Protein Adsorption on Hybrids of Thermoresponsive Polymers and Single-Walled Carbon Nanotubes

Kazuo Umemura,Teruo Okano,Yoshikazu Kumashiro,Katsuki Izumi,Shusuke Oura

doi:10.1155/2016/3539609

Abstract

Poly(N-isopropylacrylamide) (PNIPAAm) is one of the most popular thermoresponsive polymers. Adsorption of RecA proteins onto hybrids of PNIPAAm and single-walled carbon nanotubes (SWNTs) was observed in the presence and absence of DNA molecules. Although RecA molecules were adsorbed efficiently onto the hybrid surfaces at 37°C, even in the absence of DNA molecules, the adsorption of RecA was inhibited at 4°C. These results suggest that the thermoresponsive functions of PNIPAAm were effective, even on the SWNT surfaces, which supports the possibility of developing nanobiodevices using PNIPAAm-SWNT hybrids. However, although RecA is a DNA binding protein, there was no significant difference in the adsorption of RecA onto PNIPAAm-SWNT surfaces with and without DNA molecules. This study provides fundamental information for potential biological applications of PNIPAAm-SWNT hybrids.

Highlights

Poly(N-isopropylacrylamide) (PNIPAAm) is one of the most common thermoresponsive polymers owing to its lower critical solution temperature (LCST) of 32∘C
We demonstrate the reactions of RecA proteins and DNA with PNIPAAm-single-walled carbon nanotubes (SWNTs) hybrids at two different temperatures (37∘C and 4∘C)
DNA molecules and/or RecA proteins reacted with the PNIPAAm-SWNT hybrids at 4∘C and 3 (4∘C) Sample 7 (37∘C)

Summary

Introduction

Poly(N-isopropylacrylamide) (PNIPAAm) is one of the most common thermoresponsive polymers owing to its lower critical solution temperature (LCST) of 32∘C. The LCST does not depend on the polymer molecular weight, as long as Mw is greater than 50,000 Da [5]. Because of these unique properties, PNIPAAm and related polymers have been intensively studied [6, 7]. These polymers have been used for various biomedical applications, such as the preparation of cell sheets [3, 4]. The fabrication of PNIPAAm polymer brushes on reduced graphene oxide and hydrogel-forming polymer films have been reported, respectively [8, 9]

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Results