Vanadium-doped porous Co3O4 (V-porous
Co3O4) was synthesized via a simple soft-templating
method and used as a superior peroxidase mimic for the simultaneous
colorimetric determination of glucose and total cholesterol (TC) in
whole blood samples on a two-dimensional microfluidic paper-based
analytical device (2D-μPAD). The large surface area and the
presence of two metals in V-porous Co3O4 contributed
to its excellent catalytic activity toward 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic
acid) (ABTS) and 3,3′,5,5′- tetramethylbenzidine (TMB)
with Michaelis–Menten constants (K
M) of 0.1301 and 0.0141 mM, respectively. The 2D-μPAD was fabricated
using simple wax screen-printing and cutting techniques. The colorimetric
reactions of both glucose and TC on 2D-μPAD were simultaneously
performed by adding a single drop of a whole blood sample on the sample
zone made of the LF1 membrane. After the enzymatic reactions, the
generated hydrogen peroxide (H2O2) was oxidized
by V-porous Co3O4 to produce hydroxy radicals
(•OH), inducing ABTS and TMB to generate colored
products. The generated H2O2 was proportional
to the intensities of the green and blue products of the glucose and
TC systems, respectively. The developed 2D-μPAD required a short
analysis time (∼5 min) with small volumes of samples (15 μL
of whole blood) whereby no sample preparation was needed. Owing to
several advantages including simplicity, low cost, long-term stability,
and simultaneous readout, the novel V-porous Co3O4 coupled with 2D-μPAD proved to be promising for practical
uses as a pioneering portable device for the determination of glucose,
TC, and other important biomarkers without the need of technical supports.