Centrifugal microfluidics for rapid target analyte quantification in airborne bioaerosols

Bioaerosols comprise an array of airborne particles that can be benign, contain irritants (i.e., allergens), or disseminate pathogens. Current fieldable devices are incapable of discriminating between benign bioaerosols and pathogenic bioaerosols. Thus, rapid on-site detection and identification at the point of exposure of the components comprising bioaerosols is critical to assess health risks; elimination of both false positives and false negatives is essential to ensure that the correct countermeasures are deployed. The sandwich enzyme-linked immunosorbent assay (sandwich ELISA) remains a gold standard technique for accurate, sensitive detection of proteins, bacteria, and viruses. ELISAs require recognition of the target by two biorecognition elements (BREs) and thus effectively eliminate false positives. The sandwich ELISA, however, suffers from laborious manual processes, which severely impacts its utility in point-of-care (POC). Centrifugal microfluidics offers an automated solution to execute multi-step ELISAs. Here, we introduce a centrifugal microfluidic device that operates based on passive capillary and siphon valving networks to detect human serum albumin (HSA) concentrations in collected bioaerosol samples. We investigate key aspects for minimizing the assay operation time by investigating siphon valve mechanisms, co-incubation time for HSA with a capture antibody and detection antibody conjugated with streptavidin-horse radish peroxidase (strep-HRP), and incubation time for tetramethylbenzidine with strep-HRP for electrochemical amperometric detection. The fully integrated device quantifies HSA concentrations in 15 minutes based on a small sample volume of 12.5 μL. Using the device, we successfully quantify HSA concentrations in bioaerosol samples and obtain results similar to standard 96 well plate-based ELISA.