Generation of synglet oxygen by different photosensitizers excited by nanoparticles presenting upconversion and application in RAW 264.7 macrophages

Author(s)

Amanda da Annunciação Farhat

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2025-02-21

Examining board members

Paolo Di Mascio; Hermi Felinto de Brito; Magnus Ake Gidlund

• Advisor: Paolo Di Mascio

Abstract

Molecular oxygen electronically excited to the singlet state 1Δg (1O2) is known for its reactivity in proximity to organic molecules with high electron density. Reactions of 1O2 with biomolecules have been studied in recent decades as a source of study of lesions related to cytotoxic and pathophysiological processes, which is indicative of the importance of studying this molecule in complex systems. Nanoparticles doped with trivalent rare earth ions (RE3+) can present the phenomenon of upconversion, which consists of the excitation of the material with two or more photons and a subsequent emission of a photon of greater energy. Similarly, an excitation source can be applied in the region of the biological window and obtain emissions in the UV-visible using these nanoparticles. In addition, materials doped with RE3+ present emissions in the entire UV and visible spectrum under various excitation wavelengths. Therefore, this work aimed to synthesize nanoparticles with upconversion in the hexagonal form β-NaREF4:RE3+@β-NaYF4 to subsequently excite them in the near infrared (close to the biological window region) through a 980 nm pulsed laser, obtaining an emission tuned to the visible for sensitization of a respective photosensitizer, capable of absorbing the emission of visible light and generating 1O2 with high quantum yield. The synthesis proved to be efficient, obtaining homogeneous samples with sizes below the average found in the literature, important characteristics for the subsequent applications of the nanoparticles. For the application of the nanomaterial with the photosensitizer, the central objective of the work, an intermediate polymer layer was added, improving the fixation of the dye, which resulted in a material composed of the nanoparticle in the core@shell form, coated with a polymer and which was then coated with the photosensitizer. The emission results obtained allowed us to guarantee the efficiency of the polymer coating process and the excitation of the dye used. Finally, the material with the photosensitizer was placed in contact with samples of RAW 264.7 macrophage cells and the toxicity of the singlet oxygen generated by the system was verified in relation to cell viability, proving the possibility of using nanoparticles for biological applications. (AU)

• FAPESP's process: 19/17363-5 - Singlet oxygen generation by different photosensitizers excited by nanoparticle presenting upconversion and biological applications
• Grantee: Amanda da Annunciação Farhat
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)