Multifunctional platforms based on inorganic-organic hybrids UCNPS@SiO2-Ln3+-Ir3+ aiming for sensing, cell imaging, and singlet oxygen generation by upconversion process

Abstract

Currently, the search for multifunctional materials with theranostic (diagnostic and therapeutic) potential for cancer is growing exponentially, as this disease represents the second biggest cause of deaths in the world, mainly due to late diagnosis. It is worth mentioning that such platforms can combine different diagnostic and treatment techniques in a single system, making them attractive for clinical applications. Cancer cells can be detected by measuring the concentration of molecular oxygen (3O2) in tissues because hypoxic environments can indicate pathological processes such as inflammatory diseases, cardiac ischemia, brain abnormalities, and cancer. Therefore, the quantification of this analyte has received considerable attention in the biomedical field, both in academic and applied areas. Furthermore, singlet molecular oxygen (1O2) generation has been strategically used as a therapeutic tool for treating cancer. Thus, in this work, inorganic-organic hybrid systems composed of upconversion nanoparticles (UCNPs) will be developed, synthesized by the thermal decomposition method, coated with SiO2 (Stöber method), and decorated with Ir3+-Ln3+ bimetallic complexes. The blue (NaYF4:Yb3+,Nd3+,Tm3+) and green (NaYF4:Yb3+,Nd3+,Er3+) upconversion cores will act as sensitizing centers, which can be excited at low energy wavelengths (near infrared region - NIR). The upconversion process greatly minimizes damage to the cellular structure compared with UV excitation. Emissions in the ultraviolet and blue (Tm3+) or green (Er3+) regions of the visible and NIR regions. The emissions attributed to the Ir3+-Ln3+ system transitions will be used for ratiometric O2 sensing, which will act as luminescent probes of the oxygen concentration. Therefore, this project will develop multifunctional luminescent platforms for molecular oxygen sensing, cellular imaging, and singlet molecular oxygen generation, which may be useful in the diagnosis and treatment of early-stage cancer.