Polymeric micelle-based nanoagents enable phototriggering combined chemotherapy and photothermal therapy with high sensitivity

A new type of polymeric nanomicelle-based nanoagent (denoted as PT@MFH hereafter) capable of the highly sensitive release of the chemotherapeutic drug paclitaxel (PTX) upon exposure to a near-infrared (NIR) laser trigger was developed. Specifically, PTX and a photothermal polymer (T-DPPT) were encapsulated in the cavity of nanomicelles, which were constructed from an amphiphilic block copolymer (PCL-PEEP) with a lower critical solution temperature (LCST) of ∼54 °C. Owing to the unprecedented ability of the T-DPPT moiety to harvest near-infrared light, with a mass extinction coefficient at 808 nm of up to ∼80.8 L g-1 cm-1, and convert NIR light to heat, with a photothermal conversion efficiency (η) of up to ∼70%, local hyperthermia was promptly realized via irradiation from an 808 nm laser with extraordinarily low output power. This enabled remarkable contrast in the local temperature and drug release between the "silent" state (prior to phototriggering) and the "activated" state (after phototriggering). This NIR-light-activated local hyperthermia and drug release presented the basis for combined chemotherapy and photothermal therapy (PTT) in antitumor treatment and displayed superb therapeutic efficacy. This pattern together with the high spatial precision imparted by laser triggering jointly contributed to the maximum combined antitumor efficacy to the tumor, while exhibiting minimal side effects on the normal tissues, as preliminarily verified in the in vivo experiment regarding the ability of PT@MFH to efficiently inhibit tumor growth in tumor-bearing model mice.