Aminopropyl-functionalized cubic Ia3d mesoporous silica nanoparticle as an efficient support for immobilization of superoxide dismutase

In this research, the immobilization of superoxide dismutase (SOD) onto aminopropyl-functionalized KIT-6 [n-PrNH2-KIT-6] was investigated. This organo-functionalized mesoporous silica nanoparticle was prepared using a non-ionic surfactant and was fully characterized by XRD, nitrogen adsorption-desorption isotherm assay, IR and TGA techniques. An activity assay demonstrated that the immobilized SOD had a higher activity than the free enzyme. Further investigations using FT-IR, circular dichroism (CD), and probe 1-anilino-8-naphthalene sulfonate (ANS) fluorescence intensity measurements indicated that the structure of the enzyme did not change upon binding to the mesoporous silica, and that immobilized SOD was also less affected by higher temperatures. The melting temperatures of the free and immobilized enzymes were measured by differential scanning calorimetry (DSC), which showed that a fraction of immobilized enzyme was more stable and revealed that immobilized enzyme was partly reversible. (C) 2011 Elsevier B.V. All rights reserved.