Ultra-bright intercellular lipids pseudo di-BODIPY probe with low molecular weight, high quantum yield and large two-photon action cross-sections

Small fluorescent molecules are widely used to label compartments in biological systems; nevertheless, small molecules with high quantum yield and large two-photon absorption (2PA) cross-section (δ) are rarely reported. Herein, two novel pseudo di-BODIPY derivatives have been synthesized and fully characterized. One of which (B1) showed high planarity of the conjugated system from crystal structural information and can generate superior 2PEF as well as prodigious Φδmax and high quantum value compared to another fluorescent molecules (B2) tested. It was found that compound B1 possessed prodigious two-photon (2P) action cross-section (Φδmax = 869.72 GM) in high polar solvent and higher quantum yield (Φ = 0.84), and can be capable of labeling lipid-rich endoplasmic reticulum (ER) in living cells in the range of 10−9 molar concentrations effectively. In addition, its recognition mechanism has been further confirmed with molecular modeling calculations and 1H NMR spectral methods The high affinity of B1 towards lipid rich organ was also explored over mouse and zebrafish tissue models. These pseudo di-BODIPY derivatives offer a new strategy to design molecules targetting universal membrane subcellular structures in vitro and in vivo.