Simultaneous Multiplexed Detection of Protein and Metal Ions by a Colorimetric Microfluidic Paper-based Analytical Device

Abstract

In order to improve the efficiency of disease diagnosis and environmental monitoring, it is desirable to detect the concentration of proteins and metal ions simultaneously, since the current popular diagnostic platform can only detect proteins or metal ions independently. In this work, we developed a colorimetric microfluidic paper-based analytical device (µPAD) for simultaneous determination of protein (bovine serum albumin, BSA) and metal ions [Fe(III) and Ni(II)]. The µPAD consisted of one central zone, ten reaction zones and ten detection zones in one device, in which reaction solutions were effectively optimized for different types of chromogenic reactions. Fe(III), Ni(II) and BSA can be easily identified by the colored products, and their concentrations are in good accordance with color depth based on the established standard curves. The detection limits are 0.1 mM for Fe(III), 0.5 mM for Ni(II) and 1µM for BSA, respectively. Best of all, we demonstrated the efficiency of the µPAD with accurate detection of Fe(III), Ni (II) and BSA from river water samples within 15 minutes. The µPAD detection is efficient, instrument-free, and easy-to-use, holding great potential for simultaneous detection of cross type analytes in numerous diagnostic fields.

Keywords: BSA; Colorimetric detection; Fe(III); Microfluidic paper-based analytical device; Ni(II); Simultaneous.

Scheme 1

Schematic of the µPAD for simultaneous multiplexed detection of Fe(III), Ni(II) and BSA.

Figure 1

Main steps of fabricating µPADs by UV-exposure method.

Figure 2

The injection process and interval time of reaction mixture and colorimetric reagent for detection of Fe(III), Ni(II) and BSA.

Figure 3

Color palettes for visual simultaneous determination of Fe(III), Ni(II) and BSA. (a) Chromogenic reactions for 0.1, 0.7 and 5 mM Fe(III), 0.5, 5 and 50 mM Ni(II), 0.001, 0.03 and 0.1mM BSA. (b) Chromogenic reactions for 0.3, 1 and 10 mM Fe(III), 1, 10 and 100 mM Ni(II), 0.005, 0.05 and 0.15 mM BSA. (c) Chromogenic reactions for 0.5, 3 and 17.9 mM Fe(III), 2, 20 and 200 mM Ni(II), 0.01, 0.07 and 0.2 mM BSA. Yellow corresponds to 0 mM BSA as control.

Figure 4

Calibration curves between color intensity and log target concentration for (a) Fe(III), (b) Ni(II), and (c) BSA detection. The error bars present standard deviation (SD) obtained from three independent measurement (n=3).

Figure 5

Interference study of the microfluidic paper-based analytical device. 1 BSA detection zone, 2 Fe(III) detection zone, 3 Ni(II) detection zone.

Figure 6

Simultaneous detection of Fe(III), Ni(II) and BSA in an actual river sample (a) µPAD with reaction mixture solutions and colorimetric reagents added. (b) µPAD showing detection of an actual river sample.