Monitoring Vaccine-Induced Antibody Levels Using Carbon Nanotube-Based Field-Effect Transistors

Vaccines are powerful public health tools to protect against emerging infectious pathogens. Multiple vaccine doses are typically required to achieve robust protection that is often mediated by the induction of pathogen-specific antibodies. Thus, monitoring the levels of vaccine-induced antibodies in immunized individuals is crucial to ensuring vaccine effectiveness and compliance. However, existing antibody-detection techniques are resource- and time-inefficient, highlighting the need for improved technologies for monitoring vaccine-induced antibody levels. Here, we developed a field-effect transistor (FET) biosensor platform based on antigen-functionalized semiconducting single-walled carbon nanotubes (SWCNTs) for the rapid and convenient detection of pathogen-specific antibodies. Our antibody sensor platform was designed to produce robust signals with a high signal-to-noise ratio upon antigen-antibody interactions altering the electrical conductivity of interconnected SWCNTs. Key physicoelectrochemical characteristics of our SWCNT FET biosensor were validated by atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman spectroscopy, and FET measurements. Robust and rapid antibody detection capability of our SWCNT FET biosensor platform was demonstrated by measuring virus-specific antibodies (e.g., anti-hemagglutinin (anti-HA), anti-SARS-CoV-2 nucleocapsid (anti-N), and anti-SARS-CoV-2 spike (anti-S) antibodies) in different systems. Our nanoelectronic sensor platform was able to detect these antibodies in a wide linear concentration range of 100 ag/mL to 100 ng/mL. Owing to the direct attachment of the corresponding antigens to SWCNTs, desirable limits of detection of 0.20 and 20.6 ag/mL were obtained for the detection of anti-HA and anti-S antibodies, respectively. Together, our SWCNT FET biosensor platform offers a next-generation antibody detection technology capable of low-cost, rapid, accessible, and convenient monitoring of vaccine-induced antibodies.