Reactive oxygen species (ROS) play an essential role in regulating various physiological functions of living organisms; however, as the concentration of ROS increases in the area of a lesion, this may undermine cellular homeostasis, leading to a series of diseases. Using cell-product species as triggers for targeted regulation of polymer structures and activity represents a promising approach for the treatment. ROS-responsive polymer carriers allow the targeted delivery of drugs, reduce toxicity and side effects on normal cells, and control the release of drugs, which are all advantages compared with traditional small-molecule chemotherapy agents. These formulations have attracted great interest due to their potential applications in biomedicine. In this review, recent progresses on ROS responsive polymer carriers are summarized, with a focus on the chemical mechanism of ROS-responsive polymers and the design of molecular structures for targeted drug delivery and controlled drug release. Meanwhile, we discuss the challenges and future prospects of its applications.

The complexity of the tumor microenvironment presents significant challenges to cancer therapy, while providing opportunities for targeted drug delivery. Using characteristic signals of the tumor microenvironment, various stimuli-responsive drug delivery systems can be constructed for targeted drug delivery to tumor sites. Among these, the pH is frequently utilized, owing to the pH of the tumor microenvironment being lower than that of blood and healthy tissues. pH-responsive polymer carriers can improve the efficiency of drug delivery in vivo, allow targeted drug delivery, and reduce adverse drug reactions, enabling multifunctional and personalized treatment. pH-responsive polymers have gained increasing interest due to their advantageous properties and potential for applicability in tumor therapy. In this review, recent advances in, and common applications of, pH-responsive polymer nanomaterials for drug delivery in cancer therapy are summarized, with a focus on the different types of pH-responsive polymers. Moreover, the challenges and future applications in this field are prospected.

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As an alternating copolymer of CO 2 and propylene oxide, poly(1,2-propylene carbonate) (PPC) should be composed of fully carbonate structure, whereas it generally contains certain ether linkage due to the existence of competitive formation of ether linkage by consecutive epoxide enchainment. Though the ether linkage was not always the dominant structure in PPC, a new understanding was provided in that the ether linkage was crucial structure factor on the PPC performances, especially for oxygen barrier property, transparency, thermal and mechanical properties. The gas barrier properties and transparency of PPC film became worse with increasing ether linkages, the oxygen, nitrogen and carbon dioxide permeability of PPC with ether linkage of 0.6 % were 14 cm 3 /m 2 /24 h/0.1 MPa, 11 cm 3 /m 2 /24 h/ 0.1 MPa and 220 cm 3 /m 2 /24 h/0.1 MPa, respectively, while for PPC with ether linkage of 54.1 %, they became 116 cm 3 / m 2 /24 h/0.1 MPa, 108 cm 3 /m 2 /24 h/0.1 MPa and 599 cm 3 / m 2 /24 h/0.1 MPa, respectively. When the ether linkage in PPC increased from 0.6 % to 54.1 %, the thermal decomposition temperature at 5 wt% loss(T d-5% ) increased from 218.6°C to 241.0°C, while the glass-transition temperature (T g ) decreased from 45.2°C to 11.1°C, meanwhile, the room temperature tensile strength decreased from 55.4 MPa to 2.3 MPa, and the elongation at break increased from 8.5 % to 1558.2 %.

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The aggressive growth of cancer cells brings extreme challenges to cancer therapy while triggering the exploration of the application of multimodal therapy methods. Multimodal tumor therapy based on photothermal nanomaterials is a new technology to realize tumor cell thermal ablation through near-infrared light irradiation with a specific wavelength, which has the advantages of high efficiency, less adverse reactions, and effective inhibition of tumor metastasis compared with traditional treatment methods such as surgical resection, chemotherapy, and radiotherapy. Photothermal nanomaterials have gained increasing interest due to their potential applications, remarkable properties, and advantages for tumor therapy. In this review, recent advances and the common applications of photothermal nanomaterials in multimodal tumor therapy are summarized, with a focus on the different types of photothermal nanomaterials and their application in multimodal tumor therapy. Moreover, the challenges and future applications have also been speculated.