Piperazine-Based Mitochondria-Immobilized pH Fluorescent Probe for Imaging Endogenous ONOO^– and Real-Time Tracking of Mitophagy

Abstract

ONOO– is mainly produced in mitochondria, and dysfunctional and damaged mitochondria are degraded in lysosomes through autophagy, so it is important to synthesize a single probe for dual detection of ONOO– and mitophagy. Unfortunately, mitochondria-immobilized fluorescent probes for dual detection of ONOO– and mitophagy have not yet been developed. Hence, we first reported a piperazine-based mitochondria-immobilized red-emitting fluorescent probe (PMR), which not only can detect ONOO– but also could be used to image cellular mitophagy by the pH variations because of the protonation of the piperazine moiety. PMR was designed and prepared by introducing a piperazine ring as the pH response group, a lipophilic cation as the targeting mitochondria moiety, and benzyl chloride for immobilizing mitochondrial proteins through thiol groups. PMR displayed an enhanced fluorescence response at 640 nm through mitochondrial acidification. Using these advantages of PMR, which was successfully used for visualizing the mitophagy process induced by rapamycin or starvation, and chloroquine can inhibit rapamycin-induced mitophagy and prevent the fusion of autophagosomes and lysosomes. PMR also showed good sensitivity with a detection limit of 23 nM to ONOO–, which was successfully applied in imaging exogenous/endogenous ONOO–. Combining the above design, PMR may be used to study the detailed function of the mitophagy and ONOO–-associated physiological and pathological processes.

Rational Design of MMP-Independent Near-Infrared Fluorescent Probes for Accurately Monitoring Mitochondrial Viscosity

“…The dihydroxanthene fluorophores (denoted as DHX ) are the most commonly utilized NIR dyes due to their long wavelength emission, good water solubility, and biocompatibility. , As shown in Scheme a, a rigid dihydroxanthene fluorophore was selected as part of the core structure, a pH-insensitive methoxy group was selected as the electron donor, and pyridinium units served as the electron-accepting and mitochondria-targeting group. Mitochondria-immobilized probes have been developed based on fixed groups, such as benzyl chloride, − aldehyde, − 1,3-cyclohexanedione, maleimide, and alkyne . The reactive fixed groups react with nucleophiles, such as the reactive thiol groups present in mitochondrial polypeptides and proteins, and form covalent bonds to immobilize the probes within mitochondria, even if the MMP decreases or dissipates.…”

Exploring Multifunctional Response of Ca10(PO4)6(OH)2–K0.5Na0.5NbO3 Ceramic Composite for Biomedical Applications

“…56 These interesting results open up new arenas of application of fluorescent biomaterials as bioimaging probes for internal organs and tissues. 57 In addition, the use of KNN attributes the composite to piezoelectric properties, which is the subject matter for the group's ongoing research work. From an application perspective, such piezoactive composites would be useful for designing 3D-printed scaffolds in bone tissue engineering applications.…”

Advances in Small-Molecule Fluorescent pH Probes for Monitoring Mitophagy

“…Due to the participation of two organelles, including mitochondria and lysosomes, the change in pH is particularly obvious. Under normal physiological conditions, mitochondria remain weakly alkaline environment (pH = ∼8), but during mitophagy, damaged mitochondria in lysosomes become weakly acidic (pH = ∼4.5). − This shift in pH is a significant factor in the process of mitophagy.…”