Merocyanine Complexes Coupled with Plasmonic Au Nanoparticles for Inhibiting Tau Aggregation

Abstract

Singlet oxygen (1O2) has been recently identified as the key mechanism for depressing β-amyloid (Aβ) accumulation and neurofibrillary tangles (NFTs). Slow cell internalization and short half-life of photosensitizing effects still impede the application of nanophotosensitizers for photodynamic therapy (PDT). The current major challenge of using spiropyran for PDT is the extremely short half-life of its ring-opened isomer, merocyanine. Merocyanine is the center of generation of 1O2. Here, we report that the complexation of spiropyran onto Au nanoparticles greatly enhances the stability of merocyanine (half-life is 91.6 h). Additionally, Au nanoparticles sharply decelerate the reversion of merocyanine back to spiropyran (a ring-closed form) by modifying the energy configuration of merocyanine, resulting in generation of a long-lived 1O2 phototherapy response (24 h) in the intracellular environment for depressing tau aggregation (a 32% reduction of NFT formation).

Last Advances on Hydrogel Nanoparticles Composites in Medicine: An Overview with Focus on Gold Nanoparticles

“…The system made its delivery possible in the active form to the intracellular environment. [62] More generally, Au NPs alone have been widely employed not only in disease treatments but also in sensor chemistry, thanks to the tunability of their optoelectrical properties as well as the easy functionalization of their surface. [121,122] The benefit of detecting extremely low quantities of a compound has been exploited both in the pollutant, pesticides and metal ions detection, as well as in the biomedical field.…”

“…Indeed, in a recently published work, a photosensitizer agent (merocyanine) promoting the production of reactive oxygen species (ROS) against β‐amyloid aggregation has been stabilized by the presence of Au NPs into a hydrogel. The system made its delivery possible in the active form to the intracellular environment [62] …”

Recent Development of Photochromic Polymer Systems: Mechanism, Materials, and Applications

“…Although SP polymer films have good photoresponse, their fatigue resistance is poor, and long-term light exposure will reduce the performance of the films and limit their application range. Therefore, researchers have discovered SP polymer NPs with excellent fatigue resistance [ 75 ], in which SP is chemically doped into hydrophobic or low-polarity polymers to improve their photochromic efficiency [ 76 ], such as in terms of light stability and photoreversibility. The photochromic polymers can also be modified by functionalized monomers, and the photochromic polymers can be chemically attached to different substrates to reduce the effects of environmental degradation.…”