The COVID-19 pandemic will have caused over 6 million deaths worldwide and 790,000 deaths in the US alone projected for 1 January 2022. Worldwide actions to slow or stop the pandemic include vaccinations, widespread testing, and other prevention strategies. Among these activities, testing is considered to lag far below what is needed. We report here a low-cost COVID-19 assay that can be done at home or in a low-resource clinic using saliva samples and a smartphone. The assay uses a 3D printed micropipette tip functionalized with SARS-CoV-2 specific monoclonal antibodies and a synthetic SARS-CoV-2 specific receptor particle (COVR) for detection. The COVRs were designed with binding sites complementary in size and shape to the SARS-CoV-2 spike (S) protein. These sites were synthesized on silica nanoparticles using the S protein as a template and polydopamine as the substructure which introduces multiple functional groups complementary to S protein. COVRs can produce a colorimetric signal generated by the horseradish peroxidase’s reaction with 3,3’,5-5’-tetramethylbenzidine (HRP-TMB). The COVRs specifically and selectively bind to S proteins with high binding constants which were ~2-47-fold better than other proteins tested in 10 % artificial saliva-0.01%-triton X-100. During the COVR synthesis, particle size variation, surface charge monitoring, and particle morphological changes were studied using DLS, ZETA potential, SEM, and TEM respectively. Upon running the assay using the 3D printed micropipette tip, COVR particles, and a smartphone using a Color Grab app, we obtained a limit of detection (LOD) of 200 TCID50/mL (TCID=Tissue Culture Infectious Dose 50%) in artificial saliva and an analytical spike recovery of 100±20% in pooled human saliva. Moreover, with an advanced image processing algorithm developed specifically for this array system, we were able to detect color changes undetectable by the Color Grab app. Using this algorithm, we reached a limit of detection of 10 TCID50/mL in artificial saliva. This COVID-19 detection test gives a quantifiable colorimetric read in less than 30 minutes.

Smartphone camera assisted point-of-care COVID-19 virus test in a 3D-printed micropipette tip

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.