Near-infrared-light responsive nanoscale drug delivery systems for cancer treatment

• Photothermal effects could be utilized for the preparation of various different near-infrared (NIR)-responsive nanoscale drug delivery systems (NDDSs).
• Two-photon excitation was another promising NIR-light for the fabrication of novel NIR-responsive NDDSs.
• Upconversion nanoparticles (UCNPs) could be employed as an efficient NIR-light transducer for the activation of many conventional molecules, originally in response to visible or UV light.

Owning to its excellent tissue penetration capacity, near-infrared (NIR)-light has attracted intensive research interests in nanomedicine for either direct photothermal killing of cancers or precisely controlled drug release in recent years. Unlike conventional nanoscale drug delivery systems (NDDSs), NIR-responsive NDDSs can specifically destroy cancer cells under exposure to NIR light, which in the meanwhile shows better tissue penetration compared to visible or UV light with shorter wavelengths. To date, a great number of NIR-light responsive drug delivery systems, by utilizing NIR-light induced photothermal effect, two-photon excitation (TPE), or upconversion nanoparticles (UCNPs), have been successfully fabricated and shown promising treatment outcomes in preclinical experiments. Moreover, by combining with other therapeutic modalities (e.g. chemotherapy, photodynamic therapy, gene therapy), such NIR-light responsive NDDSs may offer promising synergistic effects in cancer treatment. In this review, we will introduce different types of NIR-light responsive systems and the latest progresses in their applications for cancer therapy.