A difluoro boron (BF2) derived fluorescent probe for intracellular pH imaging

• 1、College of Chemistry, Chemical Engineering and Materials Science, Shandong Normal University, Jinan 250014, P. R. China

Abstract：In this paper, a difluoro boron (BF2) derived fluorescent probe DFBP for cellular pH was designed and synthesized. The probe was reversible and can be used as a naked eye chemosensor. DFBP is characterized of a molecular skeleton of donor-π-accepter, in which the BF2 moiety is electron deficient and the sulfydryl and amino from an o-amino thiophenol moiety are electron rich. This results in an electron push-pull construction of DFBP. The pKa of DFBP is calculated to be 5.60. The fluorescence intensity of DFBP increases with pH augment in the pH range of 4.0~8.0 and it turns red (pH<5.0) and yellow (pH>6.0) at different pH regions, indicating that DFBP is sensitive to minor pH variation under weakly acid conditions. Moreover, the Stokes shift of DFBP is as large as 143 nm, which contributes to the shielding of excitation light during detection. The probe showed good photostability and cell membrane permeability, as well as low cytotoxicity. The probe was successfully applied to the imaging of pH in human HG2 cells with good sensitivity and selectivity.

Keywords： analytical chemistry BF2 derivatives pH fluorescent probe intracellular imaging