The embedding of meta-tetra(hydroxyphenyl)-chlorin into silica nanoparticle platforms for photodynamic therapy and their singlet oxygen production and pH-dependent optical properties.

This study relates to nanoparticle (NP) platforms that attach to tumor cells externally and only deliver singlet oxygen for photodynamic therapy (PDT) while conserving the embedded photosensitizers (PS). As a model, we demonstrate the successful embedding of the PS meta-tetra(hydroxyphenyl)-chlorin (m-THPC) in NP that are based on a sol-gel silica matrix and also show its positive effect on the singlet oxygen production. The embedding of m-THPC inside silica NP is accomplished by a modified Stöber sol-gel process, in which (3-aminopropyl)-triethoxysilane is introduced during the reaction. Singlet oxygen delivery by the targetable photodynamic NP exceeds that from free PS molecules. In the physiological pH range, there is no significant pH-induced decrease in the fluorescence of m-THPC embedded in silica NP, which might otherwise affect the efficiency of PDT.