Ultrasensitive and rapid pathogen detection generally relies on nucleic acid extraction followed by amplification, or labeling with dyes, enzymes or fluors. Signal detection in these techniques requires elaborate instrumentation. This work introduces embedded, microfabricated linear retroreflectors as bio-sensing surfaces, using micron-sized magnetic particles as light-blocking labels in a semi-homogeneous format, resulting in a highly sensitive diagnostic immunoassay.Retroreflectors return light directly to its source and are easily detectable using inexpensive optics. Many everyday items such as road signs, running shoes and safety equipment incorporate retroreflectors for their optical properties. The detection principle for our platform involving retroreflectors is similar to that of an eclipse, in that a decrease in the amount of light returned from a retroreflector indicates the presence of analyte.The target is immunomagnetically separated from a complex sample and then optimally captured by an antibody decorated microfluidic sensing surface, thereby dimming the retroreflectors. A highly sensitive and fully automated difference imaging algorithm that can see single 3.0 �m magnetic particles without optical calibration is used to detect and quantify signal intensity from each 1 sq. mm. array of retroreflectors. Rickettsia conorii, the causative agent of Mediterranean Spotted Fever and an NIAID Category C priority pathogen, is used as a model pathogen to implement the microfluidic assay. The magnetic properties of the particle labels are useful in sample preparation from complex matrices and pre-concentration to increase sensitivity, while fluidic force discrimination is used to increase specificity of the assay.The unique combination of large sensing areas, optimized surface chemistry and microfluidic protocols, automated image capture and analysis, and high sensitivity of the difference imaging results in a rapid and sensitive assay for pathogen detection, with a current limit of detection of less than 4000 R. conorii spiked into 1 mL of buffer.

Embedded microretroreflector-based immunodiagnostic platform for sensitive pathogen detection

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.