A Colorimetric Biosensor Integrated with a Self-Driven Superabsorbent Polymer-Based Concentrator for Effective...

The typically low concentration of airborne pathogens necessitates the collection of large air volumes coupled with effective enrichment strategies to achieve detectable levels for reliable analysis. In this study, an integrated colorimetric biosensing platform was developed that sequentially combined aerosol‑to‑hydrosol (ATH) collection, passive hydrosol‑to‑hydrosol (HTH) enrichment, and nanozyme‑amplified signal readout. Bacterial aerosols were first collected into a liquid medium using an FA-4 impinger. The collected bacterial suspension was then concentrated 20‑fold within 20 min via a self‑driven superabsorbent polymer (SAP)‑based concentrator integrated with a 0.45 μm polycarbonate track‑etched (PCTE) membrane. Following concentration, target bacteria were specifically labeled with immune Pd/Pt nanozymes. The resulting bacteria-nanozyme complexes were captured on the membrane, while unbound nanozymes were removed by washing. The immobilized nanozymes were used to catalyze the oxidation of the colorless H₂O₂-TMB substrate to generate the blue TMBox. A linear correlation between the absorbance of the catalysate and bacterial concentration was established for quantitative detection of bacterial aerosols. Under the optimal conditions, the platform achieved an ATH enrichment factor of 3750 and an HTH enrichment factor of 20, yielding a total enrichment capacity of 75,000. The colorimetric biosensor demonstrated a detection limit of 427 CFU/m³ air for target bacteria, with the entire process from air sampling to quantitative readout completed within 2 h. The platform was further validated by field sampling in three poultry housing systems, where it successfully detected airborne bacteria in complex environmental backgrounds, with the results consistent with conventional culture methods. This proposed platform achieves rapid, sensitive, and specific detection of bacterial aerosols, providing a novel and reliable solution for monitoring of bioaerosols.