Covalent Organic Framework Functionalized with Fluorescein Isothiocyanate for the Selective and Sensitive Detection of Toxic Mycotoxin
Wubin Sui, Qianqian Jin, Tiesheng Shi, Yanxin Yu, Steven L. Suib
Abstract
Staining of foods by toxic mycotoxins is a general severe problem in the world. To explore simple methods for effective monitoring of mycotoxin-stained foods has extraordinary significance. Herein, we designed and prepared a covalent organic framework (COF)-derived fluorescent composite (DhBd-PT-COF-FITC) by anchoring a continually utilized fluorescent tag, fluorescein isothiocyanate (FITC), in the nanopore channel of a two-dimensional imine COF (DhBd-PT-COF) to detect a major existent mycotoxin of moldy sugar cane─3-nitropropionic acid (3-NPA), which is closely related to toxicosis events of humans. Tying FITC molecules into the pore channels of DhBd-PT-COF can not only enhance the fluorescence intensity of FITC by relying on the confinement effect of DhBd-PT-COF but also retain inherent pH-responsive characteristics. As a result, DhBd-PT-COF-FITC showed the selective and sensitive response to 3-NPA. The detection limit of DhBd-PT-COF-FITC toward 3-NPA is achieved to be ultralow as 12.5 nM. More attractively, facile recovery of DhBd-PT-COF-FITC can be obtained via simple alkaline treatment. The prepared sensor has also been used to detect 3-NPA in actual sugar cane samples with satisfying recovery. Our work not only exhibits fascinating performance of COF-derived fluorescent composites toward 3-NPA monitoring but also offers a prospective approach to develop various specific materials for other targets.