Hue-Recognition Strategy-Based Immunoassay Using Functionalized Dendritic Silica Colloids and Gold Nanoclusters for Point-of-Care Testing of C-Reactive Proteins

Considering that hue-recognition has drawn increasing research interests for visual detection because of its high accuracy and flexible analysis modalities, the exploration of a rational hue-recognition sensing system is highly demanded. Here, we report a hue-recognition-based lateral flow immunoassay (HLFIA) by ratiometric modulation of emission from two nanoprobes, in which red-emitting ruthenium(II)-doped dendritic silica colloids and green-emitting gold nanoclusters function as reporter and reference, respectively. The HLFIA strip can generate a visually discernible green-to-orange-red color gradient alternation, enabling the naked-eye semiquantitative inspection of successive C-reactive protein (CRP) concentration and concentration intervals (0–50, 50–150, and 150–500 ng mL–1) with a visual detection limit of 10 ng mL–1. By integrating with a customized smartphone-based portable imaging device and RGB color space recognition, the precise quantification of CRP can be achieved with a linear range of 0–100 ng mL–1 and a limit of detection of 0.64 ng mL–1. The HLFIA strip is robust and validated for CRP detection in real serum, holding great promise for noninstrumental and deprofessionalized point-of-care immunoassay of biomarkers.