A red-emitting fluorescent probe imaging release of calcium ions from lysosome induced by chloroquine based on a photochromic crowned spirobenzopyran

Abstract

Abstract Calcium ions play an important role in intracellular signaling, metabolism and a wide range of cellular processes. An abnormal calcium concentration may cause many adverse symptoms, such as physiological responses in obesity, immune responses and pathological responses in Alzheimer s disease. Therefore, the development of specific fluorescent probes for monitor Ca2+ in living organism is of great significance. Herein, a red-emitting probe SP-CE was successfully designed and synthesized based on spiropyran derivatives as the fluorophore and aza-15-crown-5 as the sensing moiety for the recognition of calcium ions. Under the ultraviolet light irradiation, SP-CE was transformed to merocyanine (MC) form, which releasing negative oxygen ions, thereby achieving the recognition of calcium ions with the collaboration of crown ethers. According to the literature, chloroquine (CQ) could stimulate the up-regulation of pH in the sub-organelle lysosome in cells, resulting in changes of the calcium ions abundance in the cytoplasm. Interestingly, SP-CE could be used to visualize the occurrence of the above mentioned physiological processes in living cells. In addition, the probe SP-CE has been successfully employed for labeling calcium ions in living zebrafish model.