Single-chip multitarget detection by EGOFET-based aptasensors

Liquid multisensors are in high demand due to their wide range of applications. Recent advances in electronics allow an integration of several individual devices for target and control measurements on one chip. We studied aptamer-modified electrolyte-gated field-effect transistors (EGOFETs) as basic sensor elements for single-chip multitarget detection. We used an aptamer with a pH-dependent conformational switch as a model recognition element allowing application of the EGOFET as a single element for detecting three targets of different nature. The fabricated EGOFET device has been shown to be sensitive to the conformation of the aptamer. The sensor is sensitive to the pH changes in the range of pH 6-8 due to the H⁺-dependent assembly of an i-motif DNA structure. Under the i-motif-unfavorable conditions (pH ≥ 7.3), the unfolded cytosine loop forms a complex with Ag⁺ ions providing a new conformation. Finally, under the i-motif-favorable conditions (pH < 7.3), the folded i-motif binds to influenza A virus. The EGOFET signals for these three analytes lie in different ranges allowing their clear discrimination. Applicability of the designed device under biologically relevant conditions was proved for biological fluids such as saliva and plasma with a viral load typical for patients with influenza. The proof-of-concept for single-chip multitarget detection based on EGOFETs with one recognition element is implemented for the first time. This example of the model recognition element with combined properties integrated into the EGOFET paves the way to managing the properties of the EGOFET-based biosensors and, in the future, to developing single-chip multisensors on the EGOFET platform.