Self‐Assembled Polyprodrug Amphiphile for Subcutaneous Xenograft Tumor Inhibition with Prolonged Acting Time In Vivo

Polymeric drug delivery system termed as “polyprodrug amphiphile” poly(2‐methylacryloyloxyethyl phosphorylcholine)‐b‐poly(10‐hydroxy‐camptothecin methacrylate (pMPC‐b‐pHCPT) is developed for the prolonged‐acting cancer therapy. It is obtained by two‐step reversible addition–fragmentation chain transfer polymerization of zwitterionic monomer MPC and an esterase‐responsive polymerizable prodrug methacrylic anhydride–CPT, respectively. This diblock polymer is composed of both antifouling (pMPC) and bioactive (pHCPT) segments and the drug is designed as a building block to construct the polymer skeleton directly. Due to its distinct amphiphilicity, the polymer can self‐assemble into micelles with different dynamic sizes by facilely tuning the ratio of MPC/HCPT under physiological conditions. The outer pMPC shell is superhydrophilic to form dense hydrate layer preventing the nanosystem from unwanted nonspecific protein adsorption, which is the main lead cause of the rapid clearance of nanoparticles in vivo, thus facilitating the accumulation of drugs in tumor sites via enhanced permeability and retention effect. The configuration of the polyprodrug amphiphile is confirmed by several measurements. The resistance to albumin adsorption, prolonged plasma retention time, accumulation in tumor sites, and anticancer activity of the micelles is also investigated in vitro and in vivo. This novel amphiphile can be expected as a promising agent for the passive targeted prolonged‐acting cancer therapy.     

Polymeric Gene Carriers Bearing Pendant β‐Cyclodextrin: The Relevance of Glycoside Permethylation on the “In Vitro” Cell Response

The incorporation of cyclodextrins (CDs) to nonviral cationic polymer vectors is very attractive due to recent studies that report a clear improvement of their cytocompatibility and transfection efficiency. However, a systematic study on the influence of the CD derivatization is still lacking. In this work, the relevance of β‐CD permethylation has been addressed by preparing and evaluating two series of copolymers of the cationic N‐ethyl pyrrolidine methacrylamide (EPA) and styrenic units bearing pendant hydroxylated and permethylated β‐CDs (HCDSt and MeCDSt, respectively). For both cell lines, CDs permethylation shows a strong influence on plasmid DNA complexation, “in vitro” cytocompatibility and transfection efficiency of the resulting copolymers over two murine cell lines. While the incorporation of the hydroxylated CD moiety increased the cytotoxicity of the copolymers in comparison with their homopolycationic counterpart, the permethylated copolymers have shown full cytocompatibility as well as superior transfection efficiency than the controls. This behavior has been related to the different chemical nature of both units and tentatively to a different distribution of units along the polymeric chains. Cellular internalization analysis with fluorescent copo­lymers supports this behavior.

     

Catalytic chain transfer polymerization of isobutylene: The role of nucleophilic impurities

Fast polymerization of isobutylene (IB) initiated by tert‐butyl chloride using ethylaluminum dichloride·bis(2‐chloroethyl) ether complex (T. Rajasekhar, J. Emert, R. Faust, Polym. Chem. 2017, 8, 2852) was drastically slowed down in the presence of impurities, such as propionic acid, acetone, methanol, and acetonitrile. The effect of impurities on the polymerization rate was neutralized by using two different approaches. First, addition of a small amount of iron trichloride (FeCl₃) scavenged the impurity and formed an insoluble · impurity complex in hexanes. The polymerization rate and exo‐olefin content were virtually identical to that obtained in the absence of impurities. Heterogeneous phase scavenger (FeCl₃) exhibited better performance than homogenous phase scavengers. In the second approach, conducting the polymerization in wet hexanes, the fast polymerization of IB was retained in the presence of impurities with a slight decrease in exo‐olefin content. ¹H NMR studies suggest that nucleophilic impurities are protonated in the presence of water, and thereby neutralized. Mechanistic studies suggest that the rate constant of activation (k_a), rate constant of propagation (k_p), and rate constant of β‐proton elimination (k_tr) are not affected by the presence of impurities. To account for the retardation of polymerization in the presence of impurities, delay of proton transfer to monomer in the chain transfer step is proposed. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3697–3704     

Solubility Switching of Metallophthalocyanines and Their Larger Derivatives upon Encapsulation

Metallophthalocyanines (MPcs) are very useful pigments but scarcely soluble without appropriate functional groups in common solvents. Herein, we report that bent polyaromatic amphiphiles act as excellent solubilizing reagents for nonfunctionalized MPcs and larger MPc derivatives (e.g., CuPc, perhalogenated CuPcs, Cu‐naphthalocyanine, CuPc polymers, and double‐decker MPcs) in neutral water upon encapsulation. The resultant MPc nanocomposites display high stability towards heat and pH change. More importantly, the encapsulated MPcs can be released by simple protocols under mild conditions both into a bulk solvent and onto glass or polymer plates.     

Antifungal Imidazole‐Decorated Cationic Amphiphiles with Markedly Low Hemolytic Activity

Herein we report that an imidazole‐decorated cationic amphiphile derived from the pseudo‐disaccharide nebramine has potent antifungal activity against strains of Candida glabrata pathogens. In combination with the natural bis‐benzylisoquinoline alkaloid tetrandrine the reported antifungal cationic amphiphile demonstrated synergistic antifungal activity against Candida albicans pathogens. This unique membrane disruptor caused no detectible mammalian red blood cell hemolysis at concentrations up to more than two orders of magnitude greater than its minimal inhibitory concentrations against the tested C. glabrata strains. We provide evidence that potency against C. glabrata may be associated with differences between the drug efflux pumps of C. albicans and C. glabrata. Imidazole decorated‐cationic amphiphiles show promise for the development of less toxic membrane‐disrupting antifungal drugs and drug combinations.     

阴离子Gemini表面活性剂和阳离子传统表面活性剂混合体系双水相中囊泡形貌的转变

通过电子显微镜观察了阴离子gemini表面活性剂C₁₁- p-PhCNa和阳离子传统表面活性剂DTAB混合体系双水相中囊泡形貌随体系组成和浓度的转变。结果表明,双水相较浓的一相中形成了多层囊泡,囊泡的大小和壁厚随相的组成和浓度而改变,两组分等电荷混合有利于形成较大且壁较厚的囊泡。分析表明, gemini表面活性剂在聚集体中采取的反式构象可能是其容易形成厚壁多层囊泡的重要原因,C₁₁- p-PhCNa联接链上的苯氧基与DTA⁺之间的p-阳离子相互作用以及两组分相反电性头基之间的静电吸引使囊泡壁的多层结构更加稳定。     

Metallocene-mediated cationic polymerization of vinyl ethers: Kinetics of polymerization and synthesis and characterization of statistical copolymers

The cationic polymerization of ethyl, n-butyl and iso-butyl vinyl ether, EVE, BVE and iBVE, respectively, was efficiently conducted using bis(η⁵-cyclopentadienyl)dimethyl hafnium, Cp₂HfMe₂, or bis(η⁵-cyclopentadienyl)dimethyl zirconium, Cp₂ZrMe₂ in combination with either tris(pentafluorophenyl)borate, B(C₆F₅)₃, or tetrakis(pentafluorophenyl)borate dimethylanilinum salt, [B(C₆F₅)₄]^?[Me₂NHPh]⁺, as initiation systems. The evolution of polymer yield, molecular weight and molecular weight distribution with time was examined. In addition, the influence of the initiating system, the monomer and the reaction conditions on the control of the polymerization was studied. Furthermore, statistical copolymers of EVE with BVE were prepared employing Cp₂HfMe₂ and [B(C₆F₅)₄]^?[Me₂NHPh]⁺ as the initiation system. The reactivity ratios were estimated using both linear graphical and non-linear methods. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the mean sequence length, which were derived using the monomer reactivity ratios. The glass transition temperatures, Tg, of the copolymers were measured by Differential Scanning Calorimetry, DSC, and the results were compared with predictions based on several theoretical models. The kinetics of thermal decomposition of the copolymers along with the respective homopolymers was studied by thermogravimetric analysis within the framework of the Ozawa-Flynn-Wall and Kissinger methodologies.     

Magnetically assisted removal and separation of cationic dyes from aqueous solution by magnetic nanocomposite hydrogels

Magnetic poly(acrylic acid‐acrylamide‐butyl methacrylate) (P(AAB)) nanocomposite hydrogels were prepared and used as adsorbents for removal and separation of cationic dyes from aqueous solution. These magnetic P(AAB) nanocomposite hydrogels were characterized by scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). It was found that these magnetic P(AAB) nanocomposite hydrogels had magnetic responsive characters. The dynamic swelling, removal, and separation of cationic dye, crystal violet (CV), and basic magenta (BM) by these magnetic nanocomposite hydrogels were studied. The adsorption capacity and isotherm studies of cationic dyes onto magnetic P(AAB) nanocomposite hydrogels have been evaluated. The magnetic P(AAB) nanocomposite hydrogels containing Fe₃O₄ particles can be easily manipulated in magnetic field for removal and separation of cationic dyes from aqueous solution. Adsorption process agreed very well with the Langmuir and Freundlich models. Copyright © 2010 John Wiley & Sons, Ltd.     

Investigation of the tensile properties of “epoxy resin‐monomer” systems using cationic UV‐crosslinkable blends

The compatibility of cycloaliphatic and aromatic multifunctional epoxides with several epoxide resins allows the development of a wide range of cationic radiation‐curable formulations. The influence of different “epoxide resin‐monomer” systems UV‐cured in the presence of suitable cationic photoinitiators on the resulting physicochemical film properties was studied, and the results are stated. Copyright © 2004 John Wiley & Sons, Ltd.     

Preparation of block copolymer vesicles in solution

Block copolymer vesicles can be prepared in solution from a variety of different amphiphilic systems. Polystyrene‐block‐poly(acrylic acid), polystyrene‐block‐poly(ethylene oxide), and many other block copolymer systems can produce vesicles of a wide range of sizes; those in the range of 100–1000 nm have been explored extensively. Different factors, such as the absolute and relative block lengths, the presence of additives (ions, homopolymers, and surfactants), the water content in the solvent mixture, the nature and composition of the solvent, the temperature, and the polydispersity of the hydrophilic block, provide control over the types of vesicles produced. Their high stability, resistance to many external stimuli, and ability to package both hydrophilic and hydrophobic compounds make them excellent candidates for use in the medical, pharmaceutical, and environmental fields. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 923–938, 2004