The behavior and biotoxic effects of two silver nanoparticles(AgNPs)modified by polyethyleneimine(BPEI-AgNPs with positive charge)and citric acid(Citrate-AgNPs with negative charge)on Microcystis aeruginosa(M.aeruginosa)were investigated to evaluate the surface charge-dependent biotoxicity of AgNPs on M.aeruginosa.A more pronounced suppressive influence on the growth and photosynthetic activity of M.aeruginosa was observed with the Citrate-AgNPs than with the BPEI-AgNPs.The peak content of malondialdehyde(MDA)in 0.5mg/L Citrate-AgNP group(100.8nmol/mgprot)was higher than that in the same concentration BPEI-AgNP group(82.5nmol/mgprot).Compared with BPEI-AgNPs,Citrate-AgNPs demonstrated a significant up-and down-regulation on sod2 and GPX gene expression in M.aeruginosa,resulting in a higher peroxidation in algal cells.The extracellular polymer(EPS)secretion was observed with BPEI-AgNPs,amounting up to 32.21mg/gSS in 0.5mg/L BPEI-AgNP group(16d).Subsequently,the toxicity of BPEI-AgNPs was neutralized by the coating effect of EPS.The final intracellular Ag+released in the 0.5mg/L Citrate-AgNP group was 2.13 times that of the 0.5mg/L BPEI-AgNP group,and M.aeruginosa cells were seriously ruptured.Therefore,the surge of Ag+ions triggered severe cellular impairment to cells by Citrate-AgNPs.Furthermore,Citrate-AgNPs significantly inhibited the expression of photosynthesis(rbcS and rbcL)and energy metabolism(por)genes.
维普
万方数据