Super-resolution optical microscopy techniques have revolutionized how we see and understand biology. In recent past, a new super-resolution optical microscopy technique called expansion microscopy (ExM) was developed. Unlike other pre-existing super-resolution imaging techniques, this technique achieves super-resolution by physically expanding biological specimens via a swellable hydrogel. After the development of ExM, various techniques based on ExM but with improved performance in various aspects, have been developed. In this review, we introduce the basic principles of ExM and its variants. and compare the advantages and disadvantages of these techniques. In addition, we present the applications of ExM techniques in various fields.
Heterogeneous tissue models require
the assembly and co-culture
of multiple types of cells. Our recent work demonstrated taste signal
transmission from gustatory cells to neurons by grafting single-stranded
DNA into the cell membrane to construct multicellular assemblies.
However, the weak DNA linkage and low grafting density allowed the
formation of large gustatory cell self-aggregates that cannot communicate
with neurons efficiently. This article presents the construction of
artificial taste buds exhibiting active intercellular taste signal
transmission through the hybridization of gustatory–neuronal
multicellular interfaces using bioorthogonal click chemistry. Hybrid
cell clusters were formed by the self-assembly of neonatal gustatory
cells displaying tetrazine with a precultured embryonic hippocampal
neuronal network displaying trans-cyclooctene. A bitter taste signal
transduction was provoked in gustatory cells using denatonium benzoate
and transmitted to neurons as monitored by intracellular calcium ion
sensing. In the multicellular hybrids, the average number of signal
transmissions was five to six peaks per cell, and the signal transmission
lasted for ∼5 min with a signal-to-signal gap time of 10–40
s. The frequent and extended intercellular signal transmission suggests
that the cell surface modification by the bioorthogonal click chemistry
is a promising approach to fabricating functional multicellular hybrid
clusters potentially useful for cell-based biosensors, toxicity assays,
and tissue regeneration.
Nanoemulsions have recently become increasingly important as potential vehicles for the controlled delivery of cosmetics and for the optimized dispersion of active ingredients in particular skin layers. The preparation of conventional nanoemulsions requires mainly high‐pressure homogenization, which is unproductive and requires high energy due to its lower efficiency, limiting their practical applications. In order to solve these problems novel nanoemulsions were studied using a model system of pseudo‐ternary water/emulsifier/paraffin oil. Nanoemulsions were prepared by stirring a mixture of the tocopherol‐containing block co‐polymer emulsifier PPG‐20 Tocophereth‐50, paraffin oil, and distilled water at the Θ‐point using weight fractions of the dispersed phase (φ) of 0.31 to 0.82 and an emulsifier content of 1.0 to 9 wt.%. The emulsifying property of PPG‐20 Tocophereth‐50 in nanoemulsions was compared with that of the conventional emulsifiers Tocophereth‐43, a mixture of polysorbate 60 and sesquioleate (3/1), and phospholipids. Also the emulsifying property of PPG‐20 Tocophereth‐50 in the more hydrophilic oils caprylic/capric triglyceride and octyldodecanol was compared with that in paraffin oil. The stability and morphology of the resulting nanoemulsions were studied by visual inspection, optical microscopy, particle size analysis, and cryo‐scanning electron microscopy. In the nanoemulsion systems containing caprylic/capric triglyceride and octyldodecanol, respectively, as an oil phase PPG‐20 Tocophereth‐50 showed emulsification properties similar to those in paraffin oil. The conventional emulsifiers Tocophereth‐43, a mixture of polysorbate 60 and sesquioleate (3/1), and phospholipids did not give nanoemulsions with high‐speed stirring. The block co‐polymer nonionic emulsifier PPG‐20 Tocophereth‐50 was found to produce stable nanoemulsions of mean droplet diameters ranging from 204 to 499 nm. The emulsification method of high‐speed stirring at the Θ‐point using PPG‐20 Tocophereth‐50 was found to be very effective for the preparation of stable nanoemulsions useful for applications in skincare cosmetics, cosmeceuticals, and drugs.
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