Accuracy of the detection of binding events using 3D single particle tracking

Abstract

BackgroundNanoparticles can be used as markers to track the position of biomolecules, such as single proteins, inside living cells. The activity of a protein can sometimes be inferred from changes in the mobility of the attached particle. Mean Square Displacement analysis is the most common method to obtain mobility information from trajectories of tracked particles, such as the diffusion coefficient D. However, the precision of D sets a limit to discriminate changes in mobility caused by biological events from changes that reflect the stochasticity inherent to diffusion. This issue is of particular importance in an experiment aiming to quantify dynamic processes.ResultsHere, we present simulations and 3D tracking experiments with Gold Nanorods freely diffusing in glycerol solution to establish the best analysis parameters to extract the diffusion coefficient. We applied this knowledge to the detection of a temporary change in diffusion, as it can occur due to the transient binding of a particle to an immobile structure within the cell, and tested its dependence on the magnitude of the change in diffusion and duration of this event.ConclusionsThe simulations show that the spatial accuracy of particle tracking generally does not limit the detection of short binding events. Careful analysis of the magnitude of the change in diffusion and the number of frames per binding event is required for accurate quantification of such events.Electronic supplementary materialThe online version of this article (doi:10.1186/s13628-017-0035-8) contains supplementary material, which is available to authorized users.

Analytical approaches for characterizing and quantifying engineered nanoparticles in biological matrices from an (eco)toxicological perspective: old challenges, new methods and techniques

“…Individual nanorods in living U2OS cells could be followed in three dimensions for N30 min with a photon noise limited accuracy and time resolution of 50 ms in 2D and 500 ms in 3D. In a follow-up study, a concept of proof on the accuracy of detecting binding events using 3D single particle tracking was reported by Carozza et al (2017) Van Pomeren et al (under review) used several imaging techniques to track Au NPs within living zebrafish larvae. The two-photon laser set up as used by Carozza et al could follow agglomerated Au NP within the body of a 5 days old zebrafish larvae (Carozza et al, 2017).…”

“…In a follow-up study, a concept of proof on the accuracy of detecting binding events using 3D single particle tracking was reported by Carozza et al (2017) Van Pomeren et al (under review) used several imaging techniques to track Au NPs within living zebrafish larvae. The two-photon laser set up as used by Carozza et al could follow agglomerated Au NP within the body of a 5 days old zebrafish larvae (Carozza et al, 2017). The technique enabled qualitative detection of agglomerated as well as single Au NPs and their biodistribution dynamics.…”

Improvements in Gold Nanorod Biocompatibility with Sodium Dodecyl Sulfate Stabilization

“…At the same time, GNRs act as excellent contrast agents for photoacoustic imaging with long-lasting photothermal stability [21,22] during nanosecond-pulsed NIR laser illumination. This NIR-absorption property has also been investigated for singleparticle level detection showing that GNRs can be used as small probes for early cancer diagnosis [23,24].…”

Improvements in Gold Nanorod Biocompatibility with Sodium Dodecyl Sulfate Stabilization

“…At the same time, GNRs act as excellent contrast agents for photoacoustic imaging with long-lasting photothermal stability [21,22] during nanosecond-pulsed NIR laser illumination. This NIR-absorption property has also been investigated for single-particle level detection showing that GNRs can be used as small probes for early cancer diagnosis [23,24].…”