You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Evaluation of the adjuvant effect of silver nanoparticles both in vitro and in vivo. The immunological adjuvant effect of silver nanoparticles (AgNPs) was investigated both in vitro and in vivo. The in vivo adjuvant effect of AgNPs was evaluated with model antigen ovalbumin (OVA) and bovine serum albumin (BSA) in mice by intraperitoneal and subcutaneous immunization. Serum antigen-specific IgG level significantly increased in AgNPs-treated mice comparing to the control group. AgNPs induced the increase of IgG1/IgG2a ratio and antigen-specific IgE, indicating that AgNPs elicited Th2-biased immune responses. By in vitro assay, the mechanism of adjuvant effect was explored. After 48h treatment with AgNPs, both the number of leukocytes and levels of cytokines TNF-α and IFN-γ in abdominal lavage fluid of mice increased. The expression of the major histocompatibility complex class II molecule on the surface of peritoneal macrophages significantly increased. AgNPs can be easily phagocytosed by peritoneal macrophages, while do not affect antigen uptake by the cell. We therefore conclude that AgNPs have significant adjuvant effect and the mechanism of this effect is mainly ascribed to the recruitment and activation of local leukocytes and especially macrophages. For the first time we found the remarkable adjuvant effect of AgNPs, and the result is beneficial for the future applications, especially in biomedicine.
{"Chemical": ["silver"]}