Spatiotemporal Mapping of the Evolution of Silver Nanoparticles in Living Cells
Neng Yan, Yan Wang, Tin Yan Wong, Zhiwei Wu, Xiuxiu Wang, Minwei Xie, Alessandro Parodi, Wen‐Xiong Wang, Jianbo Shi
Abstract
Bioaccumulated silver nanoparticles (AgNPs) can undergo transformation and release toxic Ag +, which can be further reduced and form secondary AgNPs (Ag 0 NPs). However, the intricate interconversions among AgNPs, Ag +, and Ag 0 NPs remain speculative. Herein, we developed a bioimaging method by coupling the aggregation-induced emission method with the label-free confocal scattering and hyperspectral imaging techniques to quantitatively visualize the biodistribution and biotransformation of AgNPs, Ag 0 NPs, and Ag + in living cells. We demonstrated that AgNPs were first dissolved in the medium, and the released Ag + was converted into Ag 0 NPs with the presence of algal extracellular polymeric substances and light. Under these conditions, AgNPs alone accounted for 12.4% of the total AgNP toxicity, a percentage comparable to that of Ag 0 NPs (15.6%). However, Ag + remained the primary contributor to overall AgNP toxicity. Additionally, we found that about 9.00% of the accumulated AgNPs within the algal cells were transformed after 24 h exposure. Of these transformed AgNPs, 4.70% remained as Ag + forms (located in the apical region, nucleus, and pyrenoid), while 4.30% persisted as Ag 0 NP forms (located in the cytosol) that were only detectable after a 4 h exposure. We further showed that AgNP exposure upregulated algal glutathione production with a 38.3-fold increase in glutathione reductase activity, which potentially resulted in Ag 0 NP formation at the active site. Overall, this study differentiated the toxicity of AgNPs, Ag +, and Ag 0 NPs and directly visualized the ongoing transformation and translocation of AgNPs, Ag +, and Ag 0 NPs within living cells, which are critical in unveiling the toxicity mechanisms of AgNPs.