Nanopipette Delivery of Individual Molecules to Living Cells for Single-Molecule Fluorescence Tracking
Dr. Andreas Bruckbauer,
Cancer Research UK, London Research Institute
Tapered glass capillaries with tip diameters of 100 nm (nanopipettes) have a variety of biophysical applications: As tips in scanning probe microscopy they are used to measure the topography of living cells, filled with biomolecules they can be used to locally deliver pulses of these molecules, which can be used to pattern sub-micron structures onto surfaces. Furthermore they can be used to trap molecules using dielectrophoresis which allows to locally sense concentrations of chemicals.
I will focus on a recently developed nanopipette method which combines the distance control of the scanning ion-conductance microscopy (SICM) and voltage driven pulsed delivery of fluorescently labelled probe molecules to label proteins on the membrane of living cells. These probes are then followed using single molecule fluorescence tracking (SMT). The advantage of nanopipette delivery is that the labels can be applied to a defined region of the cell. We validated the method by performing a SMT study of the diffusion of individual membrane glycoproteins labelled with Atto 647-wheat germ agglutin in different surface domains of boar spermatozoa.
Delivery and trapping experiments using nanopipettes suggest that a combination of electrophoretic, electroosmotic and dielectrophoretic forces are responsible for the different observed effects.