A Motion Free Image Based TRF Reader for Quantitative Immunoassay

Time resolved acquisition of fluorescence provides advantages of reduced background reflection and reduced analyte autofluorescence, considerably improving the signal to background ratio. Europium chelate with its relatively longer fluorescence decay in milliseconds can be analyzed with inexpensive detectors with simpler timing considerations. In this work we present a Time Resolved Fluorescence (TRF) reader using a monochrome camera and its associated exposure trigger circuit to capture TRF from Europium chelate striped on nitrocellulose membrane. The reader is imaging based and does not require complex mechanical moving parts to read the test strip under investigation. Ten different concentrations of Europium between 100 ng/ml and 1000 ng/ml were imaged and the output of the developed TRF reader was found to be linear (R2=0.9873) over the range of concentrations. An improvement of 70% was observed in the signal to background ratio using TRF technique.