New Approach to Generate Ratiometric Signals on Immunochromatographic Strips for Small Molecules

Abstract

The self-calibration capability of ratiometric signals has been widely considered to enhance the accuracy, sensitivity, and anti-interference ability of immunoassays. Exploring a new approach to generate ratiometric signals can provide more options for various requirements. Herein, we integrated the negative-readout competitive and positive-readout noncompetitive immunoassays into a single assay by employing different color tracers, labeled peptidomimetic and anti-immunocomplex peptides, to create a new unconstrained ratiometric signal approach. Using an immunochromatographic strip (ICS) and a fungicide benzothiostrobin as the analytical platform and analyte, respectively, we showed that this approach can be extensively applied to fluorescence and colorimetry readouts, which have also been proven for strong anti-interference ability to an external light environment. Moreover, the enormous intuitional color changes of ratiometric fluorescent and colorimetric ICSs (RFICS and RCICS) enabled the formation of the color reference cards (like the pH paper) for visual judgment. After adaptation with a portable smartphone, the quantitative detection limits for RFICS and RCICS were 0.17 and 0.44 ng mL −1 , respectively. In addition, the ICSs showed good accuracy for the detection of benzothiostrobin in spiked samples.

Development of Ic-ELISA and Colloidal Gold Lateral Flow Immunoassay for the Determination of Cypermethrin in Agricultural Samples

“…Colloidal gold particles were synthesized with trisodium citrate as a reducing agent according to our previous work [ 28 ]. For the preparation of colloidal gold mAb, 6.65 μg/mL anti-CYP mAbs were added to the colloidal gold solution adjusted to pH 8.2 using 0.2 mol/L K 2 CO 3 with shaking at room temperature for 1 h. BSA (1%) was used to block free colloidal gold particles.…”

Semiconductor/Carbon Quantum Dot‐based Hue Recognition Strategy for Point of Need Testing: A Review

“…Lately, a new unconstrained ratiometric signal approach was successfully applied to immunochromatographic strips for visual determination of benzothiostrobin by Chen and co‐workers. [75a] This innovation possessed important reference value for hue recognition of small molecules by lateral flow immunoassay (LFIA). The study can be widely utilized to FL or colorimetry reading by fluorescent or colorimetric labels.…”

“…Thanks to the analyte‐induced IFE between gold nanoparticles and nanohybrid, a ratiometric system with two reversed signals and a logic gate strategy were successfully constructed for the visual determination of melamine with a color hue evolution from green to orange‐red. Lately, a new unconstrained ratiometric signal approach was successfully applied to immunochromatographic strips for visual determination of benzothiostrobin by Chen and co‐workers [75a] . This innovation possessed important reference value for hue recognition of small molecules by lateral flow immunoassay (LFIA).…”

A smartphone-based device for simultaneous measurement of ratiometric fluorescence and absorbance demonstrated by the determination of hypochlorous acid

“…It should be noted that eqn (10) is an approximation because only the first term of the Taylor series in eqn ( 8) is used. Anyway, eqn (10) is also helpful to explain the near-linear correlations between the light intensity or hue of the colorimetric images and concentration of target analytes in visible regions, [37][38][39][40][41][42][43][44][45] which are also due to the non-linear response of the CCD in the camera to light intensity (eqn (3)). But the value of G 3 is dependent on the values of G 1 and G 30 .…”