Recent progress in lysosome-targetable fluorescent BODIPY probes for bioimaging applications

Lysosomes as the acidic cellular organelle play a major role in degrading obsolete or potentially harmful macromolecules by hydrolysis. It houses numerous hydrolytic enzymes including peptidases, proteases, glycosidases, and nucleases. In addition to the intracellular digestive functions, lysosomes are also involved in immunogenic defense mechanism, apoptosis, membrane repair, cholesterol homeostasis etc. Dysfunction in lysosomes could result in cancer, neurodegenerative disorders, cardiovascular diseases and lysosome storage disorders with further implications in human health. Therefore, understanding the biochemical processes in lysosome and monitoring the membrane traffic to and from lysosome had become important. Fluorescent probes have been particularly useful for this purpose due to their non-invasiveness and high resolution. Several commercial fluorophores that preferentially localize in lysosome exploit its low pH (3.8–5.5). In the last two decades BODIPY based fluorescent probes, owing to their excellent absorption-emission properties and facile synthetic modification have been developed as tools to target lysosome or lysosomal analytes. In this review, the recent development of lysosome-targetable BODIPY-functionalized fluorescent probes will be highlighted and the design strategy will be analyzed.