Versatile Histochemical Approach to Detection of Hydrogen Peroxide in Cells and Tissues Based on Puromycin Staining

Hydrogen peroxide (H₂O₂) is a central reactive oxygen species (ROS) that contributes to diseases from obesity to cancer to neurodegeneration but is also emerging as an important signaling molecule. We now report a versatile histochemical approach for detection of H₂O₂ that can be employed across a broad range of cell and tissue specimens in both healthy and disease states. We have developed a first-generation H₂O₂-responsive analogue named Peroxymycin-1, which is based on the classic cell-staining molecule puromycin and enables covalent staining of biological samples and retains its signal after fixation. H₂O₂-mediated boronate cleavage uncages the puromycin aminonucleoside, which leaves a permanent and dose-dependent mark on treated biological specimens that can be detected with high sensitivity and precision through a standard immunofluorescence assay. Peroxymycin-1 is selective and sensitive enough to image both exogenous and endogenous changes in cellular H₂O₂ levels and can be exploited to profile resting H₂O₂ levels across a panel of cell lines to distinguish metastatic, invasive cancer cells from less invasive cancer and nontumorigenic counterparts, based on correlations with ROS status. Moreover, we establish that Peroxymycin-1 is an effective histochemical probe for in vivo H₂O₂ analysis, as shown through identification of aberrant elevations in H₂O₂ levels in liver tissues in a murine model of nonalcoholic fatty liver disease, thus demonstrating the potential of this approach for studying disease states and progression associated with H₂O₂. This work provides design principles that should enable development of a broader range of histochemical probes for biological use that operate via activity-based sensing

Synthesis and Electrochemical, Photophysical, and Self-Assembly Studies on Water-Soluble pH-Responsive Alkynylplatinum(II) Terpyridine Complexes

A series of water-soluble pH-responsive alkynylplatinum­(II) terpyridine complexes have been synthesized and characterized. The electronic absorption, emission, and electrochemical properties of the complexes have been studied. The self-assembly processes of representative complexes in aqueous media, presumably through Pt···Pt and/or π–π interactions, have been investigated by concentration- and temperature-dependent UV–vis absorption measurements and dynamic light scattering experiments. Interestingly, some of the complexes have been found to undergo induced self-assembly and disassembly in aqueous media through modulation of the pH value of the solutions, resulting in remarkable UV–vis absorption and emission spectral changes. The emission spectral changes have been rationalized by the change in the hydrophilicity of the complexes, electrostatic repulsion among the complex molecules, and/or the extent of photoinduced electron transfer (PET) quenching upon protonation/deprotonation of the pH-responsive groups on the complexes. By simple modifications of the chemical structures of the complexes, induced self-assembly/disassembly of the complexes can occur at different and/or multiple pH regions, thus allowing the probing of changes at the desired pH region by triplet metal–metal-to-ligand charge-transfer emission of the complexes in the near-infrared (NIR) region. Fixed-cell imaging experiments have further demonstrated the potential of this class of complexes as pH-responsive NIR luminescent probes in vitro, while the NIR emissions of the complexes from live cells have been found to show good differentiation of acidic organelles such as lysosomes from other cellular compartments

Metal–Metal and π–π Interactions Directed End-to-End Assembly of Gold Nanorods

The end-to-end aggregation of gold nanorods (GNRs) has been demonstrated to be directed by a thioacetate-containing alkynylplatinum­(II) terpyridine complex. The <i>in situ</i> deprotected complex is preferentially attached at the ends of the gold nanorods (GNRs) and induce the aggregation of GNRs in an “end-to-end” manner by Pt···Pt and π–π interactions, which have been characterized by electron microscopy, energy dispersed X-ray (EDX) analysis, and UV–vis absorption spectroscopy. The assembly of the nanorods into chain-like nanostructures can be controlled by the concentration of the Pt­(II) complexes