Modified nanoporous titanium dioxide as a novel carrier for enzyme immobilization.

ε-Poly-L-lysine (EPL)-modified mesoporous titanium dioxide (M-TiO2) was assembled through the electrostatic attraction between EPL and M-TiO2. Through modification, the M-TiO2 surface tends to form multilayered and complex architectures, which can be used as artificial matrices to change the microenvironment of carriers for enzyme immobilization. The modified M-TiO2 was characterized through scanning electron microscopy, Fourier transform infrared spectroscopy, zeta potential analysis, and thermogravimetric analysis. All of the immobilized enzymes with negative charges display strong storage stability, thermal stability, and good reusability. Results indicate that EPL can self-assemble onto the surface of M-TiO2 and form a considerable number of active coatings. Our results also demonstrate that this simple and novel method can be potentially used to immobilize negatively charged enzymes for biosensor applications.