title: Ultrasensitive Label-Free Nanosensing and High-Speed Tracking of Single Proteins.
abstract: Label-free detection, analysis, and rapid tracking of nanoparticles is crucial for future ultrasensitive sensing applications, ranging from understanding of biological interactions to the study of size-dependent classical-quantum transitions. Yet optical techniques to distinguish nanoparticles directly among their background remain challenging. Here we present amplified interferometric scattering microscopy (a-iSCAT) as a new all-optical method capable of detecting individual nanoparticles as small as 15 kDa proteins that is equivalent to half a GFP. By balancing scattering and reflection amplitudes the interference contrast of the nanoparticle signal is amplified 1 to 2 orders of magnitude. Beyond high sensitivity, a-iSCAT allows high-speed image acquisition exceeding several hundreds of frames-per-second. We showcase the performance of our approach by detecting single Streptavidin binding events and by tracking single Ferritin proteins at 400 frames-per-second with 12 nm localization precision over seconds. Moreover, due to its extremely simple experimental realization, this advancement finally enables a cheap and routine implementation of label-free all-optical single nanoparticle detection platforms with sensitivity operating at the single protein level.
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels, Barcelona, Spain.
authors.forename: Matz
authors.initials: M
authors.lastname: Liebel
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels, Barcelona, Spain.
authors.forename: James T
authors.initials: JT
authors.lastname: Hugall
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels, Barcelona, Spain.|ICREA-Institució Catalana de Recerca i Estudis Avançats , 08010 Barcelona, Spain.
authors.forename: Niek F
authors.identifier: 0000-0003-4630-1776
authors.initials: NF
authors.lastname: van Hulst
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D004058:Diffusion; D005453:Fluorescence; D006046:Gold / Q000737:chemistry; D006801:Humans; D033862:Iron-Binding Proteins / Q000032:analysis*; D008857:Microscopy, Interference / Q000379:methods*; D008962:Models, Theoretical; D008970:Molecular Weight; D053758:Nanoparticles / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry; D036103:Nanotechnology; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000032:analysis*; D019809:Streptavidin / Q000032:analysis*; D014025:Titanium / Q000737:chemistry
chemical_list: D033862:Iron-Binding Proteins; D011956:Receptors, Cell Surface; C027293:ferritin receptor; D006046:Gold; D019809:Streptavidin; D014025:Titanium
keywords: Interferometric scattering; balanced interference; digital holography; iSCAT; interference microscopy; label-free; single particle tracking; single-molecule detection; superresolution