What it does
The test is specific for SARS-CoV-2.
How I built it
The test procedure comprises three steps, i.e. (i) saliva collection and filtration, (ii) nucleic acid extraction and amplification, and (iii) detection. As for the amplification, we opted for a MNAzyme (Multicomponent DNAzyme) catalyzed amplification, due to the non proteinaceous nature, the large temperature range of the catalytic activity, the low cost and prompt availability for large quantities, which are all necessary characteristics to meet the requirements. The MNAzyme catalyzed reaction results in the production of a DNA fragment that, in the presence of hemin, assembles into a G-quadruplex structure with peroxydase activity (known as HRP-mimicking). Hence, the amplification product is loaded in a plastic (polystyrene) microfluidic device where it is purified through paper chromatografy and further incubated to associate with hemin. Then the peroxydase activity is exploited in a plasmonic detection step. To this end, a solution containing gold(III) is loaded in the reagent reservoirs and distributed in the test well to promote the formation of gold nanoparticles (AuNP). Finally, the device is pictured with a smartphone and the results sent for remote analysis.
Challenges I ran into
The project is presently in a pre-launch stage, while we are waiting for the materials needed to test the first prototype with a synthetic nucleic acid target and become confident with the expected performances of the designed prototype. In the meanwhile, we are already eager to receive comments and contributions on the present design.