Biomedical application of synthetic Cholesteric Liquid-crystal Polymers.

Mercedes Perez-Mendez ICTP, Madrid, Spain

Cholesteric liquid crystal polymers (CLCP) are multifunctional materials. We have synthetized and characterized in our laboratory chiral CLCP with cholesteric mesophase: PTOBEE [C26H20O8]n and PTOBDME [C34H36O8]n being fully characterized as thermotropic1. The amphiphilic shape of their monomers makes them polymerize along helical chains. The CLCP helical macromolecules also behave as lyotropic with mesophase in solution, which self-associates both by the effect of temperature and concentration, adopting diferent conformations dependind on the solvent. Due to their lyotropic behaviour cholesteric PTOBEE and PTOBDME have proved to being able to entrap smaller molecules inside2. Also they are able to interact with biomacromolecules such as nucleic acids and lipids both neutral and cationic. Their structures in the complexes, identified by synchrotron radiation source 3, 4, have been applied as non-viral vectors in gene therapy . In order to determine their interaction mechanism CLCpolymers have been dispersed in aqueous media and complexed with commercial DNA of increasing complexity [Poly-A]; [Poly-C], [Poly-G], [PolydT], [PolyC-PolyG], [PolyAC-PolydT], calf thymus DNA and plasmid. Three different proportions CLCP:DNA were studied respectively: (1:2), (1:1), and (2:1). The structure of the complexes has been studied by SAXS at the BM16 beamline at ESRF, at room temperature. A monochromatized beam at .= 0,9795 Å was used. A 2D detector camera was placed at 5975 cm from the sample. The spectra were converted into 1D and with Fit2D, and normalized. Information about size [Rg (Guinier)] and shape could be estimated based on Ln I(q) versus Ln q slope. Previous neutron diffraction experiments had shown contrast enough between length densities of the CLCP´s (1.5 . 1.9 x 10^ 0 /cm2) and oligonucleotides, for instance [PolyC-PolyG] (3.32 x 10^10 /cm2). We expect to be able to .see separately. both components structures within the complexes, without any selective deuteration by using different contrasts H2O:D2O to match the CLC polymers, the oligonucleotide and the whole complex, hence providing additional information to that attained by SAXS data.

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