Nitric oxide (NO) has emerged as a potent anticancer agent due to its ability to disrupt mitochondrial function and induce apoptosis in tumor cells. However, the therapeutic efficacy of NO is often hindered by the hypoxic nature of solid tumors, where conventional NO delivery systems relying on oxygen or hydrogen peroxide face significant limitations. To address this challenge, we developed a novel phototherapeutic nanoplatform based on hole-mediated oxidation that enables NO production without dependence on molecular oxygen. The system utilizes poly-L-arginine-modified carbon-dot-doped graphitic carbon nitride (ArgCCN), which generates highly oxidizing photogenerated holes under red light irradiation (660 nm).
The design of ArgCCN begins with the synthesis of carbon-dot-doped g-C₃N₄ (CCN), which exhibits a narrowed bandgap and elevated valence band energy compared to pristine g-C₃N₄. This modification allows efficient activation by red light and enhances the oxidative potential of photogenerated holes. Poly-L-arginine is then covalently conjugated to CCN via amide bond formation, resulting in ArgCCN. Characterization techniques including TEM, DLS, and AFM confirm the uniform hydrodynamic size (~120 nm), suitable for passive tumor targeting through the EPR effect. UV-vis spectroscopy reveals strong absorption in the visible region, particularly at 660 nm, while XRD patterns indicate preserved crystallinity with reduced peak intensity, suggesting structural changes from polymer conjugation.
Upon laser irradiation, ArgCCN efficiently produces H₂O₂ through water oxidation by photogenerated holes, as confirmed by colorimetric assays. The generated H₂O₂ subsequently oxidizes arginine residues on the conjugated poly-L-arginine chain to release NO. Crucially, no NO is detected in control groups lacking either the laser or the arginine component, but a rapid increase in NO concentration (up to 16 μM within 30 minutes) is observed only in the ArgCCN + laser group. Electron spin resonance (ESR) analysis shows negligible production of singlet oxygen, hydroxyl radicals, or superoxide anions—key ROS typically involved in photodynamic therapy. Notably, even under hypoxic conditions, substantial NO generation persists, confirming O₂ independence.BTN2A2 Antibody custom synthesis
Intracellular studies using MCF-7 cells demonstrate efficient cellular uptake of ArgCCN, primarily via clathrin- and energy-dependent endocytosis. Fluorescence imaging with DAF-FM DA reveals intense green signal in cells treated with ArgCCN + laser, indicating robust intracellular NO release. Importantly, this signal remains strong under hypoxia, proving the strategy’s resilience in low-oxygen environments. Furthermore, no significant change in intracellular O₂ levels is observed, confirming that the process does not consume oxygen.METTL7A Antibody custom synthesis
Cytotoxicity assays show that ArgCCN + laser induces over 55% cell death in both normoxic and hypoxic conditions, effectively triggering apoptosis.PMID:35193819 In vivo experiments using MCF-7 tumor-bearing mice reveal that the ArgCCN + laser group exhibits marked inhibition of tumor growth over 14 days. TUNEL staining confirms extensive DNA fragmentation in treated tumors, while H&E staining displays hallmark features of apoptosis, including nuclear condensation and increased intercellular space. Histopathological evaluation of major organs shows no significant damage, and body weight remains stable throughout treatment, indicating excellent biocompatibility.
This study presents a paradigm shift in phototherapy by focusing on photogenerated holes rather than electrons or ROS. By enabling O₂-independent NO production, ArgCCN overcomes a fundamental limitation of traditional cancer treatments in hypoxic microenvironments. Future work will focus on extending the light absorption into the near-infrared window and incorporating active targeting ligands to improve tumor specificity and deep-tissue penetration. These advances position ArgCCN as a promising platform for next-generation oxygen-independent cancer therapeutics.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