Glycopeptide-Conjugated Aggregation-Induced Emission Luminogen: A pH-Responsive Fluorescence Probe with Tunable Self-Assembly Morphologies for Cell Imaging.

Abstract

pH values play an important role in various cell biological processes. Abnormal pH values in living systems are frequently associated with the development of diseases such as cancers, infection, and other diseases. Real-time monitoring of the changes of pH values in vivo will give us the significant indication for these diseases' progression. Within those pH-sensitive imaging probes, aggregation-induced emission (AIE) molecules exhibit great potential in aqueous imaging environment due to their high fluorescence quantum yield and stability. However, the modulation of the AIE probe with pH sensitivity and light-up property face challenges. Here, we introduced a new glycopeptide-modified AIE probe (TGO) based on the optimized solid-phase peptide synthesis approach. The response to pH of the peptide: DDDD progression changed hydrophobicity and hydrophilicity, resulting in the change of the amphipathicity balance. When modulating the pH from 5.5 to 8.0, the adverse protonation of the peptide induced assembled nanostructure transformation from nanolamellae to nanomicelles. Meanwhile, the pH-induced charge change in peptides can greatly influence the microenvironment of the AIEgen, resulting in the increase of fluorescence intensity.