title: Trojan-horse mechanism in the cellular uptake of silver nanoparticles verified by direct intra- and extracellular silver speciation analysis.
abstract: The so-called "Trojan-horse" mechanism, in which nanoparticles are internalized within cells and then release high levels of toxic ions, has been proposed as a behavior in the cellular uptake of Ag nanoparticles (AgNPs). While several reports claim to have proved this mechanism by measuring AgNPs and Ag ions (I) in cells, it cannot be fully proven without examining those two components in both intra- and extracellular media. In our study, we found that even though cells take up AgNPs similarly to (microglia (BV-2)) or more rapidly than (astrocyte (ALT)) Ag (I), the ratio of AgNPs to total Ag (AgNPs+Ag (I)) in both cells was lower than that in outside media. It could be explained that H2O2, a major intracellular reactive oxygen species (ROS), reacts with AgNPs to form more Ag (I). Moreover, the major speciation of Ag (I) in cells was Ag(cysteine) and Ag(cysteine)2, indicating the possible binding of monomer cysteine or vital thiol proteins/peptides to Ag ions. Evidence we found indicates that the Trojan-horse mechanism really exists.
authors.affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu, Taiwan 30013.
authors.forename: I-Lun
authors.initials: IL
authors.lastname: Hsiao
authors.affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu, Taiwan 30013.
authors.forename: Yi-Kong
authors.initials: YK
authors.lastname: Hsieh
authors.affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu, Taiwan 30013.
authors.forename: Chu-Fang
authors.initials: CF
authors.lastname: Wang
authors.affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu, Taiwan 30013.
authors.forename: I-Chieh
authors.initials: IC
authors.lastname: Chen
authors.affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu, Taiwan 30013.
authors.forename: Yuh-Jeen
authors.initials: YJ
authors.lastname: Huang
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000737:chemistry; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D003470:Culture Media; D004705:Endocytosis / Q000187:drug effects; D005110:Extracellular Space / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D042541:Intracellular Space / Q000737:chemistry*; D007477:Ions; D008070:Lipopolysaccharides / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D051379:Mice; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism; D012834:Silver / Q000378:metabolism* / Q000633:toxicity
chemical_list: D003470:Culture Media; D007477:Ions; D008070:Lipopolysaccharides; D017382:Reactive Oxygen Species; D012834:Silver; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid