Novel Optical Measurement Approach for the Quantitation of Liposome Immunomigration Assays

Abstract

In a recent series of papers^1–3 the use of dye-containing liposomes as a component of immunochemical field assay methods for the detection and measurement of environmental contaminants has been demonstrated. These assays produce a colored measurement zone on a plastic-backed nitrocellulose strip, with the amount of color in the zone being proportional to the amount of analyte present in the test sample. The color in this zone has been measured using scanning densitometry of the strips. While giving a quantitative measurement, such a system is not field-portable and cannot differentiate between multiple colors in the measurement zone. The human eye is also limited in the case of mixed colors. In this report, the use of a Colortron^TM 32-band digital color sensor for the quantitation measurement is demonstrated. This instrument is designed for inexpensive color analysis in the desktop publishing industry, but the fact that it can be used as a portable scanning reflectometer means that it has great potential for the spectral analysis of colors produced on a solid surface as analytical signals. As it is a scanning reflectometer rather than a single wavelength instrument, it can discriminate and quantitate a mixture of dyes, and thus has the potential to become part of a field-portable, multianalyte assay system.