4Pi microscopy of quantum dot-labeled cellular structures

The most prominent restrictions of fluorescence microscopy are the limited resolution and the finite signal. Established conventional, confocal, and multiphoton microscopes resolve at best similar to 200 nm in the focal plane and only >= 500 nm in depth. Additionally, organic fluorophores and fluorescent proteins are bleached after 10(4)-10(5) excitation cycles. To overcome these restrictions, we synergistically combine the 3- to 7-fold improved axial resolution of 4Pi microscopy with the greatly enhanced photostability of semiconductor quantum dots. Co-localization studies of immunolabeled microtubules and mitochondria, demonstrate the feasibility of this approach for routine biological measurements. In particular, we visualize the three-dimensional entanglement of the two networks with unprecedented detail. (c) 2006 Elsevier Inc. All rights reserved.