Quantitative Detection
of Single Walled Carbon Nanotube
in Water Using DNA and Magnetic Fluorescent Spheres
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Abstract
Carbon nanotubes (CNTs) possess unique properties that
have led
to an increase in their research and usage for a wide variety of fields.
This growing demand of CNTs poses a major public health risk given
its unregulated release into the environment. Unfortunately there
is a significant information gap on the actual quantity of CNTs in
the environment due to limitation of existing detection methods. This
is mainly owing to the ubiquitous carbon chemistry of CNT. In response
we developed a method (<i>CNT-capture method</i>) that is
able to structurally differentiate CNT from other interference carbon
materials in an aqueous medium. The affinity between single walled
nanotubes (SWNTs) and specific single stranded DNA (ssDNA) was employed
to capture SWNTs in water. SWNT-specific separation was obtained via
magnetic separation. Dual fluorescent labels attached to sandwich
ssDNA probes were used for quantification. The specific affinity between
DNA and SWNTs was verified and no significant side-interactions were
observed. With optimized incubation duration (30 min) and buffer composition
(10<sup>–7</sup> % sodium dodecyl sulfate and pH 7.9), a calibration
curve of quantification (<i>R</i><sup>2</sup> = 0.90) was
obtained with a range of SWNT concentration (0.05–10 μg/mL)
against graphene as a planar analog. Comparison to other spectroscopy
based methods was carried out to highlight the specificity and sensitivity
of the presented method for CNT detection in aquatic sample