Nanomaterials are used frequently in microelectronics, cosmetics and sunscreen, and research for the development of nanomaterial-based drug delivery systems is promising. We previously reported that the intravenous administration of unmodified silica particles with a diameter of 70 nm (SP70) caused hepatic injury. Here, we examined the acute hepatic toxicity of SP70 modified with amino group (SP70-N) or carboxyl group (SP70-C). When administered intravenously into mice, SP70-N and SP70-C dose-dependently increased the serum level of alanine aminotransferase (ALT). However, the toxicity levels of surface charge-modified silica particles were much less weaker than the level of unmodified particles. When SP70 was repeatedly administered at 40 mg/kg twice a week for 4 weeks into mice, the hydroxyproline content of the liver significantly increased. Azan staining of the liver section indicated the extensive fibrosis. To the contrary, the repeated administration of SP70-N or SP70-C at 60 mg/kg twice a week for 4 weeks into mice did not cause the hepatic fibrosis. These findings suggest that the surface charge of nanomaterials could change their toxicity.