(217do) Fabrication and Application of Catalase Covalently Immobilized On TiO2 Nanotubes

 At present, nanotubes, especially carbon nanotubes (CNTs), have evolved as an important kind of enzyme carriers because of their high surface-to-volume ratio and amazing mechanical properties. Nevertheless, the poor biocompatibility and hydrophilicity of CNTs are not beneficial to afford the suitable microenvironment for immobilized enzymes. Herein, TiO₂ nanotubes (TNTs) with desirable biocompatibility and hydrophilicity were firstly fabricated by a hydrothermal method with rutile TiO₂ nanopowders as the crude material. Transmission electron microscope (TEM) images exhibit that the obtained TNTs are uniformly dispersed with the external diameter about 10 nm and the length about 120 nm. Their Raman spectra indicate that the TNTs are composed of orthorhombic protonic lepidocrocite titanate. Their water contact angle and BET surface specific area are 27.7° and 305.4 m²·g^-1, respectively, both of which are in favor of the enzyme immobilization. Catalase (CAT) pre-modified by 3, 4-dihydroxyphenylpropionic acid was covalently attached on the surface of TNTs via the chelation interaction between catechol groups from pre-modified catalases and Ti⁴⁺ from TNTs. The dispersive X-ray spectroscope (EDX) mapping and Fourier Transform Infrared (FTIR) spectra testify the successful immobilization of enzyme. Thermogravimetric analysis (TGA) of TNTs-CAT with different content CAT demonstrates that the highest loading quantity can reach 800 mg protein/(g supports) and TNTs-CAT activity can reach 60% of free CAT activity. Further stability experiment results demonstrate the enhanced thermal and storage stabilities of TNTs-CAT over native CAT; moreover, the reusability of TNTs-CAT is realized and reserved 52.6% of the initial activity after 9 cycles. It is reasonably believed that covalently immobilized TNTs-CAT showed distinct advantages over the native CAT for potential industrial application.