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Issue 3, 2005
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Single molecule studies of quantum dot conjugates in a submicrometer fluidic channel

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Abstract

A microfluidic and optical system was created for the detection and analysis of single molecules in solution. Fluidic channels with submicrometer dimensions were used to isolate, detect and identify individual quantum dots conjugated with organic fluorophores. The channels were fabricated in fused silica with a 500 nm square cross section. The resulting focal volume of approximately 500 aL reduced fluorescent background and increased the signal to noise ratio of single molecule detection. The channels also enabled the rapid detection of 99% of quantum dots and organic fluorophores traversing the focal volume. Conjugates were driven through the channels electrokinetically at 2.3 kV cm−1, excited with a single 476 nm wavelength laser and detected with a confocal microscope. Fluorescence emission was collected simultaneously from green (500–590 nm) and red (610–680 nm) regions of the spectrum. Signal rejection was minimized by the narrow and symmetric emission spectra of the quantum dots. To demonstrate efficient multicolor detection and characterization of single molecule binding, Qdot 655 Streptavidin Conjugates were bound to Alexa Fluor 488 molecules and individually detected. Photon counting histogram analysis was used to quantify coincident detection and degree of binding. Fluorescence correlation spectroscopy was used to measure the mobility of bound and unbound species. The union of fluidic channels with submicrometer dimensions and quantum dots as fluorescent labels resulted in efficient and rapid multiplexed single molecule detection and analysis.

Graphical abstract: Single molecule studies of quantum dot conjugates in a submicrometer fluidic channel

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Article information


Submitted
19 Oct 2004
Accepted
17 Dec 2004
First published
13 Jan 2005

Lab Chip, 2005,5, 337-343
Article type
Paper

Single molecule studies of quantum dot conjugates in a submicrometer fluidic channel

S. M. Stavis, J. B. Edel, K. T. Samiee and H. G. Craighead, Lab Chip, 2005, 5, 337
DOI: 10.1039/B416161K

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