A highly sensitive fluorescent indicator probe based on tetramethylcucurbit[6]uril for visual detection of spermine and spermidine

Spermine (SP) and spermidine (SPD) are crucial biomarkers for the early diagnosis of cancer. In this work, we present a novel supramolecular approach of preparing and using a cucurbit[6]uril derivative, tetramethylcucurbit[6]uril (TMeQ[6])-based host−guest assembly for SP/SPD sensing in aqueous solution. A pyridinium-modified anthraquinone cationic guest ( DEPy + ) was designed as the fluorescent response unit for detecting SP/SPD through a fluorescence indicator displacement (FID) mechanism, facilitated by the TMeQ[6]-based 1:1 binary complex. In a complex system with various organic species and ions, DEPy + @TMeQ[6] showed excellent anti-interference ability in detecting SP/SPD and achieved a low detection limit. Combined with smartphone RGB analysis, it can visually and semi-quantitative detect SP/SPD without precision instruments. This study presents an efficient and convenient method for SP/SPD detection and expands the application of supramolecular fluorescent probes in the field of sensing. Illustration of the fluorescence indicator displacement process based on host-guest interactions and application. • A novel supramolecular fluorescent complex, DEPy + @TMeQ[6], was synthesized and characterized. • After encapsulation by TMeQ[6], DEPy + shows enhanced fluorescence and its quantum yield increases from 0.59 % to 2.43 %. • DEPy + @TMeQ[6] shows high selectivity for spermine/spermidine with a low detection limit based on the FID mechanism. • With RGB on smartphones, spermine/spermidine can be recognized and applied for in human urine and serum.