Magnetic-Powered Janus Cell Robots Loaded with Oncolytic Adenovirus for Active and Targeted Virotherapy of Bladder Cancer

Delivering Microrobots in the Musculoskeletal System

Disorders of the musculoskeletal system are the major contributors to the global burden of disease and current treatments show limited efficacy. Patients often suffer chronic pain and might eventually have to undergo end-stage surgery. Therefore, future treatments should focus on early detection and intervention of regional lesions. Microrobots have been gradually used in organisms due to their advantages of intelligent, precise and minimally invasive targeted delivery. Through the combination of control and imaging systems, microrobots with good biosafety can be delivered to the desired area for treatment. In the musculoskeletal system, microrobots are mainly utilized to transport stem cells/drugs or to remove hazardous substances from the body. Compared to traditional biomaterial and tissue engineering strategies, active motion improves the efficiency and penetration of local targeting of cells/drugs. This review discusses the frontier applications of microrobotic systems in different tissues of the musculoskeletal system. We summarize the challenges and barriers that hinder clinical translation by evaluating the characteristics of different microrobots and finally point out the future direction of microrobots in the musculoskeletal system.

Dual-Engineered Macrophage-Microbe Encapsulation for Metastasis Immunotherapy

Lung metastases are the leading cause of death among cancer patients. The challenges of inefficient drug delivery, compounded by a robust immunosuppressive microenvironment, make effective treatment difficult. Here, an innovative dual-engineered macrophage-microbe encapsulation (Du-EMME) therapy is developed that integrates modified macrophages and engineered antitumor bacteria. These engineered macrophages, termed R-GEM cells, are designed to express RGD peptides on extracellular membranes, enhancing their tumor cell binding and intratumor enrichment. R-GEM cells are cocultured with attenuated Salmonella typhimurium VNP20009, producing macrophage-microbe encapsulation (R-GEM/VNP cells). The intracellular bacteria maintain bioactivity for more than 24 h, and the bacteria released from R-GEM/VNP cells within the tumor continue to exert bacteria-mediated antitumor effects. This is further supported by macrophage-based chemotaxis and camouflage, which enhance the intratumoral enrichment and biocompatibility of the bacteria. Additionally, R-GEM cells loaded with IFNγ-secreting strains (VNP-IFNγ) form R-GEM/VNP-IFNγ cells. Treatment with these cells effectively halts lung metastatic tumor progression in three mouse models (breast cancer, melanoma, and colorectal cancer). R-GEM/VNP-IFNγ cells vigorously activate the tumor microenvironment, suppressing tumor-promoting M2-type macrophages, MDSCs, and Tregs, and enhancing tumor-antagonizing M1-type macrophages, mature DCs, and Teffs. Du-EMME therapy offers a promising strategy for targeted and enhanced antitumor immunity in treating cancer metastases.

Imaging and Downstaging Bladder Cancer with the 177Lu-Labeled Bioorthogonal Nanoprobe

Efforts on bladder cancer treatment have been shifting from extensive surgery to organ preservation in the past decade. To this end, we herein develop a multifunctional nanoagent for bladder cancer downstaging and bladder-preserving therapy by integrating mucosa penetration, reduced off-target effects, and internal irradiation therapy into a nanodrug. Specifically, an iron oxide nanoparticle was used as a carrier that was coated with hyaluronic acid (HA) for facilitating mucosa penetration. Dibenzocyclooctyne (DBCO) was introduced into the HA coating layer to react through bioorthogonal reaction with azide as an artificial receptor of bladder cancer cells, to improve the cellular internalization of the nanoprobe labeled with 177Lu. Through magnetic resonance imaging, the targeted imaging of both nonmuscle-invasive bladder cancer (NMIBC) and muscle-invasive bladder cancer (MIBC) was realized after intravesical instillation of the multifunctional probe, both NMIBC and MIBC were found downstaged, and the metastasis was inhibited, which demonstrates the potential of the multifunctional nanoprobe for bladder preservation in bladder cancer treatment.

Emerging delivery strategy for oncolytic virotherapy

Oncolytic virotherapy represents a promising approach in cancer immunotherapy. The primary delivery method for oncolytic viruses (OVs) is intratumoral injection, which apparently limits their clinical application. For patients with advanced cancer with disseminated metastasis, systemic administration is considered the optimal approach. However, the direct delivery of naked viruses through intravenous injection presents challenges, including rapid clearance by the immune system, inadequate accumulation in tumors, and significant side effects. Consequently, the development of drug delivery strategies has led to the emergence of various bio-materials serving as viral vectors, thereby improving the anti-tumor efficacy of oncolytic virotherapy. This review provides an overview of innovative strategies for delivering OVs, with a focus on nanoparticle-based or cell-based delivery systems. Recent pre-clinical and clinical studies are examined to highlight the enhanced efficacy of systemic delivery using these novel platforms. In addition, prevalent challenges in current research are briefly discussed, and potential solutions are proposed.

Biohybrid microrobots locally and actively deliver drug-loaded nanoparticles to inhibit the progression of lung metastasis

Lung metastasis poses a formidable challenge in the realm of cancer treatment, with conventional chemotherapy often falling short due to limited targeting and low accumulation in the lungs. Here, we show a microrobot approach using motile algae for localized delivery of drug-loaded nanoparticles to address lung metastasis challenges. The biohybrid microrobot [denoted "algae-NP(DOX)-robot"] combines green microalgae with red blood cell membrane-coated nanoparticles containing doxorubicin, a representative chemotherapeutic drug. Microalgae provide autonomous propulsion in the lungs, leveraging controlled drug release and enhanced drug dispersion to exert antimetastatic effects. Upon intratracheal administration, algae-NP(DOX)-robots efficiently transport their drug payload deep into the lungs while maintaining continuous motility. This strategy leads to rapid drug distribution, improved tissue accumulation, and prolonged retention compared to passive drug-loaded nanoparticles and free drug controls. In a melanoma lung metastasis model, algae-NP(DOX)-robots exhibit substantial improvement in therapeutic efficacy, reducing metastatic burden and extending survival compared to control groups.

Janus structure hydrogels: recent advances in synthetic strategies, biomedical microstructure and (bio)applications

Janus structure hydrogels (JSHs) are novel materials. Their primary fabrication methods and various applications have been widely reported. JSHs are primarily composed of Janus particles (JNPs) and polysaccharide components. They exhibit two distinct physical or chemical properties, generating intriguing characteristics due to their asymmetric structure. Normally, one side (adhesive interface) is predominantly constituted of polysaccharide components, primarily serving excellent adhesion. On the other side (functional surface), they integrate diverse functionalities, concurrently performing a plethora of synergistic functions. In the biomedical field, JSHs are widely applied in anti-adhesion, drug delivery, wound healing, and other areas. It also exhibits functions in seawater desalination and motion sensing. Thus, JSHs hold broad prospects for applications, and they possess significant research value in nanotechnology, environmental science, healthcare, and other fields. Additionally, this article proposes the challenges and future work facing these fields.

Mild magnetic hyperthermia-activated immuno-responses for primary bladder cancer therapy

Surgical intervention followed by chemotherapy is the principal treatment strategy for bladder cancer, which is hindered by significant surgical risks, toxicity from chemotherapy, and high rates of recurrence after surgery. In this context, a novel approach using mild magnetic hyperthermia therapy (MHT) for bladder cancer treatment through the intra-bladder delivery of magnetic nanoparticles is presented for the first time. This method overcomes the limitations of low magnetic thermal efficiency, inadequate tumor targeting, and reduced therapeutic effectiveness associated with the traditional intravenous administration of magnetic nanoparticles. Core-shell Zn-CoFe2O4@Zn-MnFe2O4 (MNP) nanoparticles were developed and further modified with hyaluronic acid (HA) to enhance their targeting ability toward tumor cells. The application of controlled mild MHT using MNP-HA at temperatures of 43-44 °C successfully suppressed the proliferation of bladder tumor cells and tumor growth, while also decreasing the expression levels of heat shock protein 70 (HSP70). Crucially, this therapeutic approach also activated the body's innate immune response involving macrophages, as well as the adaptive immune responses of dendritic cells (DCs) and T cells, thereby reversing the immunosuppressive environment of the bladder tumor and effectively reducing tumor recurrence. This study uncovers the potential immune-activating mechanism of mild MHT in the treatment of bladder cancer and confirms the effectiveness and safety of this strategy, indicating its promising potential for the clinical management of bladder cancer with a high tendency for relapse.

Engineered Microrobots for Targeted Delivery of Bacterial Outer Membrane Vesicles (OMV) in Thrombus Therapy

In the realm of thrombosis treatment, bioengineered outer membrane vesicles (OMVs) offer a novel and promising approach, as they have rich content of bacterial-derived components. This study centers on OMVs derived from Escherichia coli BL21 cells, innovatively engineered to encapsulate the staphylokinase-hirudin fusion protein (SFH). SFH synergizes the properties of staphylokinase (SAK) and hirudin (HV) to enhance thrombolytic efficiency while reducing the risks associated with re-embolization and bleeding. Building on this foundation, this study introduces two cutting-edge microrobotic platforms: SFH-OMV@H for venous thromboembolism (VTE) treatment, and SFH-OMV@MΦ, designed specifically for cerebral venous sinus thrombosis (CVST) therapy. These platforms have demonstrated significant efficacy in dissolving thrombi, with SFH-OMV@H showcasing precise vascular navigation and SFH-OMV@MΦ effectively targeting cerebral thrombi. The study shows that the integration of these bioengineered OMVs and microrobotic systems marks a significant advancement in thrombosis treatment, underlining their potential to revolutionize personalized medical approaches to complex health conditions.

Bioinspired Adaptive Microdrugs Enhance the Chemotherapy of Malignant Glioma: Beyond Their Nanodrugs

Solid nanoparticle-mediated drug delivery systems are usually confined to nanoscale due to the enhanced permeability and retention effect. However, they remain a great challenge for malignant glioma chemotherapy because of poor drug delivery efficiency and insufficient tumor penetration resulting from the blood-brain barrier/blood-brain tumor barrier (BBB/BBTB). Inspired by biological microparticles (e.g., cells) with excellent adaptive deformation, it is demonstrated that the adaptive microdrugs (even up to 3.0 µm in size) are more efficient than their nanodrugs (less than 200 nm in size) to cross BBB/BBTB and penetrate into tumor tissues, achieving highly efficient chemotherapy of malignant glioma. The distinct delivery of the adaptive microdrugs is mainly attributed to the enhanced interfacial binding and endocytosis via adaptive deformation. As expected, the obtained adaptive microdrugs exhibit enhanced accumulation, deep penetration, and cellular internalization into tumor tissues in comparison with nanodrugs, significantly improving the survival rate of glioblastoma mice. It is believed that the bioinspired adaptive microdrugs enable them to efficiently cross physiological barriers and deeply penetrate tumor tissues for drug delivery, providing an avenue for the treatment of solid tumors.

Engineered CpG-Loaded Nanorobots Drive Autophagy-Mediated Immunity for TLR9-Positive Cancer Therapy

Smart nanorobots have emerged as novel drug delivery platforms in nanomedicine, potentially improving anti-cancer efficacy and reducing side effects. In this study, an intelligent tumor microenvironment-responsive nanorobot is developed that effectively delivers CpG payloads to Toll-like receptor 9 (TLR9)-positive tumors to induce autophagy-mediated cell death for immunotherapy. The nanorobots are fabricated by co-self-assembly of two amphiphilic triblock polymer peptides: one containing the matrix metallopeptidase 2 (MMP2)-cleaved GPLGVRGS motif to control the mechanical opening of the nanorobots and provide targeting capability for TLR-9-positive tumors and the other consisting of an arginine-rich GRRRDRGRS sequence that can condense nuclear acid payloads through electrostatic interactions. Using multiple tumor-bearing mouse models, it is investigated whether the intravenous injection of CpG-loaded nanorobots could effectively deliver CpG payloads to TLR-9-positive tumors and elicit anti-tumor immunity through TLR9 signaling and autophagy. Therefore, besides being a commonly used adjuvant for tumor vaccination, CpG-loaded nanorobots can effectively reprogram the tumor immunosuppressive microenvironment and suppress tumor growth and recurrence. This nanorobot-based CpG immunotherapy can be considered a feasible approach to induce anti-tumor immunity, showing great therapeutic potential for the future treatment of TLR9-positive cancers.

Autonomous Nanorobots as Miniaturized Surgeons for Intracellular Applications

Artificial nanorobots have emerged as promising tools for a wide range of biomedical applications, including biosensing, detoxification, and drug delivery. Their unique ability to navigate confined spaces with precise control extends their operational scope to the cellular or subcellular level. By combining tailored surface functionality and propulsion mechanisms, nanorobots demonstrate rapid penetration of cell membranes and efficient internalization, enhancing intracellular delivery capabilities. Moreover, their robust motion within cells enables targeted interactions with intracellular components, such as proteins, molecules, and organelles, leading to superior performance in intracellular biosensing and organelle-targeted cargo delivery. Consequently, nanorobots hold significant potential as miniaturized surgeons capable of directly modulating cellular dynamics and combating metastasis, thereby maximizing therapeutic outcomes for precision therapy. In this review, we provide an overview of the propulsion modes of nanorobots and discuss essential factors to harness propulsive energy from the local environment or external power sources, including structure, material, and engine selection. We then discuss key advancements in nanorobot technology for various intracellular applications. Finally, we address important considerations for future nanorobot design to facilitate their translation into clinical practice and unlock their full potential in biomedical research and healthcare.

Cell-Based Micro/Nano-Robots for Biomedical Applications: A Review

Micro/nano-robots are powerful tools for biomedical applications and are applied in disease diagnosis, tumor imaging, drug delivery, and targeted therapy. Among the various types of micro-robots, cell-based micro-robots exhibit unique properties because of their different cell sources. In combination with various actuation methods, particularly externally propelled methods, cell-based microrobots have enormous potential for biomedical applications. This review introduces recent progress and applications of cell-based micro/nano-robots. Different actuation methods for micro/nano-robots are summarized, and cell-based micro-robots with different cell templates are introduced. Furthermore, the review focuses on the combination of cell-based micro/nano-robots with precise control using different external fields. Potential challenges, further prospects, and clinical translations are also discussed.

Living virus-based nanohybrids for biomedical applications

Living viruses characterized by distinctive biological functions including specific targeting, gene invasion, immune modulation, and so forth have been receiving intensive attention from researchers worldwide owing to their promising potential for producing numerous theranostic modalities against diverse pathological conditions. Nevertheless, concerns during applications, such as rapid immune clearance, altering immune activation modes, insufficient gene transduction efficiency, and so forth, highlight the crucial issues of excessive therapeutic doses and the associated biosafety risks. To address these concerns, synthetic nanomaterials featuring unique physical/chemical properties are frequently exploited as efficient drug delivery vehicles or treatments in biomedical domains. By constant endeavor, researchers nowadays can create adaptable living virus-based nanohybrids (LVN) that not only overcome the limitations of virotherapy, but also combine the benefits of natural substances and nanotechnology to produce novel and promising therapeutic and diagnostic agents. In this review, we discuss the fundamental physiochemical properties of the viruses, and briefly outline the basic construction methodologies of LVN. We then emphasize their distinct diagnostic and therapeutic performances for various diseases. Furthermore, we survey the foreseeable challenges and future perspectives in this interdisciplinary area to offer insights. This article is categorized under: Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Therapeutic Approaches and Drug Discovery > Emerging Technologies.

A Novel Superparamagnetic Multifunctional Nerve Scaffold: A Remote Actuation Strategy to Boost In Situ Extracellular Vesicles Production for Enhanced Peripheral Nerve Repair

Extracellular vesicles (EVs) have inherent advantages over cell-based therapies in regenerative medicine because of their cargos of abundant bioactive cues. Several strategies are proposed to tune EVs production in vitro. However, it remains a challenge for manipulation of EVs production in vivo, which poses significant difficulties for EVs-based therapies that aim to promote tissue regeneration, particularly for long-term treatment of diseases like peripheral neuropathy. Herein, a superparamagnetic nanocomposite scaffold capable of controlling EVs production on-demand is constructed by incorporating polyethyleneglycol/polyethyleneimine modified superparamagnetic nanoparticles into a polyacrylamide/hyaluronic acid double-network hydrogel (Mag-gel). The Mag-gel is highly sensitive to a rotating magnetic field (RMF), and can act as mechano-stimulative platform to exert micro/nanoscale forces on encapsulated Schwann cells (SCs), an essential glial cell in supporting nerve regeneration. By switching the ON/OFF state of the RMF, the Mag-gel can scale up local production of SCs-derived EVs (SCs-EVs) both in vitro and in vivo. Further transcriptome sequencing indicates an enrichment of transcripts favorable in axon growth, angiogenesis, and inflammatory regulation of SCs-EVs in the Mag-gel with RMF, which ultimately results in optimized nerve repair in vivo. Overall, this research provides a noninvasive and remotely time-scheduled method for fine-tuning EVs-based therapies to accelerate tissue regeneration, including that of peripheral nerves.

System integration of magnetic medical microrobots: from design to control

Magnetic microrobots are ideal for medical applications owing to their deep tissue penetration, precise control, and flexible movement. After decades of development, various magnetic microrobots have been used to achieve medical functions such as targeted delivery, cell manipulation, and minimally invasive surgery. This review introduces the research status and latest progress in the design and control systems of magnetic medical microrobots from a system integration perspective and summarizes the advantages and limitations of the research to provide a reference for developers. Finally, the future development direction of magnetic medical microrobot design and control systems are discussed.

Local Drug Delivery in Bladder Cancer: Advances of Nano/Micro/Macro-Scale Drug Delivery Systems

Treatment of bladder cancer remains a critical unmet need and requires advanced approaches, particularly the development of local drug delivery systems. The physiology of the urinary bladder causes the main difficulties in the local treatment of bladder cancer: regular voiding prevents the maintenance of optimal concentration of the instilled drugs, while poor permeability of the urothelium limits the penetration of the drugs into the bladder wall. Therefore, great research efforts have been spent to overcome these hurdles, thereby improving the efficacy of available therapies. The explosive development of nanotechnology, polymer science, and related fields has contributed to the emergence of a number of nanostructured vehicles (nano- and micro-scale) applicable for intravesical drug delivery. Moreover, the engineering approach has facilitated the design of several macro-sized depot systems (centimeter scale) capable of remaining in the bladder for weeks and months. In this article, the main rationales and strategies for improved intravesical delivery are reviewed. Here, we focused on analysis of colloidal nano- and micro-sized drug carriers and indwelling macro-scale devices, which were evaluated for applicability in local therapy for bladder cancer in vivo.

Swarming magnetic nanorobots bio-interfaced by heparinoid-polymer brushes for in vivo safe synergistic thrombolysis

Biocompatible swarming magnetic nanorobots that work in blood vessels for safe and efficient targeted thrombolytic therapy in vivo are demonstrated. This is achieved by using magnetic beads elaborately grafted with heparinoid-polymer brushes (HPBs) upon the application of an alternating magnetic field B(t). Because of the dense surface charges bestowed by HPBs, the swarming nanorobots demonstrate reversible agglomeration-free reconfigurations, low hemolysis, anti-bioadhesion, and self-anticoagulation in high-ionic-strength blood environments. They are confirmed in vitro and in vivo to perform synergistic thrombolysis efficiently by "motile-targeting" drug delivery and mechanical destruction. Moreover, upon the completion of thrombolysis and removal of B(t), the nanorobots disassemble into dispersed particles in blood, allowing them to safely participate in circulation and be phagocytized by immune cells without apparent organ damage or inflammatory lesion. This work provides a rational multifaceted HPB biointerfacing design strategy for biomedical nanorobots and a general motile platform to deliver drugs for targeted therapies.

Joining Forces: The Combined Application of Therapeutic Viruses and Nanomaterials in Cancer Therapy

Cancer, on a global scale, presents a monumental challenge to our healthcare systems, posing a significant threat to human health. Despite the considerable progress we have made in the diagnosis and treatment of cancer, realizing precision cancer therapy, reducing side effects, and enhancing efficacy remain daunting tasks. Fortunately, the emergence of therapeutic viruses and nanomaterials provides new possibilities for tackling these issues. Therapeutic viruses possess the ability to accurately locate and attack tumor cells, while nanomaterials serve as efficient drug carriers, delivering medication precisely to tumor tissues. The synergy of these two elements has led to a novel approach to cancer treatment-the combination of therapeutic viruses and nanomaterials. This advantageous combination has overcome the limitations associated with the side effects of oncolytic viruses and the insufficient tumoricidal capacity of nanomedicines, enabling the oncolytic viruses to more effectively breach the tumor's immune barrier. It focuses on the lesion site and even allows for real-time monitoring of the distribution of therapeutic viruses and drug release, achieving a synergistic effect. This article comprehensively explores the application of therapeutic viruses and nanomaterials in tumor treatment, dissecting their working mechanisms, and integrating the latest scientific advancements to predict future development trends. This approach, which combines viral therapy with the application of nanomaterials, represents an innovative and more effective treatment strategy, offering new perspectives in the field of tumor therapy.

Interfacial Polymerization Produced Magnetic Particles with Nano-Filopodia for Highly Accurate Liquid Biopsy in the PSA Gray Zone

Magnetic particles are leading separation materials for biological purification and detection. Existing magnetic particles, which almost rely on molecule-level interactions, however, often encounter bottlenecks in highly efficient cell-level separation due to the underestimate of surface structure effects. Here, immune cell-inspired magnetic particles with nano-filopodia (NFMPs) produced by interfacial polymerization for highly efficient capture of circulating tumor cells (CTCs) and further accurate clinical diagnosis of prostate cancer are reported . The unprecedented construction of nano-filopodia on polymer-based magnetic particles is achieved by introducing electrostatic interactions in emulsion interfacial polymerization. Due to the unique nano-filopodia, the NFMPs allow remarkably enhanced CTCs capture efficiency (86.5% ± 2.8%) compared with smooth magnetic particles (SMPs, 35.7% ± 5.7%). Under the assistance of machine learning by combining with prostate-specific antigen (PSA) and free to total PSA (F/T-PSA), the NFMPs strategy demonstrates high sensitivity (100%), high specificity (93.3%), and a high area under the curve (AUC) value (98.1%) for clinical diagnosis of prostate cancer in the PSA gray zone. The NFMPs are anticipated as an efficient platform for CTCs-based liquid biopsy toward early cancer diagnosis and prognosis evaluation.

Magnetically Powered Immunogenic Macrophage Microrobots for Targeted Multimodal Cancer Therapy

Motile microrobots open a new realm for disease treatment. However, the concerns of possible immune elimination, targeted capability and limited therapeutic avenue of microrobots constrain its practical biomedical applications. Herein, a biogenic macrophage-based microrobot loaded with magnetic nanoparticles and bioengineered bacterial outer membrane vesicles (OMVs), capable of magnetic propulsion, tumor targeting, and multimodal cancer therapy is reported. Such cell robots preserve intrinsic properties of macrophages for tumor suppression and targeting, and bioengineered OMVs for antitumor immune regulation and fused anticancer peptides. Cell robots display efficient magnetic propulsion and directional migration in the confined space. In vivo tests show that cell robots can accumulate at the tumor site upon magnetic manipulation, coupling with tumor tropism of macrophages to greatly improve the efficacy of its multimodal therapy, including tumor inhibition of macrophages, immune stimulation, and antitumor peptides of OMVs. This technology offers an attractive avenue to design intelligent medical microrobots with remote manipulation and multifunctional therapy capabilities for practical precision treatment.

Four-Dimensional Micro/Nanorobots via Laser Photochemical Synthesis towards the Molecular Scale

Miniaturized four-dimensional (4D) micro/nanorobots denote a forerunning technique associated with interdisciplinary applications, such as in embeddable labs-on-chip, metamaterials, tissue engineering, cell manipulation, and tiny robotics. With emerging smart interactive materials, static micro/nanoscale architectures have upgraded to the fourth dimension, evincing time-dependent shape/property mutation. Molecular-level 4D robotics promises complex sensing, self-adaption, transformation, and responsiveness to stimuli for highly valued functionalities. To precisely control 4D behaviors, current-laser-induced photochemical additive manufacturing, such as digital light projection, stereolithography, and two-photon polymerization, is pursuing high-freeform shape-reconfigurable capacities and high-resolution spatiotemporal programming strategies, which challenge multi-field sciences while offering new opportunities. Herein, this review summarizes the recent development of micro/nano 4D laser photochemical manufacturing, incorporating active materials and shape-programming strategies to provide an envisioning of these miniaturized 4D micro/nanorobots. A comparison with other chemical/physical fabricated micro/nanorobots further explains the advantages and potential usage of laser-synthesized micro/nanorobots.

Four-Dimensional-Printed Microrobots and Their Applications: A Review

Owing to their small size, microrobots have many potential applications. In addition, four-dimensional (4D) printing facilitates reversible shape transformation over time or upon the application of stimuli. By combining the concept of microrobots and 4D printing, it may be possible to realize more sophisticated next-generation microrobot designs that can be actuated by applying various stimuli, and also demonstrates profound implications for various applications, including drug delivery, cells delivery, soft robotics, object release and others. Herein, recent advances in 4D-printed microrobots are reviewed, including strategies for facilitating shape transformations, diverse types of external stimuli, and medical and nonmedical applications of microrobots. Finally, to conclude the paper, the challenges and the prospects of 4D-printed microrobots are highlighted.

Microrobots for Biomedicine: Unsolved Challenges and Opportunities for Translation

Microrobots are being explored for biomedical applications, such as drug delivery, biological cargo transport, and minimally invasive surgery. However, current efforts largely focus on proof-of-concept studies with nontranslatable materials through a "design-and-apply" approach, limiting the potential for clinical adaptation. While these proof-of-concept studies have been key to advancing microrobot technologies, we believe that the distinguishing capabilities of microrobots will be most readily brought to patient bedsides through a "design-by-problem" approach, which involves focusing on unsolved problems to inform the design of microrobots with practical capabilities. As outlined below, we propose that the clinical translation of microrobots will be accelerated by a judicious choice of target applications, improved delivery considerations, and the rational selection of translation-ready biomaterials, ultimately reducing patient burden and enhancing the efficacy of therapeutic drugs for difficult-to-treat diseases.

In vivo applications of micro/nanorobots

Untethered robots in the size range of micro/nano-scale offer unprecedented access to hard-to-reach areas of the body. In these challenging environments, autonomous task completion capabilities of micro/nanorobots have been the subject of research in recent years. However, most of the studies have presented preliminary in vitro results that can significantly differ under in vivo settings. Here, we focus on the studies conducted with animal models to reveal the current status of micro/nanorobotic applications in real-world conditions. By a categorization based on target locations, we highlight the main strategies employed in organs and other body parts. We also discuss key challenges that require interest before the successful translation of micro/nanorobots to the clinic.

Long-Term Retention Microbubbles with Three-Layer Structure for Floating Intravesical Instillation Delivery

Intravesical instillation is an effective treatment for bladder cancer. However, clinical anticancer agents always suffer rapid excretion by periodic urination, leading to low therapeutic efficacy. Prolonging the retention time of drugs in the bladder is the key challenge for intravesical instillation treatment. Herein, a facile and powerful surface cross-linking-freeze drying strategy is proposed to generate ultra-stable albumin bovine air microbubbles (BSA-MBs) that can float and adhere to the bladder wall to overcome the excretion of urination and exhibit a remarkable property of long-term retention in the bladder. More noteworthy, BSA-MBs are endowed with a specific three-layer structure, namely, the outer membrane, middle drug loading layer and inner air core, which makes them have a low density to easily float and possess a high drug loading capacity. Based on their unique superiorities, the therapeutic potential of doxorubicin (DOX)-loaded BSA-MBs (DOX-MBs) is exemplified by intravesical instillation for bladder cancer. After injection into the bladder, DOX-MBs can remain in the bladder for a long time and sustain the release of DOX in urine, exhibiting potent anticancer efficacy. Consequently, the prolonged retention of BSA-MBs in the bladder renders them as an effective floating drug delivery system for intravesical instillation therapy.

RGD peptide modified platinum nanozyme Co-loaded glutathione-responsive prodrug nanoparticles for enhanced chemo-photodynamic bladder cancer therapy

Bladder cancer is one of the most common malignant tumors in the urinary system worldwide. The poor permeability and uncontrollable release of drug and hypoxia of tumor tissues were the main reasons leading to poor therapeutic effect of chemo-photodynamic therapy for bladder cancer. To solve the above problems, a tumor-targeting peptide Arg-Gly-Asp (RGD) modified platinum nanozyme (PtNP) co-loaded glutathione (GSH)-responsive prodrug nanoparticles (PTX-SS-HPPH/Pt@RGD-NP) was constructed. Firstly, a GSH-responsive prodrug (PTX-SS-HPPH) was prepared by introducing a disulfide bond between paclitaxel (PTX) and photosensitizer 2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a (HPPH), which could realize the GSH-responsive release of the drug at the tumor sites. Also, the distearoylphosphoethanolamine-poly (ethylene glycol)-RGD peptide (DSPE-PEG-RGD) modified the prodrug to enhance the targeting and permeability ability to bladder cancer cells. Besides, to alleviate the hypoxia of tumor tissues, PtNP was introduced to produce oxygen (O₂) and improve photodynamic therapy efficiency. The results showed that the PTX-SS-HPPH/Pt@RGD-NP could achieve GSH-responsive drug release in tumor microenvironment, enhance the drug accumulation time and permeability at tumor sites in T24 subcutaneous tumor model and T24 orthotopic bladder tumor model, and alleviate hypoxia in tumor tissues, thus realizing enhanced chemo-photodynamic therapy for bladder cancer, and providing new strategies and methods for clinical treatment of bladder cancer.

Designing Intelligent Nanomaterials to Achieve Highly Sensitive Diagnoses and Multimodality Therapy of Bladder Cancer

Bladder cancer (BC) is among the most common malignant tumors of the genitourinary system worldwide. In recent years, the rate of BC incidence has increased, and the recurrence rate is high, resulting in poor quality of life for patients. Therefore, how to develop an effective method to achieve synchronous precise diagnoses and BC therapies is a difficult problem to solve clinically. Previous reports usually focus on the role of nanomaterials as drug delivery carriers, while a summary of the functional design and application of nanomaterials is lacking. Summarizing the application of functional nanomaterials in high-sensitivity diagnosis and multimodality therapy of BC is urgently needed. This review summarizes the application of nanotechnology in BC diagnosis, including the application of nanotechnology in the sensoring of BC biomarkers and their role in monitoring BC. In addition, conventional and combination therapies strategy in potential BC therapy are analyzed. Moreover, different kinds of nanomaterials in BC multimodal therapy according to pathological features of BC are also outlined. The goal of this review is to present an overview of the application of nanomaterials in the theranostics of BC to provide guidance for the application of functional nanomaterials to precisely diagnose and treat BC.

Mechanisms and strategies to enhance penetration during intravesical drug therapy for bladder cancer

Bladder cancer (BCa) is one of the most prevalent cancers worldwide. The effectiveness of intravesical therapy for bladder cancer, however, is limited due to the short dwell time and the presence of permeation barriers. Considering the histopathological features of BCa, the permeation barriers for drugs to transport across consist of a mucus layer and a nether tumor physiological barrier. Mucoadhesive delivery systems or mucus-penetrating delivery systems are developed to enhance their retention in or penetration across the mucus layer, but delivery systems that are capable of mucoadhesion-to-mucopenetration transition are more efficient to deliver drugs across the mucus layer. For the tumor physiological barrier, delivery systems mainly rely on four types of penetration mechanisms to cross it. This review summarizes the classical and latest approaches to intravesical drug delivery systems to penetrate BCa.

A Janus Au-Polymersome Heterostructure with Near-Field Enhancement Effect for Implant-Associated Infection Phototherapy

Polymer-inorganic hybrid Janus nanoparticles (PI-JNPs) have attracted extensive attention due to their special structures and functions. However, achieving the synergistic enhancement of photochemical activity between polymer and inorganic moieties in PI-JNPs remains challenging. Herein, the construction of a novel Janus Au-porphyrin polymersome (J-AuPPS) heterostructure by a facile one-step photocatalytic synthesis is reported. The near-field enhancement (NFE) effect between porphyrin polymersome (PPS) and Au nanoparticles in J-AuPPS is achieved to enhance its near-infrared (NIR) light absorption and electric/thermal field intensity at their interface, which improves the energy transfer and energetic charge-carrier generation. Therefore, J-AuPPS shows a higher NIR-activated photothermal conversion efficiency (48.4%) and generates more singlet oxygen compared with non-Janus core-particle Au-PPS nanostructure (28.4%). As a result, J-AuPPS exhibits excellent dual-mode (photothermal/photodynamic) antibacterial and anti-biofilm performance, thereby significantly enhancing the in vivo therapeutic effect in an implant-associated-infection rat model. This work is believed to motivate the rational design of advanced hybrid JNPs with desirable NFE effect and further extend their biological applications.

Emerging Nano-/Biotechnology Drives Oncolytic Virus-Activated and Combined Cancer Immunotherapy

Oncolytic viruses (OVs) as one promising antitumor methods have made important contributions to tumor immunotherapy, which arouse increasing attention. They provide the dual mechanisms including direct killing effect toward tumor cells and immune activation for elevating antitumor responses, which have been proved in many preclinical studies. Especially, natural or genetically modified viruses as clinical immune preparations have emerged as a new promising approach objective to oncology treatment. The approval of talimogene laherparepvec (T-VEC) by the U.S. Food and Drug Administration (FDA) for the therapy of advanced melanoma could be considered as a milestone achievement in the clinical translation of OV. In this review, we first discussed the antitumor mechanisms of OVs with an emphasis on targeting, replication, and propagation. We further outlined the state of the art of current OVs in tumor and underlined the activated biological effects especially including immunity. More significantly, the enhanced immune responses based on OVs were systematically discussed from different perspectives such as combination with immunotherapy, genetic engineering of OVs, integration with nanobiotechnology or nanoparticles, and antiviral response counteraction, where their principles were shed light on. The development of OVs in the clinics was also highlighted to analyze the actuality and concerns of different OV applications in clinical trials. At last, the future perspectives and challenges of OVs as an already widely accepted treatment means were discussed. This review will provide a systematic review and deep insight into OV development and also offer new opportunities and guidance pathways to drive the further clinical translation.

Recent Progress and Trends in X-ray-Induced Photodynamic Therapy with Low Radiation Doses

The prominence of photodynamic therapy (PDT) in treating superficial skin cancer inspires innovative solutions for its congenitally deficient shadow penetration of the visible-light excitation. X-ray-induced photodynamic therapy (X-PDT) has been proven to be a successful technique in reforming the conventional PDT for deep-seated tumors by creatively utilizing penetrating X-rays as external excitation sources and has witnessed rapid developments over the past several years. Beyond the proof-of-concept demonstration, recent advances in X-PDT have exhibited a trend of minimizing X-ray radiation doses to quite low values. As such, scintillating materials used to bridge X-rays and photosensitizers play a significant role, as do diverse well-designed irradiation modes and smart strategies for improving the tumor microenvironment. Here in this review, we provide a comprehensive summary of recent achievements in X-PDT and highlight trending efforts using low doses of X-ray radiation. We first describe the concept of X-PDT and its relationships with radiodynamic therapy and radiotherapy and then dissect the mechanism of X-ray absorption and conversion by scintillating materials, reactive oxygen species evaluation for X-PDT, and radiation side effects and clinical concerns on X-ray radiation. Finally, we discuss a detailed overview of recent progress regarding low-dose X-PDT and present perspectives on possible clinical translation. It is expected that the pursuit of low-dose X-PDT will facilitate significant breakthroughs, both fundamentally and clinically, for effective deep-seated cancer treatment in the near future.