Fast Quantitative Single-Molecule Detection at Ultralow Concentrations

Abstract

The applicability of single-molecule fluorescence assays in liquids is limited by diffusion to concentrations in the low picomolar range. Here, we demonstrate quantitative single-molecule detection at attomolar concentrations within 1 min by excitation and detection of fluorescence through a single-mode optical fiber in presence of turbulent flow. The combination of high detectability and short measurement times promises applications in ultrasensitive assays, sensors, and point-of-care medical diagnostics.

Remote detection of single emitters via optical waveguides

“…However, truncated dielectric waveguides are commonly considered to have too low photon collection efficiency and a too low signal-to-noise ratio (SNR) to allow for direct lens-free single-molecule detection. Nevertheless, recent experiments suggest that single-molecule detection in aqueous solution via dielectric waveguides is possible [12,13]. In the present paper we confirm by theoretical considerations, numerical simulations, and experiments that single-emitter detection via dielectric waveguides is indeed possible.…”

Single Macromolecule Diffusion in Confined Environments

“…We show in Figure 1 data exemplifying why single molecule imaging reveals more information than ensemble averaging techniques; here molecular motion is smeared out of the signal when the data are averaged (box 4 in Figure 1), but time-stop imaging reveals a complex molecular trajectory (box 3 in Figure 1). Techniques designed to examine the diffusive properties of molecules within a sample, such as neutron spin echo, [20][21][22] dynamic light scattering, [23,24] fluorescence correlation spectroscopy (FCS), [25][26][27][28] and single mode optical fibre detectors, [29] generally do not involve imaging in real space, but require spectroscopic determination of signal intensity and the timescales of fluctuations that occur within the sample. However, one can also use fluorescence spectroscopy for single molecule imaging and tracking.…”

AFM fishing of proteins under impulse electric field

“…Для повышения эффективности доставки молекул белка на поверхность чипа используются гидродинамические, электрические и магнитные силы [10]. Повышение эффективности за счёт гидродинамических сил реализуется обычно при использовании быстрого турбулентного режима перемешивания раствора белка [5,11]. Однако реализация такого подхода сопряжена с методическими трудностями, заключающимися в сложности поддержания стабильного режима перемешивания.…”