A self-assembled nanoprobe based on Schiff base for the rapid and selective detection of serum albumin with cell imaging applications

Abstract

Here, we report the design and synthesis of a Schiff base probe, DBNHC ((E)-2-(2,4-dihydroxybenzylidene)-N-(naphthalen-1-yl)hydrazine-1-carbothioamide), and its interaction with bovine serum albumin (BSA). In ∼100% PBS buffer, the probe DBNHC can self-assemble into nonfluorescent nanoaggregates due to the aggregation caused quenching (ACQ) effect. However, it becomes highly fluorescent (∼14 fold) in the presence of BSA which facilitates the disassembly of nanoaggregates into its monomer. The site-selective fluorescence displacement assay and molecular docking simulations reveal that mainly hydrogen bonding, π⋯sulphur and π⋯alkyl interactions are responsible for the disassembly of nanoaggregates leading to encapsulation of DBNHC monomer at site II in BSA, resulting in a cyan green emission. The detection limit determined by the 3σ/slope method was found to be 58 nM, and the lower dissociation constant [K_d = (1.506 ± 0.196) μM] value suggests strong binding between the probe and BSA. Further, DBNHC was used for cell incubation and in vitro fluorescence imaging of BSA.