Scalable and Isotropic Expansion of Tissues with Simply Tunable Expansion Ratio

Abstract

Tissue expansion techniques physically expand swellable gel‐embedded biological specimens to overcome the resolution limit of light microscopy. As the benefits of expansion come at the expense of signal concentration, imaging volume and time, and mechanical integrity of the sample, the optimal expansion ratio may widely differ depending on the experiment. However, existing expansion methods offer only fixed expansion ratios that cannot be easily adjusted to balance the gain and loss associated with expansion. Here, a hydrogel conversion‐based expansion method is presented, that enables easy adjustment of the expansion ratio for individual needs, simply by changing the duration of a heating step. This method, termed ZOOM, isotropically expands samples up to eightfold in a single expansion process. ZOOM preserves biomolecules for post‐processing labelings and supports multi‐round expansion for the imaging of a single sample at multiple zoom factors. ZOOM can be flexibly and scalably applied to nanoscale imaging of diverse samples, ranging from cultured cells to thick tissues, as well as bacteria, exoskeletal Caenorhabditis elegans, and human brain samples.

Expansion Microscopy for Cell Biology Analysis in Fungi

“…This simple idea was rapidly adapted by various laboratories, leading to the development of new protocols that allow expansion factors of up to 10× (Truckenbrodt et al, 2019) or even 20× by iterative expansion (Chang et al, 2017). Other protocols focus on preservation and isotropic expansion of ultrastructure (U-ExM) (Gambarotto et al, 2019) or on precise tuning of the expansion factor between 2 and 8 (ZOOM) (Park et al, 2019). Recently, ExM has been applied also to bacterial pathogens (Kunz et al, 2019) and to plants (Kao and Nodine, 2019), paving the way for new methodological approaches in these fields.…”

Residual wall thickness of water‐powered projectile‐assisted injection molding pipes

“…Fluid‐assisted injection molding technique (FAIM), such as the gas‐assisted injection molding (GAIM) process and the water‐assisted injection molding (WAIM) process, enables the efficient production of complex, highly integrated parts in one process step with the help of pressurized fluid . In the case of WAIM, the polymer melt is displaced by water.…”

“…Furthermore, larger part diameters are possible with WAIM . In FAIM, however, the residual wall thickness (RWT) is determined largely by the rheological properties of the polymer and fluid used . FAIM is known to have some problems in the uniformity of the inner diameter, the uniformity of the RWT, the smoothness of the inner surface, and the production of pipes with diameters greater than 40 mm .…”

“…In FAIM, however, the residual wall thickness (RWT) is determined largely by the rheological properties of the polymer and fluid used . FAIM is known to have some problems in the uniformity of the inner diameter, the uniformity of the RWT, the smoothness of the inner surface, and the production of pipes with diameters greater than 40 mm . For FAIM parts with large diameters, the achievable wall thicknesses are relatively thick, which leads to an unfavorably heavy part weight and relatively long cycle times to cool down the final product .…”

Visualizing subcellular structures in neuronal tissue with expansion microscopy

“…However, one consequence of tissue expansion is a decrease in the fluorescence intensity of labeled proteins primarily due to the digestion process and the dilution of fluorescence signal per unit volume. Various ExM protocols have described different methods for improving fluorescence retention, primarily by modifying fixation, crosslinking, and/or digestion conditions to preserve protein epitopes [2][3][4][5][6][7][8] . One common ExM protocol uses a strong protease-based digestion (Proteinase K 2 ), but other gentler proteases have also been used (LysC 2,3 ), as well as a combination of heat and detergents in place of proteases (e.g.…”