The photocatalytic inactivation effect of Ag–TiO2 on β-amyloid peptide (1–42)

Due to its low toxicity and excellent biocompatibility, titanium dioxide and its alloyed are widely used in biomedical applications. Furthermore, TiO2 can be excited by UV light to create charge carriers giving rise to photocatalytic redox reactions at its surface and photo-induced super-hydrophilicity. In this work, TiO2 films were modified with silver (Ag–TiO2) by the photocatalytic reduction of Ag+ from solution. The films and the adsorption of β-amyloid (1–42), were studied using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and atomic force microscopy (AFM). These films were confirmed to contain mainly anatase crystallites and the photo-reduced Ag was predominantly Ag0 (>0%). Ag loading of the TiO2 markedly enhanced the Raman signal (ca. 15-fold), but caused significant changes to the protein spectrum indicating non-specific binding of β-amyloid side chain residues to the silver. The amide modes remained well-resolved and were used to estimate the conformational change induced in the protein by the silver. Raman analysis showed an increase in the intensity of the band at ∼1665 cm−1 assigned to the disordered conformation of the β-amyloid, suggesting that the adsorption to the silver sites induces conformational changes. Contaminated surfaces were exposed to UVB irradiation, caused further conformational changes in the β-amyloid, which mildly inhibited amyloid fibril formation, thought to be induced through a photocatalytic mechanism.