X-ray-Controlled Bilayer Permeability of Bionic Nanocapsules Stabilized by Nucleobase Pairing Interactions for Pulsatile Drug Delivery

Bilirubin ameliorates osteoarthritis via activating Nrf2/HO-1 pathway and suppressing NF-κB signalling

Osteoarthritis (OA) is a chronic degenerative joint disease that affects worldwide. Oxidative stress plays a critical role in the chronic inflammation and OA progression. Scavenging overproduced reactive oxygen species (ROS) could be rational strategy for OA treatment. Bilirubin (BR) is a potent endogenous antioxidant that can scavenge various ROS and also exhibit anti-inflammatory effects. However, whether BR could exert protection on chondrocytes for OA treatment has not yet been elucidated. Here, chondrocytes were exposed to hydrogen peroxide with or without BR treatment. The cell viability was assessed, and the intracellular ROS, inflammation cytokines were monitored to indicate the state of chondrocytes. In addition, BR was also tested on LPS-treated Raw264.7 cells to test the anti-inflammation property. An in vitro bimimic OA microenvironment was constructed by LPS-treated Raw264.7 and chondrocytes, and BR also exert certain protection for chondrocytes by activating Nrf2/HO-1 pathway and suppressing NF-κB signalling. An ACLT-induced OA model was constructed to test the in vivo therapeutic efficacy of BR. Compared to the clinical used HA, BR significantly reduced cartilage degeneration and delayed OA progression. Overall, our data shows that BR has a protective effect on chondrocytes and can delay OA progression caused by oxidative stress.

Radiation responsive PROTAC nanoparticles for tumor-specific proteolysis enhanced radiotherapy

Proteolysis targeting chimeras (PROTACs) is a promising strategy for cancer therapy. However, the always-on bioactivity of PROTACs may lead to non-target toxicity, which restricts their antitumor performance. Here, we developed an X-ray radiation responsive PROTAC nanomicelle (RCNprotac) by covalently conjugating a reported small molecule PROTAC (MZ1) to hydrophilic PEG via a diselenide bond-containing carbon chain, which then self-assembled into a 141.80 ± 5.66 nm nanomicelle. The RCNprotac displayed no bioactivity during circulation due to the occupation of the hydroxyl group on the E3 ubiquitin ligand component and could effectively accumulate at the tumor site owing to the enhanced permeability and retention effect. Upon exposure to X-ray radiation, the radiation-sensitive diselenide bonds were broken to specifically release MZ1 for tumor BRD4 protein degradation. Furthermore, the reduction in the BRD4 protein level could increase the tumor's sensitivity to radiation. RCNprotac showed a synergistic enhancement of antitumor effects both in vitro and in vivo. We believe that this X-ray-responsive PROTAC nanomicelle could provide a new strategy for the X-ray-activated spatiotemporally controlled protein degradation and for the BRD4 proteolysis enhanced tumor radiosensitivity.

Nanomaterials for light-mediated therapeutics in deep tissue

Light-mediated therapeutics, including photodynamic therapy, photothermal therapy and light-triggered drug delivery, have been widely studied due to their high specificity and effective therapy. However, conventional light-mediated therapies usually depend on the activation of light-sensitive molecules with UV or visible light, which have poor penetration in biological tissues. Over the past decade, efforts have been made to engineer nanosystems that can generate luminescence through excitation with near-infrared (NIR) light, ultrasound or X-ray. Certain nanosystems can even carry out light-mediated therapy through chemiluminescence, eliminating the need for external activation. Compared to UV or visible light, these 4 excitation modes penetrate more deeply into biological tissues, triggering light-mediated therapy in deeper tissues. In this review, we systematically report the design and mechanisms of different luminescent nanosystems excited by the 4 excitation sources, methods to enhance the generated luminescence, and recent applications of such nanosystems in deep tissue light-mediated therapeutics.

Hydrogen-Bonding Interactions from Nucleobase-Decorated Supramolecular Polymer: Synthesis, Self-Assembly and Biomedical Applications

The fabrication of supramolecular materials for biomedical applications such as drug delivery, bioimaging, wound-dressing, adhesion materials, photodynamic/photothermal therapy, infection control (as antibacterial), etc. has grown tremendously, due to their unique properties, especially the formation of hydrogen bonding. Nevertheless, void space in the integration process, lack of feasibility in the construction of supramolecular materials of natural origin in living biological systems, potential toxicity, the need for complex synthesis protocols, and costly production process limits the actual application of nanomaterials for advanced biomedical applications. On the other hand, hydrogen bonding from nucleobases is one of the strategies that shed light on the blurred deployment of nanomaterials in medical applications, given the increasing reports of supramolecular polymers that promote advanced technologies. Herein, we review the extensive body of literature about supramolecular functional biomaterials based on nucleobase hydrogen bonding pertinent to different biomedical applications. It focuses on the fundamental understanding about the synthesis, nucleobase-decorated supramolecular architecture, and novel properties with special emphasis on the recent developments in the assembly of nanostructures via hydrogen-bonding interactions of nucleobase. Moreover, the challenges, plausible solutions, and prospects of the so-called hydrogen bonding interaction from nucleobase for the fabrication of functional biomaterials are outlined.

Nanocarrier-based targeting of metabolic pathways for endometrial cancer: Status and future perspectives

Cancer is the second-most lethal global disease, as per health reports, and is responsible for around 70% of deaths in low- and middle-income countries. Endometrial cancer is one of the emerging malignancies and has been predicted as a public health challenge for the future. Insulin resistance, obesity, and diabetes mellitus are the key metabolic factors that promote risks for the development of endometrial cancer. Various signaling pathways and associated genes are involved in the genesis of endometrial cancer, and any mutation or deletion in such related factors leads to the induction of endometrial cancer. The conventional way of drug delivery has been used for ages but is associated with poor management of cancer due to non-targeting of the endometrial cancer cells, low efficacy of the therapy, and toxicity issues as well. In this context, nanocarrier-based therapy for the management of endometrial cancer is an effective alternate choice that overcomes the problems associated with conventional therapy. In this review article, we highlighted the nanocarrier-based targeting of endometrial cancer, with a special focus on targeting various metabolic signaling pathways. Furthermore, the future perspectives of nanocarrier-based targeting of metabolic pathways in endometrial cancer were also underpinned. It is concluded that targeting metabolic signaling pathways in endometrial cancer via nanocarrier scaffolds is the future of pharmaceutical design for the significant management and treatment of endometrial cancer.

X-Ray-Induced Drug Release for Cancer Therapy

Drug delivery systems (DDSs) are designed to deliver therapeutic agents to specific target sites while minimizing systemic toxicity. Recent developments in drug-loaded DDSs have demonstrated promising characteristics and paved new pathways for cancer treatment. Light, a prevalent external stimulus, is widely utilized to trigger drug release. However, conventional light sources primarily concentrate on the ultraviolet (UV) and visible light regions, which suffer from limited biological tissue penetration. This limitation hinders applications for deep-tissue tumor drug release. Given their deep tissue penetration and well-established application technology, X-rays have recently received attention for the pursuit of controlled drug release. With precise spatiotemporal and dosage controllability, X-rays stand as an ideal stimulus for achieving controlled drug release in deep-tissue cancer therapy. This article explores the recent advancements in using X-rays for stimulus-triggered drug release in DDSs and delves into their action mechanisms.

Recent advances in permeable polymersomes: fabrication, responsiveness, and applications

Polymersomes are vesicular nanostructures enclosed by a bilayer-membrane self-assembled from amphiphilic block copolymers, which exhibit higher stability compared with their biological analogues (e.g. liposomes). Due to their versatility, polymersomes have found various applications in different research fields such as drug delivery, nanomedicine, biological nanoreactors, and artificial cells. However, polymersomes prepared with high molecular weight components typically display low permeability to molecules and ions. It hence remains a major challenge to balance the opposing features of robustness and permeability of polymersomes. In this review, we focus on the design and strategies for fabricating permeable polymersomes, including polymersomes with intrinsic permeability, the formation of nanopores in the membrane bilayers by protein insertion, and the construction of stimuli-responsive polymersomes. Then, we highlight the applications of permeable polymersomes in the fields of biomimetic nanoreactors, artificial cells and organelles, and nanomedicine, to underline the challenges in the development of polymersomes as soft matter with biomedical utilities.

Recent advances in stimuli-responsive nano-heterojunctions for tumor therapy

Stimuli-responsive catalytic therapy based on nano-catalysts has attracted much attention in the field of biomedicine for tumor therapy, due to its excellent and unique properties. However, the complex tumor microenvironment conditions and the rapid charge recombination in the catalyst limit catalytic therapy's effectiveness and further development. Effective heterojunction nanomaterials are constructed to address these problems to improve catalytic performance. Specifically, on the one hand, the band gap of the material is adjusted through the heterojunction structure to promote the charge separation efficiency under exogenous stimulation and further improve the catalytic capacity. On the other hand, the construction of a heterojunction structure can not only preserve the function of the original catalyst but also achieve significantly enhanced synergistic therapy ability. This review summarized the construction and functions of stimuli-responsive heterojunction nanomaterials under the excitation of X-rays, visible-near infrared light, and ultrasound in recent years, and further introduces their application in cancer therapy. Hopefully, the summary of stimuli-responsive heterojunction nanomaterials' applications will help researchers promote the development of nanomaterials in cancer therapy.

Diffusion-mediated carving of interior topologies of all-natural protein nanoparticles to tailor sustained drug release for effective breast cancer therapy

Proteins are promising base materials for developing drug carriers with efficient blood circulation due to low possibilities of clearance by macrophages. However, such natural biopolymers have highly sophisticated molecular structures, preventing them from being assembled into nano-platforms with manipulable payload release profiles. Here, we report the self-assembly of two natural proteins (milk casein and rice protein) into protein nanoparticles (NPs, ∼150 nm) with tailorable release profiles. Diffusion of plant-derived paclitaxel (PTX)-containing eugenol into the hydrophobic cores of the NPs and subsequent dialysis to remove eugenol from the cores lead to the carving of the NP interiors. With the increase in the mass ratios of casein and rice protein, this process generates all-natural NPs with PTX loaded in their full cavities, semi-full cavities, or solid cores. These NPs can be efficiently uptaken by breast cancer cells and could kill the cancer cells efficiently. PTX in these NPs demonstrates increasingly sustained in vivo release profiles from full cavities, semi-full cavities, to solid cores, gradually extending its pharmacokinetic profiles in blood plasma to favor drug accumulation in breast tumor models. Consequently, the NPs with solid cores completely inhibit tumor growth in vivo, more effectively than those with full and semi-full cavities. Our work opens up a new avenue to the use of diffusion-mediated nanoscale carving in producing biomaterials with controllable interior topologies relevant to drug release profiles.

Reaching new lights: a review on photo-controlled nanomedicines and their in vivo evaluation

The selective and efficient delivery of bioactive molecules to sites of interest remains a formidable challenge in medicine. In recent years, it has been shown that stimuli-responsive drug delivery systems display several advantages over traditional drug administration such as an improved pharmacokinetic profile and the desirable ability to gain control over release. Light emerged as one of the most powerful stimuli due to its high biocompatibility, spatio-temporal control, and non-invasiveness. On the road to clinical translation, various chemical systems of high complexity have been reported with the aim to improve efficacy, safety, and versatility of drug delivery under complex biological conditions. For future research on the chemical design of such photo-controlled nanomedicines, it is essential to gain an understanding of their in vivo translation and efficiency. Here, we discuss photo-controlled nanomedicines that have been evaluated in vivo and provide an overview of the state-of-the-art that should guide future research design.

Advanced materials and technologies for oral diseases

Oral disease, as a class of diseases with very high morbidity, brings great physical and mental damage to people worldwide. The increasing burden and strain on individuals and society make oral diseases an urgent global health problem. Since the treatment of almost all oral diseases relies on materials, the rapid development of advanced materials and technologies has also promoted innovations in the treatment methods and strategies of oral diseases. In this review, we systematically summarized the application strategies in advanced materials and technologies for oral diseases according to the etiology of the diseases and the comparison of new and old materials. Finally, the challenges and directions of future development for advanced materials and technologies in the treatment of oral diseases were refined. This review will guide the fundamental research and clinical translation of oral diseases for practitioners of oral medicine.

Advancing X-ray Luminescence for Imaging, Biosensing, and Theragnostics

X-ray luminescence is an optical phenomenon in which chemical compounds known as scintillators can emit short-wavelength light upon the excitation of X-ray photons. Since X-rays exhibit well-recognized advantages of deep penetration toward tissues and a minimal autofluorescence background in biological samples, X-ray luminescence has been increasingly becoming a promising optical tool for tackling the challenges in the fields of imaging, biosensing, and theragnostics. In recent years, the emergence of nanocrystal scintillators have further expanded the application scenarios of X-ray luminescence, such as high-resolution X-ray imaging, autofluorescence-free detection of biomarkers, and noninvasive phototherapy in deep tissues. Meanwhile, X-ray luminescence holds great promise in breaking the depth dependency of deep-seated lesion treatment and achieving synergistic radiotherapy with phototherapy.In this Account, we provide an overview of recent advances in developing advanced X-ray luminescence for applications in imaging, biosensing, theragnostics, and optogenetics neuromodulation. We first introduce solution-processed lead halide all-inorganic perovskite nanocrystal scintillators that are able to convert X-ray photons to multicolor X-ray luminescence. We have developed a perovskite nanoscintillator-based X-ray detector for high-resolution X-ray imaging of the internal structure of electronic circuits and biological samples. We further advanced the development of flexible X-ray luminescence imaging using solution-processable lanthanide-doped nanoscintillators featuring long-lived X-ray luminescence to image three-dimensional irregularly shaped objects. We also outline the general principles of high-contrast in vivo X-ray luminescence imaging which combines nanoscintillators with functional biomolecules such as aptamers, peptides, and antibodies. High-quality X-ray luminescence nanoprobes were engineered to achieve the high-sensitivity detection of various biomarkers, which enabled the avoidance of interference from the biological matrix autofluorescence and photon scattering. By marrying X-ray luminescence probes with stimuli-responsive materials, multifunctional theragnostic nanosystems were constructed for on-demand synergistic gas radiotherapy with excellent therapeutic effects. By taking advantage of the capability of X-rays to penetrate the skull, we also demonstrated the development of controllable, wireless optogenetic neuromodulation using X-ray luminescence probes while obviating damage from traditional optical fibers. Furthermore, we discussed in detail some challenges and future development of X-ray luminescence in terms of scintillator synthesis and surface modification, mechanism studies, and their other potential applications to provide useful guidance for further advancing the development of X-ray luminescence.

Lipid-Based Intelligent Vehicle Capabilitized with Physical and Physiological Activation

Intelligent drug delivery system based on “stimulus-response” mode emerging a promising perspective in next generation lipid-based nanoparticle. Here, we classify signal sources into physical and physiological stimulation according to their origin. The physical signals include temperature, ultrasound, and electromagnetic wave, while physiological signals involve pH, redox condition, and associated proteins. We first summarize external physical response from three main points about efficiency, particle state, and on-demand release. Afterwards, we describe how to design drug delivery using the physiological environment in vivo and present different current application methods. Lastly, we draw a vision of possible future development.

Catalytic radiosensitization: Insights from materials physicochemistry

Radiotherapy is indispensable in clinical cancer treatment, but because both tumor and normal tissues have similar sensitivity to X-rays, their clinical curative effect is intrinsically limited. Advanced nanomaterials and nanotechnologies have been developed for radiotherapy sensitization, typically employing high atomic number (high-Z) materials to enhance the energy deposition of X-rays in tumor tissues, but the efficiency is largely limited by the toxicity of heavy metals. A new and promising approach for radiosensitization is catalytic radiosensitization, which takes advantage of the catalytic activity of nanomaterials triggered by radiation. The efficiency of catalytic radiosensitization can be greatly enhanced by electron modulation and energy conversion of nanocatalysts upon X-ray irradiation, further enhancing the clinical curative effect. In this review, we highlight the challenges and opportunities in cancer radiosensitization, discuss novel approaches to catalytic radiosensitization, and finally describe the development of catalytic radiosensitization based on an in-depth understanding of radio-nano interactions and catalysis-biological interactions.

Nucleobase-Interaction-Directed Biomimetic Supramolecular Self-Assembly

ConspectusThe design and fabrication of synthetic self-assembled systems that can mimic some biological features require exquisitely sophisticated components that make use of supramolecular interactions to attain enhanced structural and functional complexity. In nature, nucleobase interactions play a key role in biological functions in living organisms, including transcription and translation processes. Inspired by nature, scientists are progressively exploring nucleobase synthons to create a diverse range of functional systems with a plethora of nanostructures by virtue of molecular-recognition-directed assembly and flexible programmability of the base-pairing interactions. To that end, nucleobase-functionalized molecules and macromolecules are attracting great attention because of their versatile structures with smart and adaptive material properties such as stimuli responsiveness, interaction with external agents, and ability to repair structural defects. In this regard, a range of nucleobase-interaction-mediated hierarchical self-assembled systems have been developed to obtain biomimetic materials with unique properties. For example, a new "grafting to" strategy utilizing complementary nucleobase interactions has been demonstrated to temporarily control the functional group display on micellar surfaces. In a different approach, complementary nucleobase interactions have been explored to enable morphological transitions in functionalized diblock copolymer assembly. It has been demonstrated that complementary nucleobase interactions can drive the morphological transformation to produce highly anisotropic nanoparticles by controlling the assembly processes at multiple length scales. Furthermore, nucleobase-functionalized bottle brush polymers have been employed to generate stimuli-responsive hierarchical assembly. Finally, such interactions have been exploited to induce biomimetic segregation in polymer self-assembly, which has been employed as a template to synthesize polymers with narrow polydispersity. It is evident from these examples that the optimal design of molecular building blocks and precise positioning of the nucleobase functionality are essential for fabrication of complex supramolecular assemblies. While a considerable amount of research remains to be explored, our studies have demonstrated the potential of nucleobase-interaction-mediated supramolecular assembly to be a promising field of research enabling the development of biomimetic materials.This Account summarizes recent examples that employ nucleobase interactions to generate functional biomaterials by judicious design of the building blocks. We begin by discussing the molecular recognition properties of different nucleobases, followed by different strategies to employ nucleobase interactions in polymeric systems in order to achieve self-assembled nanomaterials with versatile properties. Moreover, some of their prospective biological/material applications such as enhanced drug encapsulation, superior adhesion, and fast self-healing properties facilitated by complementary nucleobase interactions are emphasized. Finally, we identify issues and challenges that are faced by this class of materials and propose future directions for the exploration of functional materials with the aim of promoting the development of nucleobase-functionalized systems to design the next generation of biomaterials.

Triggered azobenzene-based prodrugs and drug delivery systems

Azobenzene-based molecules show unique trans-cis isomerization upon ultraviolet light irradiation, which induce the change of polarity, crystallinity, stability, and binding affinity with pharmacological target. Moreover, azobenzene is the substrate of azoreductase that is often overexpressed in many pathological sites, e.g. hypoxic solid tumor. Therefore, azobenzene can be a multifunctional molecule in material science, pharmaceutical science and biomedicine because of its sensitivity to light, hypoxia and certain enzymes, hence showing potential application in site-specific smart therapy. Herein we focus on the employment of azobenzene and its derivatives for engineering triggered prodrug and drug delivery systems, and provide an overview of photoswitchable azo-based prodrugs, the associated problems regarding ultraviolet light and reversible isomerization, as well as the potential solutions. We also present the advance of azo-bearing delivery vehicles wherein azobenzene act as the linker, capping agent, and building block, and discuss the corresponding mechanisms for controlled cargo release, endocytosis enhancement and sensitization of free radical cancer therapy.

Highly porous nitrogen-doped carbon superstructures derived from the intramolecular cyclization-induced crystallization-driven self-assembly of poly(amic acid)

Hierarchically porous carbon nanomaterials have shown significant potential in electrochemical energy storage due to the promoted charge and mass transfer. Herein, a facile template-free method is proposed to prepare nitrogen-doped carbon superstructures (N-CSs) with multi-level pores by pyrolysis of polymeric precursors derived from the intramolecular cyclization-induced crystallization-driven self-assembly (ICI-CDSA) of poly(amic acid) (PAA). The excellent thermal stability of PAA enables the N-CSs to inherit the hierarchical structure of the precursors during pyrolysis, which facilitates the formation of meso- and macropores while the decomposition of the precursors promotes the creation of micropores. Electrochemical tests demonstrate the ultrahigh surface-area-normalized capacitance (76.5 μF cm-2) of the N-CSs facilitated by the hierarchically porous structure, promoting the charge and mass transfer, as well as the high utilization of pyridinic and pyrrolic nitrogen (12.9%) to provide significant pseudocapacitance contribution up to 40.6%. Considering the diversity of monomers of PAA, this ICI-CDSA strategy could be extended to prepare carbon nanomaterials with various morphologies, pore structures and chemical compositions.

Stimuli-Responsive Nanoparticles for Controlled Drug Delivery in Synergistic Cancer Immunotherapy

Cancer immunotherapy has achieved promising clinical progress over the recent years for its potential to treat metastatic tumors and inhibit their recurrences effectively. However, low patient response rates and dose-limiting toxicity remain as major dilemmas for immunotherapy. Stimuli-responsive nanoparticles (srNPs) combined with immunotherapy offer the possibility to amplify anti-tumor immune responses, where the weak acidity, high concentration of glutathione, overexpressions of enzymes, and reactive oxygen species, and external stimuli in tumors act as triggers for controlled drug release. This review highlights the design of srNPs based on tumor microenvironment and/or external stimuli to combine with different anti-tumor drugs, especially the immunoregulatory agents, which eventually realize synergistic immunotherapy of malignant primary or metastatic tumors and acquire a long-term immune memory to prevent tumor recurrence. The authors hope that this review can provide theoretical guidance for the construction and clinical transformation of smart srNPs for controlled drug delivery in synergistic cancer immunotherapy.

Molecular recognition-driven supramolecular nanoassembly of a hydrophobic uracil prodrug and hydrophilic cytarabine for precise combination treatment of solid and non-solid tumors

Combination chemotherapy has shown distinct therapeutic advantages over monotherapy in clinical cancer treatment, especially for two chemotherapeutic drugs with different mechanisms of action. However, how to achieve efficient co-delivery of two or more drugs with different physicochemical and pharmacokinetic properties for synergistic therapy is still a huge challenge. In particular, it is even more difficult to efficiently co-deliver a hydrophilic drug and a hydrophobic drug into one nanosystem. Herein, inspired by the natural Watson-Crick base pair molecular recognition in nucleic acids, a reduction-sensitive uracil prodrug of doxorubicin (U-SS-DOX) is synthesized and performs supramolecular co-assembly with cytarabine (Ara-C). Interestingly, the hydrophilic Ara-C molecules could readily co-assemble with U-SS-DOX, and multiple hydrogen bonds are found in the nanoassembly with an ultra-high drug loading rate. Moreover, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbocyanine iodide (DiR) is used as a fluorescent probe to investigate the pharmacokinetics of U : C NPs. It turns out that the DiR-labeled U : C NPs significantly prolong the systemic circulation and promote the tumor-specific accumulation of DiR when compared with DiR solution. Furthermore, the supramolecular nanoassembly demonstrates potent satisfactory therapeutic effects in treating both solid and non-solid tumors in vivo. This study provides a novel molecular co-assembly nanoplatform for efficient co-delivery of hydrophilic and hydrophobic drugs.

NIR-II Fluorescent Activatable Drug Delivery Nanoplatform for Cancer-Targeted Combined Photodynamic and Chemotherapy

Nanotheranostics with integrated imaging functions can help monitor nanoparticle accumulation in tumors, thus achieving synergism and higher therapeutic accuracy in cancer therapy. However, it remains challenging to monitor the release of therapeutic drugs in real time from a nanoparticulate drug delivery system (nano-DDS) in the body. Herein, we developed a nano-DDS for fluorescence imaging in the second near-infrared window (NIR-II) region, which can be used for monitoring the responsive release of drugs and cancer-targeted combined photodynamic and chemotherapy. There is a linear correlation between the cumulative release of the drug and the NIR-II fluorescence intensity. Moreover, hyaluronidase/glutathione dual-response RGD-SS-DOX/Ce6@HA-IR-1061 (RSSDCHI) exhibited a higher tumor-to-normal-tissue ratio in NIR-II fluorescence imaging and enhanced antitumor efficacy in vivo. This makes it possible to visualize drug release at the cellular level by the nanocomposites and to predict the treatment effect according to the NIR-II fluorescence intensity in the tumor site, serving as a promising nanoplatform for precision nanomedicine.

Polymeric nanostructures based on azobenzene and their biomedical applications: synthesis, self-assembly and stimuli-responsiveness

Amphiphilic polymers can self-assemble to form nanoparticles with different structures under suitable conditions. Polymer nanoparticles functionalized with aromatic azo groups are endowed with photo-responsive properties. In recent years, a variety of photoresponsive polymers and nanoparticles have been developed based on azobenzene, using different molecular design strategies and synthetic routes. This article reviews the progress of this rapidly developing research field, focusing on the structure, synthesis, assembly and response of photo-responsive polymer assemblies. According to the molecular structure, photo-responsive polymers can be divided into linear polymers containing azobenzene in a side chain, linear polymers containing azobenzene in the main chain, linear polymers containing azobenzene in an end group, branched polymers containing azobenzene and supramolecular polymers containing azobenzene. These systems have broad biomedical application prospects in the field of drug delivery and imaging applications.

Photoreactive Cytosine-Functionalized Self-Assembled Micelles with Enhanced Cellular Uptake Capability for Efficient Cancer Chemotherapy

Design, fabrication, and control of photoreactive supramolecular macromers─which are composed of a thermoresponsive polymer backbone and photoreactive nucleobase end-groups─to achieve the desired physical-chemical performance and provide the high efficiency required for chemotherapy drug delivery purposes still present challenges. Herein, a difunctional cytosine-terminated supramolecular macromer was successfully obtained at high yield. UV-irradiation induces the formation of cytosine photodimers within the structure. The irradiated macromer can self-assemble into nanosized spherical micelles in water that possess a number of interesting and unique features, such as desired micellar size and morphology, tunable drug-loading capacity, and excellent structural stability in serum-containing medium, in addition to well-controlled drug-release behaviors in response to changes in environmental temperature and pH; these extremely desirable, rare features are required to augment the functions of polymeric nanocarriers for drug delivery. Importantly, a series of in vitro studies demonstrated that photodimerized cytosine moieties within the drug-loaded micelles substantially enhance their internalization and accumulation inside cells via endocytosis and subsequently lead to induction of massive apoptotic cell death compared with the corresponding nonirradiated micelles. Thus, this newly developed "photomodified" nanocarrier system could provide a potentially fruitful route to enhance the drug delivery performance of nanocages without the need to introduce targeting moieties or additional components.

NIR-activated self-sensitized polymeric micelles for enhanced cancer chemo-photothermal therapy

NIR-activated therapies based on light-responsive drug delivery systems are emerging as a remote-controlled method for cancer precise therapy. In this work, fluorescent dye indocyanine green (ICG)-conjugated and bioactive compound gambogic acid (GA)-loaded polymeric micelles (GA@PEG-TK-ICG PMs) were smoothly fabricated via the self-assembly of the reactive oxygen species (ROS)-responsive thioketal (TK)-linked amphiphilic polymer poly(ethyleneglycol)-thioketal-(indocyanine green) (PEG-TK-ICG). The resultant micelles demonstrated increased resistance to photobleaching, enhanced photothermal conversion efficiency, NIR-controlled drug release behavior, preferable biocompatibility, and excellent tumor accumulation performance. Moreover, upon an 808 nm laser irradiation, the micellar photoactive chromophore ICG converted the absorbed optical energy to both hyperthermia for photothermal therapy (PTT) and ROS as the feedback trigger to the micelles for the tumor-specific release of GA, which could serve as not only a chemotherapeutic drug to directly kill tumor cells but also a heat shock protein 90 (HSP90) inhibitor to realize the photothermal sensitization. As a result, an extremely high tumor inhibition rate (97.9%) of mouse 4 T1 breast cancer models was achieved with negligible side effects after the chemo-photothermal synergistic therapy. This NIR-activated nanosystem with photothermal self-sensitization function may provide a feasible option for the effective treatment of aggressive breast cancers.

Reactive oxygen species-activatable self-amplifying Watson-Crick base pairing-inspired supramolecular nanoprodrug for tumor-specific therapy

Intratumoral upregulated reactive oxygen species (ROS) has been extensively exploited as exclusive stimulus to activate drug release for tumor-specific therapy. However, insufficient endogenous ROS and tumor heterogeneity severely restrict clinical translation of current ROS-responsive drug delivery systems. Herein, a tailored ROS-activatable self-amplifying supramolecular nanoprodrug was developed for reinforced ROS-responsiveness and highly selective antitumor therapy. A novel ROS-cleavable CA-based thioacetal linker CASOH was synthesized with ROS generator cinnamaldehyde (CA) incorporated into its molecular structure, to skillfully realize self-amplifying positive feedback loop of "ROS-activated CA release with CA-induced ROS regeneration". CASOH was modified with a cytosine analogue gemcitabine (GEM) to obtain ROS-activatable self-immolative prodrug CAG, which could be selectively activated in tumor cells and further achieve self-boosting "snowballing" activation via ROS compensation, while keep inactive in normal cells. Through Watson-Crick nucleobase pairing (G≡C)-like hydrogen bonds, CAG efficiently crosslinked with a matched guanine-rich acyclovir-modified hyaluronic acid conjugate HA-ACV, to self-assemble into pH/ROS dual-responsive supramolecular nanoprodrug HCAG. With high stability, beneficial tumor targeting capacity and pH/ROS-responsiveness, HCAG nanoformulation exhibited remarkable in vivo antitumor efficacy with minimal systemic toxicity. Based on unique tumor-specific self-amplifying prodrug activation and Watson-Crick base pairing-inspired supramolecular self-assembly, this study provides an inspirational strategy of exploiting novel ROS-responsive nanoplatform with reinforced responsiveness and specificity for future clinical translation.

Advances in Application of Azobenzene as a Trigger in Biomedicine: Molecular Design and Spontaneous Assembly

Azobenzene is a well-known derivative of stimulus-responsive molecular switches and has shown superior performance as a functional material in biomedical applications. The results of multiple studies have led to the development of light/hypoxia-responsive azobenzene for biomedical use. In recent years, long-wavelength-responsive azobenzene has been developed. Matching the longer wavelength absorption and hypoxia-response characteristics of the azobenzene switch unit to the bio-optical window results in a large and effective stimulus response. In addition, azobenzene has been used as a hypoxia-sensitive connector via biological cleavage under appropriate stimulus conditions. This has resulted in on/off state switching of properties such as pharmacology and fluorescence activity. Herein, recent advances in the design and fabrication of azobenzene as a trigger in biomedicine are summarized.

Utilizing Stimuli Responsive Linkages to Engineer and Enhance Polymer Nanoparticle-Based Drug Delivery Platforms

The devastating nature of cancer continues to be one of the leading causes of death in the world. Chemotherapy is among the most common forms of cancer treatment but comes with a host of adverse effects caused by the therapeutic agents damaging healthy tissue and organs. To limit these side effects, scientists have been designing stimuli responsive drug delivery vessels for targeted release. This Review focuses on the incorporation of stimuli responsive linkages in targeted drug delivery systems to enhance therapeutic efficiency. These platforms are primarily employed to control the distribution of anticancer agents in the body to reduce the adverse side effects caused by their toxicities. We will outline how drug delivery vessels are constructed so that exposure to select environmental and external stimuli releases the enclosed drug only at the target site. Stimuli responsive components are integrated within drug delivery vessels in the form of cross-linkers, polymers, and surface modifications. The changes, these moieties undergo upon stimuli exposure, cascade into larger scale alterations to the platforms, resulting in complete disassembly, reversible morphological variations, and enhanced cellular uptake. The ability for these modes of delivery to be initiated exclusively under stimuli exposure allows for release of toxic therapeutic agents to be confined only to the affected area.

In Vivo X-ray Triggered Catalysis of H2 Generation for Cancer Synergistic Gas Radiotherapy

To date, hydrogen (H₂ ) therapy has received widespread attention. However, X-ray triggered sustainable H₂ -producing materials with controlled release for cancer treatment have not been reported. Herein, an X-ray triggered sustainable in situ H₂ producing platform, Au NR-TiO₂ @ZnS:Cu,Co-A(Au-TiO₂ @ZnS), composed of Au-amorphous TiO₂ nano-dumbbell-shaped heterostructure coated with long afterglow particles, was developed for cancer synergistic H₂ -radiotherapy. The mechanism of H₂ production was verified by theoretical calculations and in vitro experiments. Changes in the apoptosis pathway caused by the synergistic effect of H₂ and radiotherapy were reported. Guided by its excellent photoacoustic imaging capabilities, mice with orthotopic liver cancer achieved excellent therapeutic effects and low inflammatory side effects, suggesting that Au-TiO₂ @ZnS has promising application potential for cancer treatment and prognosis.

Photodynamic-Chemodynamic Cascade Reactions for Efficient Drug Delivery and Enhanced Combination Therapy

Nanomedicines with photodynamic therapy and reactive oxygen species (ROS)-triggered drug release capabilities are promising for cancer therapy. However, most of the nanomedicines based on ROS-responsive nanocarriers still suffer from serious ROS consumption during the triggered drug release process. Herein, a photodynamic-chemodynamic cascade strategy for the design of drug delivery nanosystem is proposed. A doxorubicin hydrochloride-loaded ROS-responsive polymersome (DOX-RPS) is prepared via the self-assembly of amphiphilic poly(ethylene glycol)-poly(linoleic acid) and poly(ethylene glycol)-(2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-α)-iron chelate (PEG-HPPH-Fe). The RPS can effectively deliver a drug to tumor site through passive targeting effect. Upon laser irradiation, the photosensitizer HPPH can efficiently generate ROS, which further causes in situ oxidation of linoleic acid chain and subsequent RPS structural destruction, permitting triggered drug release. Intriguingly, catalyzed by HPPH-Fe, ROS will be regenerated from linoleic acid peroxide through a chemodynamic process. Therefore, ROS-triggered drug release can be achieved without ROS over-consumption. The in vitro and in vivo results confirmed ROS generation, triggered drug release behavior, and potent antitumor effect of the DOX-RPS. This photodynamic-chemodynamic cascade strategy provides a promising approach for enhanced combination therapy.

Janus Nanoparticles: From Fabrication to (Bio)Applications

Janus nanoparticles (JNPs) refer to the integration of two or more chemically discrepant composites into one structure system. Studies into JNPs have been of significant interest due to their interesting characteristics stemming from their asymmetric structures, which can integrate different functional properties and perform more synergetic functions simultaneously. Herein, we present recent progress of Janus particles, comprehensively detailing fabrication strategies and applications. First, the classification of JNPs is divided into three blocks, consisting of polymeric composites, inorganic composites, and hybrid polymeric/inorganic JNPs composites. Then, the fabrication strategies are alternately summarized, examining self-assembly strategy, phase separation strategy, seed-mediated polymerization, microfluidic preparation strategy, nucleation growth methods, and masking methods. Finally, various intriguing applications of JNPs are presented, including solid surfactants agents, micro/nanomotors, and biomedical applications such as biosensing, controlled drug delivery, bioimaging, cancer therapy, and combined theranostics. Furthermore, challenges and future works in this field are provided.

Near-Infrared Photo-controlled Permeability of a Biomimetic Polymersome with Sustained Drug Release and Efficient Tumor Therapy

Synthetic polymersomes have structure similarity to bio-vesicles and could disassemble in response to stimuli for "on-demand" release of encapsulated cargos. Though widely applied as a drug delivery carrier, the burst release mode with structure complete destruction is usually taken for most responsive polymersomes, which would shorten the effective drug reaction time and impair the therapeutic effect. Inspired by the cell organelles' communication mode via regulating membrane permeability for transportation control, we highlight here a biomimetic polymersome with sustained drug release over a specific period of time via near-infrared (NIR) pre-activation. The polymersome is prepared by the self-assembling amphiphilic diblock copolymer P(OEGMA-co-EoS)-b-PNBOC and encapsulates the hypoxia-activated prodrug AQ4N and upconversion nanoparticle (PEG-UCNP) in its hydrophilic centric cavity. Thirty minutes of NIR pre-activation triggers cross-linking of NBOC and converts the permeability of the polymersome with sustained AQ4N release until 24 h after the NIR pre-activation. The photosensitizer EoS is activated and aggravates environmental hypoxic conditions during a sustained drug release period to boost the AQ4N therapeutic effect. The combination of sustained drug release with concurrent hypoxia intensification results in a highly efficient tumor therapeutic effect both intracellularly and in vivo. This biomimetic polymersome will provide an effective and universal tumor therapeutic approach.

Deep Drug Penetration of Nanodrug Aggregates at Tumor Tissues by Fast Extracellular Drug Release

Herein, a new nanodrug of azobenzene-functionalized interfacial cross-linked reverse micelles (AICRM) with 5-fluorouracil loading (5-FU@AICRM) is reported. Upon irradiation with 530 nm light in water, the surface azobenzenes of the nanoparticles change from polar cis-conformation to nonpolar trans-conformation, resulting in the aggregation of 5-FU@AICRM within minutes. Simultaneously, the conformation change unlocks hydrophilic 5-FU with a strong water immigration propensity, allowing them to spray out from the AICRM quickly. This fast release ensures a thorough release of the drug, before the aggregates are internalized by adjacent cells, making it possible to achieve deep tissue penetration. A study of in vivo anticancer activity in A549 tumor-bearing nude mice shows that the tumor inhibition rate (TIR) of 5-FU@AICRM is up to ≈86.2%, 31.6% higher than that of group without green light irradiation and 20.7% higher than that of carmofur (CF, a hydrophobic analog of 5-FU)-loaded AICRM (CF@AICRM), in which CF is released slowly under light irradiation because of its hydrophobicity. Fast drug release upon nanodrug aggregation provides a good solution for balancing the contradiction of "aggregation and penetration" in tumor treatment with nanodrugs.

Cascade Drug-Release Strategy for Enhanced Anticancer Therapy

Chemotherapy serves as one of the most effective approaches in numerous tumor treatments but also suffers from the limitations of low bioavailability and adverse side effects due to premature drug leakage. Therefore, it is crucial to realize accurate on-demand drug release for promoting the application of chemotherapeutic agents. To achieve this, stimuli-responsive nanomedicines that can be activated by delicately designed cascade reactions have been developed in recent years. In general, the nanomedicines are triggered by an internal or external stimulus, generating an intermediate stimulus at tumor site, which can intensify the differences between tumor and normal tissues; the drug release process is then further activated by the intermediate stimulus. In this review, the latest progress made in cascade reactions-driven drug-release modes, based on the intermediate stimuli of heat, hypoxia, and reactive oxygen species, is systematically summarized. The perspectives and challenges of cascade strategy for drug delivery are also discussed.

Prodrug-based self-assembled nanoparticles formed by 3′,5′-dioleoyl floxuridine for cancer chemotherapy

Amphiphilic prodrug molecules (3′,5′-dioleoyl floxuridine, DOF) were constructed to form prodrug nanoparticles (DOF NPs) through a self-assembly process in water. The DOF NPs were easily prepared, relatively stable, and displayed improved anti-tumor activity.

An ultra-stable bio-inspired bacteriochlorin analogue for hypoxia-tolerant photodynamic therapy

Photodynamic therapy (PDT) greatly suffers from the weak NIR-absorption, oxygen dependence and poor stability of photosensitizers (PSs). Herein, inspired by natural bacteriochlorin, we develop a bacteriochlorin analogue, tetrafluorophenyl bacteriochlorin (FBC), by one-step reduction of tetrafluorophenyl porphyrin (TFPP). FBC can realize deep tissue penetration, benefitting from the strong NIR absorption. The reactive oxygen species (ROS) generation capacity of FBC can retain around 60% with a 1.0 cm-thick pork skin as the barrier. Besides, FBC could not only produce oxygen-dependent 1O2, but also generate less oxygen-dependent O2 -˙ and ˙OH to achieve excellent PDT even in hypoxic tumors. Moreover, FBC exhibits an ultra-high stability and it is almost unchanged even under visible light at room temperature for 15 months. Interestingly, the high reactivity of the fluorophenyl group makes it easy for FBC to produce FBC derivatives. A biocompatible FBC nanogel could be directly formed by blending FBC with SH-PEG-SH. The FBC nanogel displays excellent photodynamic efficacy in vitro and in vivo. Thus, FBC would be a promising PS for the clinical PDT of deep tumors.

Current trends in pyrrole and porphyrin-derived nanoscale materials for biomedical applications

This article is written to provide an up-to-date review of pyrrole-based biomedical materials. Porphyrins and other tetrapyrrolic molecules possess unique magnetic, optical and other photophysical properties that make them useful for bioimaging and therapy. This review touches briefly on some of the synthetic strategies to obtain porphyrin- and tetrapyrrole-based nanoparticles, as well as the variety of applications in which crosslinked, self-assembled, porphyrin-coated and other nanoparticles are utilized. We explore examples of these nanoparticles' applications in photothermal therapy, drug delivery, photodynamic therapy, stimuli response, fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, computed tomography and positron emission tomography. We anticipate that this review will provide a comprehensive summary of pyrrole-derived nanoparticles and provide a guideline for their further development.

TME-Responsive Polyprodrug Micelles for Multistage Delivery of Doxorubicin with Improved Cancer Therapeutic Efficacy in Rodents

It is of great significance to develop multifunctional biomaterials to effectively deliver anticancer drug to tumor cells for cancer therapy. Here, inspired by the specific tumor microenvironment (TME) cues, a unique multistage pH/redox-responsive polyprodrug composed of amphiphilic pH-sensitive diblock copolymer poly(ethylene glycol) methyl ether-b-poly(β-amino esters) conjugated with doxorubicin (DOX) via redox-sensitive disulfide bonds (mPEG-b-PAE-ss-DOX) is designed and developed. This polyprodrug can self-assemble into micelles (DOX-ss@PMs) at low concentration with high serum stability, indicating that DOX-ss@PMs have prolonged circulation time. The dual pH/redox-responsiveness of the multistage platform is thoroughly evaluated. In vitro results demonstrate that DOX-ss@PMs can highly accumulate at tumor site, followed by responding to the acidity for disassembly and effectively penetrating into the tumor cells. DOX is released from the platform due to the cleavage of disulfide bonds induced by high glutathione (GSH) concentration, thereby inducing the apoptosis of tumor cells. In vivo studies further reveal that multistage DOX-ss@PMs can more efficiently inhibit the growth of tumors and improve the survival of tumor-bearing mice in comparison to the free drug and control. These results imply that multistage delivery system might be a potential and effective strategy for drug delivery and DOX-ss@PMs could be a promising nanomedicine for cancer chemotherapy.

Tumor Microenvironment-Responsive, Multistaged Liposome Induces Apoptosis and Ferroptosis by Amplifying Oxidative Stress for Enhanced Cancer Therapy

Tumor cells usually display metabolic, genetic, and microenvironment-related alterations, which are beneficial to tumor proliferation, tumor development, and resistance occurrence. Many transporters and enzymes, including ATB^0,+, xCT, and matrix metalloproteinases (MMPs), are involved in the altered cell metabolism and tumor microenvironment and often abnormally upregulated in malignant tumors. Meanwhile, these dysregulated transporters and enzymes provide targets not only for a pharmacological blockage to suppress tumor progress but also for tumor-specific delivery. Although transporters and MMPs have been widely reported for antitumor drug delivery, the feasibility of utilizing two strategies has never been elucidated yet. Herein, we developed an MMP2-activated and ATB^0,+-targeted liposome with doxorubicin and sorafenib (DS@MA-LS) loaded for optimal tumor drug delivery for cancer therapy. DS@MA-LS was designed to prolong blood circulation and deshield the PEG shell from MMP2 cleavage to expose lysine and target overexpressed ATB^0,+ for enhanced tumor distribution and cancer cellular uptake. Besides the anticancer effects of loaded drugs, the endocytosed liposomes could further increase ROS production and suppress the antioxidant system to amplify oxidative stress. As expected, DS@MA-LS displayed enhanced targeted drug delivery to tumor sites with the MMP2-controlled ligand exposure and ATB^0,+-mediated uptake. More importantly, DS@MA-LS successfully inhibited the tumor growth and cancer cell proliferation both in vitro and in vivo by enhancing apoptosis and ferroptosis, which thanks to the increased ROS generation and impaired GSH synthesis synergistically amplified oxidative stress. Our results suggested that the tumor microenvironment-responsive, multistaged nanoplatform, DS@MA-LS, has excellent potential for optimal drug delivery and enhanced cancer treatment.

Engineering blood exosomes for tumor-targeting efficient gene/chemo combination therapy

Rationale: Developing an effective nanoplatform to realize 'multi-in-one' is essential to broaden the therapeutic potential of combination therapy. Exosomes are ideal candidates since their intrinsic abilities of integrating multiple contents and functions. However, only limited efforts have been devoted to engineering exosomes to integrate the needed properties, also considering the safety and yield, for tumor-targeted and efficient gene/chemo combination therapy.

Methods: Herein, by manipulating the exosome membrane, blood exosomes with high abundance and safety are engineered as a versatile combinatorial delivery system, where the doxorubicin (Dox) and cholesterol-modified miRNA21 inhibitor (miR-21i) are co-embedded into the lipid bilayer of exosomes, and the magnetic molecules and endosomolytic peptides L17E are bind to the exosome membrane through ligand-receptor coupling and electrostatic interactions, respectively.

Results: It is proved that such engineering strategy not only preserves their intrinsic features, but also readily integrates multiple properties of tumor targeting, efficient transfection and gene/chemo combination therapy into blood exosomes. The lipid bilayer structure of exosomes allows them to co-load Dox and miR-21i with high-payloads. Moreover, profiting from the integration of magnetic molecules and L17E peptides, the engineered exosomes exhibit an enhanced tumor accumulation and an improved endosome escape ability, thereby specifically and efficiently delivering encapsulated cargos to tumor cells. As a result, a remarkable inhibition of tumor growth is observed in the tumor-bearing mice, and without noticeable side effects.

Conclusions: This study demonstrates the potential of engineered blood exosomes as feasible co-delivery nanosystem for tumor-targeted and efficient combination therapy. Further development by replacing the drugs combined regimens can potentially make this engineered exosome become a general platform for the design of safe and effective combination therapy modality.

Electrochemiluminescence Biosensor for Hyaluronidase Based on the Ru(bpy)32+ Doped SiO2 Nanoparticles Embedded in the Hydrogel Fabricated by Hyaluronic Acid and Polyethylenimine

Hyaluronidase (HAase), a specific enzyme of hyaluronic acid (HA), has been reported as a potential tumor biomarker in recent years. Hence, developing some simple, rapid, and sensitive methods for HAase assay is necessary. In this work, a simple and sensitive biosensor constructed by a reliable controlled release system and a mature electrochemiluminescence (ECL) analytical technique has been devised for the quantification of HAase with high efficiency and selectivity. Tris (2,2'-bipyridyl) ruthenium(II) chloride hexahydrate doped SiO₂ nanoparticles (Ru@SiO₂ NPs), as ECL signal probes, were trapped in the hydrogel fabricated by HA and polyethylenimine evenly and steadily. When HAase existed, the hydrogel was decomposed by HAase, and the Ru@SiO₂ NPs escaped from the hydrogel into the supernate. The ECL signal produced from the supernate can be detected and used to characterize HAase concentration. The result showed a good linear relationship between ECL intensity, and HAase concentration ranged from 2 to 60 U/mL and the limit of detection was 2 U/mL. The developed controlled release ECL biosensor has been used for HAase quantification in urine samples with satisfactory results.

Organelle-localized radiosensitizers

This feature article highlights the recent advances of organelle-localized radiosensitizers and discusses the current challenges and future directions.