Lateral flow immunoassays (LFIAs) are rapid diagnostic tests that can detect the presence of the SARS-CoV-2 virus quickly, with the aid of nanoparticles and specific proteins. The gold nanoparticles produced with our technology exhibited the stability and target concentration necessary for use as markers in LFIA rapid diagnostic tests. A prototype LFIA test strip with these gold nanoparticles was prepared, showing their application in the development of rapid diagnostic tests.