic↗

PubMed2004

Evidence for restrictive parameters in formulation of insulin-loaded nanocapsules.

Poly(isobutylcyanoacrylate) nanocapsules with an oily core were originally proposed for lipophilic drug encapsulation [Int. J. Pharm. 28 (1986) 125] but insulin, a hydrosoluble protein, has also been successfully encapsulated by Damgé et al. [Diabetes 37 (1988) 246]. The aim of this work was to understand if several parameters were restrictive for the encapsulation of insulin into the oily core of the nanocapsules prepared by interfacial polymerization. The encapsulation efficiency of insulin was not affected by the type of insulin since the peptides adopted the same association state after their addition to the organic phase. Formulation parameters mainly affected the size of the nanocapsules obtained but did not influence the insulin encapsulation efficiency. In contrast, the order of introduction of insulin and of the monomer in the organic phase was shown to control the formation and the characteristics of the nanocapsules. The key parameters, which were found to clearly influence the encapsulation efficiency of insulin, were the pH of the aqueous insulin solution and the origin of the monomer. Both of these parameters can affect the rate of the interfacial polymerization. Consequently, the ability of insulin to be entrapped into the oil containing nanocapsules appeared to be governed more by the rate of the monomer polymerization.

Animals↗

PubMed2003

Optimization of a thermally reversible W/O/W multiple emulsion for shear-induced drug release.

PURPOSE: The present work aimed at improvement of the formulation of a previously developed thermo-reversible W/O/W multiple emulsion by increasing the emulsion stability and reaching a higher fraction of an encapsulated drug released under shear. The emulsion was based on high molecular weight graft-copolymers of poly(acrylic acid) and Pluronic F127 as stabilizing agents. METHODS: Once a stable W/O/W thermo-reversible multiple emulsion was obtained via a fine-tuning of the formulation, rheological, granulometric and conductometric tests were performed to assess the thermo-reversible behavior and the fragmentation-release characteristics of the new W/O/W multiple emulsion. RESULTS: The emulsion exhibited a 10(3) fold increase in viscosity over a range of temperatures from 20 to 40 degrees C. At moderate shearing, a complete release of the marker encapsulated in the internal aqueous phase was observed (99.6%) at 35 degrees C, whereas only 30% was released at 20 degrees C. Under similar conditions at 35 degrees C, slightly more than 50% was released for the initial formula. CONCLUSION: Additionally, the ease of fabrication of the thermo-reversible W/O/W multiple emulsion combined with the complete release under shear at body temperature and the superior emulsion stability suggest numerous applications in the controlled release of drugs.

Chemistry, Pharmaceutical↗

PubMed2003

A new delivery system for antisense therapy: PLGA microspheres encapsulating oligonucleotide/polyethyleneimine solid complexes.

Microspheres for the controlled release of an antisense oligonucleotide against the Transforming growth factor beta(1) were designed. Free oligonucleotide or its solid complexes with polyethylenimine (PEI) at different nitrogen/phosphate (N/P) ratios, were encapsulated within poly(lactide-co-glycolide) (PLGA) microspheres prepared by the multiple emulsion-solvent evaporation technique. The encapsulation of the oligonucleotide in form of solid complexes, the N/P ratio, as well as the PLGA type affected microspheres characteristics in term of loading, morphology, oligonucleotide distribution inside matrix and in vitro release profile. The designed microspheres allow the encapsulation and slow release of oligonucleotide/PEI solid complexes that should be effectively internalized inside cells.

Antibodies↗

PubMed2003

The stenlying effect of high hydrostatic pressure on thermally and hydrolytically labile nanosized carriers.

PURPOSE: To investigate whether high hydrostatic pressure (HHP) treatment allows the sterilization of thermosensitive polymer nanoparticle suspensions without jeopardizing their physicochemical integrity. METHODS: Application of HHP was explored on a wide variety of thermosensitive poly(cyanoacrylate) nanoparticles, varying by their type (nanospheres or nanocapsules), by their preparation method (nanoprecipitation or emulsion/solvent evaporation), as well as by their surface characteristics. Physicochemical characterization before and after pressurization included turbidimetry, size measurement, zeta potential, scanning electron microscopy and infrared analysis. A sterility test also conducted according to pharmacopoeial requirements on an importantly contaminated nanoparticle suspension. RESULTS: Poly(cyanoacrylate) nanoparticles appeared to be extremely baroresistant. Continuous or oscillatory HHP treatment up to 500 MPa during 30 min induced generally neither physical, nor chemical damage. However, precautions should be taken when surface modifiers are adsorbed onto nanoparticles, as a layer destabilization may occur. Finally, this process allowed the successful inactivation of vegetative bacteria, yeast, and fungi. CONCLUSIONS: This work proposes HHP as a new method for polymer drug carriers sterilization, taking into account that further exploration in this area is needed to propose novel protocols for spores inactivation.

Chemistry, Pharmaceutical↗

PubMed2003

Novel polyester-polysaccharide nanoparticles.

PURPOSE: The aim of the present study was to develop a new type of core-shell nanoparticles from a family of novel amphiphilic copolymers, based on dextran (DEX) grafted with poly(epsilon-caprolactone) (PCL) side chains (PCL-DEX). METHODS: A family of PCL-DEX copolymers was synthesized in which both the molecular weight and the proportion by weight of DEX in the copolymer were varied. The nanoparticles were prepared by a technique derived from emulsion-solvent evaporation, during which emulsion stability was investigated using a Turbiscan. The nanoparticle size distribution, density, zeta potential, morphology, and suitability for freeze-drying were determined. RESULTS: Because of their strongly amphiphilic properties, the PCL-DEX copolymers were able to stabilize o/w emulsions without the need of additional surfactants. Nanoparticles with a controlled mean diameter ranging from 100 to 250 nm were successfully prepared. A mechanism of formation of these nanoparticles was proposed. Zeta potential measurements confirmed the presence of a DEX coating. CONCLUSION: A new generation of polysaccharide-decorated nanoparticles has been successfully prepared from a family of PCL-DEX amphiphilic copolymers. They may have potential applications in drug encapsulation and targeting.

Chemistry, Pharmaceutical↗