A new time-gated fluorescence-based imaging method to analyse microRNAs directly from human serum using dynamic chemistry labelling.

We report a platform combining multicomponent reaction synthesis and automated cell-based screening to develop biocompatible NIR-BODIPY fluorophores. From a library of over 60 fluorophores, we optimised compound NIRBD-62c as a multimodal probe with suitable properties for STED super-resolution and fluorescence lifetime imaging. Furthermore, we employed NIRBD-62c for imaging trafficking inside cells and to examine how pharmacological inhibitors can alter the vesicular traffic between intracellular compartments and the plasma membrane.

Unraveling cellular physiological processes via luminescent probes that target specific cellular microenvironments is quite challenging due to the uneven distribution of probes. Herein, we designed a new dynamic excimer (DYNEX) imaging method that involves the sensitive detection of nanosecond-scale dynamic molecular contacts of a fluorescent acridone derivative and reveals the cell microenvironment polarity. Using our method, we specifically tracked cell lipid droplets in fibroblast colon carcinoma cells. These organelles play a central role in metabolic pathways, acting as energy reservoirs in regulatory processes. DYNEX imaging provides the inner polarity of cell lipid droplets, which can be related to lipid contents and metabolic dysfunctions. This new methodology will inspire development of novel multidimensional fluorescent sensors that are able to provide target-specific and orthogonal information at the nanosecond scale.

Herein, the use of solvatochromic fluorescent probes for detecting polarity in cellular microenvironments, a complex physicochemical parameter that influences various biological processes, is reviewed. The nature of polarity itself is related to the physicochemical properties of the environment that affect the spectroscopic properties of luminophores. The mechanisms of solute–solvent interactions and photophysical processes, such as intramolecular charge transfer and photoinduced electron transfer, which are fundamental to understanding the response of the probes to polarity changes are discussed. In the intracellular context, solvatochromic probes have been used to determine polarity in different organelles and subcellular structures. The review puts emphasis on the various targeting strategies and the most commonly utilized photophysical parameters for estimating polarity are focused here. A special attention is paid to those approaches capable of providing absolute quantification of intracellular polarity, for instance, through ratiometric measurements or the use of fluorescence lifetime imaging to improve the accuracy of measurements. Reliable intracellular polarity measurements may provide invaluable information to understand physiological and pathological processes, including neurodegenerative diseases or cancer.