Madeleine Besnard

Stealth® PEGylated polycyanoacrylate nanoparticles for intravenous administration and splenic targeting

The aim of the present work was to investigate the biodistribution characteristics of PEG-coated polycyanoacrylate nanoparticles prepared by the nanoprecipitation/solvent diffusion method using the previously synthesized poly(MePEGcyanoacrylate-hexadecylcyanoacrylate) copolymer. It was observed that [14C]-radiolabeled PEGylated nanoparticles remained for a longer time in the blood circulation after intravenous administration to mice, compared to the non-PEGylated poly(hexadecylcyanoacrylate) (PHDCA) nanoparticles. Furthermore, hepatic accumulation was dramatically reduced, whereas a highly increased spleen uptake was shown. The PEGylation degree of the polymer seemed not to affect the in vivo behavior of the nanoparticles, whereas previously obtained in vitro data have shown a modification of plasma protein adsorption depending on the density of PEG at the surface of the particles. Moreover, the study of the in vitro cytotoxicity of the nanoparticles revealed that the PEGylation of the cyanoacrylate polymer reduced its toxicity. These results open up interesting perspectives for the targeting of drugs to other tissues than the liver.

Novel Polyester-Polysaccharide Nanoparticles

AbstractPurpose. 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(ε–caprolactone) (PCL) side chains (PCL-DEX).nMethods. 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.nResults. 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.nConclusion. 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.

Dexamethasone acetate encapsulation into Trojan particles

We have combined the therapeutic potential of nanoparticles systems with the ease of manipulation of microparticles by developing a hybrid vector named Trojan particles. We aim to use this new delivery vehicle for intravitreal administration of dexamethasone. Initialy, dexamethasone acetate (DXA) encapsulation into biodegradable poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles was optimized. Then, Trojan particles were formulated by spray drying 1,2-Dipalmitoyl-sn-Glycero-3-Phosphocholine (DPPC), hyaluronic acid (HA) and different concentrations of nanoparticle suspensions. The effect of nanoparticles concentration on Trojan particle physical characteristics was investigated as well as the effect of the spray drying process on nanoparticles size. Finally, DXA in vitro release from nanoparticles and Trojan particles was evaluated under sink condition. SEM and confocal microscopy show that most of Trojan particles are spherical, hollow and possess an irregular surface due to the presence of nanoparticles. Neither Trojan particle tap density nor size distribution are significantly modified as a function of nanoparticles concentration. The mean nanoparticles size increase significantly after spray drying. Finally, the in vitro release of DXA shows that the excipient matrix provides protection to encapsulated nanoparticles by slowing drug release.

Squalenoylation Favorably Modifies the in Vivo Pharmacokinetics and Biodistribution of Gemcitabine in Mice

Gemcitabine (2′,2′-difluorodeoxyribofuranosylcytosine; dFdC) is an anticancer nucleoside analog active against wide variety of solid tumors. However, this compound is rapidly inactivated by enzymatic deamination and can also induce drug resistance. To overcome the above drawbacks, we recently designed a new squalenoyl nanomedicine of dFdC [4-(N)-trisnorsqualenoyl-gemcitabine (SQdFdC)] by covalently coupling gemcitabine with the 1,1′,2-trisnorsqualenic acid; the resultant nanomedicine displayed impressively greater anticancer activity compared with the parent drug in an experimental murine model. In the present study, we report that SQdFdC nanoassemblies triggered controlled and prolonged release of dFdC and displayed considerably greater t1/2 (∼3.9-fold), mean residence time (∼7.5-fold) compared with the dFdC administered as a free drug in mice. It was also observed that the linkage of gemcitabine to the 1,1′,2-trisnorsqualenic acid noticeably delayed the metabolism of dFdC into its inactive difluorodeoxyuridine (dFdU) metabolite, compared with dFdC. Additionally, the elimination of SQdFdC nanoassemblies was considerably lower compared with free dFdC, as indicated by lower radioactivity found in urine and kidneys, in accordance with the plasmatic concentrations of dFdU. SQdFdC nanoassemblies also underwent considerably higher distribution to the organs of the reticuloendothelial system, such as spleen and liver (p < 0.05), both after single- or multiple-dose administration schedule. Herein, this paper brings comprehensive pharmacokinetic and biodistribution insights that may explain the previously observed greater efficacy of SQdFdC nanoassemblies against experimental leukemia.

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

PURPOSEnThe 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.nnnMETHODSnOnce 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.nnnRESULTSnThe 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.nnnCONCLUSIONnAdditionally, 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.

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.

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

AbstractPurpose. To investigate whether high hydrostatic pressure (HHP) treatment allows the sterilization of thermosensitive polymer nanoparticle suspensions without jeopardizing their physicochemical integrity.nMethods. 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.nResults. 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.nConclusions. 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.

Removal of ciprofloxacin in simulated digestive media by activated charcoal entrapped within zinc-pectinate beads

Beads made of a zinc-pectinate matrix containing activated charcoal were designed for the adsorption of colonic residual antibiotics responsible of the emergence of resistance. Bead stability was shown to correlate with bead zinc content, 0.08 mg/mg being the minimal amount of zinc that protects the egg-box structure against total disintegration. Moreover, the stability in simulated gastro-intestinal media was shown to be related to the composition of the incubation medium. Indeed, gastric medium was shown to extract a large amount of zinc inducing an early disintegration of the beads in the intestinal medium, making necessary their protection by gastro-resistant capsules. Simulated intestinal medium buffered by phosphate was not adapted for the disintegration studies since the formation of a zinc phosphate precipitate on beads surface enhances their resistance to further degradation by pectinases contained in colonic medium. On the other hand, beads incubated in HEPES were stable in intestinal medium and nicely degraded by pectinases contained in simulated colonic medium. Despite this stability, coating with Eudragit RS was needed to prevent the early adsorption of antibiotics in intestinal medium. Adsorption studies in the simulated colonic medium show that the adsorption capacity of activated charcoal is not modified after its encapsulation within pectin beads making the elimination of ciprofloxacin reaching the colon clinically feasible.

Supramolecular organization and release properties of phospholipid-hyaluronan microparticles encapsulating dexamethasone

We describe the supramolecular organization of hybrid microparticles encapsulating dexamethasone (DXM) prepared by spray drying 1,2-Dipalmitoyl-sn-Glycero-3-Phosphocholine (DPPC) and hyaluronic acid (HA). The effect of DXM concentration on size distribution and encapsulation efficacy was evaluated as a function of HA concentration. In the absence of HA, DXM leads to a strong particle aggregation, whereas in the presence of HA, the aggregation is practically suppressed. DXM percentage of encapsulation is high (95+/-6%), independently of composition. Drug-excipient interactions were analyzed by differential scanning calorimetry (DSC) and X-ray diffraction. DSC demonstrates that only a small fraction of DXM interacts with DPPC, whereas X-ray diffraction does not detect this interaction. Finally, in vitro release studies show that HA does not influence DXM release kinetics. In all cases, a burst release of DXM is observed during the first hour. Under sink conditions, powder concentration in the release medium governs the extent of the burst. Under non sink conditions, DXM release is mostly governed by DXM solubility in the release medium. In the dry microparticles, DXM is probably mostly in amorphous domains within the DPPC-HA matrix. Upon hydration, the majority of the drug is released and only a small amount of DXM interacts with DPPC.

Original tamoxifen-loaded gels containing cyclodextrins: in situ self-assembling systems for cancer treatment

Tamoxifen represents the endocrine treatment of choice for hormone-dependent breast cancer. However, undesirable side effects appeared after long-term therapy. Therefore, the concept of a drug delivery system at the tumour site is an interesting alternative. The aim of this work was to evaluate the potential of an original in situ forming gel to allow sustained delivery of tamoxifen. The gel forms spontaneously when two aqueous polymeric solutions are put in contact: a cyclodextrin (CD) polymer and dextran grafted with alkyl side chains. Some hydrophobic chains form inclusion complexes with CDs, leaving also free CDs available for the inclusion of drug molecules. Phase solubility studies showed a dramatically increased apparent solubility of tamoxifen in water (80-fold) in the presence of the CD polymer. Moreover, this drug was successfully entrapped in the gels, with loading efficiencies around 90%. Tamoxifen was released following a zero-order release profile during four days, followed by gel dissolution. The estimated amount of gel to be formed in situ to achieve in vivo anti-proliferative effects was found to be compatible with an injection. Moreover, this new concept opens a large domain of perspectives for other types of pathologies, where soft matrices allowing local drug sustained release are required.