Viral particles imaging through evanescent wave scattering in a total internal reflection laser microscope

• Published in: Sensing and Bio-Sensing Research Vol. 37; p. 100517
• Main Authors: Lo Savio, Roberto, Piselli, Sara, Bertelli, Cinzia, Pizzato, Massimo, Carloni, Adolfo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2022; Elsevier
• Subjects: Biosensing; Microscopy; Nanoparticles; Scattering; Virus; Nanoparticles; Virus; Microscopy; Scattering; Biosensing
• ISSN: 2214-1804; 2214-1804
• DOI: 10.1016/j.sbsr.2022.100517

Optical imaging of objects at the nanometric scale is limited by light diffraction, and for this reason several sub-diffractive optical microscopy techniques have been developed in the last decades. In this article we present an optical laser microscope specifically designed for detection of nano-materials exploiting the Mie scattering between the evanescent wave generated by a laser beam travelling in a transparent substrate through total internal reflection and the nano-objects deposited on the substrate itself. The setup, including the laser source, can be fully integrated inside an optical microscope requiring only a geometric alignment with the substrate thus reducing the complexity and the cost. We also report two possible applications: quantitative detection of Au nanoparticles in the 20-100 nm size range and semi-quantitative detection of virions immobilized on the substrate through bioreceptor / antigen binding, including, but not limited to, SARS-CoV-2. A minimum virus amount of ≈105 in the reaction volume is observed. The results presented here open the route towards unprecedent applications in molecular biology or molecular diagnostics. •Laser microscope for detection of nano-objects through evanescent wave scattering.•Quantitative detection of Au nanoparticles with minimum size of 20 nm.•Detection label-free of SARS-CoV-2 with LOD sensitivity of 105 virions.