Christophe Schatz

The intracellular drug delivery and anti tumor activity of doxorubicin loaded poly(γ-benzyl L-glutamate)-b-hyaluronan polymersomes

We have investigated the intracellular delivery of doxorubicin (DOX) loaded poly(gamma-benzyl L-glutamate)-block-hyaluronan (PBLG-b-HYA) based polymersomes (PolyDOX) in high (MCF-7) and low (U87) CD44 expressing cancer cell models. DOX was successfully loaded into polymersomes using nanoprecipitation method and in vitro drug release pattern were achieved at pH 5.5 and 7.4 up to 10 days. Block copolymer vesicles without loaded DOX were non cytotoxic in both cells at concentration 150-650 microg/mL. Flow cytometry data suggested successful uptake of PolyDOX in cells and high accumulation was found in MCF-7 than U87 cells. Microscopy imagings revealed that in MCF-7 cells PolyDOX was more in cytoplasm and free DOX in nuclei, whereas in U87 cells free DOX was also found in the cytoplasm. Cytotoxicity of the drug was concentration and exposure time dependent. In addition, PolyDOX significantly enhanced reactive oxygen species (ROS) level in both cells. PolyDOX also suppressed growth of breast tumor on female Sprague-Dawley (SD) rats as compared to phosphate buffer saline pH 7.4 (PBS) control group. In addition reduced level of serum enzymes (LDH and CPK) by PolyDOX formulation indicated less cardiotoxicity of DOX after loading in polymersomes. Results suggest that intracellular delivery of PolyDOX was depended on the CD44 expression level in cells due to presence of hyaluronic acid on the surface of polymersomes, and could be used as a self-targeting drug delivery cargo in over-expressed CD44 glycoprotein cells of breast cancer.

A simple method to achieve high doxorubicin loading in biodegradable polymersomes.

Doxorubicin (Dox), an anthracycline anticancer drug, was successfully incorporated into block copolymer vesicles of poly(trimethylene carbonate)-b-poly(L-glutamic acid) (PTMC-b-PGA) by a solvent-displacement (nanoprecipitation) method. pH conditions were shown to have a strong influence on loading capacity and release profiles. Substantial drug loading (47% w/w) was achieved at pH 10.5. After pH neutralization, aqueous dispersions of drug-loaded vesicles were found stable for a prolonged period of time (at least 6months) without vesicle disruption or drug precipitation. Dox-loaded vesicles exhibited in vitro pH and temperature-dependent drug release profiles: release kinetics fastened in acid conditions or by increasing temperature. These features strongly support the interest of developing PTMC-b-PGA polymersomes as carriers for the controlled delivery of Dox.

Polysaccharide-block-polypeptide Copolymer Vesicles : Towards Synthetic Viral Capsids

Natural inspiration: Amphiphilic polysaccharide-block-polypeptide copolymers were synthesized by click chemistry from dextran end-functionalized with an alkyne group and poly(gamma-benzyl L-glutamate) end-functionalized with an azide group. The ability of these copolymers to self-assemble into small vesicles (see picture) suggests the possibility of a new generation of drug- and gene-delivery systems whose structure mimics that of viruses.

pH and Temperature Responsive Polymeric Micelles and Polymersomes by Self-Assembly of Poly[2-(dimethylamino)ethyl methacrylate]-b-Poly(glutamic acid) Double Hydrophilic Block Copolymers

The aqueous solution behavior of novel polypeptide-based double hydrophilic block copolymers (DHBCs), namely, poly[2-(dimethylamino)ethyl methacrylate]-b-poly(glutamic acid) (PDMAEMA-b-PGA), exhibiting pH- and temperature-responsiveness is presented using a combination of scattering techniques (light and neutron) and transmission electron microscopy. Close to the isoelectric point (IEP), direct or inverse electrostatic polymersomes are generated by electrostatic interactions developing between the two charged blocks and driving the formation of the hydrophobic membrane of the polymersomes, with the latter being stabilized in water by uncompensated charges. Under basic conditions, that is, when PDMAEMA is uncharged, the thermosensitivity of the DHBCs relates to the lower critical solution temperature (LCST) behavior of PDMAEMA around 40 degrees C. As a consequence, at pH = 11 and below this LCST, free chains of DHBC unimers are evidenced, while above the LCST the hydrophobicity of PDMAEMA drives the self-assembly of the DHBCs in a reversible manner. In this case, spherical polymeric micelles or polymersomes are obtained, depending on the PGA block length. These possibilities of variation in size and shape of morphologies that can be achieved as a function of temperature and/or pH variations open new routes in the development of multiresponsive nanocarriers for biomedical applications.

Biocompatible and Biodegradable Poly(trimethylene carbonate)-b-Poly(l-glutamic acid) Polymersomes: Size Control and Stability

Poly(trimethylene carbonate)-b-poly(L-glutamic acid) (PTMC-b-PGA) diblock copolymers have been synthesized by ring-opening polymerization (ROP) of gamma-benzyl-L-glutamate N-carboxyanhydride (BLG) initiated by amino functionalized PTMC and subsequent hydrogenation. Self-assembly in water gave well-defined vesicles which have been studied combining light and neutron scattering techniques with electron microscopy imaging. The size and dispersity of vesicles have been tuned by varying preparation conditions, direct dissolution, or nanoprecipitation. In addition, PGA conformation could be reversibly manipulated as a function of environmental changes such as pH and ionic strength. Vesicles showed high tolerance and stability toward nonionic surfactant and pH due to a thick membrane and were revealed to be nonpermeable to water. Nevertheless, they can be rapidly degraded by enzymatic hydrolysis of the polycarbonate block. The ability to tune their size through the formation process, their stimuli responsiveness, their high stability, and their biodegradability make them suitable for biomedical applications.

Polysaccharide-Containing Block Copolymers: Synthesis, Properties and Applications of an Emerging Family of Glycoconjugates

While polysaccharide graft copolymers and glycopolymers have been widely studied and used in various applications, linear block copolymer structures combining a polysaccharide segment and a synthetic one have been less described. The limited availability of the polysaccharide reducing-end, the difficulty of finding a common solvent of both blocks and the need sometimes to protect the lateral hydroxyl groups of the polysaccharide chain may explain the relatively low number of studies on this copolymer family despite its potential interest. Polysaccharide block copolymers feature physicochemical properties not only close to those of synthetic block copolymers but also bring an added value such as the biodegradability, the biocompatibility or the bioactivity in some cases. This review aims at presenting the synthetic pathways towards such structures, from the basic polymerization techniques to the most recent ones including controlled/living polymerization mechanisms and also by emphasizing the chemical reactions used to functionalize the reducing-end of the polysaccharide block. The amphiphilic nature of most of the polysaccharide-based block copolymers reported so far gives rise to various self-assembly morphologies in the solid state or in selective solvents. In addition, the rigidity of the polysaccharide block is expected to influence the microphase separation of the block copolymer by increasing the thermodynamic incompatibility between dissimilar blocks. A special interest was drawn to the formation and the properties of polymer vesicles (polymersomes) in aqueous solutions. Polysaccharide block copolymers might represent a new class of biomaterials with potential applications in different fields such as the plastic industry, the detergency and also the pharmaceutics where the design of nanodevices carrying a native polysaccharide chain is of interest for therapy, vaccination and diagnosis purposes.

In vitro and In vivo Evaluation of Docetaxel Loaded Biodegradable Polymersomes

Formulation of docetaxel (DOC), a hydrophobic anticancer drug, was successfully achieved in poly(gamma-benzyl L-glutamate)-block-hyaluronan polymersomes using a simple and reproducible nanoprecipitation method. The prepared DOC loaded polymersomes (PolyDOC) was stable either in solution or in a lyophilized form, and showed controlled release behaviour over several days. PolyDOC showed high in vitro toxicity after 24 h in MCF-7 and U87 cells compared to free DOC. Biodistribution data demonstrated that (99m)Tc labelled PolyDOC t(1/2) and MRT significantly increased compared to a DOC solution (DS). In addition, PolyDOC uptake in Ehrlich Ascites Tumor (EAT) tumor bearing mice was larger at each time point compared to DS, making such a polymer vesicle formulation an efficient drug nanocarrier for improved DOC cancer therapy.

The in vivo behavior and antitumor activity of doxorubicin-loaded poly(γ-benzyl L-glutamate)-block-hyaluronan polymersomes in Ehrlich ascites tumor-bearing BalB/c mice

UNLABELLED The in vivo efficacy of doxorubicin (DOX)-loaded poly(γ-benzyl l-glutamate)-block-hyaluronan (PBLG(23)-b-HYA(10))-based polymersomes (PolyDOX) was evaluated. Samples were efficiently labeled with technetium-99m radionuclide with good stability for in vivo studies. PolyDOX enhanced circulation time compared to free DOX. Biodistribution studies revealed selective accumulation of PolyDOX in the Ehrlich ascites tumor (EAT) as a result of passive accumulation and active targeting (CD44-mediated endocytosis) in EAT-bearing mice. Toxicity studies demonstrated PolyDOX is a safe drug carrier, and no hemolysis was observed with PolyDOX equivalent to 200 μg/mL of free DOX. PolyDOX dominantly controlled tumor growth by delaying doubling time of EATs compared to free DOX over 30 days after treatment. PolyDOX also increased life span six times more than free DOX. Hence, it is reasonable to expect that higher DOX levels attributable to PolyDOX improve the therapeutic index and reduce side effects due to site-specific drug accumulation. FROM THE CLINICAL EDITOR In this preclinical project, doxorubicin loaded polymersomes enhanced intracellular uptake of doxorubicin in a murine model of Ehrlich Ascites Tumor (EAT) through CD44 receptor mediated endocytosis, resulting in prolonged Tumor Doubling Time and increase in life span of mice.

Thermoresponsive polymer brush-functionalized magnetic manganite nanoparticles for remotely triggered drug release

A thermoresponsive hybrid system for drug delivery purposes is designed by modifying the surface of silica-coated magnetic lanthanum strontium manganite nanoparticles with block copolymers following a non-covalent approach. Block copolymers containing a short poly(L-lysine) segment and a polyether segment of varying composition are adsorbed through electrostatic interactions between positively charged lysine units and negatively charged SiO− groups at the silica surface, giving rise to mixed polyether brushes with a good control over the chain surface density and thickness of the polymer layer. The thermoresponsiveness of the assemblies is controlled by the ethylene oxide/propylene oxide ratio in the polymer brush and the corresponding LCST of the polyether blocks. Important parameters like the aggregation temperature of the particles can be finely adjusted by modifying this ratio. The polarity of the polymer layer can also be varied to maximize the encapsulation efficiency of a moderately hydrophobic drug like doxorubicin. Drug release experiments are performed by taking advantage of the ac magnetically induced heating properties of the magnetic core to speed up the release of doxorubicin owing to structural changes within the polyether brush.

Manganite perovskite nanoparticles for self-controlled magnetic fluid hyperthermia: about the suitability of an aqueous combustion synthesis route

Unaggregated La0.82Sr0.18MnO3 + δ perovskite nanoparticles with a mean crystallite size of 22 nm were successfully synthesized through an aqueous combustion process (Glycine Nitrate Process, GNP) which takes advantage of exothermic, fast and self-sustaining chemical reactions between metal nitrates and glycine as a suitable organic reducing agent. The influence of G/N molar ratio on the phase purity, crystallite size and manganese valency was screened. Fuel-rich conditions were selected to improve chelation of the cations in acidic pH and ensure an accurate control of the cationic composition. Fast calcination was optimized to enhance crystallinity of the nanoparticles and subsequent milling step was performed to favour their desaggregation. The manganite nanoparticles were thoroughly characterized by X-ray diffraction (XRD), elemental chemical analysis, Mohr salt titration and transmission electron microscopy (TEM). According to a process derived from the Stobers method, they were uniformly coated with a 5 nm thick silica shell, as evidenced by TEM, infrared spectroscopy, ζ potential measurements and dynamic light scattering experiments. Preliminary heating experiments in a ac magnetic field showed these core@shell nanoparticles fulfill the requirements for self-controlled magnetic fluid hyperthermia, considering their size (20–70 nm) and their maximum heating temperature (43 °C) which is controlled by the Curie temperature of the magnetic cores.