Biological Toxicity Of Cellulose Nanocrystals Against E.coli

In recent years,as a new type of nano materials,cellulose nanocrystals have been applied widely in many fields of paper making,cosmetics,automobiles,electronic products and so on.Widely studied,producted and applied,cellulose nanocrystals can be released through various channels into air,soil and water.However,there are few reports whether cellulose nanocrystals are harmful to organisms.In order to investigate the effects of three kinds of cellulose nanocrystals on the toxicity of E.coli,bacterial growth,cell membrane permeability,antioxidant enzyme activity and cell morphology were studied.When the concentration was 250mg/L,carboxyl cotton cellulose nanocrystals(CCCNCs)and carboxyl wood pulp cellulose nanociystals(CWPCNCs)could not inhibit the growth of E.coli,while hydroxylated cotton cellulose nanocrystals(HCCNCs)can inhibit the growth of E.coli.When the concentration range is 750mg/L-2500mg/L,the inhibition rate increased with increased concentration.At the same concentration,the inhibition rates of different cellulose nanocrystals on E.coli were different.Among them,The inhibitory effect was HCCNCs>CCCNCs>CWPCNCs.Cotton cellulose nanocrystals can affect the growth cycle of E.coli.The shortened log phase and the prolonged stable phase of E.coli both resulted from the toxicity of cotton cellulose nanocrystals.In the concentration range of this experiment,CWPCNCs had no effect on the growth cycle of E.coli.Cellulose nanocrystals can cause lipid peroxidation of cell membrane,change the permeability of cell membrane,and damage cell membrane.Cellulose nanocrystals can make lactic acid dehydrogenase and protein outside the cell,affect the structure and function of the cell,and thus cause the toxicity of E.coli.Different cellulose nanocrystals have different effects on the cell membrane.At the same concentration,E.coli treated with HCCNCs,the content of MDA,the activity of extracellular lactate dehydrogenase of was highest,the content of intracellular protein was the lowest,and the damage of cell membrane was the most serious.However,in E.coli treated with CWPCNCs,the content of MDA,the activity of extracellular lactate dehydrogenase of was lowest,the content of intracellular protein was highest,and the damage of cell membrane was the least serious.Cellulose nanocrystals may affect the activity of superoxide dismutase and catalase activity and antioxidant capacity,resulting in toxic effects on E.coli.The activity of superoxide dismutase,catalase activity and antioxidant capacity showed a trend of increasing first and then decreasing.The effects of different cellulose nanocrystals on the activity of superoxide dismutase,catalase activity and antioxidant capacity of E.coli were different.At the same concentration,the activity of superoxide dismutase and the antioxidant capacity of three kinds of cellulose nanocrystals were CWPCNCs>CCCNCs>HCCNCs.By comparing inhibition rate,the damage degree of cell membrane,antioxidant enzymes and antioxidant capacity,we can draw the biological toxicity of three kinds of cellulose nanocrystals on E.coli was CWPCNCs<CCCNCs<HCCNCs.The biological toxicity of three kinds of cellulose nanocrystals to E.coli was affected by functional groups,structure,particle size and other factors.E.coli treated with cellulose nanocrystals,cell shape was changed,cell wall and cell membrane were damaged.The change of cell membrane permeability and the leakiness of intracellular material in E.coli were detected.Chromatin and ribosome disappeared.The E.coli appeared vacuolar degeneration.