Malignant tumors have the capability to metastasize and colonize, meaning that they can spread to other organs and tissues, distributing metastatic focus and are hard to target. Although significant advances have been made in cancer treatment, it remains one of the leading causes of death around the globe. In recent years, new-emerging implantable systems and devices have been developed to tackle the challenge of metastatic tumors. In this review, implantable systems for suppressing tumors and preventing tumor recurrence are reported. In particular, we emphasize the responsive drug delivery systems and the external field assisted catalytic therapy for tumor treatment, as well as implantable biosensors for tumor microenvironment monitoring. We also conclude the open challenges and future perspectives of implantable systems and devices for cancer therapy and sensing.

Electrochemical system with electro-Fenton reaction is an effective pathway for oxidative degradation of refractory organic pollutants for water treatment. However, the method is limited by the low catalytic efficiency and high electrical cost in practical applications. This work presents a self-powered and high-efficient electrochemical system for water treatment including pollutant degradation and bacterial inactivation, which is composed of a self-powered triboelectric nanogenerator (TENG) converting mechanical energy into electrical energy, a power management circuit integrated with a supercapacitor to store the harvesting electrical energy temporarily, and an electrochemical setup integrated with two-dimentional Co(OH)₂/Pt nanosheet as electrocatalyst. The nanocatalyst, ultrafine Pt nanoparticles (Pt NPs) loaded on Co(OH)₂ nanosheet (Co(OH)₂/Pt), is synthesized by a facile one step hydrothermal reaction without any surfactant, which can improve H₂O₂ and hydroxyl radical production via redox reaction. This self-powered electrocatalytic system is able to degrade nearly 100% of organic pollutant within 100 min, and efficiently kill bacteria. This work shows great potential to develop high-efficient and self-powered electrochemical water treatment system through integrating TENG and nanocatalyst.

Recently, the development of chemodynamic therapy (CDT) offers a potential approach for fighting bacteria and treating infectious diseases, in which those CDT nanoagents can catalyze the generation of hydroxyl radicals (•OH) to destroy bacteria. In this work, to improve the efficiency of CDT, we have designed a new kind of metformin (Met)-capped two-dimensional Cu₂(OH)₃Cl nanosheets (CuOHCl-Met NSs) with good monodispersity, highly positive charge, and good biocompatibility for improving antibacterial effect and accelerating wound healing. With the capped Met, CuOHCl-Met NSs can effectively kill bacteria under a low concentration (6 μg·mL⁻¹) and a short treatment time (in 15 min), showing great advantages over the counterpart without Met. In vivo results demonstrated that CuOHCl-Met NSs accelerated the tissue regeneration of staphylococcus aureus-infected dermal wounds. This study provides a new pathway for improving efficiency of CDT nanoagent through using old drug.

With the rapid development of photo-responsive nanomaterials, photo-triggered therapeutic strategies such as photothermal therapy (PTT) and photodynamic therapy (PDT) have been new alternatives to current cancer therapeutic methods. Herein, we have fabricated oxygen vacancy-engineered BaTiO₃ (BTO-Ov) nanoparticles (NPs) for near-infrared (NIR) light-triggered PTT, PDT, and catalytic therapy cooperatively for significantly improving cancer therapy. Compared to pristine BaTiO₃ nanoparticles, BTO-Ov has stronger NIR light absorption and narrower band gap structure, which results in superior photothermal conversion and superoxide radical generation capabilities through PTT and PDT. Meanwhile, due to the existence of Ti³⁺, BTO-Ov also exhibits peroxidase (POD)-like activity to produce hydroxyl radical under tumor environment, which can be further improved under 808 nm light irradiation. Both in vitro and in vivo results demonstrate that such a multifunctional therapeutic nanoplatform can achieve a high therapeutic efficacy triggered by a single NIR light irradiation. The defect engineering strategy can be used as a general approach to fabricate multifunctional cancer therapeutic nanoplatform.