Colorimetric detection of protein microarrays based on nanogold probe coupled with silver enhancement

This work presents a method for analyzing protein microarrays using a colorimetric nanogold probe coupled with silver enhancement (gold-silver detection). In this method, the gold nanoparticles were introduced to the microarray by the specific binding of the gold-conjugated antibodies or streptavidins and then coupled with silver enhancement to produce black image of microarray spots, which can be easily detected with a commercial CCD camera. The method showed high detection sensitivity (1 pg of IgG immobilized on slides or 2.75 ng/ml IgG in solution) and a good linear correlation between the signal intensity and the logarithm of the sample concentration. The examination of this method in analyzing a demonstrational ToRCH antigen microarray developed in our lab showed an identical result as in the fluorescent method. These results suggest the colorimetric gold-silver detection method has potential applications in proteomics research and clinical diagnosis.