Pyrrolidinium Groups Research Articles

Unsymmetrical Low-Generation Cationic Phosphorus Dendrimers as a Nonviral Vector to Deliver MicroRNA for Breast Cancer Therapy.

The development of nonviral dendritic polymers with a simple molecular backbone and great gene delivery efficiency to effectively tackle cancer remains a great challenge. Phosphorus dendrimers or dendrons are promising vectors due to their structural uniformity, rigid molecular backbones, and tunable surface functionalities. Here, we report the development of a new low-generation unsymmetrical cationic phosphorus dendrimer bearing 5 pyrrolidinium groups and one amino group as a nonviral gene delivery vector. The created AB5-type dendrimers with simple molecular backbone can compress microRNA-30d (miR-30d) to form polyplexes with desired hydrodynamic sizes and surface potentials and can effectively transfect miR-30d to cancer cells to suppress the glycolysis-associated SLC2A1 and HK1 expression, thus significantly inhibiting the migration and invasion of a murine breast cancer cell line in vitro and the corresponding subcutaneous tumor mouse model in vivo. Such unsymmetrical low-generation phosphorus dendrimers may be extended to deliver other genetic materials to tackle other diseases.

Alkaline stable pyrrolidinium-type main-chain polymer: The synergetic effect between adjacent cations

The structure evolution of individual cation approach to enhance the alkaline stability of anion exchange membranes (AEMs), has attracted considerable attention in recent years. However, the synergetic effect between adjacent cations was ignored even though it actively affects alkaline stability. Herein, a series of small organic compounds and main-chain polymers with pyrrolidinium cations tethered with different methylene groups were successfully synthesized and characterized. The increasing cation charge density of the pyrrolidinium compounds conferred better alkaline stability while the long spacer between adjacent pyrrolidinium cations accelerated the degradation of the cations in alkaline solutions. Then, DFT calculations indicated that the synergetic effect between the adjacent pyrrolidinium cations leads to a lower charge density on the α-C in the pyrrolidinium groups and enhance the energy barrier value for the attack by OH−, thereby improving excellent alkaline stability. The mechanically and chemically robust AEMs were prepared with pyrrolidinium-based main-chain polymers. The uncovered synergetic effect between the cations makes the synthesized AEMs a potential membrane for alkaline fuel cells.

The Ability of Functionalized Fullerenes and Surface‐Modified TiO2 Nanoparticles to Photosensitize Peroxidation of Lipids in Selected Model Systems

Photochemical properties of a new class of inorganic nanoparticles, namely a cationic C60 fullerene substituted with three quaternary pyrrolidinium groups (BB6) and a surface-modified nanocrystalline TiO2 with bromopyrogallol red (Brp@TiO2 ) were examined for their effectiveness in photogenerating singlet oxygen and free radicals. In particular, their ability to photosensitize peroxidation of unsaturated lipids was analyzed in POPC:cholesterol liposomes and B16 mouse melanoma cells employing a range of spectroscopic and analytical methods. Because melanoma cells typically are pigmented, we examined the effect of melanin on the photosensitized peroxidation of lipids in liposomes and B16 melanoma cells, mediated by BB6 and Brp@TiO2 nanoparticles. The obtained results suggest that peroxidation of unsaturated lipids, photosensitized by BB6 occurs mainly, although not exclusively, via Type II mechanism involving singlet oxygen. On the other hand, if surface-modified TiO2 is used as a photosensitizer, Type I mechanism of lipid peroxidation dominates, as indicated by the predominant formation of the free radical-dependent cholesterol oxidation products. The protective effect of melanin was particularly evident when BB6 was used as a photosensitizer, suggesting that melanin could efficiently interfere with Type II processes.

Pyrrolidinium-functionalized poly(arylene ether sulfone)s for anion exchange membranes: Using densely concentrated ionic groups and block design to improve membrane performance

To design and construct high ionic conductive anion exchange membranes (AEMs), tetra-pyrrolidinium-based block poly(arylene ether sulfone)s were synthesized. Pyrrolidinium groups were densely and controllably introduced into the polymer scaffold using a novel tetra-functionalized monomer, 4, 4′-oxybis (2,6-bis(pyrrolidinyl-1-methyl) phenol) (OBBPYP), which was synthesized via the Mannich reaction. To obtain chemically stable pyrrolidinium cations, the alkaline stabilities of pyrrolidinium-based cationic model compounds with various N-substituted alkyl chains (methyl, ethyl, butyl) were studied using 1H nuclear magnetic resonance (1H NMR) spectroscopy, in which methyl as the N-substituent group exhibited the highest alkaline stability. Based on the results above, a targeted, well-controlled, multiblock structure AEM (QQBPES-2.4OH) with densely concentrated pyrrolidinium cations was obtained via an iodomethane quaternization reaction. The densely concentrated ionic groups provide ionic nanochannels for hydroxide conduction, and the hydrophobic polymer backbone is responsible for the critical membrane mechanical support. As confirmed by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS), the QQBPES-2.4OH membrane exhibited a more obvious hydrophilic-hydrophobic microphase structure, compared to the random di-pyrrolidinium cation-based AEM (DQRPES-2.4OH) and tetra-pyrrolidinium cation-based AEM (QQRPES-2.4OH). Moreover, the QQBPES-2.4OH membrane exhibited considerably higher hydroxide conductivity, up to 68.0mScm−1 at 80°C, better flexibility and lower water swelling. The results of this work suggest a novel and scalable approach to the functionalization of polymers for AEMs.

A green catalysis of CO2 fixation to aliphatic cyclic carbonates by a new ionic liquid system

A mixed ionic liquid system has been developed for the efficient catalysis of CO2 addition to aliphatic epoxides without involving any transition metal catalysts or other additives. The ionic liquid integrated with pyridinium and pyrrolidinium groups (1·(Br)3) together with a non-polar ionic liquid (3·(Ntf)2) effectively transformed non-polar aliphatic epoxides to cyclic carbonates by the reaction with CO2 under mild CO2 pressure (3.0MPa) and reaction temperature (80°C). The presence of 3·(Ntf)2 remarkably improved the catalytic activity of 1·(Br)3 towards non-polar epoxides by increasing the miscibility of catalyst with the substrates. The mixed ionic liquid system is robust enough to be recycled without any significant loss of catalytic activity. GC–MS studies were performed to reveal the reaction pathways to the cyclic carbonates and a feasible model accounting for the effective CO2 activation in the ionic liquid system was proposed using density functional theory (DFT) calculations.

Polycationic phosphorus dendrimers: synthesis, characterization, study of cytotoxicity, complexation of DNA, and transfection experiments

Four series of phosphorus dendrimers (generations 1 and 4) having various types of amine terminal groups (pyrrolidine, morpholine, methyl piperazine, or phenyl piperazine) are synthesized. After protonation, the fourth generations of three of them are found water-soluble, and used for several biological experiments. First, the cytotoxicity of these polycationic dendrimers towards three cell strains (one healthy: HUVEC, and two cancerous: HEK 293 and HeLa) is assayed and found low. Second, their ability to interact with DNA is tested by electrophoresis: the dendrimer terminated by pyrrolidinium groups is found efficient to form dendriplexes. Finally, the polycationic dendrimers are used as transfection agents to deliver single- and double-stranded DNA into the three above-mentioned cell strains. Here also the dendrimer having pyrrolidinium groups is found the most efficient.

Cationic Fullerenes Are Effective and Selective Antimicrobial Photosensitizers

Fullerenes are soccer ball-shaped molecules composed of carbon atoms, and, when derivatized with functional groups, they become soluble and can act as photosensitizers. Antimicrobial photodynamic therapy combines a nontoxic photosensitizer with harmless visible light to generate reactive oxygen species that kill microbial cells. We have compared the antimicrobial activity of six functionalized C(60) compounds with one, two, or three hydrophilic or cationic groups in combination with white light against gram-positive bacteria, gram-negative bacteria, and fungi. After a 10 min incubation, the bis- and tris-cationic fullerenes were highly active in killing all tested microbes (4-6 logs) under conditions in which mammalian cells were comparatively unharmed. These compounds performed significantly better than a widely used antimicrobial photosensitizer, toluidine blue O. The high selectivity and efficacy exhibited by these photosensitizers encourage further testing for antimicrobial applications.

Nicotinium tetrachlorocuprate(II)

The structure of the title compound, (C10H16N2)[CuCl4], comprises two crystallographically non-equivalent tetrahedral [CuCl4]2− anions, each of which is linked to two doubly protonated nicotinium cations via hydrogen bonds. There are two different types of hydrogen-bonding interactions present, namely (i) the protonated pyridinium groups exclusively form bifurcated hydrogen bonds to two cis-Cl atoms of both [CuCl4]2− units and (ii) the protonated pyrrolidinium groups exclusively form a two-center hydrogen bond with a chloride of both [CuCl4]2− units.

Probing the Electron-Accepting Reactivity of Isomeric Bis(pyrrolidinium) Fullerene Salts in Aqueous Solutions

A series of water-soluble isomer bis(pyrrolidinium) salts, with C60(C4H10N+)2 as cationic moiety (2a−2d), were probed in radical- and light-induced reduction studies and compared to bis(carboxylates) C60[C(COO-)2]2 and to γ-CD-encapsulated C60. Pulse radiolytic reduction of 2a−2d with hydrated electrons and (CH3)2•COH radicals leads to the formation of the fullerene π-radical anion, exhibiting fingerprint absorption characteristics in the near-IR region. Because of the electron-withdrawing nature of the pyrrolidinium groups the electron-acceptor properties of the investigated bis(pyrrolidinium) salts are markedly improved relative to the bis(carboxylates) (C60[C(COO-)2]2) and also relative to C60. For example, the rate constants for the fullerene reduction of 2a−2d with hydrated electrons ((0.88−2.2) × 1010 M-1 s-1) and (CH3)2•COH radicals ((4.7−7.1) × 108 M-1 s-1) are clearly faster than those noted for C60[C(COO-)2]2 (eaq-: (0.19−0.34) × 1010 M-1 s-1; (CH3)2•COH: (0.9−2.2) × 108 M-1 s-1), and C60 (eaq...

Covalent Conversion of Cyclic Onium Salt End Groups of Poly(tetrahydrofuran) by Bulky Counteranions in the Absence and Presence of Macrocyclic Compounds

A series of bulky carboxylates was introduced as a counteranion for N-methylpyrrolidinum salt end groups of poly(tetrahydrofuran), poly(THF), having molecular weights of ca. 5000. 4-(7,7,7-Triphenylheptoxy)benzoate was found to remain intact as a counteranion at ambient temperature but to cause the ring-opening reaction of pyrrolidinium groups at 90 °C to produce poly(THF) with bulky stopper groups in a pure form in 71% yield. The relevant ring-opening reaction also took place in the presence of such macrocyclics as 30-crown-10 and cyclodextrins, but an effective entrapping of cyclic components in polyrotaxanes was not achieved presumably because of the entropic repulsion between the two components.