ABSTRACT
We are presenting the application of an optical and computational pipeline FAMOUS for revealing the presence of free viral particles named “virions”. The idea of such a protocol is to give rise to images of virions in their environment with a soft solution for recording the native image, contrary to the standard solution of imaging virions with electron microscopy (EM) for visualizing viral particles. The final aim of the current work is to observe free viral particles of SARS-CoV-2, the virions responsible for the worldwide pandemic of Covid-19. But such particles have diameters between 80 and 120 nm, a dimension smaller than the resolution limit of optical-only microscopy solutions. We have chosen to start with the biggest free virions, cytomegalovirus (CMV), a virus from the herpesvirus family also named “Human Herpes Virus 5”. Two kinds of cultures were involved: a fluorescent culture (BAD) and a label-free one (VHLE), both being collected from infected cell culture. VHLE virions were first observed after secondary immunostaining and concentrated with magnetic nanoparticles and then without labelling. The optical protocol rests on a standard solution of multiphoton microscopy combined with a computational strategy based on the point-spread-function (PSF) recordings, its mathematical modeling and the restauration of the image resting on the PSF model. A test with free viral particles of SARS-CoV-2 is led, delivering an optical visualization of the free-viral particles. The visualization of objects aggregates obtained in both situations confirm the relevance of the pipeline FAMOUS for imaging free virions. © 2022 SPIE.
ABSTRACT
Visible Infrared Imaging Radiometer Suite (VIIRS) - Day/Night Band (DNB) images have been used as an indicator of socioeconomic activity in annual time-series as well as within a year, given the availability of monthly composites. The capacity of VIIRS monthly data to reveal the socioeconomic activity disruption caused by the COVID-19 pandemic is explored here. The light emissions for each municipality in Greece are examined. In specific, monthly 2020 values are compared to the corresponding 2017-9 monthly average values, taken to represent the 'normality'. Two interesting results are derived. First, the impact of the pandemic is actually visible despite the fine spatial scale. Second, and less expected, the magnitude of night-lights dimming is not proportional to the magnitude of the pandemic impact. Dense urbanized areas tend to fluctuate less than sparse urban areas. At the same time it is shown that tourism-dependent areas, that normally attract a high amount of seasonal population and activity, are substantially more affected. © 2021 IEEE.
ABSTRACT
The outbreak of life-threatening pandemic like COVID-19 necessitated the development of novel, rapid and cost-effective techniques that facilitate detection of viruses like SARS-CoV-2. The presently popular approach of a collection of samples using the nasopharyngeal swab method and subsequent detection of RNA using the real-time polymerase chain reaction suffers from false-positive results and a longer diagnostic time scale. Alternatively, various optical techniques namely optical sensing, spectroscopy, and imaging shows a great promise in virus detection. Herein, a comprehensive review of the various photonics technologies employed for virus detection, particularly the SARS-CoV family, is discussed. The state-of-art research activities in utilizing the photonics tools such as near-infrared spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, fluorescence-based techniques, super-resolution microscopy, surface plasmon resonance-based detection, for virus detection accounted extensively with an emphasis on coronavirus detection. Further, an account of emerging photonics technologies of SARS-CoV-2 detection and future possibilities is also explained. The progress in the field of optical techniques for virus detection unambiguously show a great promise in the development of rapid photonics-based devices for COVID-19 detection.