Iron oxide nanoparticles functionalized with novel hydrophobic and hydrophilic porphyrins as potential agents for photodynamic therapy

The preparation of novel porphyrin derivatives and their immobilization onto iron oxide nanoparticles to build up suitable nanotools for potential use in photodynamic therapy (PDT) has been explored. To achieve this purpose, a zinc porphyrin derivative, ZnPR-COOH, has been synthesized, characterized at the molecular level and immobilized onto previously synthesized iron oxide nanoparticles covered with oleylamine. The novel nanosystem (ZnPR-IONP) has been thoroughly characterized by a variety of techniques such as UV-Vis absorption spectroscopy, fluorescence spectroscopy, X-ray photoloectron spectroscopy (XPS) and transmission electron microscopy (TEM). In order to probe the capability of the photosensitizer for PDT, the singlet oxygen production of both ZnPR-IONP and the free ligand ZnPR-COOH have been quantified by measuring the decay in absorption of the anthracene derivative 9,10-anthracenedipropionic acid (ADPA), showing an important increase on singlet oxygen production when the porphyrin is incorporated onto the IONP (ZnPR-IONP). On the other hand, the porphyrin derivative PR-TRIS3OH, incorporating several polar groups (TRIS), was synthesized and immobilized with the intention of obtaining water soluble nanosystems (PR-TRIS-IONP). When the singlet oxygen production ability was evaluated, the values obtained were similar to ZnPR-COOH/ZnPR-IONP, again much higher in the case of the nanoparticles PR-TRIS-IONP, with more than a twofold increase. The efficient singlet oxygen production of PR-TRIS-IONP together with their water solubility, points to the great promise that these new nanotools represent for PDT

Upconversion nanomaterials for photodynamic therapy

Photodynamic therapy (PDT) is an innovative treatment where cancerous tumors are destroyed by the reactive oxygen species generated by photosensitizer drugs following activation with light typically of visible wavelengths. However, such visible light has limited penetration depth through skin and other healthy tissues, so deep-lying tumors can be difficult to treat. Upconversion nanoparticles (UCNPs) can be used as photosensitizer nanocarriers to overcome the limitation of visible light excitation. Near infrared (NIR) light has significantly deeper penetration depth than visible light through human tissue and can be used to excite the UCNPs that then emit light at shorter wavelengths. The emission of the UCNPs overlaps with the absorption band of the vast majority of currently used photosensitizers. Thus, the upconversion luminescence emitted by the UCNPs can be used to excite the photosensitizer bound in close proximity to the nanoparticles, inducing the generation of reactive oxygen species and thereby killing the cancer cells. This chapter introduces the proof of concept in the use of UCNPs for PDT and provides an insight into the state-of-art use of these nanomaterials for both in vitro and in vivo PDT