Novel fluorescent mono-Br-BODIPYs as potential theranostic agents and their nanoscale zeolitic imidazolate framework delivery systems

Abstract

The development of bifunctional theranostic agents based on biocompatible organic luminophores is a priority for the scientific community. We have obtained new mono-Br-substituted BODIPYs (Br-BDPs) with an optimal combination of fluorescence quantum yield (0.48 ÷ 0.63) and singlet oxygen generation quantum yield (0.32 ÷ 0.51) in different nature solvents. A detailed analysis of the structure of α-Br-BDP, β-Br-BDP, and β'-Br-BDP dyes, their spectral properties depending on the position of the bromine atom attachment and the solvent nature, as well as the aggregation behavior of the dyes in water/THF solvent mixture are presented. We also selected the conditions for the host–guest encapsulation of β-Br-BDP in zeolitic imidazolate framework (ZIF-8). The resulting nanoscale β-Br-BDP@ZIF-8 delivery systems exhibit intense fluorescence. The release of the β-Br-BDP luminophore from the β-Br-BDP@ZIF-8 systems into model lipid structures in phosphate buffer pH 5.0 – 6.0 occurs on average after 24 – 50 h. These results form the basis for the further development of new theranostic drugs based on Br-BDP luminophores for fluorescence diagnostics (FD) and photodynamic therapy (PDT).