Bioimaging probes for accurately monitoring apoptosis process have extensive significance for cell biological studies and clinical investigations. Herein, novel multifunctional peptide-tailored gold nanoclusters (AuNCs) have been developed for real-time imaging of caspase-indicated cell apoptosis. The AuNCs nanoprobe was facilely prepared by a one-step peptide-mediated biomineralization with the dye (TRAMA)-tagged peptides specific to caspase 3 as both template agents and the signal switch. Unlike conventional FRET-based fluorescent probes of caspase activity, these nanoprobes relied on the unique quenching effect of AuNCs through the nanosurface energy transfer (NSET) from dye to AuNCs. Intracellular caspase 3 activation cleaved the substrate peptide and released the dye from AuNCs, leading to a significant fluorescence lighting-up for sensitive and continuous analysis of caspase 3 activity in live cells, with a high signal-background ratio, wide linear range (32 pM-10 nM), and ultralow detection limit (12 pM). Moreover, this versatile AuNCs nanoprobe can serve as a theranostic platform via codisplaying pro-apoptotic and detecting peptides, which allows in situ activation and real-time monitoring of apoptosis in cancer cells. These results indicate that the AuNCs nanoprobe provides a smart molecular imaging and therapeutic agent targeted to cell apoptosis, which has great potential for apoptosis-related diagnosis and precision chemotherapy.

A novel and versatile peptide-based bio-logic system capable of regulating cell function is developed using sortase A (SrtA), a peptide ligation enzyme, as a generic processor. By modular peptide design, we demonstrate that mammalian cells apoptosis can be programmed by peptide-based logic operations, including binary and combination gates (AND, INHIBIT, OR, and AND-INHIBIT), and a complex sequential logic circuit (multi-input keypad lock). Moreover, a proof-of-concept peptide regulatory circuit was developed to analyze the expression profile of cell-secreted protein biomarkers and trigger cancer-cell-specific apoptosis.

A charge designable and tunable green fluorescent protein (GFP)-based protein delivery strategy was proposed. The acquired His29GFP selectively permeates the cell membrane at a target pH of 6.5 and escapes from the endosome efficiently. The delivered RNase A caused substantial mRNA degradation in HeLa cells, and proliferation inhibition in different cell lines and a 3D tumor model at pH 6.5.

A click-type protein–DNA conjugation, named as MnDDC (Mn2+-activated DCV-DNA conjunction), is presented, where DCV (rep protein of duck circovirus) and its target DNA work as the modular blocks to rapidly and effectively generate Mn2+-dependent and site-specific protein–DNA linkage. On the basis of MnDCC, a fluorescent Mn2+ biosensor composed of DCV and a molecular beacon, was developed for rapid sensing of Mn2+ within 2 min with nanomolar sensitivity. Using the proposed biosensor, not only analysis of Mn2+ in real samples (e.g., serum and food), but also wash-free fluorescent imaging of Mn2+ in extracellular environment and cytoplasm have been achieved. Moreover, the MnDDC-based sensor was proved to be a powerful tool for visualization of Mn2+ during exploration of the associated cytotoxicity in living neural cells, which is helpful to reveal the cellular responses toward the disordered homeostasis of Mn2+ in both extracellular and intracellular microenvironments.