Ultra long-term cellular tracing by a fluorescent AIE bioconjugate with good water solubility over a wide pH range.

Strongly fluorescent and water soluble bioprobes are in great demand for studying important biological events and processes. The quenching effect of conventional organic dyes caused by aggregation, and the high toxicity of inorganic quantum dots are thorny issues that have constantly obsessed scientists in this area of research. In this work, a large number of tetraphenylethene (TPE) units were successfully attached to N-succinyl-chitosan (NSCS) macromolecular chains to fabricate a novel TPE-NSCS fluorescent bioconjugate, which was strongly emissive in the solid state due to its aggregation-induced emission effect. TPE-NSCS could be solubilized in water over a wide range of pH values. We were pleasantly surprised to see that stained cells still showed a bright fluorescence emission for as many as 30 passages. The water solubility over a wide pH range, ultra long-term retention in cells, and strong fluorescence signals indicate that TPE-NSCS is a promising candidate for various biomedical applications.