Enhancement of protoporphyrin IX performance in aqueous solutions for photodynamic therapy

Molecular modification of protoporphyrin IX (PpIX) was conducted to improve its water solubility and therapeutic performance for photodynamic therapy. The carboxylic acid and the two nitrogen atoms in the core of PpIX molecule were protonated following by conjugation with 3-aminopropyl triethoxysilane (APTES). Then, folic acid (FA) was conjugated to the APTES-coated PpIX (MPpIX) through chemical bonding between FA and protonated PpIX. The results showed that APTES coating can stabilize PpIX and increase its water solubility. Consequently, this leads to the enhancement in luminescence and singlet oxygen production. Upon X-ray irradiation, singlet oxygen can be detected in the MPpIX but not in PpIX. This means that MPpIX can be used for deep cancer treatment as X-ray can penetrate deeply into tissue. Molecular modification also reduces the dark toxicity of PPIX and increases their cell uptake. All these traits indicate that the Molecular modification of PpIX may potentially improve the efficacy of photodynamic therapy for cancer treatment.