N-Isopropylacrylamide is copolymerized with 4-vinylpyridine and N, N＇-methylenebisacryl amide. The obtained gel is swollen below 10 degrees C and shrunken above 40 degrees C in aqueous solutions. Coordination of Ru(EDTA) to the gel immobilized on a gold electrode is investigated by means of cyclic voltammetry. Ru-III(EDTA) or Ru-II(EDTA) coordinates to one or two pyridine rings of the gel, respectively. Ru(EDTA) coordinated to two pyridine groups gradually dissociates to be Ru(EDTA) coordinated to one pyridine ring during potential cycling. The D-app value for the swollen gel having Ru-II/III(EDTA) coordinated to one pyridine ring is estimated to be 20-fold larger than that for the shrunken gel.