Fabrication of smart biointerfaces in nanochannels with a thiolated temperature-responsive polymer

Abstract

Event Abstract Back to Event Fabrication of smart biointerfaces in nanochannels with a thiolated temperature-responsive polymer Yan Xu1, Misato Shinomiya1, 2 and Atsushi Harada2 1 Osaka Prefecture University, Nanoscience and Nanotechnology Research Center, Japan 2 Osaka Prefecture University, Department of Applied Chemistry, Graduated School of Engineering, Japan Introduction: Recently, nanofluidic devices have attracted much attention in the fields of chemistry, biology, and medicine. For example, nanofluidic devices are very promising in the development of early diagnostic tools for diseases because nanochannels in the nanofluidic devices allow confining biomolecules such as proteins, DNAs at the single molecular level[1]. However, these applications rely on the precise control of fluids in nanochannels, which is still a challenge in nanofluidics due to the extreme difficulty to construct fluid control units in nanochannels. Therefore, we proposed a concept of smart nanofluidic control (SNC). In SNC, the ‘open’ and ‘closed’ states of nanochannels are smartly controlled by the change of the external stimuli such as temperature, pH, light, through self-assembled stimuli-responsive interfaces which are locally constructed in nanochannels (Figure 1). Towards the realization of SNC, we have first achieved the fabrication of gold nanopatterns in glass nanochannels[2]-[4]. The gold nanopatterns in nanochannels provide robust surfaces to form self-assembled monolayers (SAM) when reacting with thiolated molecules. In this study, we focused on temperature-responsive SNC. A thiolated temperature-responsive polymer, poly(N-isopropylacrylamide) (referred to as PNIPAAm-SH, Figure 2), was specially designed and synthesized to fabricate smart biointerfaces in nanochannels for SNC. Materials and Methods: The SNC chips (Figure 3) were fabricated on fused-silica glass substrates using the methods previously reported by us[2]-[4]. PNIPAAm-SH was synthesized by a reversible addition fragmentation chain transfer (RAFT) polymerization. While SAMs of PNIPAAm-SH prepared on the gold-deposited glass substrates were used to characterized the bulk interfacial properties, SAMs of PNIPAAm-SH formed on the gold pattern surfaces in nanochannels were used to evaluate their capability to control fluids in nanochannels using an experimental setup previously reported by us[5]. Results and Discussion: The well-controlled structures of synthesized PNIPAAm-SH were identified by H1 NMR. Independent on polymerization time, PNIPAAm-SH with small molecular weight lower than 10,000 and narrow polydispersity lower than 1.2 were obtained, which is considered to be appropriate to inject into nanochannels. The SAMs formed on the gold surface using PNIPAAm-SH of different concentration were elementally confirmed by XPS and exhibited smooth morphology having extremely small roughness lower than that of glass substrate. Further, the synthesized PNIPAAm-SH exhibited sharp sol-gel phase transition at 30.8 °C in solution, suggesting that it would possess a quick temperature responsiveness in nanochannel, which is very ideal for SNC. Finally, nanofluidic experiments conducted below and above the sol-gel phase transition temperature revealed that the smart biointerfaces consisting of SAMs of PNIPAAm-SH on the gold pattern surfaces in the nanochannels allowed the smart control of fluids in the nanochannels. Conclusion: By fabricating a smart PNIPAAm-SH biointerfaces in nanochannels, SNC was achieved for the first time. This work was partially supported by JSPS KAKENHI Grant Numbers 26706010,26630403, and MEXT KAKENHI Grant Number 26107714, and the Asahi Glass Foundation.