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Localized Detection of Superoxide Generation and Monitoring of Photosensitizer Performance in Hypoxic Tumors by an In
Liangchao Yuan1,2, Yuyao Cao1,3, Yangtian Liu1
1State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Institute of Artificial Intelligence Biomedicine, Nanjing University, Nanjing 210023, P.R. China.
Abstract:
Type I photodynamic therapy (PDT), generating superoxide anion radicals (O2•-), presents a potent strategy against tumor resistance by virtue of its low oxygen dependence, ensuring efficacy in hypoxic tumors where traditional Type II PDT is limited. However, accurate O2•- detection with high spatiotemporal and subcellular resolution remains a critical unmet need. Herein, we report the rational design and synthesis of HPQ-CF3, a novel fluorescent probe. Upon selective reaction with O2•-, HPQ-CF3's trifluoromethanesulfonate group departs, unmasking a hydroxyl group to generate the highly fluorescent HPQ-OH, a fluorophore incorporating the HPQ moiety. Crucially, the inherent low aqueous solubility of HPQ-OH leads to its in situ precipitation, enabling precise spatial localization of O2•- generation sites. HPQ-CF3 exhibits high specificity, a rapid response (<300 s), a remarkable ∼200-fold fluorescence enhancement, a low limit of detection (LOD, 0.13 μM), and excellent linearity. HPQ-CF3 demonstrated significantly superior performance over the commercial probe DHR123 for intracellular O2•- detection; its unique precipitation-based mechanism inherently minimizes background fluorescence while anchoring the signal at its origin, affording a substantially enhanced signal-to-noise ratio and markedly improved localization accuracy. Furthermore, HPQ-CF3 successfully monitored O2•- production in complex biological settings, including solid tumors. HPQ-CF3 is anticipated to be an invaluable tool for investigating O2•--related pathophysiology and advancing Type I photosensitizer development.
Insights
A new fluorescent probe, HPQ-CF3, precisely detects superoxide anion radicals (O2•−) generated during Type I photodynamic therapy. Its unique precipitation mechanism enhances signal localization and accuracy in hypoxic tumors and biological settings.
Area of Science:
- Biomedical Engineering
- Chemical Biology
- Photodynamic Therapy
Background:
- Type I photodynamic therapy (PDT) is effective against resistant tumors due to low oxygen dependence.
- Accurate detection of superoxide anion radicals (O2•−) is crucial for understanding Type I PDT efficacy but lacks spatiotemporal resolution.
- Existing methods for O2•− detection face limitations in sensitivity and localization.
Purpose of the Study:
- To develop a novel fluorescent probe for high-resolution detection of O2•−.
- To enable precise spatial and subcellular localization of O2•− generation.
- To advance the study of O2•−-related pathophysiology and Type I PDT development.
Main Methods:
- Rational design and synthesis of the fluorescent probe HPQ-CF3.
- Investigation of HPQ-CF3's reaction mechanism with O2•−.
- Evaluation of probe specificity, response time, fluorescence enhancement, and limit of detection (LOD).
- Comparison with commercial probes (DHR123) for intracellular O2•− detection.
- In situ monitoring of O2•− production in biological samples, including solid tumors.
Main Results:
- HPQ-CF3 selectively reacts with O2•−, generating a highly fluorescent product (HPQ-OH) via trifluoromethanesulfonate departure.
- The low aqueous solubility of HPQ-OH causes in situ precipitation, enabling precise O2•− localization.
- HPQ-CF3 exhibits high specificity, rapid response (<300 s), ~200-fold fluorescence enhancement, and a low LOD (0.13 μM).
- HPQ-CF3 outperforms DHR123 in intracellular O2•− detection, offering superior signal-to-noise ratio and localization accuracy.
- Successful monitoring of O2•− production in complex biological environments, including solid tumors.
Conclusions:
- HPQ-CF3 is a highly effective fluorescent probe for precise O2•− detection with excellent spatiotemporal resolution.
- The probe's precipitation-based mechanism overcomes limitations of existing methods, improving signal localization and minimizing background noise.
- HPQ-CF3 is a valuable tool for studying O2•− in biological systems and advancing Type I PDT research.
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