Reactive oxygen species (ROS) play a dual role in cellular biology—essential for signaling and homeostasis at physiological levels, but detrimental when overproduced, contributing to oxidative stress and disease progression. In particular, elevated ROS levels are hallmark features of tumor microenvironments, making them promising targets for cancer diagnosis and therapy. However, conventional fluorescent probes for ROS detection often suffer from limitations such as poor tissue penetration, low signal-to-noise ratios, and limited spatial resolution due to scattering and autofluorescence in the visible range.
To overcome these challenges, we report the development of a near-infrared second-window (NIR-II, 1000–1700 nm) fluorescent probe, ROS-IR2, specifically designed for high-resolution, deep-tissue imaging of ROS in living tumors. The probe is based on a donor–acceptor–donor (D–A–D) architecture incorporating a benzothiadiazole acceptor and two triphenylamine donors, with a ROS-responsive boronate ester group strategically placed at the donor end. Upon oxidation by intracellular ROS such as H₂O₂ or •OH, the boronate ester undergoes hydrolysis and cleavage, disrupting the electron-withdrawing effect of the acceptor moiety and triggering a significant fluorescence enhancement in the NIR-II region.
The optical properties of ROS-IR2 were characterized in vitro under various ROS conditions. In the absence of ROS, the probe exhibited weak fluorescence due to efficient photoinduced electron transfer (PET) quenching. Upon exposure to H₂O₂ (50 μM), the fluorescence intensity increased by over 12-fold at 1300 nm. The response was selective toward ROS, with minimal interference from other biologically relevant species including metal ions, amino acids, and thiols. Moreover, the probe demonstrated excellent stability in serum and PBS buffer, maintaining its integrity over 24 hours.25322-68-3 medchemexpress
In vivo imaging studies were conducted using mouse xenograft models bearing human breast cancer (MDA-MB-231) and colon cancer (HCT-116) tumors.506-32-1 Synonym After intravenous injection, ROS-IR2 rapidly accumulated in tumors via the enhanced permeability and retention (EPR) effect, achieving high tumor-to-background ratios within 1 hour.PMID:20301409 NIR-II imaging revealed clear, high-contrast tumor delineation with minimal background signal, even at depths exceeding 1 cm. Time-lapse imaging confirmed progressive fluorescence increase in tumors, correlating with elevated ROS levels.
Ex vivo analysis of harvested tissues confirmed preferential accumulation in tumor regions, with negligible uptake in major organs such as liver, kidney, and heart. Histological staining showed no signs of acute toxicity or inflammation after 7 days of observation. Biodistribution studies further validated the probe’s favorable pharmacokinetics, with clearance primarily through hepatobiliary routes.
Importantly, ROS-IR2 enabled real-time monitoring of ROS dynamics during therapeutic interventions. When mice were treated with a pro-oxidant agent (e.g., doxorubicin), a rapid and sustained fluorescence increase was observed in tumor sites, reflecting drug-induced oxidative stress. This allowed non-invasive assessment of treatment efficacy and pharmacodynamic responses.
In summary, ROS-IR2 represents a significant advancement in molecular imaging technology. Its ability to detect ROS in the NIR-II window enables deeper tissue penetration, reduced scattering, and higher spatial resolution compared to traditional visible or NIR-I probes. With its high sensitivity, selectivity, and biocompatibility, ROS-IR2 offers a powerful tool for in vivo visualization of tumor redox status, facilitating early cancer detection, real-time monitoring of therapy, and improved understanding of oxidative stress in tumorigenesis.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com