Characterization of a novel light source for simultaneous optical and scanning ion conductance microscopy

We have developed a novel light source suitable for imaging of biological samples. The method is based on the use of a micropipet filled with fluo-3. A fluorogenic complex is formed when fluo-3 meets calcium in the bath solution. The complex is excited by focusing a laser beam at the pipet tip to produce a submicrometer light source. This source is continually renewed at the tip, eliminating problems with photobleaching, and can be controlled by varying the applied potential. We first characterized the light source using fluorescence correlation measurements in order to optimize its properties. We then recorded an image of a model sample under buffer with submicrometer resolution using ion conductance distance control to demonstrate the feasibility of this approach.