Reactive oxygen species (ROS) play an essential role in regulating various physiological functions of living organisms. The intrinsic biochemical properties of ROS, which underlie the mechanisms necessary for the growth, fitness, or aging of living organisms, have been driving researchers to take full advantage of these active chemical species for contributing to medical advances. Thanks to the remarkable advances in nanotechnology, great varieties of nanomaterials with unique ROS-regulating properties have been explored to guide the temporospatial dynamic behaviors of ROS in biological milieu, which contributes to the emergence of a new-generation therapeutic methodology, i.e., nanomaterial-guided in vivo ROS evolution for therapy. The interdependent relationship between ROS and their corresponding chemistry, biology, and nanotherapy leads us to propose the concept of “ROS science”, which is believed to be an emerging scientific discipline that studies the chemical mechanisms, biological effects, and nanotherapeutic applications of ROS. In this review, state-of-art studies concerning recent progresses on ROS-based nanotherapies have been summarized in detail, with an emphasis on underlying material chemistry of nanomaterials by which ROS are generated or scavenged for improved therapeutic outcomes. Furthermore, key scientific issues in the evolution of ROS-based cross-disciplinary fields have also been discussed, aiming to unlock the innate powers of ROS for optimized therapeutic efficacies. We expect that our demonstration on this evolving field will be beneficial to the further development of ROS-based fundamental researches and clinical applications.

The p–n diodes represent the most fundamental device building blocks for diverse optoelectronic functions, but are difficult to achieve in atomically thin transition metal dichalcogenides (TMDs) due to the challenges in selectively doping them into p- or n-type semiconductors. Here, we demonstrate that an atomically thin and sharp heterojunction p–n diode can be created by vertically stacking p-type monolayer tungsten diselenide (WSe2) and n-type few-layer molybdenum disulfide (MoS2). Electrical measurements of the vertically staked WSe2/MoS2 heterojunctions reveal excellent current rectification behavior with an ideality factor of 1.2. Photocurrent mapping shows rapid photoresponse over the entire overlapping region with a highest external quantum efficiency up to 12%. Electroluminescence studies show prominent band edge excitonic emission and strikingly enhanced hot-electron luminescence. A systematic investigation shows distinct layer-number dependent emission characteristics and reveals important insight about the origin of hot-electron luminescence and the nature of electron–orbital interaction in TMDs. We believe that these atomically thin heterojunction p–n diodes represent an interesting system for probing the fundamental electro-optical properties in TMDs and can open up a new pathway to novel optoelectronic devices such as atomically thin photodetectors, photovoltaics, as well as spin- and valley-polarized light emitting diodes, on-chip lasers.

Tumor cells metabolize in distinct pathways compared with most normal tissue cells. The resulting tumor microenvironment would provide characteristic physiochemical conditions for selective tumor modalities. Here we introduce a concept of sequential catalytic nanomedicine for efficient tumor therapy by designing and delivering biocompatible nanocatalysts into tumor sites. Natural glucose oxidase (GOD, enzyme catalyst) and ultrasmall Fe3O4 nanoparticles (inorganic nanozyme, Fenton reaction catalyst) have been integrated into the large pore-sized and biodegradable dendritic silica nanoparticles to fabricate the sequential nanocatalyst. GOD in sequential nanocatalyst could effectively deplete glucose in tumor cells, and meanwhile produce a considerable amount of H2O2 for subsequent Fenton-like reaction catalyzed by Fe3O4 nanoparticles in response to mild acidic tumor microenvironment. Highly toxic hydroxyl radicals are generated through these sequential catalytic reactions to trigger the apoptosis and death of tumor cells. The current work manifests a proof of concept of catalytic nanomedicine by approaching selectivity and efficiency concurrently for tumor therapeutics.

Ceramic biomaterials have been investigated for several decades, but their potential biomedical applications in cancer therapy have been paid much less attentions, mainly due to their lack of related material functionality for combating the cancer. In this work, we report, for the first time, that MAX ceramic biomaterials exhibit the unique functionality for the photothermal ablation of cancer upon being exfoliated into ultrathin nanosheets within atomic thickness (MXene). As a paradigm, biocompatible TiC nanosheets (MXenes) were successfully synthesized based on a two-step exfoliation strategy of MAX phase TiAlC by the combined HF etching and TPAOH intercalation. Especially, the high photothermal-conversion efficiency and in vitro/in vivo photothermal ablation of tumor of TiC nanosheets (MXenes) were revealed and demonstrated, not only in the intravenous administration of soybean phospholipid modified TiC nanosheets but also in the localized intratumoral implantation of a phase-changeable PLGA/TiC organic-inorganic hybrid. This work promises the great potential of TiC nanosheets (MXenes) as a novel ceramic photothermal agent used for cancer therapy and may arouse much interest in exploring MXene-based ceramic biomaterials to benefit the biomedical applications.

Most present nanodrug delivery systems have been developed to target cancer cells but rarely nuclei. However, nuclear-targeted drug delivery is expected to kill cancer cells more directly and efficiently. In this work, TAT peptide has been employed to conjugate onto mesoporous silica nanoparticles (MSNs-TAT) with high payload for nuclear-targeted drug delivery for the first time. Monodispersed MSNs-TAT of varied particle sizes have been synthesized to investigate the effects of particle size and TAT conjugation on the nuclear membrane penetrability of MSNs. MSNs-TAT with a diameter of 50 nm or smaller can efficiently target the nucleus and deliver the active anticancer drug doxorubicin (DOX) into the targeted nucleus, killing these cancer cells with much enhanced efficiencies. This study may provide an effective strategy for the design and development of cell-nuclear-targeted drug delivery.

The increasing demand of clinical biomedicine and fast development of nanobiotechnology has substantially promoted the generation of a variety of organic/inorganic nanosystems for biomedical applications. Biocompatible two-dimensional (2D) graphene analogues (e.g., nanosheets of transition metal dichalcogenides, transition metal oxides, g-C3N4, Bi2Se3, BN, etc.), which are referred to as 2D-GAs, have emerged as a new unique family of nanomaterials that show unprecedented advantages and superior performances in biomedicine due to their unique compositional, structural and physicochemical features. In this review, we summarize the state-of-the-art progress of this dynamically developed material family with a particular focus on biomedical applications. After the introduction, the second section of the article summarizes a range of synthetic methods for new types of 2D-GAs as well as their surface functionalization. The subsequent section provides a snapshot on the use of these biocompatible 2D-GAs for a broad spectrum of biomedical applications, including therapeutic (photothermal/photodynamic therapy, chemotherapy and synergistic therapy), diagnostic (fluorescent/magnetic resonance/computed tomography/photoacoustic imaging) and theranostic (concurrent diagnostic imaging and therapy) applications, especially on oncology. In addition, we briefly present the biosensing applications of these 2D-GAs for the detection of biomacromolecules and their in vitro/in vivo biosafety evaluations. The last section summarizes some critical unresolved issues, possible challenges/obstacles and also proposes future perspectives related to the rational design and construction of 2D-GAs for biomedical engineering, which are believed to promote their clinical translations for benefiting the personalized medicine and human health.

Tumour chemotherapy employs highly cytotoxic chemodrugs, which kill both cancer and normal cells by cellular apoptosis or necrosis non-selectively. Catalysing/triggering the specific chemical reactions only inside tumour tissues can generate abundant and special chemicals and products locally to initiate a series of unique biological and pathologic effects, which may enable tumour-specific theranostic effects to combat cancer without bringing about significant side effects on normal tissues. Nevertheless, chemical reaction-initiated selective tumour therapy strongly depends on the advances in chemistry, materials science, nanotechnology and biomedicine. This emerging cross-disciplinary research area is substantially different from conventional cancer-theranostic modalities in clinics. In response to the fast developments in cancer theranostics based on intratumoural catalytic chemical reactions, this tutorial review summarizes the very-recent research progress in the design and synthesis of representative nanoplatforms with intriguing nanostructures, compositions, physiochemical properties and biological behaviours for versatile catalytic chemical reaction-enabled cancer treatments, mainly by either endogenous tumour microenvironment (TME) triggering or exogenous physical irradiation. These unique intratumoural chemical reactions can be used in tumour-starving therapy, chemodynamic therapy, gas therapy, alleviation of tumour hypoxia, TME-responsive diagnostic imaging and stimuli-responsive drug release, and even externally triggered versatile therapeutics. In particular, the challenges and future developments of such a novel type of cancer-theranostic modality are discussed in detail to understand the future developments and prospects in this research area as far as possible. It is highly expected that this kind of unique tumour-specific therapeutics by triggering specific in situ catalytic chemical reactions inside tumours would provide a novel but efficient methodology for benefiting personalized biomedicine in combating cancer.

Traditional photodynamic therapy (PDT) suffers from the critical issues of low tissue-penetrating depth of light and potential phototoxicity, which are expected to be solved by developing new dynamic therapy-based therapeutic modalities such as sonodynamic therapy (SDT). In this work, we report on the design/fabrication of a high-performance multifunctional nanoparticulate sonosensitizer for efficient in vivo magnetic resonance imaging (MRI)-guided SDT against cancer. The developed approach takes the structural and compositional features of mesoporous organosilica-based nanosystems for the fabrication of sonosensitizers with intriguing theranostic performance. The well-defined mesoporosity facilitates the high loading of organic sonosensitizers (protoporphyrin, PpIX) and further chelating of paramagnetic transitional metal Mn ions based on metalloporphyrin chemistry (MnPpIX). The mesoporous structure of large surface area also maximizes the accessibility of water molecules to the encapsulated paramagnetic Mn ions, endowing the composite sonosensitizers with markedly high MRI performance (r = 9.43 mM s) for SDT guidance and monitoring. Importantly, the developed multifunctional sonosensitizers (HMONs-MnPpIX-PEG) with controllable biodegradation behavior and high biocompatibility show distinctively high SDT efficiency for inducing the cancer-cell death in vitro and suppressing the tumor growth in vivo. This report provides a paradigm that nanotechnology-enhanced SDT based on elaborately designed high-performance multifunctional sonosensitizers will pave a new way for efficient cancer treatment by fully taking the advantages (noninvasiveness, convenience, cost-effectiveness, etc.) of ultrasound therapy and quickly developing nanomedicine.