Tissue toxicity following the vaginal administration of nanosilver particles in rabbits

Nanosilver particles are used in various clinical settings because of their antibacterial properties. However, their safety evaluation when used for gynaecological disorders has not been established. Nanosilver particles were administrated in the vagina of New Zealand rabbits, and the pathological appearance of the surrounding tissue was examined by hematoxylin-eosin staining and transmission electron microscopy (TEM) after 1 and 3 days of treatment. The nanosilver content was assessed by plasma mass spectrometry, and the presence of particles in the hepatic portal vein blood was assessed by TEM. The results of our study show that the vaginal administration of nanosilver particles caused ultrastructural changes to the vaginal mucosa, urethra and rectum, with accumulation of particles in all tissues. These results demonstrate a new migration route of nanosilver particles following vaginal administration. They also demonstrate, for the first time, that the vaginal administration of nanosilver particles can enter the blood circulation system by examining the hepatic portal vein blood under the TEM which is the most direct visualized evidence.