Phototherapy, including photothermal therapy (PTT) and photodynamic therapy (PDT), are effective and noninvasive approachs to treat cancer. During phototherapy, photosensitizers absorb light energy and convert it into local hyperthermia or excessive reactive oxygen species, leading to cancer cell death. In recent years, many studies have focused on nanoparticle systems to combine the targeting property of nanostructures, the fluorescence of imaging agents and the tumor inhibition ability of photosensitizers for tumor theranostics. However, wide application of theranostic nanosystems has been limited by complicated components and complex synthesis.
In recent work by Yueqing Gu and colleagues at the State Key Laboratory of Natural Medicines in Nanjing, China, a small molecular fluorophore with inherent tumor specific targeting ability was synthesized for synchronous long-duration cancer imaging and enhanced dual modal phototherapy is reported. Despite the simple structure, this small molecule, NIR-03 features some unique and important advantages. (1) Tumor targeting ability: NIR-03 possesses inherent tumor targeting ability to certain tumor cell lines (U87, MDA-MB-231, A549, etc.); (2) Fluorescence imaging: NIR-03 facilitates fluorescence imaging in the near-infrared (NIR) window for real-time, in-vivo tumor monitoring; (3) Dual modal phototherapy: NIR-03 can be used for imaging-guided synergistic photodynamic (PDT) and photothermal (PTT) tumor therapy; (4) Enhanced photostability: NIR-03, with enhanced stability against photo-bleaching than traditional near infrared fluorophore indocyanine green, can prolong the time of tumor imaging and enhance the phototherapy efficiency.
Compared with normally adopted methods for phototherapy to incorporate the photothermal photosensitizers, photodynamic photosensitizers and imaging agents into nanostructures for simultaneous PDT/PTT treatment and imaging-guided laser treatment, this simple small molecular fluorophore presents a strategy to develop small-molecule-based cancer theranostic materials for simultaneous cancer targeting, imaging, and therapy.