Lijiao Ao,Daquan Li,Sai Chu,Feng wu,Jing Wang,Jun Li,Liang Huang,Quan Jin
Visual based immunoassay employs both human eye interpretation and machine-vision (smartphone imaging) quantification for equipment-independent diagnosis of biomarkers, fitting a variety of scenarios such as home-testing. Here we use hue-recognition strategy to create vivid and sensitive color changes against C-reactive protein (CRP) for accurate visual analysis. The red-to-green tonality gradient presentation was realized by ratiometric fluorescent probe using dual-emissive quantum dots (QDs) structure. The sandwich immuno-capturing process of antigen was integrated on ELISA plate, with the signal amplified and transduced by silver particle labels etching and interaction with the ratiometric QDs probe. The narrow-emissive QDs with selective response to released Ag + ions produced high color fidelity and prominent hue variation towards analyte concentration. This portable immunoassay enabled eye-perception of 5 specific CRP concentration points (0, 5, 50, 200, 500 ng/mL) and 4 concentration intervals (0-5, 5-50, 50-200, 200-500 ng/mL) with reading accuracy of 97.5% and 96.4%, respectively, which is superior against traditional lightness-gradient based reading mode. With the aid of smartphone imaging and software color-analyzing, an elaborated quantification of CRP was achieved via color information. The broad CRP responsive range (0-500 ng/mL), low limit of detection (0.062 ng/mL) and high specificity against protein substrates allowed a robust point-of-care CRP clinical diagnosis application.
Liang Huang,Ziyu Shi,Daquan Li,Chenxing Jiang,Xuexue Wang,Mei Huang,Jing Wang,Bin Su
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.
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