Films of a disk-shaped liquid crystalline molecule—DNA complex at interfaces

Abstract

In this review article, we describe the studies on disk-shaped (discotic) liquid crystalline molecule—DNA complex films at air–water (A–W) and air–solid interfaces. The interaction of DNA with molecules in a monolayer at A–W interface has drawn considerable attention in recent years to understand supramolecular organization as well as the transfer of DNA across biological membranes in gene therapy. We have formed films of a novel ionic discotic liquid crystalline molecule, pyridinium salt tethered with hexaalkoxytriphenylene (PyTp) and its complex with DNA (PyTp–DNA) at A–W interface. The PyTp b monolayer was formed on the aqueous subphase containing small amount of DNA. The electrostatic interaction between PyTp and DNA molecules results in a PyTp–DNA complex monolayer. Surface manometry and Brewster angle microscope studies of the PyTp–DNA complex monolayer film indicate the molecules to be in the edge-on configuration. The PyTp–DNA complex films were transferred onto silicon wafers using Langmuir–Blodgett (LB) technique. We find that several tens of layers of PyTp–DNA complex monolayer can be transferred with high efficiency. We also describe nanoscale electrical conductivity studies for the pure PyTp and PyTp–DNA complex LB films carried out using current-sensing atomic force microscope.