Templates for DNA-templated Fe3O4 nanoparticles

Two different strategies are reported that result in the site-specific placement of long DNA molecules, templated with Fe3O4 nanoparticles, on SiOx, surfaces. The strategies combine solution templating of inorganic nanoparticles onto biomolecules, molecular combing, the layer-by-layer method, and dip-pen nanolithography (DPN). In one methodology, the first step is to place and stretch DNA molecules via a DPN template containing features of poly(allylamine hydrochloride) (PAH). In the second step the elongated DNA is templated with Fe3O4 nanoparticles allowing them to assemble onto the DNA molecules based on electrostatic interactions. In the second methodology, DPN templates composed of PSS patterns are used to comb in a site-specific manner DNA molecules that have been pre-tempated in solution with the Fe3O4 nanoparticles. The templates generated by the two methods can serve as building blocks for the fabrication of future higher order assemblies. (C) 2004 Elsevier Ltd. All rights reserved.