Understanding specific protein-peptide interactions could offer a deep insight into the development of therapeutics for many human diseases. In this work, we designed and synthesized a far-red/near-infrared (FR/NIR) fluorescence light-up probe (DBT-2EEGWRESAI) by simply integrating two tax-interacting protein-1 (TIP-1)-specific peptide ligands (EEGWRESAI) with one 4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole (DBT) unit. We first demonstrated that DBT is an environment-sensitive fluorophore with FR/NIR fluorescence due to its strong charge transfer character in the excited state. Thanks to the environmental sensitivity of DBT, the probe DBT-2EEGWRESAI is very weakly fluorescent in aqueous solution but lights up its fluorescence when the probe specifically binds to TIP-1 protein or polyprotein (ULD-TIP-1 tetramer). It is found that the DBT-2EEGWRESAI/TIP-1 protein and the DBT-2EEGWRESAI/ULD-TIP-1 tetramer could self-assemble into spherical nanocomplexes and a nanofiber network, respectively, which lead to probe fluorescence turn-on through providing DBT with a hydrophobic microenvironment. By virtue of the self-assembly-induced FR/NIR fluorescence turn-on, DBT-2EEGWRESAI can detect and visualize specific protein/polyprotein-peptide interactions in both solution and live bacteria in a high contrast and selective manner.

Fluorescent light-up probes with aggregation-induced emission (AIE) characteristics have recently attracted great research interest due to their intelligent fluorescence activation mechanism and excellent photobleaching resistance. In this work, we report a new, simple, and generic strategy to design and prepare highly sensitive AIE fluorescent light-up bioprobe through facile incorporation of a self-assembling peptide sequence GFFY between the recognition element and the AIE luminogen (AIEgen). After the bioprobes respond to the targets, the peptide GFFY is capable of inducing the ordered self-assembly of AIEgens, yielding close and tight intermolecular steric interactions to restrict the intramolecular motions of AIEgens for excellent signal output. Using two proof-of-concepts, we have demonstrated that self-assembling peptide-incorporating AIE light-up probes show much higher sensitivity in sensing the corresponding targets in both solutions and cancer cells as compared to those without GFFY induced self-assembly. Taking the probe TPE-GFFYK(DVEDEE-Ac), for example, a detection limit as low as 0.54 pM can be achieved for TPE-GFFYK(DVEDEE-Ac) in caspase-3 detection, which is much lower than that of TPE-K(DVED-Ac) (3.50 pM). This study may inspire new insights into the design of advanced fluorescent molecular probes.

Here we reported a novel biohybrid hydrogel system with the potential for cell culture and controlled drug release.

We occasionally found that several self-assembling peptides containing D-amino acids would be preferentially enriched in cellular membranes at self-assembled stages while distributed evenly in the cytoplasma of cells at unassembled stages. Self-assembling peptides containing only Lamino acids distributed evenly in cytoplasma of cells at both self-assembled and unassembled stages. The self-assembling peptides containing D-amino acids could therefore be applied for engineering cell surface with peptides. More importantly, by integrating a protein binding peptide (a PDZ domain binding hexapeptide of WRESAI) with the self-assembling peptide containing D-amino acids, protein could also be introduced to the cell surface. This study not only provided a novel approach to engineer cell surface, but also highlighted the unusual properties and potential applications of self-assembling peptides containing D-amino acids in regenerative medicine, drug delivery, and tissue engineering.