Scientists at Imperial College London have developed a cheap, easily administered enzyme-linked immunosorbent assay (ELISA) technology for detecting a variety of pathogens that needs nothing but a (non-colorblind) eye to read the results.
When blood serum is introduced into a small plastic bottle containing a special mix that includes gold nanoparticles, they combine in specific ways depending on whether an analyte being investigated is present or not. If it is, the solution turns a shade of blue; if not, it turns red. Though the test is considerably more sensitive over nucleic acid-based testing for HIV (p24 biomarker), for example, the real benefit is being able to offer cheap and reliable testing to poorer regions of the world.
From the study abstract:
The enzyme label of an enzyme-linked immunosorbent assay (ELISA) controls the growth of gold nanoparticles and generates coloured solutions with distinct tonality when the analyte is present. Prostate specific antigen (PSA) and HIV-1 capsid antigen p24 were detected in whole serum at the ultralow concentration of 1 × 10−18 g ml−1. p24 was also detected with the naked eye in the sera of HIV-infected patients showing viral loads undetectable by a gold standard nucleic acid-based test.
Press release: Test developed to detect early-stage diseases with naked eye
Abstract in Nature Nanotechnology: Plasmonic ELISA for the ultrasensitive detection of disease biomarkers with the naked eye