Imaging and quantifying the morphology and nanoelectrical properties of quantum dot nanoparticles interacting with DNA

Rapid detection and imaging the interactions between quantum dots (QDs) and DNA are of interest for research on applications as well as for determining their potential cytotoxicity. This paper introduces Kelvin force microscopy (KFM), an electric mode of atomic force microscopy, as a technique to examine the binding of QDs with DNA in vitro and in vivo. KFM provides information about the nanoelectrical properties of QDs and DNA that is complementary to the topography and phase images that conventional AFM provides. With this unique function, KFM demonstrated its ability in determining the morphological and electrical changes in DNA after exposure to QDs as well as to distinguishing individual QDs from DNA matrices. Our results indicated that the nonspecific binding with QDs led to transformation of polymeric DNA into pearl-like spheres. In vivo experiments showed that QDs could permeate into E. coli cells and bind with genomic DNA. To the best of our knowledge, this is the first successful demonstration of KFM to detect single QD-DNA binding. KFM potentially can be used in characterization of nanomaterials and their interfacial interactions with biomolecular matrices.