High resolution imaging of the surface of cochlear outer hair cells by AFM

Marie-Cecile Giocondi*, Pierre Emmanuel Milhiet**, Marc Lenoir***, Remy Poujol***, Christian Le Grimellec*

* C.B.S., INSERM U554, Montpellier (France); ** C.B.S. and CRRET, Univ. Paris 12, Creteil (France); *** INSERM U 254, Montpellier (France).

Using contact mode AFM, several laboratories have reported details of cells surface in aqueous medium with a lateral resolution down to 10-20 nm. On the other hand, probably because of the difficulties encountered in the proper adjustment of the imaging parameters, the oscillating mode (TMAFM) has not provided so far such high resolution images of the surface of eukaryotic cells. We have applied the TMAFM force adjustment method based on the deflection signal (Vie et al., Ultramicroscopy 82, 279, 2000) to the study of isolated rat cochlear cells. The outer hair cells (OHC) from the mammalian organ of Corti are assumed to enhance the sensitivity and the selectivity of the cochlea via an electromotile response to sound stimulation. As compared to earlier data using AFM microscopy on living or fixed cells, the present data show better resolved images of a markedly improved quality. Both the quality and the lateral resolution markedly depend on the accuracy of the tapping tuning conditions.