Pierre Sibret

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.

Synthesis and pH-dependent micellization of diblock copolymer mixtures

This work focused on the preparation and the aqueous solution properties of hybrid polymeric micelles consisting of a hydrophobic poly(epsilon-caprolactone) (PCL) core and a mixed shell of hydrophilic poly(ethylene oxide) (PEO) and pH-sensitive poly(2-vinylpyridine) (P2VP). The hybrid micelles were successfully prepared by the rapid addition of acidic water to a binary solution of PCL(34)-b-PEO(114) and PCL(32)-b-P2VP(52) diblock copolymers in N,N-dimethylformamide. These micelles were pH-responsive as result of the pH-dependent ionization of the P2VP block. The impact of pH on the self-assembly of the binary mixture of diblocks-thus on the composition, shape, size and surface properties of the micelles-was studied by a variety of experimental techniques, i.e., dynamic and static light scattering, transmission electron microscopy, Zeta potential, fluorescence spectroscopy and complement hemolytic 50 test.

Chitosan-coated electrospun nanofibers with antibacterial activity

Charged nanofibers were prepared by electrospinning (ESP) poly(ε-caprolactone) with a copolymer bearing carboxylic acid functions. The presence of these functions allowed exposing some negative charges on the fiber surface, by dipping the fibers in a phosphate buffer. A layer of chitosan, a polycation in acidic medium, was then deposited on the nanofiber surface, thanks to electrostatic attraction. Fibers were characterized at each step of the process and the influence of the copolymer architecture on chitosan deposition was discussed. The antibacterial activity of the resulting fibers was finally assessed.

Tumor Targeting by RGD-Grafted PLGA-Based Nanotheranostics Loaded with Paclitaxel and Superparamagnetic Iron Oxides

Theranostic nanoparticles have the potential to revolutionize cancer diagnosis and therapy. Many groups have demonstrated differential levels of tumor growth between tumors treated by targeted or untargeted nanoparticles; however, only few have shown in vivo efficacy in both therapeutic and diagnostic approach. Herein, we first develop and characterize dual-paclitaxel (PTX)/superparamagnetic iron oxide (SPIO)-loaded PLGA-based nanoparticles grafted with the RGD peptide, for a theranostic purpose. Second, we compare in vivo different strategies in terms of targeting capabilities: (1) passive targeting via the EPR effect, (2) active targeting of αvβ3 integrin via RGD grafting, (3) magnetic guidance via a magnet placed on the tumor, and (4) the combination of the magnetic guidance and the active targeting of αvβ3 integrin. In this chapter, we present the general flowchart applied for this project: (1) the polymer and SPIO synthesis, (2) the physicochemical characterization of the nanoparticles, (3) the magnetic properties of the nanoparticles, and (4) the in vivo evaluation of the nanoparticles for their therapeutic and diagnosis purposes. We employ the electron spin resonance spectroscopy and magnetic resonance imaging to both quantify and visualize the accumulation of theranostic nanoparticles into the tumors.