BackgroundClarifying the physicochemical properties of nanomaterials is crucial for hazard assessment and the safe application of these substances. With this in mind, we analyzed the relationship between particle size and the in vitro effect of amorphous nanosilica (nSP). Specifically, we evaluated the relationship between particle size of nSP and the in vitro biological effects using human keratinocyte cells (HaCaT).ResultsOur results indicate that exposure to nSP of 70 nm diameter (nSP70) induced an elevated level of reactive oxygen species (ROS), leading to DNA damage. A markedly reduced response was observed using submicron-sized silica particles of 300 and 1000 nm diameter. In addition, cytochalasin D-treatment reduced nSP70-mediated ROS generation and DNA damage, suggesting that endocytosis is involved in nSP70-mediated cellular effects.ConclusionsThus, particle size affects amorphous silica-induced ROS generation and DNA damage of HaCaT cells. We believe clarification of the endocytosis pathway of nSP will provide useful information for hazard assessment as well as the design of safer forms of nSPs.

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Delayed perforation after duodenal endoscopic submucosal dissection (ESD) occurs at a high rate because the duodenal wall is very thin and the artificial ulcer after resection is exposed to bile and pancreatic juice. We investigated the application of the combination of a polyglycolic acid (PGA) sheet and fibrin glue. PGA sheets comprise materials widely used in surgery for absorbable thread. Fibrin glue is a heated blood product and is used for hemostasis during operations. We developed a combined method using both materials. We have used this method in two cases. One case involved an elevated lesion located in the lower duodenal angle of the duodenum. The other involved an elevated lesion in the second portion of the duodenum. About 1 week after ESD, the PGA sheets remained covering the ulcer and delayed perforation did not occur. We were able to easily carry out this method for several parts of the duodenum. This method may be helpful for the prevention of delayed perforation after duodenal ESD.