Emulsion Agglutination Assay for the Detection ofProtein–Protein Interactions: An Optical Sensor for Zika Virus

A new class of Janus emulsion agglutination assay is reported for the detection of interfacial protein–protein interactions. Janus emulsion droplets are functionalized with a thermally stable, antigen binding protein rcSso7d variant (rcSso7d-ZNS1) for the detection of Zika NS1 protein. The emulsion droplets containing fluorescent dyes in their hydrocarbon and fluorocarbon phases intensify the intrinsic optical signal with the emission intensity ratio, which can be detected by a simple optical fiber. This assay provides an opportunity for the in-field detection of Zika virus and other pathogens with a stable, inexpensive, and convenient device.