Development of a molecular K.sup.+ probe for colorimetric/fluorescent/photoacoustic detection of K.sup.

• Published in: Analytical and bioanalytical chemistry 2020-10, Vol.412 (25), p.6947
• Main Authors: Ning, Juewei, Lin, Xiangwei, Su, Fengyu, Sun, Aihui, Liu, Hongtian, Luo, Jingdong, Wang, Lidai
• Format: Article
• Language: English
• Subjects: Fluorescence; Nitriles
• ISSN: 1618-2642
• DOI: 10.1007/s00216-020-02826-y

The potassium ion (K.sup.+) plays significant roles in many biological processes. To date, great efforts have been devoted to the development of K.sup.+ sensors for colorimetric, fluorescent, and photoacoustic detection of K.sup.+ separately. However, the development of molecular K.sup.+ probes for colorimetric detection of urinary K.sup.+, monitoring K.sup.+ fluxes in living cells by fluorescence imaging, and photoacoustic imaging of K.sup.+ dynamics in deep tissues still remains an open challenge. Herein, we report the first molecular K.sup.+ probe (NK2) for colorimetric, fluorescent, and photoacoustic detection of K.sup.+. NK2 is composed of 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) as the chromophore and phenylazacrown-6-lariat ether (ACLE) as the K.sup.+ recognition unit. Predominate features of NK2 include a short synthetic procedure, high K.sup.+ selectivity, large detection range (5-200 mM), and triple-channel detection manner. NK2 shows good response to K.sup.+ with obvious color changes, fluorescence enhancements (about threefold), and photoacoustic intensity changes. The existence of other metal ions (including Na.sup.+, Mg.sup.2+, Ca.sup.2+, Fe.sup.2+) and pH changes (6.5-9.0) have no obvious influence on K.sup.+ sensing of NK2. Portable test strips stained by NK2 can be used to qualitatively detect urinary K.sup.+ by color changes for self-diagnosis of diseases induced by high levels of K.sup.+. NK2 can be utilized to monitor K.sup.+ fluxes in living cells by fluorescent imaging. We also find its excellent performance in photoacoustic imaging of different K.sup.+ concentrations in the mouse ear. NK2 is the first molecular K.sup.+ probe for colorimetric, fluorescent, and photoacoustic detection of K.sup.+ in urine, in living cells, and in the mouse ear. The development of NK2 will broaden K.sup.+ probes' design and extend their applications to different fields.