Label‐Free Analysis of Single Viruses with a Resolution Comparable to That of Electron Microscopy and the Throughput of Flow Cytometry

Abstract

Viruses are by far the most abundant biological entities on our planet, yet existing characterization methods are limited by either their speed or lack of resolution. By applying alaboratory-built high-sensitivity flowcytometer (HSFCM) to precisely quantify the extremely weak elastically scattered light from single viral particles,w eh erein report the label-free analysis of viruses with ar esolution comparable to that of electron microscopyand the throughput of flowcytometry.The detection of single viruses with diameters down to 27 nm is described. T7 and lambda bacteriophages,whichdiffer in size by as little as 4nm, could be baseline-resolved. Moreover, subtle structural differences of the same viral particles can be discriminated. Using monodisperse silica nanoparticles as the sizer eference standards,t he virus sizes measured by the HSFCM are in agreement with the equivalent particle diameters derived from their structural dimensions.T he HSFCM opens anew avenue for virus characterization.Viruses are by far the most abundant biological entities on our planet. [1] Whereas animal viruses are notoriously responsible for alarge number of fatal diseases,plant viral pathogens cause significant losses in crop yields worldwide each year.On the other hand, the high transfection efficiency of viral genetherapy vectors and their monodisperse structures with precise shapes and sizes make viral particles powerful drugdelivery vehicles and versatile nanotechnology building blocks. [2][3][4] Therefore,t he high-resolution and high-throughput analysis of single viral particles is of great importance for virology research, disease diagnosis and treatment, and biotechnology and nanotechnology applications.Tr ansmission electron microscopy (TEM) has historically been the method of choice for determining the size and morphology of single viruses.However, the tedious processes required for sample preparation and image analysis,a long with the high cost, prevent its use on aroutine basis.Recently, many newly developed single-particle techniques have been applied to single-virus analysis,s uch as surface plasmon resonance imaging, [5] whispering-gallery-mode microcavities, [6] suspended micro-and nanochannel resonators, [7] scanning probe microscopy, [8] resistive pulse sensing with nanopores, [9] and nanoparticle tracking analysis (NTA). [10] Although some of these techniques have proven to be very useful in various fields,as imple and practical approach with exceptional sensitivity and high resolution remains to be developed. Ther eal-time,l abel-free analysis of the size and composition of individual viral particles could be enabled by the quantification of their elastically scattered light intensity. However,t he sixth-power dependence of the scattered light intensity on the particle size and the low dielectric contrast with the surrounding medium make it extremely challenging to discriminate single viruses over background scattering. Recently,Manoharan et al. reported the label-free tracking of individual cowpea chlorotic mott...

Quantum noise limited nanoparticle detection with exposed-core fiber

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