Applying Nanosized Gold and Carbon Immunolabels for the Quantitative Detection of Specific Ag–Ab Complexes by Using Atomic Force Microscopy

The application of gold and carbon labels for the detection of antigen molecules using the atomic force microscopy (AFM) method is described in the current study. Direct AFM visualisation made it possible to observe the “antigen–antibody–gold+protein A” and “antigen–antibody– carbon+protein G” complexes. In addition, it was also possible to estimate the morphology and describe the distribution on a surface that used plastic microwell plates as a substrate. The sensitivity of the method for each conjugate was evaluated and compared to an enzyme-linked immunosorbent assay. The results obtained point to a high sensitivity of the approach, especially when using carbon tags. In addition, certain advantages of carbon tags are indicated, when compared with gold tags, because of their simple detection and unambiguous identification on the collected images.