Specific nanoparticle targeting of the EGF-receptor using single-domain antibodies

Introduction
For effective localization of functionalized nanoparticles at diseased tissues such as solid tumors or metastases through biorecognition, appropriate targeting vectors directed against selected tumor biomarkers are a key prerequisite. The diversity of such vector molecules ranges from proteins, including antibodies and fragments thereof, through aptamers and glycans to short peptides and small molecules.
In the presented work we analyze the specific nanoparticle targeting capabilities of a small camelid single-domain antibody (sdAb), representing a potential recognition agent for the epidermal growth factor receptor (EGFR).

Methods
Bioconjugation of EGFR-specific sdAbs to different nanomaterials and characterization of sdAb-conjugates covering in vitro cancer cell imaging, cell proliferation as well as EGFR phosphorylation and signaling are described. The specificity of the sdAb-conjugates is investigated by way of receptor RNA silencing techniques with increasing complexity in vitro by introducing increasing concentrations of human or bovine serum.

Results and Discussion
The results show that sdAb-functionalized nanomaterials can effectively target the EGFR, even in more complex bovine and human serum conditions where targeting specificity is largely conserved for increasing serum concentrations. For highly affine targeting ligands such as sdAbs, targeting a receptor such as EGFR with low serum competitor abundance, receptor recognition function can still be partially realized in complex conditions. Moreover, sdAb-mediated biorecognition of EGFR is not restricted to particular nanomaterials, but was observed to work efficiently in combination with a variety of materials.