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The pollution of heavy metal ions
within the environmental is a global problem. The rapid and precise removal of
these contaminants can be aided by identifying and quantifying the composition
of the sample. It is therefore crucial to develop effective portable analytical
techniques to determine the levels of heavy metal contamination. Paper-based
analytical devices (PADs) offer a low cost method making them an excellent
platform for onsite environmental sensors. Here we demonstrate how a PAD can be
integrated into a multi-use Nanopore platform. The PAD was functionalised with
different recognition ligands, who’s surface charge densities varied in the
presence of an analyte. The surface of the PAD was placed in contact with a
Nanopore which exhibited Ion Current Rectification (ICR). The extent of ICR,
was dependent upon the PAD’s surface charge, and the presence of the analyte of
interest i.e. the ICR phenomena was exaggerated or diminished indicating the
presence of the metal ion in solution.
We demonstrate the
potential of PAD-ICR using a PAD functionalised with a peptide aptamer specific
for nickel ions. Allowing the detection of nickel(II) as low as 0.25 μM even in
the presence of other metal ions. After any measurement, the Nanopore surface can
be wiped clean, and reused.