Science and Education Publishing American Journal of Nanomaterials 2372-3122 4 1 2016 6 12 Time-dependent Toxic Effect and Distribution of Silver Nanoparticles Compared to Silver Nitrate after Intratracheal Instillation in Rats 12 19 EN Alaa Fehaid Mohamed F. Hamed Mamdouh M. Abouelmagd Akiyoshi Taniguchi Cellular Functional Nanobiomaterials Group, Research Center for Functional Materials, National Institute for Materials Science (NIMS), Tsukuba, Ibaraki, Japan AJN2016413 10.12691/ajn-4-1-3 2015 12 16 2016 4 4 2016 6 10 Silver nanoparticles (AgNPs) are widely used because of their anti-bacterial and anti-inflammatory properties; however, the adverse health effects of these nanoparticles, especially to the lungs, have been less studied. We thus investigated the inflammatory response of polyvinylpyrrolidone (PVP)-coated AgNPs and silver nitrate (AgNO3) after 24 h, 14 days and 28 days of single intratracheal instillation in rats. The bronchoalveolar lavage fluid (BALF) samples were collected and analyzed; a significant influx of neutrophils into the lung was found in both treated groups after 24 h with a presence of AgNPs in the alveolar macrophages after 24 h, 14 days and 28 days of instillation. Pro-inflammatory cytokines and enzymatic activities showed a significant increase after 24 h in both treated groups with a higher significance in the AgNO3-treated group than the AgNPs-treated group. After 28 days, these increases were completely recovered in the AgNO3-treated group but were still present in the AgNPs-treated group. The gross examination of lung tissues revealed a clear focal inflammation in the AgNPs-treated group after 28 days. More than 29% and 9% of the initial dose of AgNPs were recovered in lung tissues after 1 day and 28 days, respectively. Comparatively, the AgNO3-treated group recovered only 16.5% and 1%, suggesting that the silver ions are easily absorbed into the circulation and distributed to different tissues more than the nanoparticles. Our results indicated that the PVP-AgNPs caused a subchronic pulmonary inflammation compared to the acute one induced by the ionic form, which can be recovered easily.