A new carbazole tricationic salt,4,4'-(1E,1'E)-2,2'-(9-(2-(1-(2-hydroxyethyl)pyridinium-4-yl)ethyl)-9H-carbazole-3,6-diyl) bis(ethane-2,1-diyl) bis(1-(2-hydroxyethyl)pyridinium) iodide (THEPC) was synthesized. Photophysical experiments have shown that THEPC has large two-photon excited fluorescence action cross-sections (33 GM in the presence of DNA),which ranks THEPC as a good biological fluorophore. The results from electronic absorption,circle dichroism and single-/two-photon fluorescence emission spectra suggest that THEPC can strongly bind to DNA,with an intrinsic binding constant of 5.79 × 106 L mol-1. THEPC has better photostability under one-or two-photon excitation conditions. Finally,the staining photos from two-photon fluorescence microscopy (TPM) show that THEPC can exclusively label the nucleus with high contrast and without image distortion. These remarkable properties and optimized imaging ability make THEPC an attractive DNA probe in TPM.
A new two-photon fluorescence DNA probe,BMVEC,with bigger σ×Φ(1437 GM) was synthesized.The absorption titration shows that there is an interaction between BMVEC and DNA because the probe can intercalate the grooves in the double helix of DNA,which enhances its two-photon fluorescent intensity.Meanwhile the double-staining results in cancer cells by means of TPM demonstrate the exclusive nucleic labeling ability of BMVEC,and the positions and amounts of nuclei labeled by BMVEC are wholly the identical as those by DAPI.Moreover,the incident power of BMVEC is lower than that of DAPI.The results indicate that BMVEC can act as the two-photon fluorescent probe of DNA.
