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Ferroptosis is a recently identified form of regulated cell death characterized by iron accumulation and lipid peroxidation. Numerous functions for ferroptosis have been identified in physiological as well as pathological processes, most notably in the treatment of cancer. The intricate balance of redox homeostasis is profoundly altered during ferroptosis, leading to alteration in cellular microenvironment. One such microenvironment is viscosity among others such as pH, polarity, and temperature. Therefore, understanding the dynamics of ferroptosis associated viscosity levels within organelles is crucial. To date, there are a very few reviews that detects ferroptosis assessing reactive species. In this review, we have summarized organelle's specific fluorescent probes that detects dynamics of microviscosity during ferroptosis. Also, we offer the readers an insight of their design strategy, photophysics and associated bioimaging concluding with the future perspective and challenges in the related field. [ABSTRACT FROM AUTHOR]

Mitochondria are the powerhouse of the cell and function at pH ∼8.0. Dysfunctions of mitochondria, includes mitochondrial damage, leading to pH alteration. Hence, researchers aim to develop efficient pH probes for tracking mitochondrial pH dynamics. Herein, we developed a PET‐based fluorescent probe for pH monitoring during mitochondrial dysfunctions. Three derivatives were synthesized with a variable spacer's length in pentacyclic pyridinium fluorophores (PM‐C2, PM‐C3, and PM‐C6). An efficient electron transfers from the receptor (tertiary amine) was observed in the case of PM‐C2 compared to the other two derivatives. This PET process was inhibited when tertiary amine was protonated in acidic pH. However, PM‐C3 showed minimal fluorescence intensity at similar conditions and almost negligible change in case of PM‐C6, suggesting poor PET process for both the derivatives. Furthermore, DFT/TD‐DFT quantum chemical calculation well supported this optical phenomena and PET process. Biocompatible, photostable, and mitochondria‐specific PM‐C2 could monitor pH dynamics during mitochondrial damage which were engulfed by lysosome, also known as mitophagy. This mitophagy process were induced by rapamycin and starvation, which can be monitored by turn‐on fluorescence enhancement. This process was further validated by tracking Parkin‐protein translocation from cytoplasm to damaged mitochondria using our developed probe. [ABSTRACT FROM AUTHOR]

This review explains various strategies for developing fluorescent probes to detect reactive carbonyl species (RCS). There are several mono and diacarbonyls among 30 varieties of reactive carbonyl species (RCSs) so far discovered, which play pivotal roles in pathological processes such as cancer, neurodegenerative diseases, cardiovascular disease, renal failure, and diabetes mellitus. These RCSs play essential roles in maintaining ion channel regulation, cellular signaling pathways, and metabolisms. Among RCSs, carbon monoxide (CO) is also utilized for its cardioprotective, anti‐inflammatory, and anti‐apoptotic effects. Fluorescence‐based non‐invasive optical tools have come out as one of the promising methods for analyzing the concentrations and co‐localizations of these small metabolites. There has been a tremendous eruption in developing fluorescent probes for selective detection of specific RCSs within cellular and aqueous environments due to their high sensitivity, high spatial and temporal resolution of fluorescence imaging. Fluorescence‐based sensing mechanisms such as intramolecular charge transfer (ICT), photoinduced electron transfer (PeT), excited‐state intramolecular proton transfer (ESIPT), and fluorescence resonance energy transfer (FRET) are described. In particular, probes for dicarbonyls such as methylglyoxal (MGO), malondialdehyde (MDA), along with monocarbonyls that include formaldehyde (FA), carbon monoxide (CO) and phosgene are discussed. One of the most exciting advances in this review is the summary of fluorescent probes of dicarbonyl compounds. [ABSTRACT FROM AUTHOR]