title: Single-domain protein A-engineered magnetic nanoparticles: toward a universal strategy to site-specific labeling of antibodies for targeted detection of tumor cells.
abstract: Highly monodisperse magnetite nanocrystals (MNC) were synthesized in organic media and transferred to the water phase by ultrasound-assisted ligand exchange with an iminodiacetic phosphonate. The resulting biocompatible magnetic nanoparticles were characterized by transmission electron microscopy, dynamic light scattering, and magnetorelaxometry, indicating that this method allowed us to obtain stable particle dispersions with narrow size distribution and unusually high magnetic resonance T(2) contrast power. These nanoparticles were conjugated to a newly designed recombinant monodomain protein A variant, which exhibited a convincingly strong affinity for human and rabbit IgG molecules. Owing to the nature of antibody-protein A binding, tight antibody immobilization occurred through the Fc fragment thus taking full advantage of the targeting potential of bound IgGs. If necessary, monoclonal antibodies could be removed under controlled conditions regenerating the original IgG-conjugatable MNC. As a proof of concept of the utility of our paramagnetic labeling system of human IgGs for biomedical applications, anti-HER-2 monoclonal antibody trastuzumab was immobilized on hybrid MNC (TMNC). TMNC were assessed by immunoprecipitation assay and confocal microscopy effected on HER-2-overexpressing MCF-7 breast cancer cells, demonstrating excellent recognition capability and selectivity for the target membrane receptor.
authors.affiliation: Dipartimento di Scienze Cliniche Luigi Sacco, Università di Milano, Ospedale L. Sacco, via G.B. Grassi 74, 20157 Milano, Italy.
authors.forename: Serena
authors.initials: S
authors.lastname: Mazzucchelli
authors.forename: Miriam
authors.initials: M
authors.lastname: Colombo
authors.forename: Clara
authors.initials: C
authors.lastname: De Palma
authors.forename: Agnese
authors.initials: A
authors.lastname: Salvadè
authors.forename: Paolo
authors.initials: P
authors.lastname: Verderio
authors.forename: Maria D
authors.initials: MD
authors.lastname: Coghi
authors.forename: Emilio
authors.initials: E
authors.lastname: Clementi
authors.forename: Paolo
authors.initials: P
authors.lastname: Tortora
authors.forename: Fabio
authors.initials: F
authors.lastname: Corsi
authors.forename: Davide
authors.initials: D
authors.lastname: Prosperi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000737:chemistry*; D000911:Antibodies, Monoclonal / Q000737:chemistry; D061067:Antibodies, Monoclonal, Humanized; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000473:pathology; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry; D008279:Magnetic Resonance Imaging / Q000379:methods; D008422:Materials Testing; D008969:Molecular Sequence Data; D053758:Nanoparticles / Q000737:chemistry; D009930:Organic Chemicals / Q000737:chemistry; D015202:Protein Engineering / Q000379:methods; D011817:Rabbits; D000068878:Trastuzumab
chemical_list: D000906:Antibodies; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D007074:Immunoglobulin G; D009930:Organic Chemicals; D000068878:Trastuzumab