O6-alkylguanine-DNA transferase (SNAP) as capture module for site-specific covalent bioconjugation of targeting protein on nanoparticles

A bimodular genetic fusion comprising a delivery module (scFv) and a capture module (SNAP) is proposed as a novel strategy for the biologically mediated site-specific covalent conjugation of targeting proteins to nanoparticles. ScFv800E6, an scFv mutant selective for HER2 antigen overexpressed in breast cancer cells was chosen as targeting ligand. The fusion protein SNAP-scFv was irreversibly immobilized on magnetofluorescent nanoparticles through the recognition between SNAP module and pegylated O 6-alkylguanine derivative. The targeting efficiency of the resulting nanoparticle against HER2-positive breast cancer cells was assessed by flow cytometry and immunofluorescence.