Conjugated polyelectrolytes with aggregation-enhanced emission characteristics: synthesis and their biological applications.

Conjugated polyelectrolytes are promising candidates for the construction of fluorescent bioprobes. In this study, a series of water-soluble fluorescent polyelectrolytes have been designed and synthesized by means of the quaternization of their tetraphenylethene-containing polyyne precursors. The polyynes can be facilely prepared through Hay-Glaser polycoupling in high yields (up to 99%) with high molecular weights (up to 38,900). All the polymers exhibit a phenomenon of aggregation-induced or -enhanced emission. The fluorimetric titrations of biomolecules such as heparin, calf thymus DNA, RNA, bovine serum albumin, and human serum albumin to buffer solutions of the polyelectrolytes suggest that they are promising fluorescent bioprobes with high sensitivity and fast response. The emission intensity of the polyelectrolytes is enhanced by up to sevenfold upon binding with biomolecules through electrostatic and hydrophobic cooperative interactions. The polyelectrolytes can also serve as fluorescent visualizers for intracellular imaging with good biocompatibility and low autofluorescence interference.