Förster Resonance Energy Transfer Mediated Rapid and Synergistic Discrimination of Bacteria over Fungi Using a Cationic Conjugated Glycopolymer.

A water-soluble polyfluorene derivative PFBTM-NMe bearing mannose as well as quaternary ammonium groups on side chains is designed and synthesized via click chemistry and Suzuki cross-coupling polymerization. The conjugated glycopolymer PFBTM-NMe displayed excellent solubility in polar solvents with absolute photoluminescence quantum yield (Φ) of 4.1% and 13.4% in water and methanol, respectively. Owing to the low doping of benzothiadiazole (BT) moieties along the backbone, PFBTM-NMe exhibited weak interchain Förster resonance energy transfer (FRET) in water. After binding with Gram-negative bacteria, that possess net negative charge and bunch of mannose binding lectins FimH on the surface, PFBTM-NMe showed strong FRET and ratiometric response owing to interchain polymer aggregation. Interestingly, Gram-positive bacteria () and fungi () did not present similar substantial response due to the absence of lectin proteins and less net negative charge on the surface. Moreover, confocal microscopy indicates that bacteria undergo aggregation after binding with PFBTM-NMe within 2 min and could be proficiently discriminate from fungi even in a mixed condition via fluorescence imaging technique, which facilitate the potential of this method for realistic use. Hence, by simply balancing the synergistic effect of electrostatic and carbohydrate-protein interactions between polymer PFBTM-NMe and microbes, the selective recognition and imaging of bacteria over fungi could be achieved within a very short period of time without employing any complicated procedures.