Immobilization of horseradish peroxidase in three-dimensional macroporous TiO2 matrices for biosensor applications

Three-dimensional macroporous TiO₂ was synthesized by a sol-gel procedure using polystyrene colloidal crystals as templates. SEM showed that a face-centered cubic (FCC) 3D macroporous structure was obtained. Horseradish peroxidase (HRP) was successfully immobilized on the surface of an optically transparent electrode (OTE). Photoelectrochemical properties were characterized using a three electrodes system and an ultraviolet lamp. The HRP/TiO₂/OTE displays a rapid photocurrent response, approximately 178.7 nA, under UV illumination (380 nm). The sensitivity of H₂O₂ detection was 70.04 μA/mM without UV illumination, and it increased to 102.97 μA/mM when illuminated by UV. The amperometric response was also enhanced. The high response was due to the good biocompatibility of TiO₂ and excellent photoelectrical property and the large effective surface of the three-dimensionally ordered macroporous structure.