Ultrasensitive and rapid pathogen detection generally relies on nucleic acid extraction followed by amplification, or labeling with dyes, enzymes or fluors, which require elaborate instrumentation. This work introduces embedded, microfabricated linear retroreflectors as bio-sensing surfaces, using micron-sized magnetic particles as light-blocking labels in a highly sensitive diagnostic immunoassay. Retroreflectors return light directly to its source and are easily detectable using inexpensive optics. The pathogen is immunocaptured by a sensing surface following immunomagnetic separation and concentration from a complex sample. An automated difference imaging algorithm that detects single 3.0 �m magnetic particles without optical calibration is used to quantify the number of labels bound to each from each 1 sq. mm. array of retroreflectors. An assay for the detection of Rickettsia conorii is implemented in a microfluidic format with fluidic force discrimination to enhance reproducibility and specificity, with a current limit of detection of less than 4000 bacteria per mL.

Embedded microfluidic retroreflectors for sensitive pathogen diagnostics

245th National Meeting (2013)

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