Multifunctional cholesteric liquid-crystal polymer, designated [PTOBEE] 10 -NH 2 , has been synthesized, from precursor PTOBEE [C 26 H 20 O 8 ] n previously reported, by functionalization with amine groups. Cholesteric PTOBEE has been shown to be able to entrap DNA, being tested as non-viral vector in gene therapy, including cationic monomeric surfactants in their formulation. The direct interaction between cationic cholesteric liquid-crystal polymer PTOBEE-NH 2 , with anionic commercial

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... -Poly-G], is proposed as new formulation for biomedical applications. The interaction mechanism is studied in three different volume ratios: (1:2), (1:1) and (2:1), respectively. Their structures, studied by SAXS at ESRF, provide information about the complexes size and shape. Based on preliminary neutron scattering experiments, showing sufficient contrast (scattering length density difference) between cholesteric PTOBEE-NH 2 (1.5 to1.9  10 10 /cm 2 ) and polynucleotide [PolyC-PolyG] (3.32  10 10 /cm 2 ), contrast variation SANS experiments were performed at NIST, with a wavelength of λ = 8Å, using different H 2 O:D 2 O mixtures (i.e., contrasts) to match the cholesteric polymer (44.5%:55.5%), the polynucleotide (65% or 70%):(35% or 30%) or the whole complex (30%:70%), being able to "observe separately" both component structures within the complexes. SANS results agree and complement the information obtained by SAXS. Different TWO SHELL molecular models are proposed for the interaction by using a combination of model-fitting (FISH).