Lateral flow immunoassays (LFIAs) are simple diagnostic devices, used to detect targeted analytes – also called rapid antigen tests. There are many wasted and expired, unused rapid tests from the Covid-19 pandemic which may be recycled into new material components. The aim of this published study was to recover gold nanoparticles that are used as markers in lateral flow immunoassays. A process using aqua regia was used for dissolving the gold nanoparticles from lateral flow immunoassays, and the resulting solution containing gold was used to produce new gold nanoparticles. The new gold nanoparticles may then be used in new products, as well as reused as markers in fresh rapid antigen tests.