Intraparticle FRET probes based on dual-emission carbon dots for analytical detection of human hemoglobin and...

Fluorescence resonance energy transfer (FRET) probes based on carbon dots (CDs) have been widely used in biosensing in recent years due to their high sensitivity, excellent accuracy, and good biocompatibility. However, the complex modifications and precise regulation of distances involved in the probe construction process have limited their development and application. In this work, ratiometric fluorescent probes (DP-CDs) with fluorescence resonance energy transfer (FRET) were designed for the simple and sensitive detection of human hemoglobin (Hb) based on o-phenylenediamine and 2, 2'-dipicolylamine. The limit of detection of this probe for Hb was as low as 1.33 nM. The DP-CDs was successfully applied to the detection of Hb in real human blood. The mechanism of interaction was explored in several ways. From the point of view of the fluorescence response mechanism, the FRET effect was enhanced by the binding of Hb to DP-CDs. The fluorescence intensity of the donor absorption peak of DP-CDs at 435 nm was decreased, and the fluorescence intensity of the acceptor absorption peak at 550 nm was increased. Moreover, molecular docking was used to simulate and predict the sites of action and binding energies of the probe and a number of proteins. Among them, Hb has abundant interaction sites and much lower free energy than other proteins (ΔG = -46.94 KJ/mol). The possible interaction mechanism between Hb and the probe was explored from a molecular point of view, explaining the selectivity of the probe for Hb. This work provides a reference idea for the design of Hb-based bio-probes.