Expansion microscopy (ExM) is a powerful imaging strategy that offers a low-cost solution for interrogating biological systems at the nanoscale using conventional optical microscopes. It achieves this by physically and isotropically magnifying preserved biological specimens embedded in a cross-linked water-swellable hydrogel. However, most reported techniques are unable to preserve endogenous epitopes due to strong protease digestion used to expand samples. In addition, these protocols rely on mechanically fragile hydrogels that only expand by at most 4.5× linearly. We present a new ExM framework, Molecule Anchorable Gel-enabled Nanoscale In-situ Fluorescence MicroscopY (MAGNIFY), that exhibits a broad retention of nucleic acids, proteins, and lipids without the need for a separate anchoring step. By using a mechanically sturdy hydrogel, MAGNIFY is capable of expanding biological specimens up to 11×. This facilitates nanoscale imaging (~25-nm effective resolution) using an ∼280-nm diffraction-limited objective lens on a conventional optical microscope and can be furthered to ~15 nm effective resolution if combined with computational methods such as Super-resolution Optical Fluctuation Imaging (SOFI). Here, we demonstrate that MAGNIFY provides a generalized solution for imaging nanoscale subcellular features of a broad range of biological specimens. We also show that MAGNIFY provides a novel, accessible tool for improving the precision, utility, and generality of nanoscopy.
Neurophotonics was launched in 2014 coinciding with the launch of the BRAIN Initiative focused on development of technologies for advancement of neuroscience. For the last seven years, Neurophotonics’ agenda has been well aligned with this focus on neurotechnologies featuring new optical methods and tools applicable to brain studies. While the BRAIN Initiative 2.0 is pivoting towards applications of these novel tools in the quest to understand the brain, in this article we review an extensive and diverse toolkit of novel methods to explore brain function that have emerged from the BRAIN Initiative and related large-scale efforts for measurement and manipulation of brain structure and function. Here, we focus on neurophotonic tools mostly applicable to animal studies. A companion article, scheduled to appear later this year, will cover diffuse optical imaging methods applicable to noninvasive human studies. For each domain, we outline the current state-of-the-art of the respective technologies, identify the areas where innovation is needed and provide an outlook for the future directions.
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