The identification of chemical species and the measurement of their concentrations with high (submicrometer) spatial resolution are of considerable importance in cell biology. In this article we report the first successful development of a ≤0.1-μm Ca2+ sensor based on a pulled micropipet, filled with a conducting porous sol-gel glass which was doped with the fluorescent calcium green 1 Ca2+ indicator. Such sensors are potentially capable of measuring Ca2+ concentrations as low as 10-8 M, in confined volumes, with a three-dimensional resolution which exceeds ~0.1 μm. A major advantage of the sensor is its capability to be integrated into a multifunctional probe which will measure chemical analyte concentrations and ion conductance.
Bibliographical noteFunding Information:
The authors acknowledge support by the Israel National Council for Research and Development. We thank Ms. D. Parnas for valuable assistance with the preparation of the cells.