Surface active properties of polyoxyethylene macromonomers and their role in radical polymerization in disperse systems

Antineoplastic Activity of Water-Soluble Form of Novel Kinase Inhibitor 1-(4-Chlorobenzyl)-3-Chloro-4-(3-Trifluoromethylphenylamino)-1H-Pyrrole-2,5-Dione Immobilized on Polymeric Poly (PEGMA-co-DMM) Carrier

The maleimide derivative 1-(4-chlorobenzyl)-3-chloro-4-(3-trifluoromethylphenylamino)-1H-pyrrole-2,5-dione (MI-1) was synthesized as inhibitor of several protein kinases, however, its application is hindered by its poor water solubility. In this study, the mechanisms of the antineoplastic action of MI-1 and its MI-1/M5 complex with M5 carrier (poly (PEGMA-co-DMM)) towards human colon carcinoma HCT116 cells were investigated by using the MTT and clonogenic assays, DNA intercalation with methyl green replacement, alkaline DNA comet assay, and Western-blot analysis. MI-1 compound and its MI-1/M5 complex possessed high toxicity towards colon (HCT116), cervical (HeLa) carcinoma cells and melanoma (SK-MEL-28) cells with GI50 value in a range of 0.75–7.22 µg/mL, and demonstrated high selectivity index (SI ˃ 6.9). The p53 status of colon cancer cells did not affect the sensitivity of these cells to the treatment with MI-1 and its MI-1/M5 complex. M5 polymer possessed low toxicity towards studied cells. The MI-1, MI-1/M5, and M5 only slightly inhibited growth of the pseudo-normal HaCaT and Balb/c 3T3 cell lines (GI50 ˃ 50 μg/mL). The MI-1 and its MI-1/M5 complex induced mitochondria-dependent pathway of apoptosis, damage of the DNA, and morphological changes in HCT116 cells, and affected the G2/M transition checkpoint. The MI-1 intercalated into the DNA molecule, while such capability of MI-1/M5 complex and M5 polymer was much lower. Thus, poly (PEGMA-co-DMM) might be a promising carrier for delivery of the maleimide derivative, MI-1, a novel kinase inhibitor, through improving its solubility in aqueous media and enhancing its antiproliferative action towards human tumor cells. Studies are in progress on the treatment of Nemeth-Kellner lymphoma (NK/Ly)-bearing mice with the MI-1 and MI-1/M5 complex.

Recent development of brush polymers via polymerization of poly(ethylene glycol)-based macromonomers

Polymerization of poly(ethylene glycol)-based macromonomers is a facile and versatile synthetic method to generate well-defined brush polymers.

Optimization of the fabrication of novel stealth PLA-based nanoparticles by dispersion polymerization using D-optimal mixture design

PURPOSE

Nanoparticle size is important in drug delivery. Clearance of nanoparticles by cells of the reticuloendothelial system has been reported to increase with increase in particle size. Further, nanoparticles should be small enough to avoid lung or spleen filtering effects. Endocytosis and accumulation in tumor tissue by the enhanced permeability and retention effect are also processes that are influenced by particle size. We present the results of studies designed to optimize cross-linked biodegradable stealth polymeric nanoparticles fabricated by dispersion polymerization.

METHODS

Nanoparticles were fabricated using different amounts of macromonomer, initiators, crosslinking agent and stabilizer in a dioxane/DMSO/water solvent system. Confirmation of nanoparticle formation was by scanning electron microscopy (SEM). Particle size was measured by dynamic light scattering (DLS). D-optimal mixture statistical experimental design was used for the experimental runs, followed by model generation (Scheffe polynomial) and optimization with the aid of a computer software. Model verification was done by comparing particle size data of some suggested solutions to the predicted particle sizes.

RESULTS AND CONCLUSION

Data showed that average particle sizes follow the same trend as predicted by the model. Negative terms in the model corresponding to the cross-linking agent and stabilizer indicate the important factors for minimizing particle size.

One-step Preparation of Comb-like Surfactants Containing Poly(ethylene oxide) Methyl Ether and Linear Alkyl Grafts

The optimum one-step method for preparing comb-like surfactants with poly(styrene-co-maleic anhydride) (SMA) as backbone was investigated to achieve a commercial way for manufacture. The side chain molecule was introduced into reaction system while the radical copolymerization of styrene (St) and maleic anhydride (MA) in anhydrous inhibitor-free tetrahydrofuran (THF) was finished. The precipitation and purification process of SMA in traditional grafting-onto route was passed over. A series comb-like surfactants with various side chain, poly(styrene-co-maleic anhydride)-g-(poly(ethylene glycol) monomethyl ether) (SMA-M), poly(styrene-co-maleic anhydride)-g-(poly(ethylene glycol) monomethyl ether & dodecane) (SMA-M+C12) and poly(styrene-co-maleic anhydride)-g-(dodecane) (SMA-C12), was prepared via this one step method respectively. The molecular weight of the products was measurement via gel permeation chromatography (GPC). The comb-like structures of the surfactants were confirmed by Infrared Spectroscopy (IR) and 1H nuclear magnetic resonance spectroscopy (1H NMR). The equilibrium surface tension was measured to evaluate the surface activity of comb-like surfactants. The surface activity of the product could be improved by using C12 to carry out a hydrophobic modification. The surface activity of comb-like surfactants could be adjusted by using various side chains with different amphiphilic property.

Use of silica particles for the formation of organic-inorganic particles by surfactant-free emulsion polymerization

Polystyrene/silica (PS/SiO(2)) and poly(styrene-co-methyl methacrylate)/SiO(2) composite latex particles were prepared by surfactant-free emulsion polymerization in the presence of a poly(ethylene glycol) monomethylether methacrylate (PEGMA) macromonomer. The resulting composite particles were stabilized by the negatively charged silica particles that adhered to the surface of the latex particles. Different process parameters were investigated in order to optimize the latex stability and maximize the reaction rate. Mixing in such a surfactant-free process is of major importance and is mainly determined by the type of impeller used during the emulsification. The concentrations of PEGMA and silica particles were also optimized in order to improve the interaction between the organic and inorganic phases and ensure a good latex stability. The presence of silica particles on the polymer particle surface was found to affect radical absorption and decrease therefore the reaction rate.

Macroinitiators on the basis of new peroxide surface active monomers

The surface active properties of new peroxide maleic monomers were investigated. The regularities of their copolymerization with styrene were studied. Peroxide polymers containing ditertiary alkyl peroxide groups in side substituents of backbone as the prospective high-temperature free radical macroinitiators were synthesized.

Small-angle neutron scattering on a core-shell colloidal system: a contrast-variation study

Small-angle neutron scattering (SANS) measurements are reported on a sterically stabilized, core-shell colloidal system using contrast variation. Aqueous dispersions of polystyrene particles bearing grafted poly(ethylene glycol) (PEG) have been studied over a large range of particle concentrations and two different solvent conditions for the PEG polymer. SANS data are analyzed quantitatively by modeling the particles as core-shell colloids. In a good solvent and under particle contrast conditions, an effective hard-sphere interaction captures excluded-volume interactions up to high concentrations. Contrast variation, through isotopic substitution of both the core and solvent, expedite a detailed study of the PEG layer, both in the dilute limit and as a function of the particle concentration. Upon diminishing the solvent quality, subtle changes in the PEG layer translate into attractions among particles of moderate magnitude.

Sterically and electrosterically stabilized emulsion polymerization. Kinetics and preparation

The principal subject discussed in the current paper is the radical polymerization in the aqueous emulsions of unsaturated monomers (styrene, alkyl (meth)acrylates, etc.) stabilized by non-ionic and ionic/non-ionic emulsifiers. The sterically and electrosterically stabilized emulsion polymerization is a classical method which allows to prepare polymer lattices with large particles and a narrow particle size distribution. In spite of the similarities between electrostatically and sterically stabilized emulsion polymerizations, there are large differences in the polymerization rate, particle size and nucleation mode due to varying solubility of emulsifiers in oil and water phases, micelle sizes and thickness of the interfacial layer at the particle surface. The well-known Smith-Ewart theory mostly applicable for ionic emulsifier, predicts that the number of particles nucleated is proportional to the concentration of emulsifier up to 0.6. The thin interfacial layer at the particle surface, the large surface area of relatively small polymer particles and high stability of small particles lead to rapid polymerization. In the sterically stabilized emulsion polymerization the reaction order is significantly above 0.6. This was ascribed to limited flocculation of polymer particles at low concentration of emulsifier, due to preferential location of emulsifier in the monomer phase. Polymerization in the large particles deviates from the zero-one approach but the pseudo-bulk kinetics can be operative. The thick interfacial layer can act as a barrier for entering radicals due to which the radical entry efficiency and also the rate of polymerization are depressed. The high oil-solubility of non-ionic emulsifier decreases the initial micellar amount of emulsifier available for particle nucleation, which induces non-stationary state polymerization. The continuous release of emulsifier from the monomer phase and dismantling of the non-micellar aggregates maintained a high level of free emulsifier for additional nucleation. In the mixed ionic/non-ionic emulsifiers, the released non-ionic emulsifier can displace the ionic emulsifier at the particle surface, which then takes part in additional nucleation. The non-stationary state polymerization can be induced by the addition of a small amount of ionic emulsifier or the incorporation of ionic groups onto the particle surface. Considering the ionic sites as no-adsorption sites, the equilibrium adsorption layer can be thought of as consisting of a uniform coverage with holes. The de-organization of the interfacial layer can be increased by interparticle interaction via extended PEO chains--a bridging flocculation mechanism. The low overall activation energy for the sterically stabilized emulsion polymerization resulted from a decreased barrier for entering radicals at high temperature and increased particle flocculation.