2 research outputs found
Membraneless Gas-Separation Microfluidic Paper-Based Analytical Devices for Direct Quantitation of Volatile and Nonvolatile Compounds
This
work presents new chemical sensing devices called “membraneless
gas-separation microfluidic paper-based analytical devices”
(MBL-GS μPADs). MBL-GS μPADs were designed to make fabrication
of the devices simple and user-friendly. MBL-GS μPADs offer
direct quantitative analysis of volatile and nonvolatile compounds.
Porous hydrophobic membrane is not needed for gas-separation, which
makes fabrication of the device simple, rapid and low-cost. A MBL-GS
μPAD consists of three layers: “donor layer”,
“spacer layer”, and “acceptor layer”.
The donor and acceptor layers are made of filter paper with a printed
pattern. The donor and acceptor layers are mounted together with a
spacer layer in between. This spacer is a two-sided mounting tape,
0.8 mm thick, with a small disc cut out for the gas from the donor
zone to diffuse to the acceptor zone. Photographic image of the color
that is formed by the reagent in the acceptor layer is analyzed using
the ImageJ program for quantitation. Proof of concept of the MBL-GS
μPADs was demonstrated by analyzing standard solutions of ethanol,
sulfide, and ammonium. Optimization of the MBL-GS μPADs was
carried out for direct determination of ammonium in wastewaters and
fertilizers to demonstrate the applicability of the system to real
samples
Facile and Compact Electrochemical Paper-Based Analytical Device for Point-of-Care Diagnostic of Dual Carcinogen Oxidative Stress Biomarkers through a Molecularly Imprinted Polymer Coated on Graphene Quantum-Dot Capped Gold
Nanoscale imprinting significantly increases the specific
surface
area and recognition capabilities of a molecularly imprinted polymer
by improving accessibility to analytes, binding kinetics, and template
removal. Herein, we present a novel synthetic route for a dual molecularly
imprinted polymer (dual-MIP) of the carcinogen oxidative stress biomarkers
3-nitrotyrosine (3-NT) and 4-nitroquinolin-N-oxide (4-NQO) as coatings
on graphene quantum-dot capped gold nanoparticles (GQDs-AuNPs). The
dual-MIP was successfully coated on the GQDs-AuNPs core via a (3-mercaptopropyl)
trimethoxysilane (MPTMS) linkage and copolymerization with the 3-aminopropyltriethoxysilane
(APTMS) functional monomer. In addition, we fabricated a facile and
compact three-dimensional electrochemical paper-based analytical device
(3D-ePAD) for the simultaneous determination of the dual biomarkers
using a GQDs-AuNPs@dual-MIP-modified graphene electrode (GQDs-AuNPs@dual-MIP/SPGE).
The developed dual-MIP device provides greatly enhanced electrochemical
signal amplification due to the improved electrode-specific surface
area, electrocatalytic activity, and the inclusion of large numbers
of dual-imprinted sites for 3-NT and 4-NQO detection. Quantitative
analysis used square wave voltammetry, with an oxidation current appearing
at −0.10 V for 4-NQO and +0.78 V for 3-NT. The dual-MIP sensor
revealed excellent linear dynamic ranges of 0.01 to 500 μM for
3-NT and 0.005 to 250 μM for 4-NQO, with detection limits in
nanomolar levels for both biomarkers. Furthermore, the dual-MIP sensor
for the simultaneous determination of 3-NT and 4-NQO provides high
accuracy and precision, with no evidence of interference from urine,
serum, or whole blood samples