Figure 2.

Principle of the aptasensor detection mechanism for VEGF₁₆₅. (A) In the absence of target molecules, unfoled VEGF₁₆₅ aptamer is electrostatically bound to a positively charged PLL-coated gold nanoparticle (GNP) surface and surface-enhanced fluorescence (SEF) of Cy3B conjugate with the VEGF₁₆₅ aptamer is created. (B) The aptamer had a reversible conformation change due to the interaction between VEGF₁₆₅ aptamer and its target, which resulted in a decreased electrostatic binding force. (C) the target-binding interaction of the aptamer caused the irreversible detachement of the aptamer from the GNP surface and no SEF effect of Cy3B was observed. (Reprinted with permission from ref. 43. Copyright (2012) American Chemical Society.