Aminoglycosides are a class of antibiotics, widely used in both human therapy and veterinary medicines. This study focuses on the photosensitized degradation of aminoglycosides in natural organic matter (NOM) solutions under simulated solar irradiation. It appears that the direct reaction of 3NOM* with aminoglycosides is minor. The contributions of reactive oxygen species (ROS) in the bulk solutions, are also unimportant through calculating with steady state concentrations and bimolecular reaction rate constants based on homogeneous reaction model. The photolysis nearly ceased by adding of sufficient isopropamide, which indicated that micro-heterogeneous reaction occurs and hydroxyl radical on the surface of NOM plays a key role in the photosensitized degradation of aminoglycosides. The hydroxyl radical reaction rate constants of aminoglycosides were measured using pulse electron radiation. In addition, molecular weight cut off filter (MWCO) has been employed to explore the adsorption of aminoglycosides on NOM, and it follows Langmuir isotherms. The positive correlation between the pseudo first-order degradation rates and the adsorption rates were observed among various aminoglycosides, which further proved that the micro-heterogeneous reaction mechanism is a universal photolysis regulation for aminoglycoside antibiotics. Based on the adsorption/photodegradation model, the steady state concentration of hydroxyl radical on the surface of NOM could be calculated at the magnitude of 10-14 M, which is 3 orders higher than the one in the bulky solution. Subsequently, the bioluminescence of the marine bacterium Vibrio fischeri was used to assay the toxicity, and the results indicated that the photodegradation products did not exhibit measurable cytotoxicity. This fundamental information is important in the assessment of the fate and transport of aminoglycosides in surface waters.

Photochemical degradation of aminoglycoside antibiotics in simulated natural waters

251st National Meeting (2016)

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