Bioinspired Peptide for Imaging Hg2+ Distribution in Living Cells and Zebrafish Based on Coordination-Mediated Supramolecular Assembling

Peptides with modular structure provide a tailorable platform for constructing responsive supramolecular assemblies, which are attractive as functional biomaterials and smart sensors. In this work, the feasibility of regulating small peptides assembly with molecular design and metal ion recognition was demonstrated. Tripeptides were designed and found to have diverse response and self-assembly behavior to Hg2+. The incorporation of an aggregation-induced emission fluorophore TPE enabled the visualization of Hg2+ recognition and the assembly phenomenon. A structural analogue (Pep2) to gamma-glutathione was identified with high specificity and nanomolar response to Hg2+ both in buffer solution and living cells. Driven by the coordination force and noncovalent intramolecular stacking, assembling of twisted nanofibers from Pep2-TPE and Hg2+ were observed. Benefiting from its biocompatibility, fast and switchable fluorescence response, Pep2-TPE was applied for imaging and monitoring Hg2+ distribution in living cells and zebrafish. With good permeability to plasma membrane and tissues, Pep2-TPE indicated the preferential distribution of Hg2+ in cell nucleoli and brain of zebrafish, which is related with the deleterious effect of inorganic mercury in living biosystems.