Label-free Optical Biodetection of Pathogen Virulence Factors in Complex Media Using Microtoroids with Multifunctional Surface Functionality.

Early detection of pathogens or their virulence factors in complex media has a key role in early diagnosis and treatment of many diseases. Nano-molar and selective detection of Exotoxin A, which is a virulence factor secreted from Pseudomonas aeruginosa in the sputum of Cystic Fibrosis (CF) patients, can pave the way for early diagnosis of P. aeruginosa infections. In this study, we conducted a preliminary study to demonstrate the feasibility of optical biodetection of P. aeruginosa Exotoxin A in a diluted artificial sputum mimicking the CF respiratory environment. Our surface engineering approach provides an effective bio-interface enabling highly selective detection of the Exotoxin A molecules in the complex media using monoclonal anti-Exotoxin A functionalized microtoroids. The highly resilient microtoroid surface towards other constituents of the sputum provides Exotoxin A detection ability in the complex media by reproducible measurements. In this study, the limit-of-detection of Exotoxin A in the complex media is calculated as 2.45 nM.