Many important biological phenomena still elude the precision of even the most sensitive microscopy techniques. Electrochemical impedance spectroscopy (EIS) is a non-invasive image method that does not require labeling of the sample. However, EIS lacks the spatial resolution nessecary to investigate heterogeneous processes or for imaging high-throughput microarrays.

Nongjian Tao and colleagues, Arizona State University, USA, have combined EIS with surface plasmon resonance (SPR) to create an electrochemical impedance microscope (EIM). The plasmon resonance detects electrical impedance changes optically, providing complimentary information from simultaneous optical and SPR imagery with enhanced resolution.

The enhanced spatial resolution of EIM allowed individual cells to be monitored during apoptosis (cell death) and electroporation with millisecond time resolution. Apoptosis was seen to occur through cellular shrinking and condensation followed by the fragmentation of nuclear material and eventual disintegration of the cells.

• Single cells and intracellular processes studied by a plasmonic-based electrochemical impedance microscopy
  W. Wang, K. Foley, X. Shan, S. Wang, S. Eaton, V. J Nagaraj, P. Wiktor, U. Patel, N. Tao,
  Nat. Chem. 2011.
  DOI: 10.1038/nchem.961