All-Integrated
and Highly Sensitive Paper Based Device
with Sample Treatment Platform for Cd<sup>2+</sup> Immunodetection
in Drinking/Tap Waters
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Abstract
Nowadays, the development of systems,
devices, or methods that
integrate several process steps into one multifunctional step for
clinical, environmental, or industrial purposes constitutes a challenge
for many ongoing research projects. Here, we present a new integrated
paper based cadmium (Cd<sup>2+</sup>) immunosensing system in lateral
flow format, which integrates the sample treatment process with the
analyte detection process. The principle of Cd<sup>2+</sup> detection
is based on competitive reaction between the cadmium–ethylenediaminetetraacetic
acid–bovine serum albumin–gold nanoparticles (Cd–EDTA–BSA–AuNP)
conjugate deposited on the conjugation pad strip and the Cd–EDTA
complex formed in the analysis sample for the same binding sites of
the 2A81G5 monoclonal antibody (mAb), specific to Cd–EDTA but
not Cd<sup>2+</sup> free, which is immobilized onto the test line.
This platform operates without any sample pretreatment step for Cd<sup>2+</sup> detection thanks to an extra conjugation pad that ensures
Cd<sup>2+</sup> complexation with EDTA and interference masking through
ovalbumin (OVA). The detection and quantification limits found for
the device were 0.1 and 0.4 ppb, respectively, these being the lowest
limits reported up to now for metal sensors based on paper. The accuracy
of the device was evaluated by addition of known quantities of Cd<sup>2+</sup> to different drinking water samples and subsequent Cd<sup>2+</sup> content analysis. Sample recoveries ranged from 95 to 105%
and the coefficient of variation for the intermediate precision assay
was less than 10%. In addition, the results obtained here were compared
with those obtained with the well-established inductively coupled
plasma emission spectroscopy (ICPES) and the analysis of certificate
standard samples