FRONTIERS PHOTONICS


LIFE SCIENCES/MEDICAL CURVED MICROCHANNEL PLATES


Space optics commercialised for medical use


A


n adapted microchannel plate that has allowed astrophysicists to study


the hot matter of exploded stars and distant galaxies has been commercialised for use in medical devices and other optical instruments. Microchannel plates work


by amplifying signals from single photons or electrons, and NASA-funded curved versions have been used in the High Resolution Camera of the Chandra X-Ray Observatory, which captures information about the composition of faraway exploded stars. Two 10-centimetre square microchannel plates contain 10s of millions of tiny tubes that multiply the electrons released when the instrument is struck by x-rays.


With NASA funding, American company Incom, a glass and polymer microstructures developer, has developed commercial versions of these curved microchannel plates, which can perform faster and more accurately than traditional flat microchannel plates. In traditional microchannel


plates, the many millions of tubes are arranged in one fixed orientation, parallel to each other, on a flat plane. But in three-dimensional environments, special optics are required in instruments to fully map natural space. The curved microchannel


plates address this problem with tubes that can be arranged on a cylindrically curved plate. Curved microchannel plates


can be fitted directly onto instruments without the need for an adapter, enabling medical devices, spectrometers, air analysers, and nuclear detection devices to amplify particles faster and more accurately. They also have a smaller footprint, which is critical for instruments used both on Earth and in space.


Incom’s microchannel plate


(MCP) technology uses a fabrication method co-developed with Argonne National Laboratory (Illinois, USA) enabling the largest imaging


area available and customisable geometries. It combines Incom’s capillary arrays with thin film coatings applied to the channels by atomic layer deposition, which functionalises the MCPs and allows the final operational parameters to be tailored to specific applications. Flat microchannel plates


have developed over the past 50 years or so, while curved ones are in their infancy – with much development to improve gain, imaging uniformity, aspect ratios, and geometries expected in the near future. l


LIGHT MICROSCOPY


Super-resolution microscopy observes how Covid replicates


I


n Spring 2022, Stanford University researchers revealed how human cells


infected with a coronavirus help it to replicate. Super resolution microscopy helped determine where specific features of the virus – such as spike proteins and genetic material – lie during different stages of infection. Professor of Chemistry


William Esco Moerner, who won a Nobel Prize alongside Eric Betzig and Stefan Hell in 2014 for developing super resolution techniques, and assistant professor Stanley Qi studied the HCoV-229E strain for their experiment. Similarly to SARS-CoV-2, it comprises a spike protein-studded envelope surrounding a strand of genomic RNA (gRNA), which contains the instructions needed for the virus to replicate. While coronavirus biology has


been studied using genomics, biochemistry, cryoelectron microscopy, and electron tomography, little is known about where the virus’ DNA sits within the cell during different parts of its life cycle. Learning more about this could increase scientists’ understanding of precisely how coronavirus infects cells to develop new therapies. Confocal microscopy provides


a high-throughput approach to screen many samples during infection. However, its optical resolution (approximately 300nm) prevents scientists from imaging inside viruses, which can be as small as 20nm. Super resolution techniques permit imaging down to 10nm. The team studied both


double-stranded RNA (dsRNA), an intermediate along the way to making new copies of the virus, and gRNA, one strand of


which gets injected into the cell, replicated and then packaged into new viruses. The researchers used magenta


coloured tags to highlight gRNA and green for dsRNA. Using confocal microscopy, blurry white clouds suggest that dsRNA and gRNA could be in the same spot throughout the cell. But the super-resolution images showed a dark sky of bright magenta clusters and green stars, and none of them ever overlapped, suggesting that dsRNA and gRNA are never in the same place at the same time. A custom epifluorescence


microscope (Nikon Diaphot 200) equipped with a Si EMCCD camera (Andor iXon DU-897) was used with a high NA oil-immersion objective (Olympus). The labelled molecules were excited with continuous-wave lasers from MPB Communications, and an exposure time of 50ms and a calibrated EM gain of 193 was used for image acquisition. The emission from fluorescent molecules was collected through a four-pass dichroic mirror (Semrock) and filtered by notch, long-pass and bandpass filters (Chroma). l


18 Photonics Frontiers 2023


CI Photos/Shutterstock.com


Incom Inc


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