Investigating low volume planar surface fluorescent immunoassays with QDs for spatial and spectral multiplexing

The simultaneous detection of two analytes, chicken IgY (IgG) and Staphylococcal enterotoxin B (SEB), in a single spot of a planar surface fluorescent immunoassay was demonstrated using luminescent semiconductor quantum dot nanocrystal (QD) tracers. This spectral multiplexing is made possible by employing one laser to serve as the excitation source for detecting two distinct QD signals from different analytes. Spatial multiplexing - detection of two analytes in different regions of the planar surface - was also demonstrated using fluid handling constructs that allowed for very low solution volumes when performing the assay. The limits of detection for detecting both chicken IgG and SEB within a single spot were 25 ng/mL and 1.6 ng/mL, respectively. A novel slide reading detection platform involving evanescent wave excitation of a planar surface was created in-house for assay measurement. This platform is potentially more amenable to a point-of-care (POC) environment than conventional slide readers because of its modular design architecture and lack of moving parts. The result is a platform which is simple to repair using primarily off-the-shelf consumer components.