Benign Nanosilver for Plasmonic Biosensors

The plasmonic properties of noble metal nanoparticles facilitate their use as agents for novel in-vivo bio-applications such as targeted drug delivery and cancer cell therapy. Nanosilver is best suited for such applications because of its minimal plasmonic losses in the visible spectrum. Its toxicity, however, can destroy the surrounding healthy tissue and thus, hinders its safe employment. Here, the toxicity of nanosilver against a model biological system (Escherichia coli) is “cured” by coating it hermetically with a thin SiO₂ layer by a scalable aerosol method, creating the opportunity to safely use powerful nanosilver for intracellular bio-applications. Uncoated or partially coated nanosilver exhibits substantial toxicity against E. coli bacteria while encapsulating it prevents this. The performance of these ready-to-use, benign (non-toxic) nanosilver particles as biosensors is demonstrated here by measuring the adsorption of bovine serum albumin (BSA) in a model sensing experiment. Furthermore, the silica coating around nanosilver prevents its agglomeration and thus, enhances its biosensitivity.