| abstract |
An apparatus and method for evanescent light fluoroassays incorporate a waveguide in a disposable cartridge for the detection and quantification of analytes. The waveguide, preferably a planar waveguide, contains on one surface an analyte-binding molecule for binding an analyte from a fluid sample, such as a blood sample. The analyte is linked directly (for a competitive immunoassay) or indirectly, through an analyte-binding molecule, (for a sandwich immunoassay) to a fluorescent molecule. Alternatively, an analyte or analyte analog is bound to a surface of the waveguide. Analyte present in a fluid sample would compete with the analyte or analyte analog on the waveguide surface for a labeled analyte-binding molecule. The disposable cartridge (20) may contain a fluid sample in a tube, which is held on a platform comprising a light source (11), a means for holding the disposable cartridge (15), and a light detecting device (17). The system holds the disposable cartridge in place so that the waveguide (25) is properly aligned with the light source (11) and the light-detecting device (17). Air pressure, vacuum or capillary action may be used to move the fluid sample onto an assay area of the disposable cartridge, where the analyte reacts with the analyte-binding molecule on the waveguide surface. Upon passage of light through the waveguide, an evanescent field is created, which selectively excites fluorescent molecules bound to the waveguide. Light emitted by the fluorescent molecule is detected by the light-detecting device, and the amount of analyte in the fluid sample is determined. Upon completion of the measurement, the entire cartridge can be discarded. The apparatus and method may be used in competitive or sandwich-type immunoassays, nucleic acid assays and enzymatic hydrolysis assays. |