A novel antiamoebic agent against Acanthamoeba sp. — A causative agent for eye keratitis infection

• The work features promising potential of [Tb(NO3)3(OH2)3].(18C6) complex as anti-amoebic agent.
• The IC50 values for Tb complex, Tb salt and 18C6 ligand were 7, 2.6 and 1.2 μg/mL, respectively.
• The mode of cell death in Acanthamoeba cells after treated with the Tb complex was apoptosis.
• The 18C6 molecule and Tb salt-treated Acanthamoeba exhibited with necrotic type.
• The percentage of DNA damage after treated showed that high percentage of score 1.

The terbium trinitrate.trihydrate.18-crown ether-6, Tb(NO3)3(OH2)3.(18C6) complex has been characterized by elemental analysis, photoluminescence and single X-ray diffraction. The IC50 values were determined based on MTT assay while light and fluorescence microscopy imaging were employed to evaluate the cellular morphological changes. Alkaline comet assay was performed to analyze the DNA damage. The photoluminescence spectrum of the Tb complex excited at 325 nm displayed seven luminescence peaks corresponding to the 5D4 → 7F0, 1, 2, 3, 4, 5, 6 transitions. The cytotoxicity and genotoxicity studies indicated that the Tb(NO3)3(OH2)3.(18C6) complex and its salt form as well as the 18C6 molecule have excellent anti-amoebic activity with very low IC50 values are 7, 2.6 and 1.2 μg/mL, respectively, with significant decrease (p < 0.05) in Acanthamoeba viability when the concentration was increased from 0 to 30 μg/mL. The mode of cell death in Acanthamoeba cells following treatment with the Tb complex was apoptosis. This is in contrast to the Tb(NO3)3.6H2O salt- and 18C6 molecule-treated Acanthamoeba, which exhibited necrotic type cells. The percentage of DNA damage following treatment with all the compounds at the IC25 values showed high percentage of type 1 with the % nuclei damage are 14.15 ± 2.4; 46.00 ± 4.2; 36.36 ± 2.4; 45.16 ± 0.6%, respectively for untreated, treated with Tb complex, Tb salt and 18C6 molecule. The work features promising potential of Tb(NO3)3(OH2)3.(18C6) complex as anti-amoebic agent, representing a therapeutic option for Acanthamoeba keratitis infection.

Overview of apoptosis in Acanthamoeba cell after exposure to the [Tb(NO3)3(OH2)3].(18C6) complex.Figure optionsDownload as PowerPoint slide