Fluorescent Probe for Monitoring Hydrogen Peroxide in COX-2-Positive Cancer Cells.

Hydrogen peroxide (H 2 O 2 ), an important marker for oxidative stress, plays a vital role in cellular biological functions. Overproduction of H 2 O 2 causes oxidative damage to cellular functions and promotes cancer and other neurodegenerative diseases. Also, cyclooxygenase-2 (COX-2) enzyme is known to be expressed in several cancer types and exerts multifaceted roles in carcinogenesis and resistance to cancer treatment. Hence, it is important to monitor the H 2 O 2 concentration changes in the COX-2-expressing cancer cells. Herein, we have developed a molecular fluorescent ratiometric H 2 O 2 -responsive probe ( NPDIN ) composed of indomethacin (COX-2 inhibitor) conjugated with 1,8-napthalimide boronate ester as fluorescent reporter through a chemical linker. The probe was capable of imaging the endogenous H 2 O 2 in COX-2 overexpressing cancer cell lines (A549, LoVo, HT29, and Caco-2). Further studies revealed the critical role of the indomethacin moiety in the cellular uptake behavior of NPDIN in COX-2-overexpressing cancer cells. Collectively, our results demonstrated NPDIN as a COX-2-positive cancer-targeting sensitive ratiometric fluorescent probe ( I 554 / I 398 ) for H 2 O 2 imaging and showed its promising biological applications in the future.