Labeling cells with silver/dendrimer nanocomposites

We have developed water-soluble, biocompatible, fluorescent, and photostable silver/dendrimer nanocomposites that have a potential to be used for in vitro cell labeling. A PAMAM_E5.NH ₂ dendrimer was used as a template to prepare first a silver-dendrimer complex in an aqueous solution at biologic pH=7.4. Conversion into nanocomposite was achieved by irradiating the solution of the [(Ag ⁺) _25-PAMAM_E5.NH ₂] complex by UV light to reduce the bound Ag ₊ to zero-valent Ag ⁰ atoms, which were simultaneously trapped in the dendrimer network. Results indicate that the {(Ag ⁰) _25-PAMAM_E5.NH ₂} silver/dendrimer nanocomposite forms positively charged single particles of 4-5 nm under the experimental conditions used. The dendrimer nanocomposite proved to be fluorescent. Toxicity testing of {(Ag ⁰) _25- PAMAM_E5.NH ₂) nanocomposite revealed a behavior similar to the template dendrimer. Intracellular internalization of the silver nanocomposite and cell labeling capabilities was confirmed by confocal microscopy.