Metal-organic frameworks (MOFs) have emerged as an important class of hybrid organic-inorganic materials. One of the reasons they have gained remarkable attention is attributed to the possibility of altering them by postsynthetic modification, thereby providing access to new and novel advanced materials. MOFs have been applied in catalysis, gas storage, gas separation, chemical sensing, and drug delivery. However, their bactericidal use has rarely been explored. Herein, we developed a two-step process for the synthesis of zirconium-based MOFs metalated with silver cations as a potent antibacterial agent. The obtained products were thoroughly characterized by powder X-ray diffraction, scanning electron microscopy, UV-visible, IR, thermogravimetric, and Brunauer-Emmett-Teller analyses. Their potency was evaluated against E. coli with a reported minimal inhibitory concentration and minimal bactericidal concentration of as low as 6.5 μg/mL of silver content. Besides the novelty of the system, the advantage of this strategy is that the MOFs could be potentially regenerated and remetalated after each antibacterial test, unlike previously reported frameworks, which involved the destruction of the framework.

We report a chemically tuned fluorogenic electrophile designed to conduct live-cell super-resolution imaging by exploiting its stochastic reversible alkylation reaction with cellular nucleophiles. Consisting of a lipophilic BODIPY fluorophore tethered to an electrophilic cyanoacrylate warhead, the new probe cyanoAcroB remains nonemissive due to internal conversion along the cyanoacrylate moiety. Intermittent fluorescence occurs following thiolate Michael addition to the probe, followed by retro-Michael reaction, tuned by the cyano moiety in the acrylate warhead and BODIPY decoration. This design enables long-term super-resolved imaging of live cells by preventing fluorescent product accumulation and background increase, while preserving the pool of the probe. We demonstrate the imaging capabilities of cyanoAcroB via two methods: (i) single-molecule localization microscopy imaging with nanometer accuracy by stochastic chemical activation and (ii) super-resolution radial fluctuation. The latter tolerates higher probe concentrations and low imaging powers, as it exploits the stochastic adduct dissociation. Super-resolved imaging with cyanoAcroB reveals that electrophile alkylation is prevalent in mitochondria and endoplasmic reticulum. The 2D dynamics of these organelles within a single cell are unraveled with tens of nanometers spatial and sub-second temporal resolution through continuous imaging of cyanoAcroB extending for tens of minutes. Our work underscores the opportunities that reversible fluorogenic probes with bioinspired warheads bring toward illuminating chemical reactions with super-resolved features in live cells.

Electron-transfer processes in lipid membranes are key to biological functions, yet challenging to study because of the intrinsic heterogeneity of the systems. Here, we report spectroelectrochemical measurements on indium tin oxide-supported lipid bilayers toward the selective induction and sensing of redox processes in membranes. Working at neutral pH with a fluorogenic α-tocopherol analogue, the dynamics of the two-electron oxidation of the chromanol to a chromanone and the rapid thermal decay of the latter to a chromoquinone are recorded as a rapid surge and drop in intensity, respectively. Continuous voltage cycling reveals rapid chromoquinone two-electron, two-proton reduction to dihydrochromoquinone at negative bias, followed by slow regeneration of the former at positive bias. The kinetic parameters of these different transitions are readily obtained as a function of applied potentials. The sensitivity and selectivity afforded by the reported method enables monitoring signals equivalent to femtoampere currents with a high signal-to-background ratio. The study provides a new method to monitor membrane redox processes with high sensitivity and minimal concentrations and unravels key dynamic aspects of α-tocopherol redox chemistry.

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The physical properties of lipid membranes depend on their lipid composition. Photosensitized singlet oxygen ( 1 O 2 ) provides a handle to spatiotemporally control the generation of lipid hydroperoxides via the ene reaction, enabling fundamental studies on membrane dynamics in response to chemical composition changes. Critical to relating the physical properties of the lipid membrane to hydroperoxide formation is the availability of a sensitive reporter to quantify the arrival of 1 O 2 . Here, we show that a fluorogenic αtocopherol analogue, H 4 BPMHC, undergoes a >360-fold emission intensity enhancement in liposomes following a reaction with 1 O 2 . Rapid quenching of 1 O 2 by the probe (k q = 4.9 × 10 8 M −1 s −1 ) ensures zero-order kinetics of probe consumption. The remarkable intensity enhancement of H 4 BPMHC upon 1 O 2 trapping, its linear temporal behavior, and its protective role in outcompeting membrane damage provide a sensitive and reliable method to quantify the 1 O 2 flux on lipid membranes. Armed with this probe, fluorescence microscopy studies were devised to enable (i) monitoring the flux of photosensitized 1 O 2 into giant unilamellar vesicles (GUVs), (ii) establishing the onset of the ene reaction with the double bonds of monounsaturated lipids, and (iii) visualizing the ensuing collective membrane expansion dynamics associated with molecular changes in the lipid structure upon hydroperoxide formation. A correlation was observed between the time for antioxidant H 4 BPMHC consumption by 1 O 2 and the onset of membrane fluctuations and surface expansion. Together, our imaging studies with H 4 BPMHC in GUVs provide a methodology to explore the intimate relationship between photosensitizer activity, chemical insult, membrane morphology, and its collective dynamics.