A Photonic Resonator Interferometric Scattering Microscope for Label-free Detection of Nanometer-Scale Objects with Digital Precision in Point-of-Use Environments (preprint)

Label-free detection and digital counting of nanometer-scaled objects such as nanoparticles, viruses, extracellular vesicles, and protein molecules enable a wide range of applications in cancer diagnostics, pathogen detection, and life science research. The contrast of interferometric scattering microscopy is amplified through a photonic crystal surface, upon which scattered light from an object combines with illumination from a monochromatic plane wave source. The use of a photonic crystal substrate for interference scattering microscopy results in reduced requirements for high-intensity lasers or oil-immersion objectives, thus opening a pathway toward instruments that are more suitable for environments outside the optics laboratory. Here, we report the design, implementation, and characterization of a compact Photonic Resonator Interferometric Scattering Microscope (PRISM) designed for point-of-use environments and applications. The instrument incorporates two innovative elements that facilitate operation on a desktop in ordinary laboratory environments by users that do not have optics expertise. First, because scattering microscopes are extremely sensitive to vibration, we incorporated an inexpensive but effective solution of suspending the main components of the instrument from a rigid metal framework using elastic bands, resulting in an average of 28.7 dBV reduction in vibration amplitude compared to an office desk. Second, an automated focusing module based on the principle of total internal reflection maintains the stability of image contrast over time and spatial position, facilitating automated data collection. In this work, we characterize the performance of the instrument by measuring the contrast from gold nanoparticles with diameters in the 10-40 nm range and by observing various biological analytes, including HIV virus, SARS-CoV-2 virus, exosomes, and ferritin protein.

The COVID-19 Pandemic: Challenges and Needs Experienced by Indigenous People in Urban Areas

The world was caught off guard by the swift spread of the COVID19 pandemic at the beginning of 2020. For vulnerable populations such as the urban Indigenous, the first wave of the pandemic was even more challenging, for multiple reasons. Because many of their usual culturally safe services were interrupted, they found themselves struggling on different levels. Our team conducted a needs assessment to shed light on how urban Indigenous people living in the Saugenay-Lac-Saint-Jean region in the province of Quebec, Canada, dealt with this situation, and what holistic health services they most wished they could have relied on. To respect Indigenous culture, data collection was completed through sharing circles in addition to a web-based survey. The results indicated that participants experienced anxiety and psychological distress during the pandemic. They identified unmet needs related to family services, support in homeschooling, access to traditional medicine, and spiritual and cultural practices, among others. Future work should involve the implementation of culturally safe services, adapted to the pandemic era, for Indigenous people living in urban areas.