Anal. Chem. 2004, 76, 2649-2655
Evaluation of 2-Methacryloyloxyethyl Phosphorylcholine Polymeric Nanoparticle for Immunoassay of C-Reactive Protein Detection Jongwon Park,†,‡ Shigeru Kurosawa,‡ Junji Watanabe,† and Kazuhiko Ishihara*,†
Department of Materials Engineering, School of Engineering, The University of Tokyo, Tokyo, Japan, and National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
To prepare novel 2-methacryloyloxyethyl phosphorylcholine (MPC)-polymeric nanoparticle (MPC-PNP), watersoluble amphiphilic phospholipid polymer, poly [MPCco-n-butyl methacrylate (BMA)-co-p-nitrophenyloxycarbonyl poly(ethylene glycol) methacrylate (MEONP) (PMBN)], which has active ester groups for bioconjugation on the side chains, was synthesized. MPC-PNP was prepared by a solvent evaporation technique where the poly(L-lactic acid) was used as core and PMBN was applied as an emulsifier and a surface modifier under systematical design of well-arranged phospholipids polar groups in its surface. Characteristics for MPC-PNP were thoroughly investigated with dynamic light scattering, electrophoresis light scattering, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy measurements. Through a protein adsorption test, the phosphorylcholine group on the surface of MPC-PNPs, which had their active ester groups substituted by glycine, were shown to suppress the nonspecific adsorption of bovine serum albumin. These particles were used for C-reactive protein (CRP) detection, where anti-CRP monoclonal antibodies were immobilized on the MPC-PNP using the active ester group, while the remaining active ester groups were thoroughly reacted with glycine. The detection limit about serum-free CRP in the calibration curve was shown to extend from 0.01 to 10 mg/dL when anti-CRP antibody immobilized MPC-PNP was used for serum-free CRP detection. This compares favorably with measurement using polystyrene nanoparticles that were shown to detect from 0.1 to 10 mg/dL by an immunoagglutination technique. Also, for the detection of CRP in serum, MPCPNP was shown to give the same calibration curve explained by the efficient suppression of nonspecific binding. Furthermore, denaturation of immobilizing antiCRP antibody on the MPC-PNP hardly occurred despite increasing the temperature. It is concluded that MPCPNP is unique due to the design of its interfacial properties, also it will perform well in a diagnostic immunoassay because of its optimized material properties. The C-reactive protein (CRP) is synthesized by the liver in response to interleukin-6 and is well known as one of the classical acute-phase reactants and as a marker of inflammation. The serum 10.1021/ac035321i CCC: $27.50 Published on Web 04/01/2004
© 2004 American Chemical Society
CRP level may rise from a normal level of
