Photo-induced Toxicity Of Quinolone Antibiotics And Manufactured Nanomaterials To Daphnia Magna

Unveiling eco-toxicological effects of pollutants is of great importance to ecological risk assessment.Toxic effects of some pollutants to ogranisms can be enhanced via photosensitization or photomodification when they are exposed to sunlight.These phenomena are considered as photo-induced toxicity.Previous studies on the photo-induced toxicity of polycyclic aromatic hydrocarbons,substituted anthraquinones and organic pesticides have revealed that photogeneration of singlet oxygen(1O2)in organisms is a molecular initiation event of photoinduced toxicity.Antibiotics and manufactured nanomaterials,as potential emerging pollutants,are attracting worldwide attentions in recent years.However,studies on their photo-induced toxicity to aquatic organisms and the mechanisms underlying the photo-induced toxicity remain unrevealed.In the present study,the photo-induced toxicity of quinolone antibiotics,graphenes and metal oxide nanoparticles to a model aquatic crustacean Daphnia magna was investigated.The main research contents and results are as follows:(1)The acute and chronic photo-induced toxicity of lomefloxacin and its mechanism of phototoxicity on Daphnia magna were revealed.Under simulated sunlight radiation(SSR)or white fluorescence light radiation(WFLR),the effects of lomefloxacin on survival,reproduction and growth of Daphnia magna were investigated.Furthermore,reactive oxygen species(ROS)concentration,lipid peroxidation and antioxidant enzyme activities in Daphnia magna were measured using fluorescence probe method.Results indicate that SSR can enhance the acute toxicity of lomefloxacin to Daphnia magna compared with WFLR.Under SSR,lomefloxacin significantly enhanced the levels of ROS and lipid peroxidation,and inhibited the activities of superoxide dismutase and catalase.UV radiation in the SSR can significantly delay the time of the first spawning,decrease the accumulated numbers of neonates and inhibit the growth of Daphnia magna,whereas lomefloxacin can diminish the damage of the UV radiation through light shielding.(2)Molecular fluorescence probe combined with time-gated luminescence imaging technology was developed to detect the distribution of photogenerated 1O2 in living Daphnia magna.The ability of photogenerating 1O2 for carboxylated graphene and aminated graphene in the aqueous medium was verified using electron paramagnetic resonance with 2,2,6,6-tetramethylpiperidine as 1O2 probe.Using a luminescent probe i.e.,[4'-(9-anthryl)-2,2':6',2"-terpyridine-6,6"-diyl]bis(methylenenitrilo)tetrakis(acetate)-Eu3+(ATTA-Eu3+),the temporal variation of 1O2 photogenerated by lomefloxacin,ciprofloxacin,carboxylated graphene and aminated graphene in aqueous media were detected.Furthermore,the levels and distribution of photogenerated 1O2 in Daphnia magna were quantified and visualized using the ATTA-Eu3+probe combined with time-gated luminescence imaging(ATLI)technology.After one hour exposure of SSR,the concentrations of 1O2 photogenerated by lomefloxacin,ciprofloxacin,aminated graphene and carboxylated graphene in Daphnia magna were estimated to be in the range of 0.5?4.8 ?M,0.7?4.0 ?M,0.9?3.8 ?M and 0.7?2.0 ?M,respectively.The luminescence signals of 1O2 mainly accumulated in the hindgut of Daphnia magna,and the mean luminescence intensity of 1O2 signals in gut,thoracic legs and post-abdominal claw of Daphnia magna enhanced with increasing irradiation time.(3)1O2 photogenerated by metal oxide nanoparticles in the aqueous medium was investigated using ATTA-Eu3+ probe.The levels and distribution of 1O2 photogenerated by metal oxide nanoparticles in Daphnia magna were quantified and visualized using the ATLI technology.With same particle concentrations,the level of the 1O2 photogenerated by metal oxide nanoparticles in the aqueous medium decreased in the order:nZnO>nSm2O3>nIn2O3>nNiO>nNd2O3>nSnO2>nSiO2>nTiO2>nPr6O11>nAl2O3>nCo3O4>nCr2O3>nGd2O3>nFe2O3>nCeO2>nHo2O3.The signals of 1O2 photogenerated by nCeO2,nNd2O3,nNiO,nPr6O11,nSiO2,nSm2O3 and nZnO in Daphnia magna mainly concentrated in gut regions.The average concentrations of 1O2 photogenerated by nZnO in Daphnia magna were the highest among these metal oxide nanoparticles,which were estimated in the range of 0.3?4.3 ?M after one hour exposure of SSR.The 1O2 photogenerated by nZnO mainly concentrated in the hindgut of Daphnia magna and the intensity of 1O2 signals in the gut,thoracic legs and post-abdominal claw of Daphnia magna increased with extended irradiation time.In summary,this study reveals the acute and chronic photo-induced toxicity of lomefloxacin and its mechanisms underlying phototoxicity towards Daphnia magna.Using ATLI technology,the levels and distribution of 1O2 photogenerated by quinolone antibiotics,functionalized graphene and metal oxide nanoparticles in a living organism Daphnia magna have been determined.The results are significant for assessing the ecological risk of quinolone antibiotics and manufactured nanomaterials.