A Highly Sensitive Ratiometric Fluorescence Probe for Zn2+ Detection in Living Cells

The emission spectra of 2-PBI (2-(2'-pyridyl) benzimidazole) show a red shift at a specific wavelength in both aqueous and acetonitrile solutions. However, 2-PBI cannot be used as ratiometric fluorescent probe for Zn2+ because of its low binding ability and variable coordination ratio to Zn2+. In this study, in order to add coordination atoms and promote the ICT effect of the probe by introducing N,N-dimethyl group at its 5-position of 2-PBI, design and synthesize a new ratiometric Zn2+ fluorescent probe DBITA. The results show that, besides large Stokes shift of 172 nm, DBITA exhibits the specific Zn2+-induced emission red-shift from 534 nm to 609 nm. DBITA combines with Zn2+ as 1:1 binding ratio. Moreover, DBITA displays the extremely high affinity toward Zn2+ of 0.16 pmol . In HeLa cells, DBITA can be used to quantitatively detect intracellular Zn2+.