Timely diagnosis and treatment of infectious diseases calls for highly sensitive, point-of-care diagnostic assays. Traditional diagnostic methods include microscopy, polymerase chain reaction (PCR), immunofluorescence (IF) and enzyme-linked immunosorbent assay (ELISA). Improvement of microfabrication technologies have enabled the development of point-of-care tests including microfluidic chip sensors, paper-based fluidic devices and lateral flow assays (LFAs), seldom with attempts to integrate sample preparation and detection into one device. Many of these diagnostic methods, however, require elaborate sample processing steps or labels (typically a dye, enzyme or fluor) which can suffer from low signal strength or photo-bleaching (of fluors), and can require elaborate instrumentation for their detection.Here, we propose a diagnostic platform utilizing lithographically-fabricated micron-scale corner-cube retroreflectors as novel, optical labels conjugated to antibodies. The retroreflector cubes serve as ultra-bright labels which are easily detectable using inexpensive, low-numerical aperture optics. The cubes, unlike traditional labels, are not susceptible to photo-bleaching and do not require any signal amplification.We demonstrate the applicability of this novel optical label in a sedimentation assay format for the direct detection of model pathogenic organisms with clinically relevant sensitivity, little or no sample preparation and color multiplexing capability by dye doping the cubes during fabrication.

Micron-scale corner-cube retroreflectors as labels for sensitive point-of-care diagnostic platforms

247th National Meeting (2014)

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