Interfacially organized DNA/polycation complexes: a route to new planar polymeric and composite nanostructures

Effects of nano-scale supramolecular organization and patterning in amphiphilic polycation monolayer formed by poly-4-vinilpyridine with 16% cetylpyridinium groups and in novel planar DNA/amphiphilic polycation complexes formed at the air-aqueous DNA solution interface and deposited on the solid substrates have been studied using AFM. Stable ordered quasi-crystalline planar polymeric monolayer structures were formed by amphiphilic polycation molecules. Extended net-like and quasi-circular toroidal condensed conformations of deposited planar DNA/amphiphilic polycation complexes were obtained in dependence on the amphiphilic polycation Langmuir monolayer state during the DNA binding. Those monolayer and multilayer DNA/polycation complex Langmuir–Blodgett films were used as templates and nanoreactors for generation of inorganic nanostructures. As a result, ultrathin polymeric nanocomposite films with integrated DNA building blocks and inorganic semiconductor (CdS) and iron oxide nanoparticle quasi-linear arrays or aggregates (nanorods) were formed successfully and characterized by TEM. The data obtained give evidence for effectiveness of the monolayer techniques for study mechanisms of DNA structural transformations caused by complexation with cationic compounds and demonstrate its perspectives for creation of new planar DNA-based self-organized stable polymeric complex nanostructures and nanocomposites with nano-scale structural ordering.