Detection of Aerosolized Protein Using a Condensation Growth Tube Coupled with an Electrochemical Immunoassay on Screen-Printed Carbon Electrodes

Rapid point-of-need detection of aerosolized pathogens remains a critical need for environmental monitoring and infection control. Traditional filter-based bioaerosol collection methods are time-consuming and nonselective, capturing both infectious and noninfectious viral particles while causing mechanical damage through desiccation and mechanical stress. Furthermore, these approaches require laboratory-based nucleic acid extraction and amplification, which limits their utility for real-time monitoring. Here, we present an integrated aerosol-to-detection platform that couples a three-stage condensation growth tube (CGT) bioaerosol sampler with sensitive electrochemical immunodetection of the SARS-CoV-2 nucleocapsid (N) protein as a model virus antigen. The CGT gently concentrates aerosolized particles into a small liquid volume while preserving biological integrity through a water-based, low-velocity collection. Screen-printed carbon electrodes (SPCEs) were modified with capture antibodies and employed in a sandwich immunoassay format using horseradish peroxidase-linked detection antibodies and 3,3',5,5'-tetramethylbenzidine (TMB) as the electrochemical probe. The electrochemical immunoassay achieved a limit of detection (LOD) of 1.2 ng/mL for spiked N-protein solutions, demonstrating comparable sensitivity to published electrochemical biosensors for SARS-CoV-2 detection. The CGT successfully captured the aerosolized N protein with high efficiency across particle sizes of 50-100 nm with collection efficiency exceeding 95% for the target size range. Electrochemical detection of CGT-captured aerosolized N protein confirmed the successful combination of the sampling and sensing platform, providing average cathodic current signals distinguishable from blank controls. These results demonstrate the feasibility of coupling efficient bioaerosol collection to rapid electrochemical detection for point-of-need pathogen monitoring.