Gold nanoparticle based immunochromatography using a resin modified micropipette tip for rapid and simple detection of human chorionic gonadotropin hormone and prostate-specific antigen

A novel bioanalysis system based on immunochromatography was developed in connection with a nitrocellulose resin-modified micropipette tip, namely as ZipTip®. The sandwich-type immunoassay was applied to our bioananalysis system. The first antibodies that were aspirated by the micropipette were immobilized on the immunochromatographic resin at the edge of micropipette tip. The blocking solution was also aspirated in the same fashion. The measurement operation was performed by aspirating the sample solution, and then the gold colloidal nanoparticles (Au naps) conjugated secondary antibody solution. Since this bioanalysis system utilizes a micropipette, it is possible to increase the sample volume, which would enable the detection of antigen at low concentrations. In addition, the washing procedure can also be performed easily to reduce the background level. After the antigen-antibody reaction, the color intensity of Au naps could be observed by the naked eye. For analytical evaluation, the color intensity was captured by a scanner, and processed by analysis software. We have achieved the detection of human chorionic gonadotropin hormone (hCG) and total prostate-specific antigen (TPSA), which are well-known as fundamental indicators of pregnancy and cancer. The limit of detection (LOD) for hCG was 8 ng/ml (0.8 ng/tip), which is comparable to that of other conventional systems based on immunochromatography. Moreover, the LOD for TPSA was improved over the existing systems with the application of different sample volumes, such as 5 ng/ml (1 ng/tip) in 200 μl sample volume, and 2 ng/ml (0.6 ng/tip) in 300 μl sample volume. Since our bioanalysis system requires a small amount of immobilized antigen, it would be greatly useful in basic research for screening the antigen-antibody reactions. Besides, our bioanalysis system can be applied to on-field screening, since its operation is simple, and the visual results can be obtained rapidly.