The von Kossa stain is used to quantify mineralization in cell culture and tissue sections.
History and method
The method was originally developed by von Kossa, and underwent several modifications. The stain principle is a precipitation reaction in which silver ions react with phosphate (not calcium) in the presence of acidic material Photochemical degradation of silver phosphate to silver then occurs under light illumination. This method is not specific for calcium itself but tissues are treated with a silver nitrate solution and the silver is deposited by replacing the calcium reduced by the strong light, and so can be visualized as metallic silver. Additional methods need to be employed to confirm the presence of calcium, such as Alizarin Red, which detects calcium deposits.