Nanoprobe-Based Magnetic Resonance Imaging of Hypoxia Predicts Responses to Radiotherapy, Immunotherapy, and Sensitizing Treatments in Pancreatic Tumors

Hypoxia-accelerating pyroptosis nanoinducers for promoting image-guided cancer immunotherapy

Precise image-guided cancer immunotherapy holds immense potential in revolutionizing cancer treatment. The strategies facilitating activatable imaging and controlled therapeutics are highly desired yet to be developed. Herein, we report a new pyroptosis nanoinducer that integrates aggregation-induced emission luminogen (AIEgen) and DNA methyltransferase inhibitor with hypoxia-responsive covalent organic frameworks (COFs) for advanced image-guided cancer immunotherapy. We first synthesize and compare three donor-acceptor type AIEgens featuring varying numbers of electron-withdrawing units, and find that the incorporation of two acceptors yields the longest response wavelength and most effective photodynamic therapy (PDT) property, surpassing the performance of analogs with one or three acceptor groups. A COF-based nanoplatform containing AIEgen and pyroptosis drug is successfully constructed via the one-pot method. The intra-COF energy transfer significantly quenches AIEgen, in which both fluorescence and PDT properties greatly enhance upon hypoxia-triggered COF degradation. Moreover, the photodynamic process exacerbates hypoxia, accelerating pyroptosis drug release. The nanoagent enables sensitive delineation of tumor site through in situ activatable fluorescence signature. Thanks to the exceptional ROS production capabilities and hypoxia-accelerating drug release, the nanoagent not only inhibits primary tumor growth but also impedes the progression of distant tumors in 4T1 tumor-bearing mice through potent pyroptosis-mediated immune response. This research introduces a novel strategy for achieving activatable phototheranostics and self-accelerating drug release for synergetic cancer immunotherapy.

Glucosylated Nanovaccines for Dendritic Cell-Targeted Antigen Delivery and Amplified Cancer Immunotherapy

Engineering nanovaccines capable of targeting dendritic cells (DCs) is desperately required to maximize antigen cross-presentation to effector immune cells, elicit strong immune responses, and avoid adverse reactions. Here, we showed that glucose transporter 1 (Glut-1) on DCs is a reliable target for delivering antigens to DCs, and thus, a versatile antigen delivery strategy using glucosylated nanovaccines was developed for DC-targeted antigen delivery and tumor immunotherapy. The developed glucosylated ovalbumin-loaded nanovaccines highly accumulated in lymph nodes and efficiently engaged with Glut-1 on DCs to accelerate intracellular antigen delivery and promote DC maturation and antigen presentation, which elicited potent antitumor immunity to prevent and inhibit ovalbumin-expressing melanoma. Moreover, immunotherapeutic experiments in DC- and macrophage-depleted animal models confirmed that the glucosylated nanovaccines functioned mainly through DCs. In addition, the neoantigen-delivering glucosylated nanovaccines were further engineered to elicit tumor-specific immune responses against MC38 tumors. This study offers a DC-targeted antigen delivery strategy for cancer immunotherapy.

Nanotechnology-based Strategies for Molecular Imaging, Diagnosis, and Therapy of Organ Transplantation

Organ transplantation is the preferred paradigm for patients with end-stage organ failures. Despite unprecedented successes, complications such as immune rejection, ischemia-reperfusion injury, and graft dysfunction remain significant barriers to long-term recipient survival after transplantation. Conventional immunosuppressive drugs have limited efficacy because of significant drug toxicities, high systemic immune burden, and emergence of transplant infectious disease, leading to poor quality of life for patients. Nanoparticle-based drug delivery has emerged as a promising medical technology and offers several advantages by enhancing the delivery of drug payloads to their target sites, reducing systemic toxicity, and facilitating patient compliance over free drug administration. In addition, nanotechnology-based imaging approaches provide exciting diagnostic methods for monitoring molecular and cellular changes in transplanted organs, visualizing immune responses, and assessing the severity of rejection. These noninvasive technologies are expected to help enhance the posttransplantation patient survival through real time and early diagnosis of disease progression. Here, we present a comprehensive review of nanotechnology-assisted strategies in various aspects of organ transplantation, including organ protection before transplantation, mitigation of ischemia-reperfusion injury, counteraction of immune rejection, early detection of organ dysfunction posttransplantation, and molecular imaging and diagnosis of immune rejection.

Transition-Metal-Based Nanozymes: Synthesis, Mechanisms of Therapeutic Action, and Applications in Cancer Treatment

Cancer, as one of the leading causes of death worldwide, drives the advancement of cutting-edge technologies for cancer treatment. Transition-metal-based nanozymes emerge as promising therapeutic nanodrugs that provide a reference for cancer therapy. In this review, we present recent breakthrough nanozymes for cancer treatment. First, we comprehensively outline the preparation strategies involved in creating transition-metal-based nanozymes, including hydrothermal method, solvothermal method, chemical reduction method, biomimetic mineralization method, and sol-gel method. Subsequently, we elucidate the catalytic mechanisms (catalase (CAT)-like activities), peroxidase (POD)-like activities), oxidase (OXD)-like activities) and superoxide dismutase (SOD)-like activities) of transition-metal-based nanozymes along with their activity regulation strategies such as morphology control, size manipulation, modulation, composition adjustment and surface modification under environmental stimulation. Furthermore, we elaborate on the diverse applications of transition-metal-based nanozymes in anticancer therapies encompassing radiotherapy (RT), chemodynamic therapy (CDT), photodynamic therapy (PDT), photothermal therapy (PTT), sonodynamic therapy (SDT), immunotherapy, and synergistic therapy. Finally, the challenges faced by transition-metal-based nanozymes are discussed alongside future research directions. The purpose of this review is to offer scientific guidance that will enhance the clinical applications of nanozymes based on transition metals.

Nanocarriers address intracellular barriers for efficient drug delivery, overcoming drug resistance, subcellular targeting and controlled release

The cellular barriers are major bottlenecks for bioactive compounds entering into cells to accomplish their biological functions, which limits their biomedical applications. Nanocarriers have demonstrated high potential and benefits for encapsulating bioactive compounds and efficiently delivering them into target cells by overcoming a cascade of intracellular barriers to achieve desirable therapeutic and diagnostic effects. In this review, we introduce the cellular barriers ahead of drug delivery and nanocarriers, as well as summarize recent advances and strategies of nanocarriers for increasing internalization with cells, promoting intracellular trafficking, overcoming drug resistance, targeting subcellular locations and controlled drug release. Lastly, the future perspectives of nanocarriers for intracellular drug delivery are discussed, which mainly focus on potential challenges and future directions. Our review presents an overview of intracellular drug delivery by nanocarriers, which may encourage the future development of nanocarriers for efficient and precision drug delivery into a wide range of cells and subcellular targets.

A two-stage exacerbated hypoxia nanoengineering strategy induced amplifying activation of tirapazamine for microwave hyperthermia-chemotherapy of breast cancer

Microwave hyperthermia (MH) is an emerging treatment for solid tumors, such as breast cancer, due to its advantages of minimally invasive and deep tissue penetration. However, MH induced tumor hypoxia is still an obstacle to breast tumor treatment failure. Therefore, an original nanoengineering strategy was proposed to exacerbate hypoxia in two stages, thereby amplifying the efficiency of activating tirapazamine (TPZ). And a novel microwave-sensitized nanomaterial (GdEuMOF@TPZ, GEMT) is designed. GdEuMOF (GEM) nanoparticles are certified excellent microwave (MW) sensitization performance, thus improving tumor selectivity to achieve MH. Meanwhile MW can aggravate the generation of thrombus and caused local circulatory disturbance of tumor, resulting in the Stage I exacerbated hypoxia environment passively. Due to tumor heterogeneity and uneven hypoxia, GEMT nanoparticles under microwave could actively deplete residual oxygen through the chemical reaction, exacerbating hypoxia level more evenly, thus forming the Stage II of exacerbated hypoxia environment. Consequently, a two-stage exacerbated hypoxia GEMT nanoparticles realize amplifying activation of TPZ, significantly enhance the efficacy of microwave hyperthermia and chemotherapy, and effectively inhibit breast cancer. This research provides insights into the development of progressive nanoengineering strategies for effective breast tumor therapy.

Using imaging modalities to predict nanoparticle distribution and treatment efficacy in solid tumors: The growing role of ultrasound

Nanomedicine in oncology has not had the success in clinical impact that was anticipated in the early stages of the field's development. Ideally, nanomedicines selectively accumulate in tumor tissue and reduce systemic side effects compared to traditional chemotherapeutics. However, this has been more successful in preclinical animal models than in humans. The causes of this failure to translate may be related to the intra- and inter-patient heterogeneity of the tumor microenvironment. Predicting whether a patient will respond positively to treatment prior to its initiation, through evaluation of characteristics like nanoparticle extravasation and retention potential in the tumor, may be a way to improve nanomedicine success rate. While there are many potential strategies to accomplish this, prediction and patient stratification via noninvasive medical imaging may be the most efficient and specific strategy. There have been some preclinical and clinical advances in this area using MRI, CT, PET, and other modalities. An alternative approach that has not been studied as extensively is biomedical ultrasound, including techniques such as multiparametric contrast-enhanced ultrasound (mpCEUS), doppler, elastography, and super-resolution processing. Ultrasound is safe, inexpensive, noninvasive, and capable of imaging the entire tumor with high temporal and spatial resolution. In this work, we summarize the in vivo imaging tools that have been used to predict nanoparticle distribution and treatment efficacy in oncology. We emphasize ultrasound imaging and the recent developments in the field concerning CEUS. The successful implementation of an imaging strategy for prediction of nanoparticle accumulation in tumors could lead to increased clinical translation of nanomedicines, and subsequently, improved patient outcomes. This article is categorized under: Diagnostic Tools In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery Emerging Technologies.

The Emerging Landscape for Combating Resistance Associated with Energy-Based Therapies via Nanomedicine

Cancer represents a serious disease with significant implications for public health, imposing substantial economic burden and negative societal consequences. Compared to conventional cancer treatments, such as surgery and chemotherapy, energy-based therapies (ET) based on athermal and thermal ablation provide distinct advantages, including minimally invasive procedures and rapid postoperative recovery. Nevertheless, due to the complex pathophysiology of many solid tumors, the therapeutic effectiveness of ET is often limited. Nanotechnology offers unique opportunities by enabling facile material designs, tunable physicochemical properties, and excellent biocompatibility, thereby further augmenting the outcomes of ET. Numerous nanomaterials have demonstrated the ability to overcome intrinsic therapeutic resistance associated with ET, leading to improved antitumor responses. This comprehensive review systematically summarizes the underlying mechanisms of ET-associated resistance (ETR) and highlights representative applications of nanoplatforms used to mitigate ETR. Overall, this review emphasizes the recent advances in the field and presents a detailed account of novel nanomaterial designs in combating ETR, along with efforts aimed at facilitating their clinical translation.

Copper-Based Single-Atom Nanozyme System Mimicking Platelet Cells for Enhancing the Outcome of Radioimmunotherapy

Background

Radiotherapy is an indispensable part of the multidisciplinary treatment of breast cancer (BC). Due to the potential for serious side effects from ionizing radiation in the treatment of breast cancer, which can adversely affect the patient's quality of life, the radiation dose is often limited. This limitation can result in an incomplete eradication of tumors.

Methods

In this study, biomimetic copper single-atom catalysts (platelet cell membrane camouflaging, PC) were synthesized with the aim of improving the therapeutic outcomes of radiotherapy for BC. Following guidance to the tumor site facilitated by the platelet cell membrane coating, PC releases a copper single-atom nanozyme (SAzyme). This SAzyme enhances therapeutic effects by generating reactive oxygen species from H2O2 and concurrently inhibiting the self-repair mechanisms of cancer cells through the consumption of intracellular glutathione (GSH) within the tumor microenvironment. PC-augmented radiotherapy induces immunogenic cell death, which triggers an immune response to eradicate tumors.

Results

With the excellent biocompatibility, PC exhibited precise tumor-targeting capabilities. Furthermore, when employed in conjunction with radiotherapy, PC showed impressive tumor elimination results through immunological activation. Remarkably, the tumor suppression rate achieved with PC-enhanced radiotherapy reached an impressive 93.6%.

Conclusion

Therefore, PC presents an innovative approach for designing radiosensitizers with tumor-specific targeting capabilities, aiming to enhance the therapeutic impact of radiotherapy on BC.

Molecular imaging of tumour-associated pathological biomarkers with smart nanoprobe: From "Seeing" to "Measuring"

Although the extraordinary progress has been made in molecular biology, the prevention of cancer remains arduous. Most solid tumours exhibit both spatial and temporal heterogeneity, which is difficult to be mimicked in vitro. Additionally, the complex biochemical and immune features of tumour microenvironment significantly affect the tumour development. Molecular imaging aims at the exploitation of tumour-associated molecules as specific targets of customized molecular probe, thereby generating image contrast of tumour markers, and offering opportunities to non-invasively evaluate the pathological characteristics of tumours in vivo. Particularly, there are no "standard markers" as control in clinical imaging diagnosis of individuals, so the tumour pathological characteristics-responsive nanoprobe-based quantitative molecular imaging, which is able to visualize and determine the accurate content values of heterogeneous distribution of pathological molecules in solid tumours, can provide criteria for cancer diagnosis. In this context, a variety of "smart" quantitative molecular imaging nanoprobes have been designed, in order to provide feasible approaches to quantitatively visualize the tumour-associated pathological molecules in vivo. This review summarizes the recent achievements in the designs of these nanoprobes, and highlights the state-of-the-art technologies in quantitative imaging of tumour-associated pathological molecules.

Multistage Self-Assembled Nanomaterials for Cancer Immunotherapy

Advances in nanotechnology have brought innovations to cancer therapy. Nanoparticle-based anticancer drugs have achieved great success from bench to bedside. However, insufficient therapy efficacy due to various physiological barriers in the body remains a key challenge. To overcome these biological barriers and improve the therapeutic efficacy of cancers, multistage self-assembled nanomaterials with advantages of stimuli-responsiveness, programmable delivery, and immune modulations provide great opportunities. In this review, we describe the typical biological barriers for nanomedicines, discuss the recent achievements of multistage self-assembled nanomaterials for stimuli-responsive drug delivery, highlighting the programmable delivery nanomaterials, in situ transformable self-assembled nanomaterials, and immune-reprogramming nanomaterials. Ultimately, we perspective the future opportunities and challenges of multistage self-assembled nanomaterials for cancer immunotherapy.

Nanomedicine Strategies in Conquering and Utilizing the Cancer Hypoxia Environment

Cancer with a complex pathological process is a major disease to human welfare. Due to the imbalance between oxygen (O2) supply and consumption, hypoxia is a natural characteristic of most solid tumors and an important obstacle for cancer therapy, which is closely related to tumor proliferation, metastasis, and invasion. Various strategies to exploit the feature of tumor hypoxia have been developed in the past decade, which can be used to alleviate tumor hypoxia, or utilize the hypoxia for targeted delivery and diagnostic imaging. The strategies to alleviate tumor hypoxia include delivering O2, in situ O2 generation, reprogramming the tumor vascular system, decreasing O2 consumption, and inhibiting HIF-1 related pathways. On the other side, hypoxia can also be utilized for hypoxia-responsive chemical construction and hypoxia-active prodrug-based strategies. Taking advantage of hypoxia in the tumor region, a number of methods have been applied to identify and keep track of changes in tumor hypoxia. Herein, we thoroughly review the recent progress of nanomedicine strategies in both conquering and utilizing hypoxia to combat cancer and put forward the prospect of emerging nanomaterials for future clinical transformation, which hopes to provide perspectives in nanomaterials design.

Bioparameter-directed nanoformulations as MRI CAs enable the specific visualization of hypoxic tumour

A malignant tumour has hypoxic cells of varying degrees. The more severe the hypoxic degree, the more difficult the prognosis of the tumour and the higher the recurrence rate. Therefore, tumour hypoxia imaging is crucial. Magnetic resonance imaging (MRI) shows its strength in high resolution, depth of penetration and noninvasiveness. However, it needs more excellent contrast agents (CAs) to combat the complex tumour microenvironment (TME) and increased targeting of tumours to enhance clinical safety. Many research studies have focused on developing hypoxia-responsive MRI CAs that take advantage of the unique characteristics of hypoxic tumours. The low oxygen pressure, acidic TME, and up-regulated redox molecule levels found in hypoxic tumours serve as biological stimuli for nanoformulations that can accurately image the hypoxic region. This review highlights the importance of developing bioparameter-directed nanoformulations as MRI CAs for accurate tumour diagnosis. The design strategies and mechanisms of tumour-hypoxia imaging with nanoformulations are exemplified, with a focus on pH-responsiveness, redox-responsiveness, and p(O2)-responsiveness. The promising future of bioparameter-responsive nanoformulations for accurate tumour diagnosis and personalised cancer treatment is discussed.

Nanoprobe-based molecular imaging for tumor stratification

The responses of patients to tumor therapies vary due to tumor heterogeneity. Tumor stratification has been attracting increasing attention for accurately distinguishing between responders to treatment and non-responders. Nanoprobes with unique physical and chemical properties have great potential for patient stratification. This review begins by describing the features and design principles of nanoprobes that can visualize specific cell types and biomarkers and release inflammatory factors during or before tumor treatment. Then, we focus on the recent advancements in using nanoprobes to stratify various therapeutic modalities, including chemotherapy, radiotherapy (RT), photothermal therapy (PTT), photodynamic therapy (PDT), chemodynamic therapy (CDT), ferroptosis, and immunotherapy. The main challenges and perspectives of nanoprobes in cancer stratification are also discussed to facilitate probe development and clinical applications.

Dynamic-Reversible MRI Nanoprobe for Continuous Imaging Redox Homeostasis in Hepatic Ischemia-Reperfusion Injury

Hepatic ischemia-reperfusion (I/R) injury accompanied by oxidative stress is responsible for postoperative liver dysfunction and failure of liver surgery. However, the dynamic non-invasive mapping of redox homeostasis in deep-seated liver during hepatic I/R injury remains a great challenge. Herein, inspired by the intrinsic reversibility of disulfide bond in proteins, a kind of reversible redox-responsive magnetic nanoparticles (RRMNs) is designed for reversible imaging of both oxidant and antioxidant levels (ONOO^-/GSH), based on sulfhydryl coupling/cleaving reaction. We develop a facile strategy to prepare such reversible MRI nanoprobe via one-step surface modification. Owing to the significant change in size during the reversible response, the imaging sensitivity of RRMNs is greatly improved, which enables RRMNs to monitor the tiny change of oxidative stress in liver injury. Notably, such reversible MRI nanoprobe can non-invasively visualize the deep-seated liver tissue slice by slice in living mice. Moreover, this MRI nanoprobe can not only report molecular information about the degree of liver injury but also provide anatomical information about where the pathology occurred. The reversible MRI probe is promising for accurately and facilely monitoring I/R process, accessing injury degree and developing powerful strategy for precise treatment.

Identifying TOPK and Hypoxia Hallmarks in Esophageal Tumors for Photodynamic/Chemo/Immunotherapy and Liver Metastasis Inhibition with Nanocarriers

Although esophageal squamous cell carcinoma (ESCC) is one of the most lethal cancers, there are major bottlenecks in its therapeutic approaches, primarily the identification of clinically relevant targets and the lack of effective targeted therapeutics. Herein, we identified the hallmarks of ESCC, namely, high T-lymphokine-activated killer cell-originated protein kinase (TOPK) expression in human ESCC tumors and its correlation with poor patient prognosis and hypoxia in the tumor microenvironment. We developed hypoxia-sensitive nanoparticles encapsulating TOPK inhibitor OTS964 and photosensitizer chlorin e6 for the imaging-directed precision therapy of ESCC tumors. The sub-100 nm monodisperse nanoparticles efficiently delivered drugs into the human ESCC KYSE 150 cancer cells to kill the cells. The nanoparticles were selectively accumulated in the ESCC tumors after intravenous (i.v.) injection, thereby enabling the diagnosis and photoacoustic imaging-guided local laser irradiation of tumors. The combination of chemotherapy and photodynamic therapy effectively eradicated human ESCC KYSE 150 tumors and inhibited liver metastasis and recurrence by suppressing TOPK and inducing ESCC cell apoptosis. The nanoparticle-based therapies further stimulated high rates of natural killer cells in ESCC tumors, thereby exhibiting the potential of immunotherapy. This study identified important therapeutic targets of ESCC tumors and delineated an effective nanocarrier-based approach for tumor microenvironment and molecular targeted therapy.

An IL-12-Based Nanocytokine Safely Potentiates Anticancer Immunity through Spatiotemporal Control of Inflammation to Eradicate Advanced Cold Tumors

Treatment of immunologically cold tumors is a major challenge for immune checkpoint inhibitors (ICIs). Interleukin 12 (IL-12) can invigorate ICIs against cold tumors by establishing a robust antitumor immunity. However, its toxicity and systemic induction of counteracting immunosuppressive signals have hindered translation. Here, IL-12 activity is spatiotemporally controlled for safely boosting efficacy without the stimulation of interfering immune responses by generating a nanocytokine that remains inactive at physiological pH, but unleashes its full activity at acidic tumor pH. The IL-12-based nanocytokine (Nano-IL-12) accumulate and release IL-12 in tumor tissues, eliciting localized antitumoral inflammation, while preventing systemic immune response, counteractive immune reactions, and adverse toxicities even after repeated intravenous administration. The Nano-IL-12-mediated spatiotemporal control of inflammation prompt superior anticancer efficacy, and synergize with ICIs to profoundly inflame the tumor microenvironment and completely eradicate ICI-resistant primary and metastatic tumors. The strategy could be a promising approach toward safer and more effective immunotherapies.

Cancer-associated fibroblast-targeted nanodrugs reshape colorectal tumor microenvironments to suppress tumor proliferation, metastasis and improve drug penetration

Cancer-associated fibroblasts (CAFs) produce a critical tumor-promoting effect by cellular crosstalk with cancer cells and remodel the extracellular matrix (ECM) to form a protective physical barrier. The simple elimination of CAFs is not sufficient to govern the CAF-shaped aggressive tumor microenvironment (TME) because of the complexity of tumors. Herein, a CAF-targeted poly (lactic-co-glycolic acid) (PLGA) nanoemulsion is tailored to simultaneously deliver doxorubicin (DOX) and small interfering RNA (siRNA) targeting hepatocyte growth factor (HGF) for the combination of chemotherapy and gene therapy. The nanoemulsion (apt-Si/DNPs) shows a high specificity towards CAFs due to the aptamer modification and efficiently induces the apoptosis of CAFs, thus decreasing ECM deposition in the TME. Importantly, the delivered siRNA reduces the expression of the HGF in the remaining CAFs, which overcomes chemotherapy-induced upregulation of HGF mRNA and prevents the reproduction of CAFs through the autocrine HGF closed-loop. Owing to these synergetic effects, tumor proliferation, migration and invasion are prominently inhibited and tumor permeability is improved significantly. Overall, these results emphasize the potential of CAF-targeted combination treatments to inhibit tumor progression and metastasis, as well as overcome therapeutic resistance.

Nanomedicine-mediated ferroptosis targeting strategies for synergistic cancer therapy

Apoptosis-based treatment plays an important role in regulating the death of tumor cells (e.g., chemotherapy, radiotherapy, and immunotherapy). Nevertheless, cancer cells can escape surveillance from apoptosis-associated signaling by bypassing other biological pathways and thus result in considerable resistance to therapies. Significantly, ferroptosis, a newly identified type of regulated cell death that is characterized by iron-dependent and lipid peroxidation accumulation, has aroused great research interest in cancer therapy. Increasing approaches have been developed to induce ferroptosis of tumor cells, including using clinically approved drugs, experimentally used compounds, and nanomedicine formulations. More importantly, the emerging nanomedicine-based strategy has made great advances in tumor treatment because of the promising targeting efficacy and enhanced therapeutic effects. In this review, we mainly overview state-of-the-art research on nanomedicine-mediated ferroptosis targeting strategies for synergistic cancer therapies, such as immunotherapy, chemotherapy, radiotherapy, and photothermal therapy. The potential targeting mechanism of nanomedicine for ferroptosis induction was also included. Finally, the future development of nanomedicine in the field of ferroptosis-based cell death in tumor treatment will be envisioned, aiming to provide new insight for tumor treatment in the clinic.

Molecular MRI-Based Monitoring of Cancer Immunotherapy Treatment Response

Immunotherapy constitutes a paradigm shift in cancer treatment. Its FDA approval for several indications has yielded improved prognosis for cases where traditional therapy has shown limited efficiency. However, many patients still fail to benefit from this treatment modality, and the exact mechanisms responsible for tumor response are unknown. Noninvasive treatment monitoring is crucial for longitudinal tumor characterization and the early detection of non-responders. While various medical imaging techniques can provide a morphological picture of the lesion and its surrounding tissue, a molecular-oriented imaging approach holds the key to unraveling biological effects that occur much earlier in the immunotherapy timeline. Magnetic resonance imaging (MRI) is a highly versatile imaging modality, where the image contrast can be tailored to emphasize a particular biophysical property of interest using advanced engineering of the imaging pipeline. In this review, recent advances in molecular-MRI based cancer immunotherapy monitoring are described. Next, the presentation of the underlying physics, computational, and biological features are complemented by a critical analysis of the results obtained in preclinical and clinical studies. Finally, emerging artificial intelligence (AI)-based strategies to further distill, quantify, and interpret the image-based molecular MRI information are discussed in terms of perspectives for the future.

Stimuli-responsive image-guided nanocarriers as smart drug delivery platforms

INTRODUCTION

In recent years, to improve the precision of drug delivery and reduce toxicity associated from the uncontrolled drug release at off-target locations, extensive efforts have been paid to develop stimuli-responsive nanocarriers, which enable precise control over on-demand drug release due to internal stimuli like pH, redox, enzyme and external stimuli like light, magnetic field, and ultrasound. Moreover, some stimuli-responsive nanocarriers have been strategically incorporated with imaging probes for simultaneous monitoring of the drug delivery process and region of interest for treatment optimization.

AREAS COVERED

In this review, the state-of-art progress in developing stimuli-responsive image-guided nanocarriers are summarized, including their designed strategies, synergistic mechanism, and biomedical applications in cancer therapy, and the current challenges and new perspectives are discussed.

EXPERT OPINION

The stimuli-responsive nanocarriers provide assurance for precise release of drugs and imaging probes, and the molecular imaging techniques can monitor the pharmacokinetics, biodistribution and bioavailability of drugs in vivo, and feedback the drug delivery profile. Therefore, stimuli-responsive image-guided nanocarriers can integrate diagnosis and therapy in one nanoplatform and facilitate optimal therapeutic efficacy.

Biomimetic nanomaterial-facilitated oxygen generation strategies for enhancing tumour treatment outcomes

Hypoxia, as a typical hallmark of the tumour microenvironment (TME), has been verified to exist in most malignancies and greatly hinders the outcome of tumour treatments, including chemotherapy, photodynamic therapy, radiotherapy, and immunotherapy. Various approaches to alleviate tumour hypoxia have been reported. Among them, biomimetic nanomaterial-facilitated tumour oxygenation strategies, based on the engagement of human endogenous proteins, red blood cells, the cell membrane, and catalase, are the most impressive due to their excellent tumour active-targeting ability and superior tumour-selective capability, which, however, have not yet been systematically reviewed. Herein, we are ready to describe the current progress in biomimetic nanomaterial-facilitated tumour oxygenation strategies and corresponding improvements in tumour treatment outputs. In this review, the underlying mechanism behind the superior effect of these biomimetic nanomaterials, compared with other materials, on alleviating the hypoxic TME is highlighted. Additionally, the ongoing problems and potential solutions are also discussed.

Emerging Biomaterials Imaging Antitumor Immune Response

Immunotherapy is one of the most promising clinical modalities for the treatment of malignant tumors and has shown excellent therapeutic outcomes in clinical settings. However, it continues to face several challenges, including long treatment cycles, high costs, immune-related adverse events, and low response rates. Thus, it is critical to predict the response rate to immunotherapy by using imaging technology in the preoperative and intraoperative. Here, the latest advances in nanosystem-based biomaterials used for predicting responses to immunotherapy via the imaging of immune cells and signaling molecules in the immune microenvironment are comprehensively summarized. Several imaging methods, such as fluorescence imaging, magnetic resonance imaging, positron emission tomography imaging, ultrasound imaging, and photoacoustic imaging, used in immune predictive imaging, are discussed to show the potential of nanosystems for distinguishing immunotherapy responders from nonresponders. Nanosystem-based biomaterials aided by various imaging technologies are expected to enable the effective prediction and diagnosis in cases of tumors, inflammation, and other public diseases.

NIR-II J-Aggregated Pt(II)-Porphyrin-Based Phosphorescent Probe for Tumor-Hypoxia Imaging

The luminescence of traditional phosphorescence-based hypoxia probes is limited to the visible and first near-infrared wavelength regions (<1000 nm), which has defects of higher light scattering and lower penetration depth in contrast with the second near-infrared wavelength window (NIR-II, 1000-1700 nm) for optical bioimaging. Herein, 5,15-bis(2,6-bis(dodecyloxy)phenyl)-porphyrin platinum(II) (PpyPt) with J-aggregation induced NIR-II phosphorescence is reported. J-aggregates of PpyPt are confirmed by the X-ray diffraction data in the crystalline state. Moreover, the emission and excitation spectra of PpyPt in the solid states reveal NIR-II luminescence feature of PpyPt in J-aggregates. More importantly, by preparation of water-soluble PpyPt nanoparticles (PpyPt NPs_4.76 ) with J-aggregates, it has NIR-II phosphorescent lifetime of microseconds and good oxygen-sensitivity in water. Moreover, the good biological hypoxia-sensing potential of PpyPt NPs_4.76 is demonstrated in cells and 4T1-tumor-bearing mice. This study provides an efficient strategy to design NIR-II phosphorescent probe for sensitive tumor-hypoxia detection through the construction of J-aggregates.

The Intracellular and Extracellular Microenvironment of Tumor Site: The Trigger of Stimuli-Responsive Drug Delivery Systems

The tumor microenvironment (TME), including intracellular and extracellular microenvironment, contains many biochemical indicators (such as acidity/alkalinity, oxygen content, and enzymatic activity) that are different from the normal physiological environment. These abnormal biochemical indicators can accelerate the heterogeneity of tumors, but on the other hand, they also provide opportunities for the design of intelligent drug delivery systems (DDSs). The TME-responsive DDSs have shown great potential in reducing the side effects of chemotherapy and improving the curative effect of tumors. In this review, the abnormal biochemical indicators of TME are introduced in detail from both the extracellular and intracellular aspects. In view of the various physiological barriers encountered during drug delivery, the strategy of constructing TME-responsive DDSs is discussed. By summarizing the typical research progress, the authors prospect the development of TME-responsive DDS in the future.

Detection of Hypoxia in Cancer Models: Significance, Challenges, and Advances

The rapid proliferation of cancer cells combined with deficient vessels cause regions of nutrient and O2 deprivation in solid tumors. Some cancer cells can adapt to these extreme hypoxic conditions and persist to promote cancer progression. Intratumoral hypoxia has been consistently associated with a worse patient prognosis. In vitro, 3D models of spheroids or organoids can recapitulate spontaneous O2 gradients in solid tumors. Likewise, in vivo murine models of cancer reproduce the physiological levels of hypoxia that have been measured in human tumors. Given the potential clinical importance of hypoxia in cancer progression, there is an increasing need to design methods to measure O2 concentrations. O2 levels can be directly measured with needle-type probes, both optical and electrochemical. Alternatively, indirect, noninvasive approaches have been optimized, and include immunolabeling endogenous or exogenous markers. Fluorescent, phosphorescent, and luminescent reporters have also been employed experimentally to provide dynamic measurements of O2 in live cells or tumors. In medical imaging, modalities such as MRI and PET are often the method of choice. This review provides a comparative overview of the main methods utilized to detect hypoxia in cell culture and preclinical models of cancer.

Development of nanotechnology-mediated precision radiotherapy for anti-metastasis and radioprotection

Radiotherapy (RT), including external beam RT and internal radiation therapy, uses high-energy ionizing radiation to kill tumor cells.