title: Insights into aquatic toxicities of the antibiotics oxytetracycline and ciprofloxacin in the presence of metal: complexation versus mixture.
abstract: Co-contamination of ligand-like antibiotics (e.g., tetracyclines and quinolones) and heavy metals prevails in the environment, and thus the complexation between them is involved in environmental risks of antibiotics. To understand toxicological significance of the complex, effects of metal coordination on antibiotics' toxicity were investigated. The complexation of two antibiotics, oxytetracycline and ciprofloxacin, with three heavy metals, copper, zinc, and cadmium, was verified by spectroscopic techniques. The antibiotics bound metals via multiple coordination sites and rendered a mixture of various complexation speciations. Toxicity analysis indicated that metal coordination did modify the toxicity of the antibiotics and that antibiotic, metal, and their complex acted primarily as concentration addition. Comparison of EC(50) values revealed that the complex commonly was highest toxic and predominately correlated in toxicity to the mixture. Finally, environmental scenario analysis demonstrated that ignoring complexation would improperly classify environmental risks of the antibiotics.
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xiyun
authors.initials: X
authors.lastname: Cai
authors.forename: Xianming
authors.initials: X
authors.lastname: Lang
authors.forename: Xianliang
authors.initials: X
authors.lastname: Qiao
authors.forename: Xuehua
authors.initials: X
authors.lastname: Li
authors.forename: Jingwen
authors.initials: J
authors.lastname: Chen
mesh_terms: D000900:Anti-Bacterial Agents; D002104:Cadmium / Q000737:chemistry / Q000633:toxicity; D002939:Ciprofloxacin / Q000737:chemistry / Q000633:toxicity*; D003300:Copper / Q000737:chemistry / Q000633:toxicity; D004784:Environmental Monitoring; D019216:Metals, Heavy / Q000737:chemistry / Q000633:toxicity*; D008956:Models, Chemical; D010118:Oxytetracycline / Q000737:chemistry / Q000633:toxicity*; D010782:Photolysis; D018675:Toxicity Tests; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000633:toxicity*; D015032:Zinc / Q000737:chemistry / Q000633:toxicity
chemical_list: D000900:Anti-Bacterial Agents; D019216:Metals, Heavy; D014874:Water Pollutants, Chemical; D002104:Cadmium; D002939:Ciprofloxacin; D003300:Copper; D015032:Zinc; D010118:Oxytetracycline