Manipulation of Energy Migration in Upconversion Nanoparticles for Long-Lived Mn²⁺ Emission and Enhanced Singlet Molecular Oxygen Generation

Author(s)

Khan, Zahid U. ; Khan, Latif U. ; Prado, Fernanda M. ; Gul, Iram ; Lopes, Thiago ; Ribeiro, Leonardo M. A. ; Bertotti, Mauro ; Gidlund, Magnus ; Brito, Hermi F. ; Di Mascio, Paolo

• Document type: Journal article
• Source: ACS APPLIED NANO MATERIALS; v. 7, n. 17, p. 10-pg., 2024-09-03.

Abstract

Nanosensitizers having long-lived upconversion emission under near-infrared (NIR) excitation offer unique advantages in terms of reduced background noise and prolonged signal detection for deep tissue therapy of cancer. Herein, we demonstrate a systematic mechanism of energy migration toward achieving long-lived Mn2+ upconversion emission in the multilayered core-shell-shell lattice of NaGdF4:Yb3+,Tm3+,Ca2+/NaGdF4:Yb3+,Ca2+/NaGdF4:Mn2+ upconversion nanoparticles (NPs), following the Yb3+ -> Tm3+ -> Gd3+ -> Mn2+ intermetal ions energy transfer pathway. Furthermore, a rational design of nanosensitizer was achieved by incorporating Er3+ ions into the intermediate shell of multishell NPs, which was subsequently conjugated with the Rose Bengal sensitizer to enable the enhancement in singlet molecular oxygen (O-1(2)) generation under excitation of a 980 nm NIR laser. An intense higher-energy emission in the UV-blue visible region from Tm3+ was achieved by optimizing the amount of Ca2+ in the core-shell NPs, followed by subsequent energy migration to the Mn2+ ion incorporated at the outer shell. The Mn2+ ions were strategically doped in the outer shell of NPs to leverage the catalytic activities of Mn2+ for H2O2 decomposition and decrease the backward energy transfer to the Tm3+ ion. Hence, this approach resulted in a long lifetime of Mn2+ (similar to 34 ms), attributed to the spin-forbidden T-4(1g) -> (6)A(1g) transition within 3d(5) configuration. Additionally, the nanosensitizer demonstrated high O-1(2) (similar to 0.39 mu M) generation even at a very low concentration (5 mu g/mL) under a laser power of 2 mW cm(-2). The hydrogenase-like catalytic activities of Mn2+ exhibited significant oxygen production through decomposition of H2O2. Hence, these findings might contribute to the development of convenient multifunctional nanosensitizers for multimodal bioimaging and therapeutic features, including efficient O-1(2) generation and catalytic decomposition of H2O2 (found excessively in a tumor environment) to oxygen for alleviating the hypoxia. (AU)

• FAPESP's process: 21/00356-6 - Multifunctional fluorescence quantum dots as amplifiers for 1O2 generation and synergistic enhanced photodynamic therapy
• Grantee: Zahid Ullah Khan
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 13/07937-8 - Redoxome - Redox Processes in Biomedicine
• Grantee: Ohara Augusto
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 21/08111-2 - Development of rare earth based light converters: luminescent markers, optical sensors, and amplifiers
• Grantee: Hermi Felinto de Brito
• Support Opportunities: Research Projects - Thematic Grants