Combined multi-plane phase retrieval and super-resolution optical fluctuation imaging for 4D cell microscopy

Super-resolution fluorescence microscopy provides unprecedented insight into cellular and subcellular structures. However, going ‘beyond the diffraction barrier’ comes at a price, since most far-field super-resolution imaging techniques trade temporal for spatial super-resolution. We propose the combination of a novel label-free white light quantitative phase imaging with fluorescence to provide high-speed imaging and spatial super-resolution. The non-iterative phase retrieval relies on the acquisition of single images at each z-location and thus enables straightforward 3D phase imaging using a classical microscope. We realized multi-plane imaging using a customized prism for the simultaneous acquisition of eight planes. This allowed us to not only image live cells in 3D at up to 200 Hz, but also to integrate fluorescence super-resolution optical fluctuation imaging within the same optical instrument. The 4D microscope platform unifies the sensitivity and high temporal resolution of phase imaging with the specificity and high spatial resolution of fluorescence microscopy.status: publishe

Quantifying molecule numbers in STED/RESOLFT fluorescence nanoscopy

Quantification of the numbers of molecules of interest in the specimen has emerged as a powerful capability of several fluorescence nanoscopy approaches. Carefully relating the measured signals from STED or RESOLFT scanning nanoscopy data to the contribution of a single molecule, reliable estimates of fluorescent molecule numbers can be obtained. To achieve this, higher-order signatures in the obtained photon statistics are analyzed, as arise from the antibunched nature of single-fluorophore emissions or in the signal variance among multiple on/off-switching cycles. In this chapter, we discuss the concepts and approaches demonstrated to date for counting molecules in STED/RESOLFT nanoscopy