The End Group Modification of Phospholipid Polymer Brush Grafted on Ferric Oxide Nanoparticles for Diagnostics
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The End Group Modification of Phospholipid Polymer Brush Grafted on Ferric Oxide Nanoparticles for Diagnostics Ryosuke Matsuno, and Kazuhiko Ishihara Center for NanoBio Integration and Department of Material Engineering, School of Engineering, The University of Tokyo, Tokyo, 113-8586, Japan ABSTRACT The end group of 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer brush on ferric oxide (Fe3O4) nanoparticles was converted from bromine (Br) to amine (NH2) by “staudinger reduction”. At first, poly(MPC) was grafted by atom transfer radical polymerization (ATRP) from surface initiator fixed on Fe3O4 nanoparticles. Br element located in MPC polymer brush was converted to azide (N3). Consequently, N3 was converted to NH2 using triphenyl phosphine (PPh3) and H2O. Characterization at each step was confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) measurements. As an example aiming for diagnostic material, fluorescein isothiocyanate (FITC) was able to immobilize via reaction between NH2 group located on the end of poly(MPC) chain and isothiocyanate. The surface structure own ability of capture biomolecular throw condensation between amine in polymer brush and carboxyl group in biomolecular. INTRODUCTION Nanoparticles are widely applied as diagnostic reagents, drug-delivery carriers or bioaffinity beads[1,2]. In particular, magnetic particles have been widely used in the study of biomedical applications. When we look ahead to the future, it is needed to construct precisely designed surface containing such as high bioaffinity and capability to capture of small amount protein or specific protein among various protein. As a method to construct precisely designed biocompatible polymer surface, atom transfer radical polymerization (ATRP) was widely used as a living free radical polymerization[3]. ATRP has advantages such as control of molecular weight, narrow polydispersivity, easy synthesis of block copolymer, and preparation of high density polymer brush under mild condition. Previously, we have demonstrated synthesis of poly (2-methacryloyloxyethyl phosphorylcholine (MPC)) brush on ferric oxide (Fe3O4) by ATRP from immobilized initiator includes bromine that ATRP moiety[4]. Here, it is known that poly(MPC) has been not affected for reduction of nonspecific binding, salt concentrations, pH and temperature. In this state, the poly(MPC)-grafted Fe3O4 could not be used for diagnostic material and collection material using magnetic interaction because poly(MPC) inhibit protein/cell adsorption and activation [5-8]. To introduce immobilization part for protein, pnitrophenyloxycarbonyl polyethylene glycol methacrylate (MEONP) monomer that has active ester was added as a block component. The poly(MPC-b-MEONP)-grafted Fe3O4 can capture proteins via active ester to amine of proteins. However, on careful consideration, this immobilization method had disadvantage for capture protein because immobilization part located in the side chain, not locate most outer surface. W
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