Methods for Increasing Sensitivity of Immunochromatographic Test Systems with Colorimetric Detection (Review)

Recently, immunochromatographic assay (ICA) methods have found a wide range of uses in medical diagnostic, quality control, and consumer safety products because of their rapidity and methodological simplicity of testing; however, ICAs are usually less sensitive than other analytical methods. In this review, we survey modern methodological solutions for ensuring high sensitivity of ICAs based on the use of nanoparticle markers and colorimetric detection and characterize the main direction of such works focusing on lowering the detection limit amplification of the detectable signal generated by a single nanoparticle and forming, during the assay, immune complexes labeled with aggregates consisting of a large number of nanoparticles. The advantages and limitations of different approaches are discussed. We show that their use provides a decrease in the detection limit of ICA by 1–3 orders of magnitude, which makes this method quite competitive compared with instrumental methods of analysis.