A self-assembled fluorescent nanoprobe recognized by FA1 site for specifically selecting HSA: Its applications in hemin detection, cell imaging and fluorescent tracing drug delivery.

As naturally essential biomacromolecule, HSA has become diagnostic indicators for various diseases and universal carriers for anticancer drug delivery, therefore, fluorescence detection and labeling for HSA possess significant application value in the biomedical field. In this paper, hydrazide Schiff base fluorescent probe NDQC was designed and synthesized, which self-assembled into nanoparticles in aqueous solution system and demonstrated excellent selectivity and sensitivity towards HSA. Through displacement assay and molecular docking simulation, the binding of NDQC with HSA in FA1 site was demonstrated, thereby no obvious fluorescence signal presented for homologous protein BSA due to their structural differences in binding site. Non-toxic probe NDQC is suitable for the fluorescence imaging of HSA in cells, and colocalization fluorescence images showed that NDQC-HSA could illuminate mitochondria. Based on the pH sensitivity of fluorescence emission for NDQC-HSA, discrimination of cancer cells and normal cells could be achieved. For practical applications, NDQC-HSA can be employed to measure the content of hemin. More importantly, NDQC could fluorescently label HSA and therefore NDQC-HSA complex act as the carrier for loading cisplatin. The present findings demonstrate that the probe NDQC has potential in exploring HSA at cellular levels and hold great promise in application of tracking drug-loading nanoparticles.