Ratiometric fluorescence probe for accurate detection of Concanavalin A by coupling fluorescent microsphere with boric acid functionalized carbon dots

Accurate and sensitive strategies for Concanavalin A (Con A) sensing are conducive to the better cognition of various important biological and physiological processes. Here, by designing dextran-functionalized fluorescent microspheres (DxFMs) and boric acid-modified carbon dots (BCDs) as recognition unit and built-in signal reference respectively, a ratiometric fluorescent detection platform was proposed for Con A detection with high reliability. In this protocol, the BCDs/DxFMs precipitation was formed due to the covalent interactions between cis-diol of DxFMs and boronic acid groups of BCDs, thus only fluorescence of BCDs could be detected in the supernatant. When Con A was presented, it could bind to DxFMs through its carbohydrate recognition ability and suppress the subsequent assembly between DxFMs and BCDs, leading to the simultaneous capture of DxFMs and BCDs fluorescence in the supernatant. Since the BCDs content was superfluous, their fluorescence intensities were basically constant in all cases. Based on the unchanged BCDs fluorescence signal and target-dependent DxFMs fluorescence signal in supernatant, the ratiometric detection of Con A was realized. Under optimized conditions, this ratiometric fluorescent platform displayed a linear detection range from 0.125 µg/mL to 12.5 µg/mL with a detection limit of 0.089 µg/mL. Moreover, satisfied analytical outcomes for Con A detection in serum samples were obtained, manifesting huge application potential of this ratiometric fluorescent platform in clinical diagnosis.