The dynamics of oxygenation to Aβ fibrils using an azobenzene–boron complex type photocatalyst and light energy

Alzheimer disease (AD) is characterized by the deposition of amyloid fibrils, such as senile plaques, composed of amyloid β peptide (Aβ). As a novel therapeutic modality, we have previously developed an azobenzene-boron complex type photocatalyst that photo-oxygenates Aβ fibrils. And the in vivo photo-oxygenation reaction using this photocatalyst successfully reduced the Aβ fibrils in the brain. Since Aβ fibril is one of the causative molecules in the brains of AD patients, the photocatalyst is expected to be a new modality for disease-modifying therapy against AD. However, the exact relationship between light energy and photo-oxygenating activity for Aβ fibrils remains unclear. In this paper, we have demonstrated using mass spectrometric analysis that the number of oxygens added to Aβ fibrils was increased in a sigmoidal curve with the logarithm of light energy. We also showed that it depended on the total light energy, not on the irradiance. These data suggest that photo-oxygenation proceeds at even lower levels of light energy, and it may be possible to induce photo-oxygenation in areas where light penetration is difficult, such as the human brain.