Inexpensive optical system for microarray ELISA

The use of antibody-based diagnostic testing has increased significantly over the past decade, giving rise to a wide range of diagnostic devices. At one end of the cost-range are rapid inexpensive point-of-care tests based on immunochromatographic strips which provide a qualitative positive or negative test outcome. On the other hand, quantitative tests generally require the use of dedicated and expensive laboratory instruments. There remains a need for diagnostic instruments and tests that can provide quantitative assessment of disease markers at low cost. This paper describes the development of a novel low cost optical device for reading colorimetric and fluorescent immunodiagnostic test results. This portable instrument uses a webcam to capture test results from a specially designed 16-well slide containing a miniaturized array of test spots. Arrays are illuminated with either LEDs or lasers, while transmitted or emitted light is captured through a long-pass filter, allowing two different types of optical measurement to be performed within the same device. This device was used to read results from an array of antibodies conjugated with either an enzymatic or fluorescent tag resulting in a colored or fluorescent readout.