Figure 1.

A schematic illustration of the methodology used in this study. From left to right, the gold-coated surface of substrate was first modified by soaking it into the ethanol solution of 16-Mercaptohexadecanoic acid (MHA) for 24 h, which formed an MHA film on the surface of gold substrate. Then, the MHA-modified surface of gold substrate was subject to NHS and EDC in PBS solution for 1 h to activate the MHA film. Afterward, the activated MHA film on the gold substrate was immersed into protein (rat anti-human IgG in this case) solution at 4 °C for 8 h, resulting formation of a well-defined protein monolayer on the MHA-modified gold substrate. Similarly, protein (human IgG in this case) monolayer was formed on an AFM tip. The antigen-functionalized AFM tip scanned across the well-ordered antibody monolayer, and at a number of randomly chosen locations the force–displacement curves between the tip, and the substrate surface were recorded and transformed into force–displacement curves by AFM

Lv et al. Nanoscale Research Letters 2010 5:1032-1038   doi:10.1007/s11671-010-9598-x