Electrochemical Aptasensing Platform for Culture-Free, Selective Detection of Airborne Bacterial Species

Current culture-based bioaerosol monitoring fails to provide the species-specificity and real-time capabilities essential for indoor air quality and disease surveillance. We developed a culture-free electrochemical aptasensor for rapid, species-specific detection of airborne bacteria. Targeting Moraxella osloensis, a prevalent indoor species identified through next-generation sequencing, we generated a high-affinity aptamer (K_d = 118.9 nM) for M. osloensis and immobilized it on screen-printed gold electrodes. The label-free electrochemical impedance spectroscopy-based sensor achieved near single-cell sensitivity (5.6 CFU/μL detection limit), log-linear quantification (R² = 0.98), and robust selectivity against six nontarget species, maintaining stability under PM2.5-equivalent dust loads (15-75 μg/m³). In aerosol chamber tests, the sensor successfully quantified airborne M. osloensis with signals correlating to delivered cell numbers and plate counts, demonstrating specificity even in complex microbial and dust conditions. This platform reduces detection time from days to minutes, enabling multiplexed, field-deployable bioaerosol surveillance for indoor air quality and infectious disease monitoring.