Division of roles of modified chains in organo-magnetic nanoparticles using Organo-modified agents having hydrophilic reactive polar groups at both ends: Formation of high-density single-particle layers and bioconjugation

Abstract

The behavior of an organo-modified chain that changes its role depending on the environment has been investigated. Long-chain carboxylic acids having a hydrophilic reactive polar group at both ends were allowed to act on magnetic nanoparticles to produce organo-modified particles. These amphiphilic organo-magnetic nanoparticles are synthesized by the reaction of a hydroxyl terminal group on the outermost surface of the magnetic particle and a carboxylic acid. With spreading at the air/water interface, an extremely condensed single-particle layer on the water surface was formed. It is evident that a long-chain carboxylic acid having a hydrophilic group at the terminal acts as a hydrophobic chain. Furthermore, when a Lysozyme enzyme as an ampholyte was allowed to act from the subphase, we observed that it adsorbed at the end of the modified chain. This implies that a hydrophilic group facing the subphase side exists. This phenomenon also occurred when the terminal comprised amino or carboxyl groups. Therefore, we observed that the surface-modified chain having the same chemical structure changed its role depending on the environment, and it can function as both a hydrophilic and a hydrophobic group.

Keywords: Adsorbed immobilization of enzyme; Amphiphilicity; Long-chain carboxylic acids having a hydrophilic reactive group at both ends; Magnetic nanoparticles; Surface modification.