A colorimetric immuno-microarray for the quantitation and direct visualization of illicit drugs in body fluids

The design and testing of integrated colorimetric microarray immunochips (immuno-microarrays) are reported for the quantitation and direct visual determination of multiple illicit drugs (e.g., morphine, cocaine and amphetamine) in body fluids. Such an immuno-microarray platform utilizes a competitive immunoassay format, which is based on silver staining for quantitative detection and multicolor staining for direct visualization (i.e., qualitative identification) of analytes present in the sample. Under optimized conditions, the dynamic response ranges of 3.7-1000, 1.1-300 and 1.5-300 ng mL^-1 were achieved for amphetamine, cocaine, and morphine, respectively, which are wider towards low concentrations than those of standard enzyme-linked immunosorbent assay (ELISA) tests. The limits of detection (LODs) for morphine, cocaine, and amphetamine were determined to be 1.5 ± 0.1, 1.1 ± 0.1 and 3.7 ± 0.2 ng mL^-1, respectively in oral fluids, which meet government regulations for law enforcement. The obvious advantages of multiplexing, simultaneous visual recognition, and accurate quantitation make the on-site detection feasible, confirming that such a colorimetric immuno-microarray holds promise for practical applications.