title: Heterogeneous photocatalysis of moxifloxacin in water: chemical transformation and ecotoxicity.
abstract: This work provides new insights on the impact of TiO2/UV catalyzed chemical transformation of moxifloxacin on ecotoxicity effects towards the green alga Pseudokirchneriella subcapitata. The moxifloxacin median effect concentration (EC-50=0.78 [0.56, 1.09] mg L(-1)), determined in accordance to the OECD 72-h growth inhibition test guideline, was 7 times lower than that of the older and widely used fluoroquinolone ciprofloxacin (EC-50=5.57 [4.86, 6.38] mg L(-1)). Applying heterogeneous photocatalysis as an advanced oxidation technique to degrade moxifloxacin in aqueous solution decreased the average growth inhibition from 72% to 14% after 150 min of treatment. No significant carbon mineralization was observed and liquid chromatography mass spectrometry analysis revealed the formation of 13 degradation products for which a chemical structure could be proposed based on accurate mass determination. Combined chemical and ecotoxicological analysis showed that as long as moxifloxacin is present in the reaction solution, it is the main compound affecting algal growth inhibition. However, also the contribution of the degradation products to the observed ecotoxicity cannot be neglected. Photocatalytically induced modifications of moxifloxacin mainly occur at the diazobicyclo-substituent as ring opening, oxidation into carbonyl groups, and hydroxylation. This results into the formation of more hydrophilic compounds with a decreased biological activity compared with moxifloxacin. The change in lipophilicity, and possibly a modified acid-base speciation, most probably also affect the cell membrane permeation of the degradation products, which might be another factor explaining the observed lower residual ecotoxicity of the photocatalytically treated reaction solutions.
authors.affiliation: Research Group EnVOC, Department of Sustainable Organic Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium.
authors.forename: Xander
authors.initials: X
authors.lastname: Van Doorslaer
authors.affiliation: Research Group EnVOC, Department of Sustainable Organic Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium; Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Jozef Plateaustraat 22, B-9000 Ghent, Belgium.
authors.forename: Israel Deneke
authors.initials: ID
authors.lastname: Haylamicheal
authors.affiliation: Research Group EnVOC, Department of Sustainable Organic Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium.
authors.forename: Jo
authors.initials: J
authors.lastname: Dewulf
authors.affiliation: Research Group EnVOC, Department of Sustainable Organic Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium.
authors.forename: Herman
authors.initials: H
authors.lastname: Van Langenhove
authors.affiliation: Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Jozef Plateaustraat 22, B-9000 Ghent, Belgium.
authors.forename: Colin R
authors.initials: CR
authors.lastname: Janssen
authors.affiliation: Research Group EnVOC, Department of Sustainable Organic Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium. Electronic address: Kristof.Demeestere@UGent.be.
authors.forename: Kristof
authors.initials: K
authors.lastname: Demeestere
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000633:toxicity; D002384:Catalysis; D000460:Chlorophyta / Q000187:drug effects* / Q000254:growth & development; D002939:Ciprofloxacin / Q000737:chemistry / Q000633:toxicity; D054750:Ecotoxicology; D024841:Fluoroquinolones / Q000737:chemistry / Q000633:toxicity; D000077266:Moxifloxacin; D014025:Titanium / Q000737:chemistry* / Q000528:radiation effects; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000633:toxicity
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D002939:Ciprofloxacin; D014025:Titanium; D000077266:Moxifloxacin
keywords: Algal growth inhibition; Ecotoxicity; Fluoroquinolone antibiotics; Mass spectrometry; Pharmaceuticals; Titanium dioxide photocatalysis