Localization matters: a nuclear targeting two-photon absorption iridium complex in photodynamic therapy

Area of Science:

• Photodynamic Therapy
• Inorganic Chemistry
• Cell Biology

Background:

• Photodynamic therapy (PDT) utilizes photosensitizers to generate reactive oxygen species (ROS) upon light activation for therapeutic purposes.
• Targeting specific intracellular organelles is crucial for enhancing PDT efficacy and minimizing off-target effects.
• Cyclometalated iridium(iii) complexes offer unique photophysical properties suitable for PDT applications.

Purpose of the Study:

• To develop and characterize a novel two-photon (2P) cyclometalated iridium(iii) complex (Ir-Es) for targeted photodynamic therapy (PDT).
• To investigate the intracellular localization, sequential migration, and dual-damage induction capabilities of the Ir-Es complex.
• To explore the impact of terminal moiety modification on the intracellular destination and PDT efficiency of iridium(iii) complexes.

Main Methods:

• Synthesis and characterization of the cyclometalated iridium(iii) complex (Ir-Es).
• Confocal microscopy and live-cell imaging to track intracellular localization and migration.
• Assessment of dual-damage induction (nuclear and mitochondrial) upon 800 nm light irradiation.
• Evaluation of photodynamic therapy (PDT) efficiency through cell viability assays.

Main Results:

• The Ir-Es complex was successfully synthesized and demonstrated efficient two-photon absorption at 800 nm.
• The complex was observed to initially target the nucleus and subsequently migrate to mitochondria within cells.
• Light exposure induced significant dual-damage to both the nucleus and mitochondria, leading to enhanced cell death.
• Preliminary studies indicated that modifications to the terminal moieties could alter the complex's intracellular trafficking and PDT efficacy.

Conclusions:

• The developed Ir-Es complex exhibits a unique nucleus-to-mitochondria sequential targeting mechanism for two-photon (2P) photodynamic therapy (PDT).
• This intracellular trafficking leads to dual-damage, enhancing the overall therapeutic potential of the complex.
• The findings highlight the potential for fine-tuning iridium(iii) complex design to control intracellular destinations and optimize PDT outcomes.