A Magnetofluorescent Carbon Dot Assembly as an Acidic H₂O₂‐Driven Oxygenerator to Regulate Tumor Hypoxia for Simultaneous Bimodal Imaging and Enhanced Photodynamic Therapy

TLDR

Carbon dots can generate singlet oxygen for photodynamic therapy, but tumor hypoxia and rapid oxygen consumption limit their effectiveness. This study aims to create a carbon‑dot oxygenerator that alleviates hypoxia and boosts PDT efficacy. The authors synthesized magnetofluorescent Mn‑CDs from manganese(II) phthalocyanine, assembled them with DSPE‑PEG, and demonstrated dual near‑infrared fluorescence and T1‑weighted MRI contrast. The Mn‑CD assembly produces singlet oxygen (quantum yield 0.40) and catalyzes H₂O₂ to generate oxygen, thereby raising tumor oxygen levels, enabling simultaneous FL/MR imaging, and markedly enhancing PDT, presenting a versatile nanotheranostic platform.

Abstract

Abstract Recent studies indicate that carbon dots (CDs) can efficiently generate singlet oxygen ( 1 O 2 ) for photodynamic therapy (PDT) of cancer. However, the hypoxic tumor microenvironment and rapid consumption of oxygen in the PDT process will severely limit therapeutic effects of CDs due to the oxygen‐dependent PDT. Thus, it is becoming particularly important to develop a novel CD as an in situ tumor oxygenerator for overcoming hypoxia and substantially enhancing the PDT efficacy. Herein, for the first time, magnetofluorescent Mn‐CDs are successfully prepared using manganese(II) phthalocyanine as a precursor. After cooperative self‐assembly with DSPE‐PEG, the obtained Mn‐CD assembly can be applied as a smart contrast agent for both near‐infrared fluorescence (FL) (maximum peak at 745 nm) and T 1 ‐weighted magnetic resonance (MR) (relaxivity value of 6.97 mM −1 s −1 ) imaging. More interestingly, the Mn‐CD assembly can not only effectively produce 1 O 2 (quantum yield of 0.40) but also highly catalyze H 2 O 2 to generate oxygen. These collective properties of the Mn‐CD assembly enable it to be utilized as an acidic H 2 O 2 ‐driven oxygenerator to increase the oxygen concentration in hypoxic solid tumors for simultaneous bimodal FL/MR imaging and enhanced PDT. This work explores a new biomedical use of CDs and provides a versatile carbon nanomaterial candidate for multifunctional nanotheranostic applications.