A highly sensitive and colorimetric fluorescent probe for visualizing hydroxylamine in immune cells

Hydroxylamine (HA) is vital industrial raw material and pharmaceutical intermediate. In addition, HA is an important cellular metabolite, which is intermediate in the formation of nitric oxide and nitroxide. However, excessive amounts of HA are toxic to both animals and plants. Conventional methods for the detection of HA are cumbersome and complicated. The detection of HA with fluorescent probes is convenient and sensitive. There are few probes available for the detection of hydroxylamine. Therefore, a fluorescent probe for the sensitive and selective detection of HA was developed in this work.

A coumarin derivative SWJT-22 was synthesized as a colorimetric fluorescent probe to detect hydroxylamine (HA), with high sensitivity and selectivity. The detection limit of the probe to HA was 0.15 μM, which was lower than most probes of HA. Upon the addition of HA to aqueous solution containing SWJT-22, the color of the solution changed from orange to yellow, and the fluorescence color also changed from orange to green. The reaction mechanism of SWJT-22 to HA was confirmed by ¹H NMR titrations, mass spectrometry and round bottom flask experiments. Moreover, SWJT-22 had been fabricated into portable test strips for the detection of HA. SWJT-22 had been successfully used in cellular imaging and could detect both endogenous and exogenous HA in HeLa cells and RAW 264.7 cells.

Due to the physiological role of hydroxylamine in organisms, it is crucial to detect hydroxylamine selectively and sensitively. This work provided a convenient tool for the detection of hydroxylamine, not only to detect endogenous and exogenous HA in cells, but also made into portable test strips. The HA fluorescent probe SWJT-22 is expected to promote the study of HA in physiological processes.