Fundamental research on design of nano-device using self-oscillating gel

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As a novel biomimetic polymer, we have been studying the polymer with an automonous self-oscillating function by utilizing oscillating chemical reactions. We succeeded in developing a novel self-oscillating polymer and gels by utilizing the Belousov-Zhabotinsky (BZ) reaction. The self-oscillating polymer is composed of poly(N-isopropylacrylamide) (PNIPAAm), in which Ru(bpy)_3 is incorporated as a catalyst for the BZ reaction. Under the coexistence of the reactants (malonic acid, sodium bromate, and nitric acid), the polymer undergoes spontaneous cyclic soluble-insoluble changes or swelling-deswelling changes (in the case of gel) without any on-off switching of external stimuli. To cause the self-oscillation of the polymer under physiological condition without utilizing non-biorelated BZ substrates, we have been attempting to construct the build-in system where the substrates other than organic acid are incorporated into the polymer itself. As the first step, acrylamide-2-methylpropanes … More ulfonic acid (AMPS) was incorporated into the poly(NIPAAm-co-Ru(bpy)_3) as the pH-control site. As the next step, we have attempted to introduce the oxidizing agent into the polymer. Methacrylamidopropyltrimethylammonium chloride (MAPTAC) with a positively charged group was incorporated into the poly(NIPAAm-co-Ru(bpy)_3) as a capture site for an anionic oxidizing agent (bromate ion). The bromate ion was introduced into the MAPTAC-containing polymer through ion-exchange process. By using the copolymer, self-oscillation only in the presence of organic acid was achieved. To synthesize an artificial biomachine with self-beating function which acts under physiological condition, we have developed another self-oscillating gel that can be driven by chemical energy of ATP decomposition. Anionic polymer gel with phosphoric groups, in which creatine kinase was immobilized, was prepared. When the gel was immersed in the ATP solution, the enzymatic reaction occurs in the gel and the concentration of calcium ion changes periodically. As a result, the gel repeats swelling and deswelling autonomously. Less