School of Environmental Science and Engineering, Shaanxi University of Science & Technology, Xi'an 710021, China; Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, United Kingdom.
School of Environmental Science and Engineering, Shaanxi University of Science & Technology, Xi'an 710021, China.
J Environ Sci (China). 2025 Apr;150:149-158. doi: 10.1016/j.jes.2024.03.019. Epub 2024 Mar 20.
Acid-base dissociable antibiotic-metal complexes are known to be emerging contaminants in the aquatic environments. However, little information is available on the photochemical properties and toxicity of these complex forms. This study investigated the spectral properties of three fluoroquinolones (FQs) with and without metal ions Fe(III), Cu(II), and Al(III) in solutions under different pH conditions, as well as evaluated the changes in toxicity due to the complex with these metal ions using luminescent bacteria (vibrio fischeri). FQs showed a higher tendency to coordinate metal ions under alkaline conditions compared to neutral and acidic conditions, and the formation of complexes weakened the ultraviolet-absorbing ability of FQs. At pH = 7.0, Cu(II) quenched the fluorescence intensity of FQs. Moreover, their Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy were explored, revealing that the coordination sites of Cu(II) in three FQs were situated in a bidentate manner through the oxygen atom of the deprotonated carboxyl group and cyclic carbonyl oxygen atom. This conclusion was further verified by the theory of molecular surface electrostatic potential. In addition, except for complexes of ciprofloxacin-metals, enhanced toxicity of FQs upon coordination with Fe(III) was observed, while reduced toxicity was found for coordination with Cu(II) and Al(III). These results are important for accurately evaluating the photochemical behavior and risk of these antibiotics in aquatic environments contaminated with metal ions.
酸基可解离抗生素-金属配合物是已知的水生环境中的新兴污染物。然而，关于这些配合物形式的光化学性质和毒性的信息很少。本研究调查了三种氟喹诺酮（FQs）在不同 pH 值条件下与金属离子 Fe(III)、Cu(II) 和 Al(III) 形成配合物时的光谱性质，并使用发光细菌（发光弧菌）评估了由于与这些金属离子形成配合物而导致的毒性变化。与中性和酸性条件相比，FQs 在碱性条件下更倾向于与金属离子配位，而配合物的形成削弱了 FQs 的紫外吸收能力。在 pH = 7.0 时，Cu(II) 猝灭了 FQs 的荧光强度。此外，还对其进行了傅里叶变换红外光谱和 X 射线光电子能谱分析，揭示了 Cu(II) 在三种 FQs 中的配位位点通过去质子化羧基和环状羰基氧原子以双齿方式配位。这一结论通过分子表面静电势理论得到了进一步验证。此外，除了环丙沙星-金属配合物外，FQs 与 Fe(III) 配位时的毒性增强，而与 Cu(II) 和 Al(III) 配位时的毒性降低。这些结果对于准确评估这些抗生素在受金属离子污染的水生环境中的光化学行为和风险非常重要。
