Temperature modulated solubility and activity alteration for oligo-(N-isopropylacrylamide)–iron tetrasulfonatophthalocyanine conjugates as a new mimetic peroxidase

Abstract

Iron tetrasulfonatophthalocyanine (FeTSPc) was covalently bound to the terminus of a temperature sensitive oligomer, oligo-N-isopropylacrylamide (ONIPAAm), to form a new mimetic enzyme (ONIPAAm–FeTSPc) to mimic the peroxidase activity of horseradish peroxidase. This FeTSPc-based mimetic enzyme exhibits a lower critical solution temperature (LCST) of 32 °C in neutral solution. It precipitates from water above the LCST and redissolves when the solution temperature is lowered below the LCST. The peroxidase activity of this mimetic enzyme was studied based on its catalytic effect on the reaction of p-hydroxyphenylpropionic acid and H₂O₂. The results show that the peroxidase activity of the new mimetic enzyme is higher than that of the free FeTSPc. The possibility of its application in the analytical field was also tested by the determination of H₂O₂ and ONIPAAm–FeTSPc; the detection limits are 8.2 × 10⁻⁹ and 1.7 × 10⁻⁹ mol L⁻¹, respectively.