Rational design of a 1,8-naphthalimide-based fluorescent probe and its application in liquid food detection of viscosity and living cells

1,8-Naphthalimide derivatives, renowned as classic fluorescent probes, have garnered widespread applications in diverse fields such as fluorescence detection, bioimaging, drug delivery, and targeted therapy. In this study, a novel water-soluble fluorescent probe based on 1,8-naphthalimide, designated as NPP-2N+, was meticulously designed and synthesized for the purpose of detecting viscosity in living cells and assessing the safety of liquid food. NPP-2N+ exhibited minimal fluorescence in low-viscosity environments, a phenomenon attributed to intramolecular rotation. Conversely, in high-viscosity settings, the intramolecular rotation of NPP-2N+ was significantly hindered, resulting in a pronounced enhancement of fluorescence emission. The probe NPP-2N+ boasts several advantageous features, including pH resistance, high selectivity, robust viscosity responsiveness, and commendable photostability. Moreover, NPP-2N+ has showcased exceptional efficacy in the detection of cellular viscosity and the monitoring of spoilage in liquid food products, underscoring its potential as a formidable molecular instrument in the realms of biomedical research and food safety surveillance.