Plasmon-enhanced colorimetric histology was recently introduced as a method for visualizing variations in the local refractive index of cells and tissues via a Surface Plasmon Resonance (SPR) induced colour variation. Here we investigate the combination of a Deep Eutectic Solvent (DES) and colorimetric histology as a promising alternative to conventional histological stains. This approach is used to enhance the optical contrast for ultrafine tissue sections whose thickness is below the optical diffraction limit. Traditional histological stains can have limitations, particularly when visualizing ultrafine sections, in terms of specificity and sensitivity. This research explores the potential of DESs to overcome these limitations and yield a massive enhancement of the contrast of histological specimens in the presence of planar plasmonic devices. This novel approach is used to visualize resin embedded cells cut into sections of 120 nm thickness using ultramicrotomy. The DES interaction with the plasmonically active substrates has a significant impact on the measured colorimetric signals which lays the foundation for a promising avenue in the field of histopathology with potential implications for diagnostic medicine and biomedical research.
The development of ultrafast X-ray free-electron laser (XFEL) sources and third-generation synchrotrons has opened many new horizons for the study of complex molecular structures and their reaction kinetics. An essential element of these types of experiment is the method used for sample delivery. Microfluidics technology provides the ideal platform for performing these types of measurements since it enables control, manipulation and delivery of small volumes of fluid inside microchannels. Several key functions including mixing, particle separation, and injection, can be integrated on a single chip making the technology very attractive for use in Xray characterisation of molecular dynamics. Key challenges however, in using microfluidics to both mix and deliver samples, include chemical inertness and mechanical stability of the devices, particularly at micron length scales. Here we report a repeatable method for fabricating microfluidic mixer-jet devices based on photolithography and SU8 with a glass substrate. In experiments we have shown that these devices can withstand the high gas pressures required to produce stable, long-range, liquid jets. Coupled with their chemical inertness and reproducibility this makes them promising candidates for time-resolved X-ray diffraction measurements of molecular dynamics. Incorporating an integrated serpentine micromixer capable of homogeneous mixing prior to the liquid jet the devices presented here can be applied to the study of the dynamics of chemically driven biomolecular reactions. The focus of the current work is on the experimental characterization of the mixer through analysis of the concentration profiles along the length of the serpentineshaped microchannel.
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