Pulmonary toxicity, distribution, and clearance of intratracheally instilled silicon nanowires in rats

Silicon nanowires (SiNWs) are being manufactured for use as sensors and transistors for circuit applications. The goal was to assess pulmonary toxicity and fate of Si NWusing an in vivo experimental model. Male Sprague-Dawley rats were intratracheally instilled with 10, 25, 50, 100, or 250 µg of Si NW (∼20-30nm diameter; ∼2-15 µm length). Lung damage and the pulmonary distribution and clearance of Si NW were assessed at 1, 3, 7, 28, and 91 days after-treatment. Si NW treatment resulted in dose-dependent increases in lung injury and inflammation that resolved over time. At day 91 after treatment with the highest doses, lung collagen was increased. Approximately 70% of deposited Si NW was cleared by 28 days with most of the Si NW localized exclusively in macrophages. In conclusion, Si NWinduced transient lung toxicity which may be associated with an early rapid particle clearance; however, persistence of Si NWover time related to dose or wire length may lead to increased collagen deposition in the lung.