No abstract

Mapping the reactivity of a redox-sensitive luminescent microobject positioned in fluxes of reactive species allows analyzing complex mechanistic processes such as the electrogenerated chemiluminescence of model systems used in immunoassays.

Herein is reported a near-field microscopy based on electrochemiluminescence (ECL) which allows to image the plasma membrane of single cells at the interface with an electrode. By analyzing photoluminescence (PL), ECL and AFM images of mammalian CHO cells, we demonstrate that, in contrast to the wide-field fluorescence, ECL emission is confined to the immediate vicinity of the electrode surface and only the basal membrane of the cell becomes luminescent. The resulting ECL microscopy reveals details which are not resolved by classic fluorescence microscopy, without any light irradiation and specific setup. The thickness of the ECL-emitting regions is ~ 500 nm due to the unique ECL mechanism which involves short-lifetime electrogenerated radicals. In addition, the reported ECL microscopy is a dynamic technique which reflects the transport properties through the cell membranes and not only the specific labeling of the membranes. Finally, disposable transparent carbon nanotube (CNT)-based electrodes inkjet-printed on classic microscope glass coverslips, were used to image cells in both reflection and transmission configurations. Therefore, our approach opens new avenues for ECL as a near-field microscopy to develop single cell assays and to image the dynamics of biological entities in cells or in membranes. ASSOCIATED CONTENTSupporting Information. ECL-potential curves. PL images of the CHO cells recorded at high magnifications in different focal planes. ECL microscopy with DBAE. DPV. Scheme and photograph of the inkjet-printed CNT electrodes on glass coverslips. Optical effects on the PET and glass coverslips.