Adsorption immobilization of biomolecules from subphase on Langmuir monolayers of organo-modified single-walled carbon nanotube

Abstract

The subphase adsorption behavior and the morphology of the trypsin enzyme, lysozyme enzyme, cytochrome C protein, and glucose oxidase present on the Langmuir monolayer of organo-modified single-wall carbon nanotubes (SWCNTs) were investigated. Furthermore, we estimated the maintenance characteristics of the three-dimensional structure of organo-modified SWCNT film-adsorbed biomolecules when exposed to a high-temperature environment. In this study, each biomolecule, which was an amphoteric electrolyte, was hydrophilized by mixed acid treatment and electrostatically adsorbed on the charged SWCNT surfaces at the air–water interface. An amide band derived from the adsorbent was confirmed by the infrared (IR) spectra of the biomolecule adsorbing organo-SWCNT multilayers. The atomic force microscopic image of the X-type monolayer of adsorbed biomolecules on organo-SWCNTs shows the adsorbent shape. The out-of-plane X-ray diffraction profiles of the biomolecule adsorbing organo-SWCNT multilayers confirmed the maintenance of the layered structure due to the presence of the adsorbent. After heat treatment, the secondary structure of the biomolecular adsorbing organo-SWCNT multilayers was maintained up to 100–150 °C, as confirmed by the IR spectrum.