Christine Jérôme

Paclitaxel-loaded PEGylated PLGA-based nanoparticles: In vitro and in vivo evaluation

The purpose of this study was to develop Cremophor EL-free nanoparticles loaded with Paclitaxel (PTX), intended to be intravenously administered, able to improve the therapeutic index of the drug and devoid of the adverse effects of Cremophor EL. PTX-loaded PEGylated PLGA-based were prepared by simple emulsion and nanoprecipitation. The incorporation efficiency of PTX was higher with the nanoprecipitation technique. The release behavior of PTX exhibited a biphasic pattern characterized by an initial burst release followed by a slower and continuous release. The in vitro anti-tumoral activity was assessed using the Human Cervix Carcinoma cells (HeLa) by the MTT test and was compared to the commercial formulation Taxol and to Cremophor EL. When exposed to 25 microg/ml of PTX, the cell viability was lower for PTX-loaded nanoparticles than for Taxol (IC(50) 5.5 vs 15.5 microg/ml). Flow cytometry studies showed that the cellular uptake of PTX-loaded nanoparticles was concentration and time dependent. Exposure of HeLa cells to Taxol and PTX-loaded nanoparticles induced the same percentage of apoptotic cells. PTX-loaded nanoparticles showed greater tumor growth inhibition effect in vivo on TLT tumor, compared with Taxol. Therefore, PTX-loaded nanoparticles may be considered as an effective anticancer drug delivery system for cancer chemotherapy.

Targeting of tumor endothelium by RGD-grafted PLGA-nanoparticles loaded with Paclitaxel

Paclitaxel (PTX)-loaded PEGylated PLGA-based nanoparticles (NP) have been previously described as more effective in vitro and in vivo than taxol. The aim of this study was to test the hypothesis that our PEGylated PLGA-based nanoparticles grafted with the RGD peptide or RGD-peptidomimetic (RGDp) would target the tumor endothelium and would further enhance the anti-tumor efficacy of PTX. The ligands were grafted on the PEG chain of PCL-b-PEG included in the nanoparticles. We observed in vitro that RGD-grafted nanoparticles were more associated to human umbilical vein endothelial cells (HUVEC) by binding to alpha(v)beta(3) integrin than non-targeted nanoparticles. Doxorubicin was also used to confirm the findings observed for PTX. In vivo, we demonstrated the targeting of RGD and RGDp-grafted nanoparticles to tumor vessels as well as the effective retardation of TLT tumor growth and prolonged survival times of mice treated by PTX-loaded RGD-nanoparticles when compared to non-targeted nanoparticles. Hence, the targeting of anti-cancer drug to tumor endothelium by RGD-labeled NP is a promising approach.

Chitosan and chitosan derivatives in drug delivery and tissue engineering

Chitosan is a nontoxic, biodegradable, and biocompatible polysaccharide of β(1-4)-linked d-glucosamine and N-acetyl-d-glucosamine. This derivative of natural chitin presents remarkable properties that have paved the way for the introduction of chitosan in the biomedical and pharmaceutical fields. Nevertheless, the properties of chitosan, such as its poor solubility in water or in organic solvents, can limit its utilization for a specific application. An elegant way to improve or to impart new properties to chitosan is the chemical modification of the chain, generally by grafting of functional groups, without modification of the initial skeleton in order to conserve the original properties. The functionalization is carried out on the primary amine group, generally by quaternization, or on the hydroxyl group. This review aims to provide an overview of chitosan and chitosan derivatives used for drug delivery, with a special emphasis on chemical modifications of chitosan to achieve specific biomedical purpose. The synthesis of the main chitosan derivatives will be reviewed. The applications of chitosan and these chitosan derivatives will be illustrated.

Dual anticancer drug/superparamagnetic iron oxide-loaded PLGA-based nanoparticles for cancer therapy and magnetic resonance imaging

We developed dual paclitaxel (PTX)/superparamagnetic iron oxide (SPIO)-loaded PLGA-based nanoparticles for a theranostic purpose. Nanoparticles presented a spherical morphology and a size of 240 nm. The PTX and iron loading were 1.84 ± 0.4 and 10.4 ± 1.93 mg/100 mg respectively. Relaxometry studies and phantom MRI demonstrated their efficacy as T₂ contrast agent. Significant cellular uptake by CT26 cells of nanoparticles was shown by Prussian blue staining and fluorescent microscopy. While SPIO did not show any toxicity in CT-26 cells, PTX-loaded nanoparticles had a cytotoxic activity. PTX-loaded nanoparticle (5 mg/kg) with or without co-encapulated SPIO induced in vivo a regrowth delay of CT26 tumors. Together these multifunctional nanoparticles may be considered as future nanomedicine for simultaneous molecular imaging, drug delivery and real-time monitoring of therapeutic response.

Targeting nanoparticles to M cells with non-peptidic ligands for oral vaccination

The presence of RGD on nanoparticles allows the targeting of beta1 integrins at the apical surface of human M cells and the enhancement of an immune response after oral immunization. To check the hypothesis that non-peptidic ligands targeting intestinal M cells or APCs would be more efficient for oral immunization than RGD, novel non-peptidic and peptidic analogs (RGD peptidomimitic (RGDp), LDV derivative (LDVd) and LDV peptidomimetic (LDVp)) as well as mannose were grafted on the PEG chain of PCL-PEG and incorporated in PLGA-based nanoparticles. RGD and RGDp significantly increased the transport of nanoparticles across an in vitro model of human M cells as compared to enterocytes. RGD, LDVp, LDVd and mannose enhanced nanoparticle uptake by macrophages in vitro. The intraduodenal immunization with RGDp-, LDVd- or mannose-labeled nanoparticles elicited a higher production of IgG antibodies than the intramuscular injection of free ovalbumin or intraduodenal administration of either non-targeted or RGD-nanoparticles. Targeted formulations were also able to induce a cellular immune response. In conclusion, the in vitro transport of nanoparticles, uptake by macrophages and the immune response were positively influenced by the presence of ligands at the surface of nanoparticles. These targeted-nanoparticles could thus represent a promising delivery system for oral immunization.

Mechanical testing of electrospun PCL fibers

Poly(ε-caprolactone) (PCL) fibers ranging from 250 to 700 nm in diameter were produced by electrospinning a polymer tetrahydrofuran/N,N-dimethylformamide solution. The mechanical properties of the fibrous scaffolds and individual fibers were measured by different methods. The Youngs moduli of the scaffolds were determined using macro-tensile testing equipment, whereas single fibers were mechanically tested using a nanoscale three-point bending method, based on atomic force microscopy and force spectroscopy analyses. The modulus obtained by tensile-testing eight different fiber scaffolds was 3.8±0.8 MPa. Assuming that PCL fibers can be described by the bending model of isotropic materials, a Youngs modulus of 3.7±0.7 GPa was determined for single fibers. The difference of three orders of magnitude observed in the moduli of fiber scaffolds vs. single fibers can be explained by the lacunar and random structure of the scaffolds.

Insight into Organometallic-Mediated Radical Polymerization

This review focuses on an emerging class of controlled radical polymerization named Organometallic-Mediated Radical Polymerization (OMRP). The latter is based on the temporary deactivation of the growing radical species by a transition metal complex and the reversible formation of a carbon-metal covalent bond. Initially developed with cobalt complexes, OMRP has extended to several metals today. As highlighted here, the choice of the metal, the structure of ligands, temperature, and additives deeply affect the course of the polymerization and its mechanism. Macromolecular engineering opportunities offered by OMRP are also described, as well as practical applications sustained by the resulting polymer materials.

Development of a Chitosan Nanofibrillar Scaffold for Skin Repair and Regeneration.

The final goal of the present study was the development of a 3-D chitosan dressing that would shorten the healing time of skin wounds by stimulating migration, invasion, and proliferation of the relevant cutaneous resident cells. Three-dimensional chitosan nanofibrillar scaffolds produced by electrospinning were compared with evaporated films and freeze-dried sponges for their biological properties. The nanofibrillar structure strongly improved cell adhesion and proliferation in vitro. When implanted in mice, the nanofibrillar scaffold was colonized by mesenchymal cells and blood vessels. Accumulation of collagen fibrils was also observed. In contrast, sponges induced a foreign body granuloma. When used as a dressing covering full-thickness skin wounds in mice, chitosan nanofibrils induced a faster regeneration of both the epidermis and dermis compartments. Altogether our data illustrate the critical importance of the nanofibrillar structure of chitosan devices for their full biocompatibility and demonstrate the significant beneficial effect of chitosan as a wound-healing biomaterial.

Mechanochemistry: targeted delivery of single molecules:

The use of scanning probe microscopy-based techniques to manipulate single molecules1 and deliver them in a precisely controlled manner to a specific target represents a significant nanotechnological challenge2,3. The ultimate physical limit in the design and fabrication of organic surfaces can be reached using this approach. Here we show that the atomic force microscope (AFM), which has been used extensively to investigate the stretching of individual molecules4,5,6,7,8,9,10,11,12, can deliver and immobilize single molecules, one at a time, on a surface. Reactive polymer molecules, attached at one end to an AFM tip, are brought into contact with a modified silicon substrate to which they become linked by a chemical reaction. When the AFM tip is pulled away from the surface, the resulting mechanical force causes the weakest bond — the one between the tip and polymer — to break. This process transfers the polymer molecule to the substrate where it can be modified by further chemical reactions.

Drug delivery to inflamed colon by nanoparticles: Comparison of different strategies

For inflammatory bowel disease (IBD) treatment, local delivery of molecules loaded in nanoparticles to the inflamed colon could be a promising strategy. The aim of this study was to investigate how drug-loaded polymeric nanoparticles target the site of inflammation and to analyse the influence of different colon-specific delivery strategies. Three different polymeric nanoparticles were formulated using ovalbumin (OVA) as a model drug. pH-sensitive nanoparticles were made with Eudragit(®) S100. Mucoadhesive nanoparticles were created with trimethylchitosan (TMC). A mix of polymers, PLGA, PEG-PLGA and PEG-PCL, were used to obtain a sustained drug delivery. Furthermore, ligands targeting immune cells (i.e. mannose) or the inflamed colon (i.e. a specific peptide) were grafted on the PEG chain of PCL. Interaction of nanoparticles with the intestinal epithelium was explored using Caco-2 monolayers designed to mimic an inflamed epithelium and then visualized using confocal laser microscopy. TMC nanoparticles had the highest apparent permeability for OVA in the untreated model. However, in the inflamed model, there were no difference between TMC, PLGA-based and Eudragit(®) nanoparticles. The uptake of nanoparticles in the inflamed mouse colon was assessed in a horizontal diffusion chamber. Mannose-grafted PLGA nanoparticles showed the highest accumulation of OVA in inflamed colon. Based on these results, active targeting of macrophages and dendritic cells may be a promising approach for targeting the colon in IBD.