Magnetic nanoparticles covered with polycyclic aromatic hydrocarbons as singlet oxygen carriers for combining photodynamic therapy and magnetic hyperthermia

We developed hybrid nanoparticles consisting of a magnetic core (zinc-doped iron oxide - IONP:Zn) and a polycyclic aromatic hydrocarbon (PAH) shell (naphthalene-@Naph or anthracene-@Anth) to improve cancer and infectious disease therapies. PAHs are employed as shell material due to their ability to capture, store, and deliver singlet oxygen (O-1(2)) on demand and under relatively controlled conditions. The magnetic core is aimed at generating heat via magnetic hyperthermia (MHT). The PAH layer will be responsible for trapping O-1(2) ex-situ (loading), carrying it into the tumor cells, and releasing O-1(2) in situ upon the heating caused by the magnetic core. We characterized the nanoparticles by Dynamic Light Scattering, X-ray diffraction, transmission electron microscopy, and fluorescence spectroscopy. Results indicate that IONP:Zn was successfully synthesized and covered with either anthracene or naphthalene. Both shells could trap O-1(2) produced ex-situ by methylene blue (MB), but the IONP:Zn@Naph presented the highest O-1(2) trapping efficiency. Fluorescence spectroscopy suggested the cycloreversion reaction and the consequent O-1(2) release only when the nanoparticles' temperature increases above 40 degrees C. Cytotoxicity experiments using E. coli bacterial growth curves revealed that the IONP:Zn@Naph NPs loaded with O-1(2) are not intrinsically toxic at 37 degrees C. However, when heated to temperatures above 40 degrees, they caused a decreased bacterial growth. Maximum toxicity occurs at 44 degrees C. Considering that the IONP:Zn@Naph nanoparticles presented a higher O-1(2) release temperature (>= 40 degrees C) compared to soluble naphthalene derivatives (>= 37 degrees C) and that the human basal temperature is similar to 37 degrees C, the IONP:Zn@Naph requires temperatures for O-1(2) release that is high enough for not releasing O-1(2) before achieving the target, and feasible to be reached by magnetic hyperthermia. Therefore, these nanodevices are promising for developing new cancer and infectious disease therapies.