Design of Stable Bionanoparticles by PEG based Surface Modifications

Acetal-poly(ethylene glycol)/poy[(2-N,N-dimethylaminoethyl) methacrylate] (acetal-PEG/ PAMA) block copolymer was prepared via an oxianionic polymerization technique, which was established by our laboratory. The acetal-end group was converted to an aldehyde group by an acidic hydrolysis reaction, followed by the installation of biotin moiety at the end of the PEG chain via a reductive amination reaction of biocytin hydrazide. The biotin-PEG/PAMA block copolymer thus prepared was mixed with CdSe/ZnS nano-particles (QD) in aqueous media. The obtained polymer-QD complex showed extremely high dispersion stability even in the physiological saline condition. The adsorbed biotin-PEG/PAMA block copolymer on the QD formed the tethered chain fashion on the surface to improve the dispersion stability by the steric factor of the tethered chains. Since the PEG chain end on the QD surface possessed biotin moiety, it could be utilized for not only immunohistochemistry but also various other biological applications.