Macroporous ordered titanium dioxide (TiO2) inverse opal as a new label-free immunosensor

Photonic crystal sensing materials have been validated that they are very sensitive to refractive index changes. Herein, three-dimensionally ordered macroporous (3DOM) (>50 nm) TiO2 inverse opal film has been fabricated by the self-assembly technique. Based on the TiO2 inverse opal film, the optical spectrometer was established for label-free immunosensor. The sensing performance of the 3DOM TiO2 was investigated using human IgG/goat anti-human IgG couple, which showed that the sensitivity of 3DOM TiO2 inverse opal film could reach to 1 μg mL−1 (equivalent to 1.5 pg mm−2) of protein concentration detection limit. The 3DOM TiO2 inverse opal has a large internal surface area, low fluorescence background and unique optical properties. These characteristics indicated the feasibility of 3DOM TiO2 inverse opal in label-free immunoassay.