Multiple presentation of scFv800E6 on silica nanospheres enhances binding efficacy toward HER-2 receptor in breast cancer cells

Spherical silica nanoparticles (SNP) have been synthesized and functionalized with anti-HER-2 scFv800E6 antibody by both localized histidine-tag recognition, leading to an oriented protein ligation, and glutaraldehyde cross-linking, exploiting a statistical reactivity of lysine amine groups in the primary sequence of the molecule. The targeting efficiency of nanocomplexes in comparison with free scFv was evaluated by flow cytometry using a HER-2 antigen-positive MCF-7 breast cancer cell line, exhibiting a 4-fold increase in scFv binding efficacy, close to the affinity of intact anti-HER-2 monoclonal antibody, which suggests the effectiveness of presenting multiple scFv molecules on nanoparticles in improving antigen recognition. Unexpectedly, the conjugation method did not affect the binding efficacy of scFv, suggesting a structural role of lysines in the scFv molecule. Confocal laser scanning microscopy confirmed the binding of nanocomplexes to HER-2 and also provided evidence of their localization at the cell surface. © 2011 American Chemical Society.