Synthesis, characterization and detection of Concanavalin A based on a mannose-substituted conjugated polymer through aggregation-enhanced FRET

Abstract

A conjugated polymer (P1) with pendant mannose linkages has been designed and synthesized, which is a highly efficient ratiometric probe for Concanavalin A (Con A) detection. P1 is doped with a low-bandgap fluorophore, porphyrin, which in conjunction with favorable spectral overlap between the poly(fluorene–phenylene) and porphyrin facilitates efficient FRET process in aqueous solutions in presence of Con A. UV/vis spectroscopy and dynamic light scattering studies indicate that P1 and Con A form into nanoparticles by carbohydrate–lectin interactions. Addition of Con A results in the quenching of the poly(fluorene–phenylene) emission at 456nm with simultaneous enhancement of porphyrin emission at 625nm, exhibiting visual emission color change from blue to purple. The intensity ratio of I625/I456 is enhanced 9.3-fold when the concentration of Con A reaches 10μmol/L. Nonspecific proteins including bovine serum albumin (BSA), pepsin (Pep), lysozyme (Lys) show poor fluorescence response, thus highlighting the selectivity and sensitivity of the FRET-based sensing of Con A by P1. Moreover, P1 shows low cytotoxicity by CCK-8 assay, which makes its potential application as fluorescent agent for cellular imaging.