Post-synthetic modification strategy for constructing dual-emission fluorescent sensor toward visual detection and...

As the biomarker of oxidative stress (OS), 3-nitrotyrosine (3-NT) levels in serum is closely associated with disease progression, and the development of rapid and reliable fluorescent sensor is therefor urgent. Metal-organic frameworks (MOFs) are attractive for their diversified, easily designed and functionalized structures, yet most MOF-based 3-NT fluorescent sensors are single-signal depended, resulting in inadequate anti-interference capability and insufficient reliability. Developing MOF-based dual-emission fluorescent sensors for precise detection of serum 3-NT levels thus remains a highly challenging and promising objective.

In this work, the post-synthetic cation exchange strategy was employed to specifically anchoring Eu³⁺ ions with the potential coordination sites of the designed 3D anionic framework, thereby constructing a dual-emission Eu³⁺@ZnMOF emitting red fluorescence. With two independent monitoring signals at 452 nm and 620 nm, Eu³⁺@ZnMOF exhibited considerable potential as a dual-emission fluorescent sensor for efficient and reliable detection of 3-NT in serum, featuring a rapid response time of 15 s, recycling performance of at least 5 cycles, and a low detection limit of 3.16 ng mL^-1 at 452 nm and 4.69 ng mL^-1 at 620 nm. Furthermore, the underlying sensing mechanism was elucidated through theoretical calculations, dynamic quenching analysis, and spectral overlapping investigations. Moreover, a logic gate system was developed based on its concentration controlled colorimetric response, enabling an intelligent sensing platform for accurate and reliable quantification of serum 3-NT levels.

This work not only developed an innovative and promising strategy to design MOF-based dual-emission fluorescent sensor toward 3-NT biomarker, but also established a promising platform for the intelligent diagnostic of serum 3-NT levels through colorimetric response. It also offers useful guidance for the design of MOF-based dual-emission fluorescent sensors targeting bioactive small molecules in complex environments.