Three-dimensional automated nanoparticle tracking using Mie scattering in an optical microscope

Abstract

Summary The forward scattering of light in a conventional inverted optical microscope by nanoparticles ranging in diameter from 10 to 50 nm has been used to automatically and quantitatively identify and track their location in three‐dimensions with a temporal resolution of 200 ms. The standard deviation of the location of nominally stationary 50‐nm‐diameter nanoparticles was found to be about 50 nm along the light path and about 5 nm in the plane perpendicular to the light path. The method is based on oscillating the microscope objective along the light path using a piezo actuator and acquiring images with the condenser aperture closed to a minimum to enhance the effects of diffraction. Data processing in the time and spatial domains allowed the location of particles to be obtained automatically so that the technique has potential applications both in the processing of nanoparticles and in their use in a variety of fields including nanobiotechnology, pharmaceuticals and food processing where a simple optical microscope maybe preferred for a variety of reasons.

Through-focus or volumetric type of optical imaging methods: a review

“…Cellular network dynamics such as spatiotemporal activity patterns in neuronal and astrocytic networks was demonstrated using TF imaging in 3D (14). 3D automated nanoparticle tracking was demonstrated using TF images (41). …”

Fidelity test for through-focus or volumetric type of optical imaging methods

“…Cellular network dynamics was demonstrated using TF imaging in three dimensions [7]. 3D automated nanoparticle tracking was demonstrated using TF images [32]. …”

“…A review of the literature reveals several types of optical methods to collect TF images [1, 5, 7, 13, 14, 29, 32–41]. Because of this, certain variations in the TF image quality can be expected depending on the TF imaging method.…”

Nanoparticle size determination using optical microscopes

“…Through-focus optical images under the low partial coherence condition were successfully used to track motion of the nanoparticles with axial, lateral, and temporal resolutions of 50 nm, 5 nm, and 200 ms, respectively. 17 However, optical microscopes are not yet used for nanoparticle size determination. In this article, we present a singleparticle counting method to determine size of nanoparticles using widely available conventional optical microscopes without complicated modifications to the optics or hardware.…”

“…High throughput is achieved in two ways: short measurement times (200 ms), 17 and the ability to simultaneously measure several nanoparticles located in the field of view, including at different heights. Ubiquitous optical microscopes will likely help this method to be implemented readily, especially for quality control.…”