Photodynamic and Photothermal Therapies using Nanotechnology Approach in Alzheimer's Disease

Alzheimer's disease is a neurodegenerative disease that impairs cognitive function. The incidence of Alzheimer's disease increases with the increase in the elderly population. Although the clear pathogenesis of Alzheimer's disease is not yet known, the formation of amyloid plaques and tau fibrils, diminished acetylcholine levels, and increased inflammation can be observed in patients. Alzheimer's disease, whose pathogenesis is not fully demonstrated, cannot be treated radically. Since it has been observed that only pharmacological treatment alone isn't sufficient, alternative approaches have become essential. Among these approaches, nanocarriers greatly facilitate the transport of drugs since the blood-brain barrier is an important obstacle to the penetration of drugs into the brain. Photosensitizers trigger activation after exposure to near-infrared radiation light of a suitable wavelength or laser light, resulting in the selective destruction of Aβ plaques. Photodynamic therapy and photothermal therapy have been investigated for their potential to inhibit Aβ plaques through photosensitizers. By ThT fluorescence measurements, TAS-loaded Ce6 micelles show inhibiting Aβ monomers from formation Aβ aggregates and degradation of protofibrills to small fragments. By using these photosensitizers, near-infrared radiation fluorescence imaging can be used as a theranostic. In this review, potential treatment options for photodynamic therapy and photothermal therapy for Alzheimer's disease are summarised, and a simultaneous or combined approach is discussed, taking into account potential nanotheranostics.