Ultrathin fluorescent layers for monitoring the axial resolution in confocal and two-photon fluorescence microscopy.

Monomolecular films of polymerized dimethyl-bis[pentacosadiinoic-oxyethyl] ammonium bromide (EDIPAB) provide one- and two-photon excited fluorescence that is sufficiently high to quantify the axial resolution of 3-D fluorescence microscopes. When scanned along the optical axis, the fluorescence of these layers is bright enough to allow online observation of the axial response of these microscopes, thus facilitating alignment and fluorescence throughput control. The layers can be used for directly measuring and monitoring the axial response of 4Pi-confocal microscopes, as well as for their initial alignment and phase adjustment. The proposed technique has the potential to supersede the conventional technique of calculating the derivative of the axial edges of a thick fluorescent layer. Coverslips with EDIPAB-layers can be used as substrates for the cultivation of cells.