Cultured macrophages cause dissolucytosis of metallic silver.

The present study proves that cultured macrophages can liberate silver ions from metallic silver surfaces by a process called dissolucytosis. Macrophages (J774) were grown on a silver plate for different periods of time and after fixation in glutaraldehyde, they were subjected to autometallograhy in order to amplify possible cellular silver-sulphur nanocrystals. Light and electron microscopic analysis of the cells revealed that silver ions released from the plate had been taken up by the macrophages and accumulated in lysosome-like structures. We found that the liberation of silver ions takes place extracellularly and is caused by chemical activity in a dissolution membrane, most likely secreted and organized by the macrophages. The liberation and the subsequent uptake of silver ions in the macrophages is a relatively fast process and the resulting silver-sulphur nanocrystals can be observed in macrophages that have been in contact with metallic silver for only a few minutes. Our findings indicate that the speed of dissolucytosis is highly influenced by the chemical nature of the object exposed to the dissolucytotic process which is likely to occur whenever macrophages encounter a non-phagocytosable foreign object.