Two novel two-photon fluorescent probes for low pH values and cell imaging based on spirobifluorene motif

摘要

Two novel spirobifluorene derivatives containing arylamine groups, SPF-M and SPF-P were synthesized. As the protonation of the aromatic amine N atoms, SPF-M and SPF-P showed significant pH-dependent spectral properties. The pK_a, values are below 3.0 and they are suitable for extremely acid conditions. Under the UV light, SPF-M permit detection with the "naked eye" which makes it particularly attractive. To our knowledge, SPF-M and SPF-P represent the first examples that two-photon pH sensors were used to measure the extremely acidic pH value. When the pH is higher than 4.0, SPF-M and SPF-P exhibited strong one- and two-photon excited fluorescence and showed no dramatic spectral changes toward pH variations. Thus, the feasibility of SPF-M and SPF-P as multiphoton luminescence bioprobe under physiological conditions is demonstrated by two-photon scanning microscopy imaging experiments on 293T cells.