Generation and detection of singlet oxygen in complex systems for cell lesions studies using upconversion nanoparticles

Abstract

Electronically excited molecular oxygen at the singlet state 1”g (1O2) is highly reactive against organic molecules with high electron density. Processes of 1O2-controlled generation may occur in physiological and pathological situations. Although, 1O2 reactions with nucleic acids (DNA and RNA) have been extensively studied, since they cause lesions related to several cytotoxic and pathological processes. Thus, it is important to study this molecule in complex systems.Trivalent rare earth ions (TR3+) doped nanoparticles can exhibit upconversion phenomenon. This process consists in the excitation of the material with two or more photons and, subsequently, emission of a higher energy photon. In this way, it is possible to use an excitation source in the biological window region and obtain UV-visible emissions. In addition, TR3+ doped materials exhibit emissions in UV and visible spectral range under different excitation wavelengths. Therefore, this class of UVA emitting nanoparticles will be used for internal and local sensitization of 6-thioguanine incorporated into nucleic acids to study oxidative processes through the photosensitization of this molecule that generates 1O2 in cells. Another proposal of this work is the upconversion generation by TR3+ doped nanoparticles through their sensitization via energy transfer from the 1O2 monomolecular emission (at 1268 nm). Until now, this indirect method of singlet oxygen detection has not been found in the literature.All necessary technology as FTIR, XRD, SEM, TEM, absorption and upconversion luminescence spectroscopy, fluorescence microscopy, HPLC, NMR and mass spectrometry are available at our Institute. The group has extensive experience in singlet oxygen generation and detection, with several publications on the subject and experience in the required techniques for the project development.