Polyoxometalate cobalt–gatifloxacin complex with DNA binding and antibacterial activity

Abstract

An unusual inorganic–organic antibacterial complex based on polyoxometalates (POMs) and the cobalt–gatifloxacin (GT), [Co^II(C₁₉FH₂₂N₃O₄)₃][C₁₉FH₂₃N₃O₄][HSiW₁₂O₄₀]·23H₂O (1), has been synthesized. Single-crystal structural analysis shows that 1 represents for the first time an unusual tripodal coordination style with three GT molecules coordinating to cobalt(II) by six carboxylate and hydroxyl oxygens. The biological activity of 1 has been evaluated by investigating its binding ability to calf thymus DNA (CT-DNA). UV spectrum study of 1 has shown that it can bind to CT-DNA by intercalation. The DNA-binding constant K_b was 9.6 × 10⁴ M L⁻¹, higher than that of pure GT, 3.8 × 10⁴M L⁻¹. Furthermore, the antibacterial activities of 1 were tested against Staphylococcus aureus and Escherichia coli, respectively, and have shown slightly lower antibacterial activity than that of free GT at the same mass concentration. If the GT component in the complexes was controlled at the same molar concentration, 1 generates the biggest antibacterial area during the Kirby–Bauer disc diffusion detection. This result indicates that the integration of heteropolyanions and GT exhibits synergistic effects on the antibacterial activity, which paves a new way to design low-cost antibacterial compound by the introduction of POMs.

Graphical Abstract

Keywords:

• Polyoxometalate
• Gatifloxacin
• Fluorescence quenching
• DNA binding
• Antibacterial

Additional information

Funding

Funding. We acknowledge the National Natural Science Foundation of China [grant number 21271034], [grant number 21103035], Heilongjiang Province Natural Science Funds for Distinguished Young Scholar [grant number JC201220], Natural Science Foundation of Heilongjiang Province [grant number QC2011C038], Heilongjiang Universities’ Science and Technology Innovation Team program [grant number 2012TD010], and financial supports from the Fundamental Research Funds for the Central Universities [grant number HIT. NSRIF. 2011025], SKLUWRE of HIT (QA201022), China Postdoctoral Science Foundation [grant number 20100471060], [grant number 2012T50313].