Single-cell Characterization of Immunization Responses
The current Covid-19 pandemic has sparked an urgent need for improvements in the characterization of the immune response to vaccinations. Although simple and robust, conventional antibody titer measurements provide little information on the phenotypic diversity of IgG-secreting cells (IgG-SCs), the functional properties of the antibodies they produce or the temporal profile of the immune reaction in response to an antigenic challenge. In a recent paper published in the Journal of Immunology  and other recent publications [2,3], a team of researchers based in Paris and Zurich describe the application of a single-cell analysis technique known as DropMap to provide quantitative analysis of the distribution of antibody secretion rates and affinities over the course of an immune response. The DropMap protocol begins with microfluidically controlled compartmentalization of single splenocytes, extracted from mice at time points up to 8 weeks after immunization, in individual 50-picoliter droplets together with immunomagnetic beads and fluorescently-labeled antigens and anti-IgG antibodies. The beads are magnetically aligned to form micrometer-sized structures that can be visualized by fluorescence microscopy using a SOLA light engine.Bead capture of red-fluorescent anti-IgG (Fc) identifies IgG-SCs, allowing determination of their frequency.Capture of green-fluorescent antigen provides information on antigen binding affinity. To accumulate population statistics, two-dimensional arrays containing >10,000 cell-containing droplets are imaged every 7.5 minutes over 37.5 minutes. The SOLA light engine provides the exceptional light output stability required to extract reliable quantitative information across thousands of droplets and multiple time points.
Metal additive manufacturing is the process of joining materials to make objects from 3D computer-aided design (CAD) model data.Laser powder bed fusion (PBF) is one such process, in which thermal energy derived from a laser beam selectively fuses regions of a powder bed.A team from Heriot-Watt University, Edinburgh, and the University of Birmingham in the UK used high-speed imaging to investigate the interaction of the laser beam with the powder bed at sub-atmospheric pressures.They used a SOLA SM Light Engine® to illuminate a circle of ~10 mm diameter on a stainless steel powder bed inside a vacuum chamber.Image sequences were recorded at 40,000 frames per second by a monochrome camera.The data obtained indicate that operating in a soft vacuum (>50 mbar) would provide the simplest implementation of PBF at sub-atmospheric pressures.The reduction in vaporization temperature at reduced pressure means that the same penetration depth can be achieved at lower laser powers, resulting in a stabilizing effect on the process.
High-speed images at 20mbar. Laser power and scan speeds of (a) 50W and 0.2m/s, (b) 100W and 0.4m/s and (c) 200W and 0.8m/s.
Characterization of Superhydrophobic Surface Coatings
When two or more water droplets coalesce on a superhydrophobic surface, the resulting droplet can jump away from the surface due to inertial−capillary energy conversion. The resulting passive shedding of micro-scale water droplets has the potential to enhance heat transfer, anti-icing, and self-cleaning properties. To study this process, researchers at the University of Illinois developed an improved imaging technique called focal plane shift imaging (FPSI) to measure three-dimensional (3D) droplet trajectories. A high-speed camera is used to obtain video recordings at variable frame rates up to 500,000 frames per second. Illumination is supplied by aSOLA SM light engine®, specifically chosen for its high-intensity, low-power consumption and narrow spectral range (380−680 nm) in order to minimize heat generation at the surface due to light absorption. The effects of initial droplet size mismatch and multiple droplet coalescence on the jumping droplet velocity are revealed, showing that multi-droplet jumping has the potential to enhance the droplet departure speed.
Multiplexed imaging of gene expression using the CELESTA light engine®
MERFISH (multiplex error robust fluorescence in situ hybridization) is an imaging technique that profiles cell populations based on the identification of thousands of RNA transcripts per cell.The CELESTA light engine is an ideal and widely-adopted illumination source for this application.In a recent paper published in Nature , Wheeler and co-workers used MERFISH imaging with a CELESTA light engine to quantify the expression of nine specific astrocyte and T-cell markers.Five of the CELESTA light engine’s seven laser lines were used in the highly multiplexed MERFISH imaging protocol.The overall objective of the research described in the paper was to characterize astrocyte populations that contribute to pathogenesis in a preclinical model of multiple sclerosis.
 MA Wheeler, JR Moffitt, IC Clark, EC Tjon, Z Li, SE J Zandee, CP Couturier, BR Watson, G Scalisi, S Alkwai, V Rothhammer, A Rotem, JA Heyman, S Thaploo, LM Sanmarco, J Ragoussis, DA Weitz, K Petrecca, JR Moffitt, B Becher, JP Antel, A Prat, FJ Quintana, Nature (2020) 578:593–5990