Stimuli-responsive protoporphyrin IX silica-based nanoparticles for photodynamic therapy in vitro

Abstract

Nanoparticle-based delivery systems have been explored recently as efficient vehicles to transport photosensitizers for photodynamic therapy (PDT). In this study; we report the synthesis, characterization and in vitro application of a stimuli-responsive silica nanoparticle platform chemically functionalized with protoporphyrin IX (RR–PpIX–SiNPs). PpIX photosensitizers have been attached to the surface of SiNPs through a redox-responsive linker. PpIX molecules can be selectively released from the RR–PpIX–SiNP platform in their monomeric form in the presence of the highly reducing environment found in cancer cells. The structural, photophysical and photochemical properties of RR–PpIX–SiNPs were characterized and compared with a control sample (PpIX–SiNPs), which does not contained a redox-responsive linker. Cell viability measurements demonstrated that RR–PpIX–SiNPs were more phototoxic than PpIX–SiNPs. Confocal microscopy shows that RR–PpIX–SiNPs are mainly localized in lysosomes. Finally, the redox-responsive release of PpIX molecules was demonstrated in solution and in vitro using UV-vis spectrometry and confocal microscopy, respectively. We envision that further modification of this platform can render colloidal stability and target-specific properties by grafting polymeric chains and small molecules or biomolecules.