Atomic
Force Microscopy Probing of Receptor–Nanoparticle
Interactions for Riboflavin Receptor Targeted Gold–Dendrimer
Nanocomposites
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Abstract
Riboflavin receptors are overexpressed
in malignant cells from
certain human breast and prostate cancers, and they constitute a group
of potential surface markers important for cancer targeted delivery
of therapeutic agents and imaging molecules. Here we report on the
fabrication and atomic force microscopy (AFM) characterization of
a core–shell nanocomposite consisting of a gold nanoparticle
(AuNP) coated with riboflavin receptor-targeting poly(amido amine)
dendrimer. We designed this nanocomposite for potential applications
such as a cancer targeted imaging material based on its surface plasmon
resonance properties conferred by AuNP. We employed AFM as a technique
for probing the binding interaction between the nanocomposite and
riboflavin binding protein (RfBP) in solution. AFM enabled precise
measurement of the AuNP height distribution before (13.5 nm) and after
chemisorption of riboflavin-conjugated dendrimer (AuNP–dendrimer;
20.5 nm). Binding of RfBP to the AuNP–dendrimer caused a height
increase to 26.7 nm, which decreased to 22.8 nm when coincubated with
riboflavin as a competitive ligand, supporting interaction of AuNP–dendrimer
and its target protein. In summary, physical determination of size
distribution by AFM imaging can serve as a quantitative approach to
monitor and characterize the nanoscale interaction between a dendrimer-covered
AuNP and target protein molecules in vitro