Different insight into amphiphilic PEG-PLA copolymers: Influence of macromolecular architecture on the micelle formation and cellular uptake

One constrain in the use of micellar carriers as drug delivery systems (DDSs) is their low stability in aqueous solution. In this study "tree-shaped" copolymers of general formula mPEG-(PLA)n (n = 1, 2 or 4; mPEG = poly(ethylene glycol) monomethylether 2K or 5K Da; PLA = atactic or isotactic poly(lactide)) were synthesized to evaluate the architecture and chemical composition effect on the micelles formation and stability. Copolymers with mPEG/PLA ratio of about 1:1 wt/wt were obtained using a "core-first" synthetic route. Dynamic Light Scattering (DLS), Field Emission Scanning Electron Microscopy (FESEM), and Zeta Potential measurements showed that mPEG2K-(PD,LLA)2 copolymer, characterized by mPEG chain of 2000 Da and two blocks of atactic PLA, was able to form monodisperse and stable micelles. To analyze the interaction among micelles and tumor cells, FITC conjugated mPEG-(PLA)n were synthesized. The derived micelles were tested on two, histological different, tumor cell lines: HEK293t and HeLa cells. Fluorescence Activated Cells Sorter (FACS) analysis showed that the FITC conjugated mPEG2K-(PD,LLA)2 copolymer stain tumor cells with high efficiency. Our data demonstrate that both PEG size and PLA structure control the biological interaction between the micelles and biological systems. Moreover, using confocal microscopy analysis, the staining of tumor cells obtained after incubation with mPEG2K-(PD,LLA) 2 was shown to be localized inside the tumor cells. Indeed, the mPEG2K-(PD,LLA)2 paclitaxel-loaded micelles mediate a potent antitumor cytotoxicity effect. \ua9 2013 American Chemical Society

Poly(vinylidene fluoride)-b-poly(styrene) block copolymers by iodine transfer polymerization (ITP): Synthesis, characterization, and kinetics of ITP

International audienceThe syntheses of poly(vinylidene fluoride)-b-poly(styrene) (PVDF-b-PS) block copolymers, from the iodine transfer polymerization (ITP) of styrene, in the presence of PVDF-I, are presented. In a first step, considering that the radical polymerization of vinylidene fluoride can lead to two different isomeric oligomers, bearing either -CH2I or -CF2I end groups, the kinetics of ITP of styrene in the presence of two chain transfer agents, C6F13-CH2CF2-I and HCF2-CF2CH2-I, were achieved as model reactions. The characterization of sampled aliquots by 19F NMR spectroscopy could monitor the average degree of polymerization in number (DPn) vs styrene conversion (RStyrene). ITPs of styrene with both these chain transfer agents showed two opposite behaviors, also confirmed by MALDI-TOF spectroscopy and SEC chromatography. (i) on the one hand, in the presence of C6F13-CH2CF2-I, the controlled character of ITP of styrene was evidenced (a linear dependence of DPn vs RStyrene was observed), theoretical DPn values were close to those of the targeted ones, with low polydispersity indexes (PDI ) 1.5) and the transfer constant value was assessed (CTr = 1); (ii) on the other hand, using HCF2- CF2CH2-I as the chain transfer agent, ITP of styrene did not occur since only a direct initiation for the polymerization of styrene was noted, with DPn value higher than the targeted one and a broad polydispersity distribution (PDI > 2). In a second part, PVDF-b-PS block copolymers were synthesized via a two step-procedure, ITP of VDF in the presence of C6F13I as the chain transfer agent leading to C6F13(VDF)n-I oligomers and, subsequently, ITP of styrene using those latter oligomers as macromolecular chain transfer agents. These block copolymers were characterized by 19F and 1H NMR and MALDI-TOF spectroscopies, and by SEC chromatography. Their morphological and thermal properties were also studied by atomic force microscopy (AFM) and by differential scanning calorimetry (DSC), respectively