A Multiple-Responsive Fluorescence Probe Based on Water-Soluble Fluorescent Conjugated Polymer for Biomolecules Detection

In this paper, we designed a multiresponsive fluorescent probe based on a synthetic water-soluble conjugated fluorescent polymer (PF-DBT-S-S-PDI) consisting of the conjugated fluorescent backbones and the hydrophilic side chains connected by a disulfide bond. Based on its specific structures, according to two different response mechanisms of fluorescence resonance energy transfer (FRET) and heavy atom effect, the polymer shows high sensitivity and selectivity toward reductive species-thiols and oxidizing substances (such as H 2 O 2 ) in different ways. Owing to the presence of disulfide bonds, the reductive mercaptan in the solution would cause the water-soluble branches in the micellar structure to break off and leave, which causes the hydrophobic framework of the polymer to aggregate and enhance the fluorescence intensity. On the other hand, because the PDIs in branches are ionic polymers with many iodide ions, H 2 O 2 in solution oxidizes iodide ions into iodide so that the heavy atomic effect of iodide would quench the fluorescence. Both mechanisms have high sensitivity; e.g., the detection limits for mercaptan (such as cysteine) were 0.052 mM, 5.26 μM for H 2 O 2, and 1.06 μM for glucose (combined with oxidase). The multiple detection ability of the polymer has been validated by evaluating free thiols and glucose levels in food samples and tissue homogenates. Our work provided a strategy for integrating multiple species detection capabilities on a single probe.