Toxic effect and mechanism of silver nanoparticles / 中国药理学通报

Silver nanoparticles ( AgNP) , the metallic silver par-ticles with the diameter of 1 ~100 nm are now widely used in many fields. Many researches show that the smaller size of Ag-NP, the stronger toxicity it shows. Generally speaking, AgNP with 20 nm shows strongest toxicity. After entering the body, they are distributed in different organs in the body, and the dis-tribution in the kidney shows a certain gender difference. They also produce some toxic effects after entering body organs. AgNP often exhibit dose effect on the toxicity in vitro cells,while in vivo experiments, their toxic effects change with the different objects and ways of acting. In addition, AgNP can produce toxic effects on reproduction, and may cause parental reproductive activity to deteriorate, and pass the toxic effects to offspring through the placenta to exert a negative influence on the growth and develop-ment of the offspring. The toxicity mechanisms of AgNP are oxi-dative stress injury caused by producing free radicals;metabolic disorders caused by reducing of drug metabolic enzyme activity;and also related gene expression defects and certain molecules, such as transcription factor NF-E2-related factor 2(Nrf2) prote-ase caused by abnormal expression. In short, AgNP can be toxic to organisms, and we must evaluate their biological safety when we use it, to minimize or even avoid the danger it brings about.

Microalgae respond differently to nitrogen availability during culturing.

Variations in the exogenous nitrogen level are known to significantly affect the physiological status and metabolism of microalgae. However, responses of red, green and yellow-green algae to nitrogen (N) availability have not been compared yet. Porphyridium cruentum, Scenedesmus incrassatulus and Trachydiscus minutus were cultured in the absence of N in the medium and subsequent resupply of N to the starved cells. Culture growth and in-gel changes in isoenzyme pattern and activity of glutamate synthase, glutamate dehydrogenase, malate dehydrogenase, aspartate aminotransferase, superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase were studied. The results demonstrated that the algae responded to the fully N-depleted and N-replete culture conditions by speciesspecific metabolic enzyme changes, suggesting differential regulation of both enzyme activity and cellular metabolism. Substantial differences in the activities of the antioxidant enzymes between N-depleted and N-replete cells of each species as well as between the species were also found. In the present work, besides the more general responses, such as adjustment of growth and pigmentation, we report on the involvement of specific metabolic and antioxidant enzymes and their isoforms in the mechanisms operating during N starvation and recovery in P. cruentum, T. minutus and S. incrassatulus.