Novel pyrimidine-based amphiphilic molecules: synthesis, spectroscopic properties and applications in two-photon fluorescence microscopic imaging

Abstract

This paper reports the synthesis, single- and two-photon spectroscopic properties of a series of pyrimidine-based monosubstituted D–π–A and disubstituted D–π–A–π–D type (Y shaped) molecules. Their potential applications in two-photon fluorescence microscopic imaging are also evaluated. The two-photon absorption cross-sections, measured by two-photon induced fluorescence method using a femtosecond Ti : sapphire laser as excitation source, were found to increase significantly (up to 12 times) when changing from monosubstituted molecules to their disubstituted counterparts. In addition, no significant difference in the single- and two-photon spectroscopic properties of these molecules can be observed when comparing the hydrophobic molecules (ethyl ester, 1a–4a) to the corresponding amphiphilic molecules (carboxylic acid salt, 1b–4b). However, single- and two-photon fluorescence microscopic imaging experiments revealed that the disubstituted amphiphilic molecules can efficiently stain the cytoplasmic region of Hep-G2 cells, while little or no dye uptake happened when incubating those cells with the hydrophobic molecules under the same experimental conditions.