Entrapment of Individual DNA Molecules and Nanoparticles in Porous Alumina Membranes

摘要

Depth-resolved fluorescence imaging allows the motionnof single DNA molecules and single nanoparticles at thenliquid/solid interface to be recorded in real time. Porousnalumina membranes were employed as model chromato-ngraphic packing material. Using a suitable pH and ionicnstrength, adsorptive interactions are suppressed. Theneffects of 3-dimensional topography, specifically the pres-nence of nanopores, on DNA and nanoparticle migrationnacross the surface are, thus, revealed. The residencentimes and the number of immobilized DNA molecules ornparticles increased as the pores size increased. Yet, wenfound that the pore diameter must be significantly largernthan the particle diameter or the DNA short radius beforenentrapment can occur. Furthermore, the depth distribu-ntion of particles does not conform to one-dimensionalndiffusion in the pores, probably because of collisions withnthe walls. These observations provide new insights intonconventional liquid chromatography as well as size-nexclusion chromatography and membrane separations.