Demonstration of Molecular Sensing Using QCM Device Coated with Stimuli-sensitive Hydrogel
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Demonstration of Molecular Sensing Using QCM Device Coated with Stimuli-sensitive Hydrogel Yoshimi. Seida1,2, Yuri, Nakano2 and Yoshio Nakano 2 1 Natural Science Laboratory, Toyo University, Tokyo, 112-8606 Japan 2 Interdisciplinary Graduate School of Science and Technology, Tokyo Institute of Technology, Yokohama, 226-8504 Japan ABSTRACT Molecular sensing using stimuli-responsive viscoelastic property of amphiphilic polymer hydrogel was demonstrated. Thermo-responsive poly(N-isopropylacrylamide); NIPA, hydrogel immobilizing bovine serum albumin (BSA) in its polymer chain was synthesized on the AT-cut QCM (Quartz crystal microbalance). The device was provided to the sensing of anti-BSA antibody. The resonance behavior of QCM in response to the adsorption of anti-BSA antibody on the hydrogel was observed based on both the resonance frequency and resistance of QCM with impedance analysis. The QCM device coated with the LCST polymer hydrogel revealed a characteristic resonance behavior in response to the adsorption of anti-BSA antibody in the collapse phase of gel at which the gel lost most of its hydrated water. The resonance frequency and resistance in the collapsed gel were highly sensitive and their changes in response to the target adsorption were much larger than in the swelling state of gel. The use of the device at the LCST of NIPA gel is ideal because the largest amplification of the adsorption signal is available along with the largest phase change of NIPA gel. INTRODUCTION The phase change of stimuli-responsive hydrogels can be interpreted to occur through a change in hydration of the constituent polymer. The change in hydration is able to be induced by a change in surrounding conditions or by some stimuli on the gels. According to the principle of phase behavior in the hydrogels, the phase change of hydrogel in response to adsorption of foreign molecules is also available. An adsorption that alters the hydration of polymer will induce a large change of property of gel. Based on this simple assumption, the gels will be candidate of molecular sensor that is working via the adsorption-induced phase change of gel. The phase change of the gels is able to monitor by quartz crystal microbalance with high sensitivity and resolution [1]. Viscoelastic change of the hydrogel occurring along with the change in the hydration of hydrogels is a good measure of gel in the application as a sensor material. The simple sensing of viscoelasticity of gel can be performed through coupling the gels with QCM [1,2]. In the present study, molecular sensing via adsorption-induced phase change of gel was examined using antigen-antibody reaction. Antigen-immobilized N-isopropyl acrylamide; NIPA gel was synthesized and coupled with QCM to demonstrate the molecular sensing based on the viscoelastic phase property of the stimuli-responsive hydrogel in response to the target adsorption.
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EXPERIMENT Synthesis of BSA-Immobilized NIPA Gel Regent grade N-hydroxy-succinimide ester, albumin from bovine serum Cohn Fraction V, pH 7.0 (BSA; W
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