Stable and Highly Efficient Antibody–Nanoparticles Conjugation

Functional ligands and polymers have frequently been used to yield target-specific bio-nanoconjugates. Herein, we provide a systematic insight into the effect of the chain length of poly(oligo (ethylene glycol) methyl ether acrylate) (POEGMEA) containing polyethylene glycol on the colloidal stability and antibody-conjugation efficiency of nanoparticles. We employed Reversible Addition–Fragmentation Chain Transfer (RAFT) to design diblock copolymers composed of 7 monoacryloxyethyl phosphate (MAEP) units and 6, 13, 35, or 55 OEGMEA units. We find that when the POEGMEA chain is short, the polymer cannot effectively stabilize the nanoparticles, and when the POEGMEA chain is long, the nanoparticles cannot be efficiently conjugated to antibody. In other words, the majority of the carboxylic groups in larger POEGMEA chains are inaccessible to further chemical modification. We demonstrate that the polymer containing 13 OEGMEA units can effectively bind up to 64% of the antibody molecules, while the binding efficiency drops to 50% and 0% for the polymer containing 35 and 55 OEGMEA units. Moreover, flow cytometry assay statistically shows that about 9% of the coupled antibody retained its activity to recognize B220 biomarkers on the B cells. This work suggests a library of stabile, specific, and bioactive lanthanide-doped nanoconjugates for flow cytometry and mass cytometry application.