Rhodamine spirolactam based photoswitchable chemodosimeter for nitric oxide detection and their live cell imaging utility

Nitric oxide (NO), the free radical produced in plant and animal tissues, play a crucial role in numerous physiological processes including immune regulation, neurotransmission, cell death, vascular relaxation etc. NO is generated in the human body by Nitric oxide synthase (NOS) enzyme which has three isoforms and express in different cells, tissues, organelles etc. However, these free radicals (the reactive oxygen and nitrogen species) are able to attack all types of macromolecules in the human body and may destroy important macromolecules also. Moreover, they are the very reactive species and their excess production may lead to the synthesis of a variety of other reactive species and cause oxidative stress. Hence, it has become crucial to detect the presence of NO radical. With this in mind, we synthesized a rhodamine-spirolactam based chemodosimeter 1 for the sensitive and selective detection of NO radical with a detection limit of 1.4 nM. The NOs are detected via an intramolecular pathway leading to the spirolactam ring opening and quenching of PET process, resulting in a turn-on fluorescence. The absorption and the emission properties of the compound 1 was carried out in aqueous media to match the physiological conditions. Further, the bio-imaging experiment of the synthesized chemodosimeter was carried out, which shows bright red fluorescence, and was determined to be biocompatible and stable over a wide pH range with rapid detection ability.