Modifying the Surface of Silica Nanoparticles with Amino or Carboxyl Groups Decreases Their Cytotoxicity to Parenchymal Hepatocytes

: We previously reported that unmodified silica nanoparticles with diameters of 70 nm (nSP70) induced liver damage in mice, whereas nSP70 modified with carboxyl or amino groups did not. In addition, we have found that both unmodified and modified nSP70s localize in both Kupffer cells and parenchymal hepatocytes. We therefore evaluated the contributions of nSP70 uptake by these cell populations to liver damage. To this end, we pretreated mice with gadolinium (III) chloride hydrate (GdCl3) to prevent nSP70 uptake by Kupffer cells, subsequently injected the mice with either type of nSP70, and then assessed plasma levels of alanine aminotransferase (ALT). In mice given GdCl3, unmodified nSP70 increased ALT levels. From these data, we hypothesized that in GdCl3-treated mice, the unmodified nSP70 that was prevented from entering Kupffer cells was shunted to parenchymal hepatocytes, where it induced cytotoxicity and increased liver damage. In contrast, GdCl3 pretreatment had no effect on ALT levels in mice injected with surface-modified nSP70s, suggesting that modified nSP70s spared parenchymal hepatocytes and thus induced negligible liver damage. In cytotoxicity analyses, the viability of a parenchymal hepatocyte line was greater when exposed to surface-modified nSP70s than to unmodified nSP70s. These findings imply that the decreased liver damage associated with surface-modified compared with unmodified nSP70 is attributable to decreased cytotoxicity to parenchymal hepatocytes.