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Chiral complex micelles prepared by 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and the poly(ethylene glycol)-block-poly(4-vinylpyridine) (PEG114-b-P4VP61) in the presence of aspartic acid (Asp), tryptophan (Trp), and lysine (Lys) were investigated in aqueous solutions at pH 2.0. TPPS formed J-aggregates in the micellar core. The morphology and optical properties of the complex micelles depended on the properties of amino acids and the preservation time for the mixed solutions of TPPS and amino acids before adding the copolymer. Prolonging the preservation time, the spherical morphology of the complex micelles remained unchanged in the presence of the Asp. On the contrary, a morphology evolution from sphere to rod took place for Trp and Lys. The intensity of the circular dichroism (CD) signals of the complex micelles increase with the preservation time, and the chirality sign was determined by amino acids. l-Trp and l-Lys led to a negative chirality sign and l-Asp a positive one while the corresponding enantiomers contributed to the opposite sign. Lower concentration of amino acids could not transfer their chirality to the aggregates of TPPS, and at higher concentrations of TPPS, it took more time for the aggregates to express the chiral information on amino acids. [ABSTRACT FROM AUTHOR]

Cationic polymers have been studied as promising nonviral gene delivery vectors. In contrast to the conventional polycations with long sequences of covalently bonded repeating units, we have developed a series of novel cationic polyrotaxanes consisting of multiple oligoethyleneimine-grafted β-cyclodextrin rings threaded on a poly(ethylene glycol)−poly(propylene glycol)−poly(ethylene glycol) triblock copolymer chain. In this study, these cationic polyrotaxanes with different oligoethyleneimine chain lengths were investigated for DNA binding ability, cytotoxicity, and gene transfection efficiency in cancer cells. Fluorescent titration assay results indicated that all the polyrotaxanes could completely condense plasmid DNA and form stable complexes at N/P ratio of 2, where the N/P ratio is the molar ration of amine groups in the cationic molecule to phosphate groups in the DNA. Particularly, tapping mode AFM imaging in aqueous environment was conducted to observe the morphology of the polyrotaxane/DNA complexes and their formation processes in real time. In both SK-OV-3 and PC3 cancer cells, these polyrotaxanes showed low cytotoxicity and high transfection efficiency which is comparable to or significantly higher than that of high molecular weight branched polyethylenimine (25 kDa), one of the most effective gene-delivery polymers studied to date. In addition, the synthesized polyrotaxanes displayed sustained gene delivery capability in PC3 cells in the presence or absence of serum. Therefore, these cationic polyrotaxanes with strong DNA binding ability, low cytotoxicity, and high and sustained gene delivery capability have a high potential as novel nonviral gene carriers in clinical cancer gene therapy. [ABSTRACT FROM AUTHOR]

In the presence of tryptophan (Trp), complex micelles were prepared by 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) and poly(ethylene glycol)-block-poly(2-(dimethylamino)ethyl methylacrylate) (PEG-b-PDMAEMA) in aqueous solutions at pH 1.8. Different mixing sequences led to different morphologies. Spheres and nanorods of small size were obtained in sequence I (P/Trp+TPPS) where TPPS was added into the mixed solution of PEG-b-PDMAEMA and Trp. More nanorods of larger length were achieved in sequence II (TPPS/Trp+P) where the copolymer was added as the last component. Two types of supramolecular chirality of TPPS aggregates caused by mixing sequences were investigated. In (P/Trp+TPPS), the circular dichroism (CD) signal of H-band was in line with the chirality of Trp while that of J-band exhibited an opposite signal (Chirality I). In (TPPS/Trp+P), chiral signals at both H- and J-bands followed that of Trp (Chirality II). The conversion between the two types of chirality can be accomplished by modulating the molar ratio of the repeating units on block PDMAEMA to TPPS, or a cycle of pH 1.8–5.5–1.8 processing on the micelle solution. In addition, the supramolecular chirality can be memorized via strong electrostatic interaction with achiral copolymer even after removal of the chiral template, but only Chirality II can be cyclically “switched-off-on”. [ABSTRACT FROM AUTHOR]

Complex 1 exhibits the crownlike structure with the unprecedented 12-membered ring system, while in 2, a cagelike cluster has been connected with two distorted cores in nickel thiolates. The synthesis of novel clusters by way of C--S bond cleavage was first reported in the field of nickel thiolates. [ABSTRACT FROM AUTHOR]