Highly stable tetradentate phosphonate-based green fluorescent Cu-MOF for anticancer therapy and antibacterial activity

Abstract

Metal-organic frameworks (MOFs) have attracted huge attention in drug delivery, cellular imaging, and anticancer therapy due to their exceptionally high surface area, large internal void space, and the possibility of building the frameworks with fluorescent ligands. Here we demonstrate the synthesis of a highly stable tetradentate phosphonate ligand-based green fluorescent bioactive Cu-MOF (H8L-Cu-Crystal) in a water medium. This new MOF displayed monoclinic crystal structure [empirical formula: C13H13CuO7P2, H2O; space group C2/c; a = 27.9337 Å, b = 12.094 Å, c = 10.560 Å; α = γ = 90°, β = 99.607° unit cell volume = 3517.3 Å3; CCDC No. 1922965] having theoretical surface area of 164 m2/g with optimized energy 1475.9634 a.u. and HOMO-LUMO gap at 3.6 eV. Upon visible light irradiation, Cu-MOF generates highly reactive singlet oxygen (1O2) species, which exhibits a superior photocytotoxic effect against human lung epithelial cancer cells (A549) with respective IC50 value = 15.96 μg/mL and nominal dark toxicity of IC50 = 225 μg/mL. Notably, the tetradentate phosphonate moiety in the MOF crystal acts as a fluorophore, which is beneficial for cancer cell imaging. Due to active surface area, reactive oxygen species (ROS) generation, porosity, and Cu-ion metal center, the MOF exerts excellent antibacterial efficacy against both Gram-positive and Gram-negative microorganisms. Minimum inhibitory concentrations (MICs) are recorded at 300 μg/mL and 350 μg/mL for Escherichia coli (ATCC8739) and Staphylococcus aureus (ATCC25923), respectively. SEM images reveal dead and deformed bacterial cellular morphologies. What's more, the MOF crystal shows a good binding affinity coefficient value (KBSA = 4.8 × 104 M−1) with bovine serum albumin (BSA) protein interaction. Overall, these results suggest that this Cu-phosphonate MOF is a promising aspirant for anti-cancer photodynamic therapy and bacterial eradication.