Focusing new light on brain functions: multiphoton microscopy for deep and super-resolution imaging

Impact of a tilted coverslip on two-photon and STED microscopy

The advent of super-resolution microscopy has opened up new avenues to unveil brain structures with unprecedented spatial resolution in the living state. Yet, its application to live animals remains a genuine challenge. Getting optical access to the brain in vivo requires the use of a 'cranial window', whose mounting greatly influences image quality. Indeed, the coverslip used for the cranial window should lie as orthogonal as possible to the optical axis of the objective, or else significant optical aberrations occur. In this work, we assess the effect of the tilt angle of the coverslip on STED and two-photon microscopy, in particular, image brightness and spatial resolution. We then propose an approach to measure and reduce the tilt using a simple device added to the microscope, which can ensure orthogonality with a precision of 0.07°.

FluoMALDI Microscopy: Matrix Co-Crystallization Simultaneously Enhances Fluorescence and MALDI Imaging

Here, the authors report that co-crystallization of fluorophores with matrix-assisted laser desorption/ionization (MALDI) imaging matrices significantly enhances fluorophore brightness up to 79-fold, enabling the amplification of innate tissue autofluorescence. This discovery facilitates FluoMALDI, the imaging of the same biological sample by both fluorescence microscopy and MALDI imaging. The approach combines the high spatial resolution and specific labeling capabilities of fluorescence microscopy with the inherently multiplexed, versatile imaging capabilities of MALDI imaging. This new paradigm simplifies registration by avoiding physical changes between fluorescence and MALDI imaging, allowing to image the exact same cells in tissues with both modalities. Matrix-fluorophore co-crystallization also facilitates applications with insufficient fluorescence brightness. The authors demonstrate  feasibility of FluoMALDI imaging with endogenous and exogenous fluorophores and autofluorescence-based FluoMALDI of brain and kidney tissue sections. FluoMALDI will advance structural-functional microscopic imaging in cell biology, biomedicine, and pathology.

Ligand-regulated three-photon AIE properties of manganese(ii) complexes for photodynamic therapy

Schematic diagram of the diagnostic system of fluorescent photosensitizer MD3.