Local Silver Nanoparticles Administration Promotes Inflammation and Hyperalgesia in Rats
Silver has no known function in the organism. However, nanosilver has the highest degree of commercialization of all nanomaterials used in healthcare. The aim of this study was to assess the potential deleterious effect of local nanosilver administration in an animal model. Wistar rats received a subcutaneous injection (hind paw) of either 500ppm nanosilver (group S1), 20ppm nanosilver (group S2) or saline (control group). Animals were tested by means of plantar test, analgesy-meter and plethysmometer. 24 h after the administration, l-carrageenan was injected (same site), which lead to localized inflammation. The above-mentioned assessments were performed repeatedly until 24 h after l-carrageenan administration. 24 h after colloidal silver administration, both S1 and S2 groups had a significantly higher sensibility to mechanical stimuli. 48 h after colloidal silver administration, the S1 group had a significantly higher sensibility to thermal stimuli. Paw edema was more pronounced in the treatment groups in the first 30 h after the nanosilver injection. Local subcutaneous nanosilver administration leads to an increased inflammatory response and to hyperalgesia. Considering the constant increase in nanosilver�s biomedical use, the current paper sends a clear warning for the need of urgent more in-depth research on the matter.