The Toxic Effects Of Imidazolium-based Ionic Liquids And The Cytotoxic Mechanism On Chlorella Pyrenoidosa

Ionic liquids（ILs） are regarded as environmentally benign alternatives in organicsynthesis, catalysis, electrochemistry and the separation sciences, with their manyapplications, they will soon be produced on an industrial scale. However, it have beenconsidered to be ‘green’ solvents, only meaning that they do not evaporate and causeair pollution. Nevertheless, most ILs are water soluble and have poor biodegradability.The release of ILs into aquatic ecosystem may lead to water pollution and relatedpotential risks. Therefore, the product designs for this promising group of compoundsshould take account, not only the technological needs, but also the eco-toxicologicalhazards. Chlorella pyrenoidosa（C. pyrenoidosa）, the indicator organism, was used tostudy acute toxic effects of imidazolium-based ionic liquids by means of biologicalmonitoring method in the present study, and96h EC₅₀-value of16ILs was tested.Meanwhile, the growth rate, contents of protein and chlorophyll in algae weremonitored to determine toxicity from [OMIM][Br] exposure. And the toxicmechanisms of C. pyrenoidosa were analyzed by the activities of SOD enzymes,POD enzymes and the MDA contents of algae. In order to gain new insights into thecytotoxic mechanism of [OMIM][Br] detection of cell cycle, apoptosis and necrosisof Chlorella pyrenoidosa were performed by flow cytometry and laser scanningcytometry. Finally, we took calculated anion and cation physicochemical parametersof16ILs as independent variables and acute toxicity data as the dependent variables.The multiple linear regression （MLR） was employed to derive the quantitativestructure-activity relationship （QSAR） models. The QSAR models might offer atheoretic illustration for the various effects of ILs on algae and give a possibleevaluation of the effect to aquatic biota by ILs. The main results were summarized asfollows:The growth of algae was inhibited by the [OMIM][Br] in treated time-responseand dose-response manners. The protein contents, the chlorophylla contents, wererespectively decreased to96.59%and57.18%in C. pyrenoidosa cells treated by[OMIM][Br] for4d. The activities of SOD and POD obviously decreased, and the contents of MDA increased with increase in dose-concentrations. The results alsosuggested that primary mechanism of [OMIM][Br] on Chlorella pyrenoidosa cellsmight be related to the oxidation damage of lipid and other biological large moleculescaused by [OMIM][Br].The effects of [OMIM][Br] on the cell-cycle distribution of C. pyrenoidosa after96h exposure were studied by DNA content analysis with a flow cytometry. Thecell-cycle analysis results indicated that [OMIM][Br] lift the G0/G1block and induceda S and G2/M arrest, which can be observed after96h exposure time. This observationsuggested that [OMIM][Br] could cause a obvious DNA damage, which wasfrequently linked to S and G2/M arrest. In the experiment to observe cell morphology,Hoechst33342staining and confocal laser scanning microscopy were used to observethe effect of [OMIM][Br] on C. pyrenoidosa. We concluded that C. pyrenoidosa wererelatively sensitive to the cytotoxic effect of [OMIM][Br], which induced furtherapoptosis in C. pyrenoidosa with increasing dosage.As shown in the models, there were three main parameters of C_hain, G_rad, Den. Thetoxicity of ILs decreased with the increase of G_radof cation and Denof anion values ofILs in the model, in contrary, it increased with the increase of C_hain. The modelshowed the influence of C_hainand G_radon the toxicity mechanism of ILs on greenalgae seemed higher Den, in other words, the contributions of the substituents andcations on toxicity of ILs were more than anions. We also observed that ILs toxicitywas mainly dependent on their side chain length and G_radof cation.