Dual-Emissive Iridium(III) Complex with Aggregation-Induced Emission: Mechanistic Insights into Electron Transfer for Enhanced Hypoxia Detection in 3D Tumor Models

Accurate
oxygen detection and measurement of its concentration
is vital in biological and industrial applications, necessitating
highly sensitive and reliable sensors. Optical sensors, valued for
their real-time monitoring, nondestructive analysis, and exceptional
sensitivity, are particularly suited for precise oxygen measurements.
Here, we report a dual-emissive iridium(III) complex, IrNPh2, featuring “aggregation-induced emission” (AIE) properties
and used for sensitive oxygen sensing. IrNPh2 exhibits
dual emissions at 450 and 515 nm, with 515 nm triplet-state emission
demonstrating remarkable oxygen sensitivity due to its long-lived
excited state (12.12 μs) and high quantum yield (68%). Stern–Volmer
analysis reveals a notable quenching constant (Ksv = 12.44%–1) and an ultralow detection
limit of 0.0397%, emphasizing its superior performance. The oxygen
quenching mechanism is driven by electron transfer (ET), supported
by computational studies showing the lowest-unoccupied molecular orbital
(LUMO) alignment of IrNPh2 with the πg* orbitals of triplet oxygen, leading to superoxide radical (O2•–) formation. Electron paramagnetic
resonance (EPR) studies further confirm this pathway. Biological evaluations
using a three-dimensional (3D) U87-MG glioma spheroid model highlight
the ability of IrNPh2 to detect hypoxic regions, with significant
fluorescence enhancement under hypoxia and minimal cytotoxicity (>80%
viability at 100 μM). With high sensitivity, low detection limits,
and biocompatibility, IrNPh2 emerges as a promising candidate
for oxygen sensing in environmental and biomedical applications, especially
tumor hypoxia detection.

精准的氧气检测及其浓度定量在生物与工业应用中均具有关键意义，因此亟需兼具高灵敏度与高可靠性的传感器件。光学传感器凭借可实现实时监测、无损分析且灵敏度优异的特点，尤其适配高精度氧气检测场景。本研究报道一种双发射铱(III)配合物IrNPh2，其具备聚集诱导发光（aggregation-induced emission, AIE）特性，可用于高灵敏度氧气传感。IrNPh2在450 nm与515 nm处呈现双发射峰，其中515 nm处的三重态发射因激发态寿命长达12.12 μs、量子产率达68%，表现出优异的氧气响应灵敏度。斯特恩-沃尔默（Stern-Volmer）分析结果显示，该配合物的淬灭常数可达12.44 %⁻¹，超低检测限低至0.0397%，进一步凸显其优异的传感性能。氧气淬灭的机制为电子转移（electron transfer, ET），计算研究证实，IrNPh2的最低未占据分子轨道（lowest-unoccupied molecular orbital, LUMO）与三重态氧气的πg*轨道能级匹配，可生成超氧自由基（O2•–）。电子顺磁共振（electron paramagnetic resonance, EPR）实验进一步验证了这一淬灭路径。通过三维（3D）U87-MG胶质瘤球体模型开展的生物学评价结果表明，IrNPh2可有效检测缺氧区域：在缺氧环境下荧光信号显著增强，且细胞毒性极低——100 μM浓度下细胞存活率仍高于80%。凭借高灵敏度、超低检测限与良好的生物相容性，IrNPh2有望成为环境与生物医学领域氧气传感的优质候选材料，尤其适用于肿瘤缺氧检测场景。