Incorporation of methylene blue into mesoporous silica nanoparticles for singlet oxygen generation

Methylene blue is a known photosensitizer with an ability to generate singlet oxygen. The main active species is the monomeric form. However, this dye has a tendency to self-aggregate to form dimers and higher aggregates, which are less active for O-1(2) generation. In this study we propose different strategies to incorporate methylene blue into porous silica nanoparticles. The design of the synthesis is a key parameter to avoid both leaching of the dye and its self-aggregation. The negatively charged silica matrix allows the incorporation of the dye, which is cationic, with no leaching, whereas the presence of phenyl functions in the matrix favors the monomeric form of methylene blue (MB). We observe that both dimeric and monomeric forms of MB can generate O-1(2) species when confined inside a silica matrix, improving the activity compared to the bare dye in solution.

Automated summary

In this study, different strategies are proposed to incorporate methylene blue into porous silica nanoparticles. The design of the synthesis plays a key role in preventing dye leaching and self-aggregation. The negatively charged silica matrix enables the incorporation of the cationic dye without leaching, and the presence of phenyl functions favors the monomeric form of methylene blue. Both dimeric and monomeric forms of methylene blue can generate O-1(2) species when confined inside a silica matrix, exhibiting improved activity compared to the bare dye in solution.