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HCN polymers are a group of complex and heterogeneous substances that are widely known in the fields of astrobiology and prebiotic chemistry. In addition, they have recently received considerable attention as potential functional material coatings. However, the real nature and pathways of formation of HCN polymers remain open questions. It is well established that the tuning of macromolecular structures determines the properties and practical applications of a polymeric material. Herein, different synthetic conditions were explored for the production of HCN polymers from NH4CN or diaminomaleonitrile in aqueous media with different concentrations of the starting reactants and several reaction times. By using a systematic methodology, both series of polymers were shown to exhibit similar, but not identical, spectroscopic and thermal fingerprints, which resulted in a clear differentiation of their morphological and electrochemical properties. New macrostructures are proposed for HCN polymers, and promising insights are discussed for prebiotic chemistry and materials science on the basis of the experimental results.

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The copolymerization reactions of acrylic systems of biomedical interest, 2-hydroxyethyl methacrylate (HEMA)/2-acrylamido-2-methylpropanesulfonic acid (AMPS) and N,N-dimethylacrylamide (DMAA)/AMPS, have been analyzed by 1H NMR. A new methodology is described for the determination of the reactivity ratios based on the quantitative in situ NMR analysis in the course of the copolymerization reaction. The methodology uses the continuous change of the intensity of resonance signals assigned unambiguously to the monomers participating in the polymerization reaction with the reaction time at a given temperature. The evaluation of the monomer concentrations leads to the determination of the instantaneous feed molar fractions and the reactivity ratios, by using a solution of the differential copolymerization equation which describes the terminal model described by Mayo and Lewis. Two approaches to obtain the reactivity ratios by nonlinear fitting of the experimental data to this integrated form are described. The first incorporates the initial conditions as third parameter in the optimization (the values obtained are r HEMA = 6.81 and r AMPS = 0.116 for the HEMA−AMPS system and r DMAA = 1.50 and r AMPS = 0.40 for DMAA−AMPS), and the second uses different points as initial conditions in the integrated equation (obtaining r DMAA = 1.53 and r AMPS = 0.36, in very good agreement with the obtained by the first method). These values are in good agreement with those described in the literature and with data for copolymers prepared at low conversion analyzed by standard methods.

Macroporous poly( N-isopropylacrylamide) (pNIPA) gels (so-called cryogels), cross-linked with different bis-acrylic compounds, N,N'-methylenebisacrylamide (MBAAm) and dimethacrylate-tyrosine-lysine-tyrosine (DMTLT), were prepared through free-radical polymerization at subzero temperature in dioxane/water media. DMTLT is a hydrolytically degradable cross-linker with relatively hydrophobic character. The effects of different synthesis conditions, namely the concentration of monomers, the cross-linker, and the initiator in the reaction mixture, on the structure of the pNIPA-cryogels have been studied. The equilibrium swelling ratio of the DMTLT cross-linked pNIPA cryogels at temperatures below lower critical solution temperature (LCST) of pNIPA, was over ten times higher than that of the gels synthesized at room temperature from the same feed composition. The MBAAm cross-linked pNIPA cryogels synthesized in water exhibited the highest equilibrium swelling and the fastest response. The critical transition temperature, T c, was lower ( T c approximately 31 degrees C) for pNIPA-cryogels synthesized in dioxane/water media or cross-linked with DMTLT as compared to MBAAm cross-linked pNIPA cryogels synthesized in water (T c approximately 33 degrees C). Scanning electron microscopy (SEM) revealed different porous structure and pore surface morphology depending on the cross-linker (MBAAm or DMTLT) and the solvent (water or dioxane/water) used. Gels and cryogels were also characterized by SAXS, showing that the nanostructure of the samples is related to swelling.

International audienceThe temperature-induced structural modifications of poly(N-isopropylacrylamide) hydrogel (pNIPA) were investigated by small-angle X-ray scattering (SAXS) over a broad range of q values (3.5 x 10(-2)-12 nm(-1)) at temperatures ranging between 18 and 37 degrees C. The sample Studied was claborated by cryopolymerization yielding a macroporous gel (cryogel). The pNIPA gel forms the walls (the thickness at 23 degrees C is about 12 mu m). The SAXS curves display an isoscattering (or isosbestic) point located at q(iso) = 3.633 nm(-1) and disappearingabovc 30 degrees C. This feature has never been reported up to now. The SAXS curves obtained at each temperature are well fitted by a sum of four equations describing respectively the scattering resulting from the gel surface (power law), from the solidlike (Guinier equation) and liquidlike (Ornstein - Zernike equation) heterogeneities, and from the chain-chain correlation yielding a broad peak (pseudo-Voigt equation) in the high-q domain. The temperature dependence of the parameters obtained from the fit is analyzed and discussed

Bacterial, protozoan and other microbial infections share an accelerated metabolic rate. In order to ensure a proper functioning of cell replication and proteins and nucleic acids synthesis processes, folate metabolism rate is also increased in these cases. For this reason, folic acid antagonists have been used since their discovery to treat different kinds of microbial infections, taking advantage of this metabolic difference when compared with human cells. However, resistances to these compounds have emerged since then and only combined therapies are currently used in clinic. In addition, some of these compounds have been found to have an immunomodulatory behavior that allows clinicians using them as anti-inflammatory or immunosuppressive drugs. Therefore, the aim of this review is to provide an updated state-of-the-art on the use of antifolates as antibacterial and immunomodulating agents in the clinical setting, as well as to present their action mechanisms and currently investigated biomedical applications.

α-Tocopheryl succinate (α-TOS) is a well-known mitochondrially targeted anticancer compound, however, it is highly hydrophobic and toxic. In order to improve its activity and reduce its toxicity, new surfactant-free biologically active nanoparticles (NP) were synthesized. A methacrylic derivative of α-TOS (MTOS) was prepared and incorporated in amphiphilic pseudoblock copolymers when copolymerized with N-vinylpyrrolidone (VP) by free radical polymerization (poly(VP-co-MTOS)). The selected poly(VP-co-MTOS) copolymers formed surfactant-free NP by nanoprecipitation with sizes between 96 and 220 nm and narrow size distribution, and the in vitro biological activity was tested. In order to understand the structure-activity relationship three other methacrylic monomers were synthesized and characterized: MVE did not have the succinate group, SPHY did not have the chromanol ring, and MPHY did not have both the succinate group and the chromanol ring. The corresponding families of copolymers (poly(VP-co-MVE), poly(VP-co-SPHY), and poly(VP-co-MPHY)) were synthesized and characterized, and their biological activity was compared to poly(VP-co-MTOS). Both poly(VP-co-MTOS) and poly(VP-co-MVE) presented triple action: reduced cell viability of cancer cells with little or no harm to normal cells (anticancer), reduced viability of proliferating endothelial cells with little or no harm to quiescent endothelial cells (antiangiogenic), and efficiently encapsulated hydrophobic molecules (nanocarrier). The anticancer and antiangiogenic activity of the synthesized copolymers is demonstrated as the active compound (vitamin E or α-tocopheryl succinate) do not need to be cleaved to trigger the biological action targeting ubiquinone binding sites of complex II. Poly(VP-co-SPHY) and poly(VP-co-MPHY) also formed surfactant-free NP that were also endocyted by the assayed cells; however, these NP did not selectively reduce cell viability of cancer cells. Therefore, the chromanol ring of the vitamin E analogues has an important role in the biological activity of the copolymers. Moreover, when succinate moiety is substituted and vitamin E is directly linked to the macromolecular chain through an ester bond, the biological activity is maintained.