Stabilizing entangled spaghetti-like materials: Controling forces between oppositely charged polymers opens new route for gene therapy vectors

Gene therapy can only be effective if delivered by a stable complex molecule. Now, scientists have determined the conditions that would stabilise complex molecular structures that are subject to inherent attractions and repulsions triggered by electric charges at the surfaces of the molecules, in a study about to be published in the European Physical Journal E, by Valentina Mengarelli and her colleagues from the Solid State Physics Laboratory at the Paris-Sud University in Orsay, France, in collaboration with Paris 7 and Évry Universities scientists.

The authors studied soluble complexes made of negatively charged DNA or another negatively charged polymer -- polystyrene-sulfonate (PSSNa) -- and a so-called condensation agent, which is a negatively charged polymer, known as linear polyethyleneimine (PEI). PEI participates in the condensation process by tying onto a molecule such as DNA, like tangled hair, to form an overall positively charged DNA/polymer complex structure. Previous research focused mainly on non-soluble complexes, while the few attempts at focusing on soluble complexes dealt either with smaller polymers or those with a weaker electric charge, which may therefore be easier to stabilise.

The French team thus confirmed experimentally that the complexation process does not depend on the rigidity of the original molecule, be it DNA or PSSNa, but on the positive/negative electric charge ratio and on the polymer concentrations. It is the interactions between electrically charged parts within the complex that govern its properties. When the condensation agent is in excess, the positively charged complex is then attracted to negatively charged biological cell membranes. This could be used to deliver the DNA into a targeted cell nucleus as part of gene therapy treatment.Future work will focus on using long DNA molecules and novel polymers to form complexes of controlled size and electric charge for gene therapy.

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The above story is reprinted from materials provided by Springer.

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Journal Reference:

Mengarelli V, Auvray L, Pastré D, and Zeghal M,. Charge inversion, condensation and decondensation of DNA and Polystyrene sulfonate by polyethylenimine. European Physical Journal E (EPJE), 2011; 34, 127 DOI: 10.1140/epje/i2011/11127-3

Shining new light on air pollutants using entangled porous frameworks

ScienceDaily (Jan. 26, 2011) — Certain types of pollution monitoring may soon become considerably easier. A group of researchers centered at Kyoto University has shown in a recent Nature Communications paper that a newly-formulated entangled framework of porous crystals (porous coordination polymers, or PCPs) can not only capture a variety of common air pollutants, but that the mixtures then glow in specific, easily-detected colors.

Lead author for the paper was Dr. Yohei Takashima.

Until now, chemical sensors have generally needed to be custom-designed to recognize specific compounds, and a separate transmission mechanism was required in order to "see" that a particular molecule had indeed been successfully captured.

"We have created what amount to be interlocking jungle-gyms, that move relative to each other and are therefore able to capture molecules of varying sizes," explained Dr. Shuhei Furukawa of Kyoto University's Institute for Integrated Cell-Material Sciences (iCeMS).

This naphthalenediimide-based PCP, known as NDI, expands and contracts to confine air-born volatile organic compounds (VOCs) such as benzene, toluene, xylene, anisole, and iodobenzene, which are common pollutants in the lower atmosphere.

"When exposed to ultraviolet light, the NDI-VOC interaction luminesces in an unusually wide range of colors, sufficiently intense to be observed even with the naked eye," elaborated iCeMS Professor and deputy director, Susumu Kitagawa.

These findings, including contributions from Dr. Virginia Martínez Martínez at the Universidad del País Vasco in Bilbao, open the door to the development of a new range of portable, solid-state pollution detectors, and possibly even new types of light sources.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Institute for Integrated Cell-Material Sciences, Kyoto University, via EurekAlert!, a service of AAAS.

Journal Reference:

Yohei Takashima, Virginia Martínez Martínez, Shuhei Furukawa, Mio Kondo, Satoru Shimomura, Hiromitsu Uehara, Masashi Nakahama, Kunihisa Sugimoto, Susumu Kitagawa. Molecular decoding using luminescence from an entangled porous framework. Nature Communications, 2011; 2 (1): 168 DOI: 10.1038/ncomms1170

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