Acoustofluidics-manipulated triple-emission fluorescent nanoprobe aggregates with multicolor-variation for colorimetric quantitative assay

Acoustofluidics-assisted colorimetric method, a promising point-of-care test (POCT) strategy, has been applied in convenient detection of target molecules using the sensing nanomaterials, but remains a formidable challenge to design fluorescent probe with profuse color evolution, realizing sensitive, simple and accurate determination of analyte. Here, a novel triple-emission fluorescent probe is constructed through a simple blend of two ratiometric fluorescent probes (blue-organosilane-polymerized carbon dots@SiO2 nanoparticles@red-CdTe/CdS quantum dots (b@SiO2@r) and blue-organosilane-polymerized carbon dots@SiO2 nanoparticles@green-CdTe/CdS quantum dots (b@SiO2@g)) at the optimized volume ratio of 11:8. As signal reporters of the triple-emission probe, outer modified r and g will be quenched in sequence by target via two-step response strategy while the inner b as internal standard remains constant. When acoustic field is applied, the effect of acoustofluidics-based nanoparticles concentration makes triple-emission probe aggregate completely, accompanying fluorescence color signal being enhanced, sensitivity of colorimetric assay being improved and multicolor-variation (from orange to dark-goldenrod to dark-olive-green to sea-green to dark-cyan to final steel-blue) with the increase of analyte amount. For POCT demonstration, hemoglobin (Hb) is used as a model target and the captured fluorescence photos of triple-emission probe aggregates are analyzed by a chromaticity analysis application on the smartphone to calculate the red, green and blue values, which are used for accurate Hb quantification with the limit of detection of 1.99 mg/L. Whole test is finished within similar to 12 min. The acoustofluidics-manipulated tripleemission probe biosensing strategy has also been applied to the rapid and visual quantitative detection of Hb in human blood.

Automated summary

In this study, a novel triple-emission fluorescent probe was successfully constructed, and acoustofluidics manipulation was used to aggregate the probe, enabling multicolor fluorescence signal and sensitive, simple, and accurate detection of target molecules. The method was successfully applied to the quantitative detection of hemoglobin in point-of-care testing (POCT).