A Biocompatible Core-Shell Nanoparticle Encapsulating Cyclometalated Iridium(III) Complexes and Ultrasmall Gold...

Area of Science:

• Biomedical Engineering
• Nanotechnology
• Chemical Biology

Background:

• Optimal oxygen levels are critical in biological systems; deviations indicate hypoxia or toxicity.
• Current luminescent oxygen probes (transition-metal complexes, organic dyes) have limitations in sensitivity, temporal resolution, and biocompatibility.
• Ultrasmall gold nanoparticles (UAuNPs) and cationic Iridium(III) complexes offer promising features like tunable emission, photostability, low toxicity, and target-specific design.

Purpose of the Study:

• To integrate the advantages of UAuNPs and Ir(III) complexes into novel bimetallic core-shell nanosensors.
• To develop and characterize two nanosensors, Ir-1@Au and Ir-2@Au, for ratiometric oxygen sensing.
• To evaluate the performance of the nanosensors for time-resolved imaging of intracellular oxygen levels.

Main Methods:

• Self-assembly of Ir(III) complexes with UAuNPs using an amphipathic copolymer to form core-shell nanosensors.
• Design of two bimetallic nanosensors, Ir-1@Au and Ir-2@Au, with varying Ir(III) ligands.
• Utilizing dual emission from Ir(III) coordination disruption and UAuNP core etching for ratiometric oxygen sensing.
• Employing microsecond-scale phosphorescence and fast lifetime imaging for time-resolved intracellular oxygen detection.

Main Results:

• Successful fabrication of Ir-1@Au and Ir-2@Au bimetallic core-shell nanosensors.
• Ir-2@Au, featuring a benzoxazole ligand, demonstrated superior membrane permeability and ratiometric oxygen sensing capabilities compared to Ir-1@Au.
• The Ir-2@Au nanosensor achieved time-resolved ratiometric imaging of intracellular dissolved oxygen down to ~0.1 mg L⁻¹, with a temporal resolution of ~200 ms.
• Hypoxia-responsive lifetime and intensity profiles were observed, indicating effective oxygen sensing.

Conclusions:

• The developed bimetallic nanosensors, particularly Ir-2@Au, offer a robust platform for studying oxygen dynamics in live cells.
• The high sensitivity, temporal resolution, and low autofluorescence mitigation make these probes suitable for live-cell imaging.
• The combination of oxygen sensing and potential therapeutic applications positions these nanoprobes for advancements in cancer theranostics.