Low-cost modular electronic pathogen sensors

The COVID-19 pandemic has shed light on the global need for inexpensive, simple-to-use pathogen testing accessible to individuals on a daily basis to move beyond point-of-care diagnostics in favor of test methods more readily available to all people. We have developed a low-cost disposable electronic sensor, designed to be used by individuals with minimal training and simple equipment has been developed for detection of multiple pathogens. Demonstrations of multiplex electronic sensors for detection of SARS-Cov-2 spike glycoproteins or hemagglutinin from Influenza A in liquid samples with characteristics resembling extracted saliva will be presented. The devices were fabricated using scalable processes with potential for economical mass-production to utilize the sensitivity and surface chemistry of a two-dimensional MoS2 transducer for attachment of antibody fragments in a conformation favorable for antigen binding. Ultra-thin layers (3 nm) of amorphous MoS2 were directly sputtered over the entire sensor chip at room temperature and laser annealed to create an array of semiconducting 2H-MoS2 active sensor regions between metal contacts. The semiconducting region was functionalized with monoclonal antibody Fab (fragment antigen binding) fragments derived from whole antibodies complementary to either SARS-CoV-2 S1 spike protein or Influenza A hemagglutinin. The high affinity of the antibody fragment base for the MoS2 transducer surface with some density of sulfur promoted antibody fragment chemisorption with antigen binding regions oriented for interaction with the sample. Additionally, the angiostatin converting enzyme 2 (ACE2) receptor protein for the SARS-CoV-2 spike glycoprotein, was tethered to a hexa-histidine (his6) tag at its c-terminus both for purification purposes, as well as a motif for binding to MoS2. This modified protein was also investigated as a bio-recognition element. Electrical resistance measurements of sensors functionalized with antibody fragments and exposed to antigen concentrations ranging from 2-20,000 picograms per milliliter revealed selective responses in the presence of complementary antigens with sensitivity to SARS-CoV-2 or influenza A on the order of pg/mL and comparable to gold-standard diagnostics such as Polymerase Chain Reaction (PCR) analysis. Lack of antigen sensitivity for the larger ACE2 BRE further demonstrates the utility of the engineered antibody fragment/transducer interface in bringing the target antigen closer to the transducer surface for sensitivity required for early detection viral diagnostics.