Supramolecular Antagonists Promote Mitochondrial Dysfunction

Noncanonical Amino Acids Dictate Peptide Assembly in Living Cells

ConspectusEmulating the structural features or functions of natural systems has been demonstrated as a state-of-the-art strategy to create artificial functional materials. Inspired by the assembly and bioactivity of proteins, the self-assembly of peptides into nanostructures represents a promising approach for creating biomaterials. Conventional assembled peptide biomaterials are typically formulated in solution and delivered to pathological sites for implementing theranostic objectives. However, this translocation entails a switch from formulation conditions to the physiological environment and raises concerns about material performance. In addition, the precise and efficient accumulation of administered biomaterials at target sites remains a significant challenge, leading to potential biosafety issues associated with off-target effects. These limitations significantly hinder the progress of advanced biomaterials. To address these concerns, the past few years have witnessed the development of in situ assembly of peptides in living systems as a new endeavor for optimizing biomaterial performance benefiting from the advances of stimuli-responsive reactions regulating noncovalent interactions. In situ assembly of peptides refers to the processes of regulating assembly via stimuli-responsive reactions at target sites. Due to the advantages of precisely forming well-defined nanostructures at pathological lesions, in situ-formed assemblies with integrated bioactivity are interesting for the development of next-generation biomedical agents.Despite the great potential of in situ assembly of peptides for developing biomedical agents, this research area still suffers from a limited toolkit for operating peptide assembly under complicated physiological conditions. Considering the advantages of amino acids in being incorporated into peptide backbones and modified with stimuli-responsive units, development of an amino acid toolkit is promising to address this concern. Therefore, our laboratory has been intensively engaged in designing and discovering stimuli-responsive noncanonical amino acids (ncAAs) to expand the toolkit for manipulating peptide assembly under various biological conditions. Thus far, we have synthesized peptides containing ncAAs 4-aminoproline, 2-nitroimidazole alanine, Se-methionine, sulfated tyrosine, and glycosylated serine, which allow us to develop acid-responsive, redox-responsive, and enzyme-responsive assembly systems. Based on these stimuli-responsive ncAAs, we have established complex self-sorting assembly, self-amplified assembly, and dissipative assembly systems in living cells to optimize the bioactivity of peptides. The resulting in situ assembly systems exhibit morphological adaptability to the biological microenvironment, which contributes to overcoming delivery barriers and improvement of targeting accumulation. Therefore, by utilizing the developed toolkit, we have further created supramolecular PROTACs, supramolecular antagonists, and supramolecular probes for cancer treatment and diagnosis to highlight the implications of ncAAs for biomedical usage. In this Account, we summarize our journey of in situ self-assembly of peptides in living cells utilizing stimuli-responsive ncAAs, with an emphasis on the mechanism for regulating peptide assembly and optimizing the bioactivity of peptides. Eventually, we also provide our forward conceiving prospects on the challenges for the further development of in situ assembly of peptides in living systems and the clinical translation of in situ-formulated biomaterials.

Functional Nucleic Acid Nanostructures for Mitochondrial Targeting: The Basis of Customized Treatment Strategies

Mitochondria, as vital organelles, play a central role in subcellular research and biomedical innovation. Although functional nucleic acid (FNA) nanostructures have witnessed remarkable progress across numerous biological applications, strategies specifically tailored to target mitochondria for molecular imaging and therapeutic interventions remain scarce. This review delves into the latest advancements in leveraging FNA nanostructures for mitochondria-specific imaging and cancer therapy. Initially, we explore the creation of FNA-based biosensors localized to mitochondria, enabling the real-time detection and visualization of critical molecules essential for mitochondrial function. Subsequently, we examine developments in FNA nanostructures aimed at mitochondrial-targeted cancer treatments, including modular FNA nanodevices for the precise delivery of therapeutic agents and programmable FNA nanostructures for disrupting mitochondrial processes. Emphasis is placed on elucidating the chemical principles underlying the design of mitochondrial-specific FNA nanotechnology for diverse biomedical uses. Lastly, we address the unresolved challenges and outline prospective directions, with the goal of advancing the field and encouraging the creation of sophisticated FNA tools for both academic inquiry and clinical applications centered on mitochondria.

Synthetic Nanoassemblies for Regulating Organelles: From Molecular Design to Precision Therapeutics

Each organelle referring to a complex multiorder architecture executes respective biological processes via its distinct spatial organization and internal microenvironment. As the assembly of biomolecules is the structural basis of living cells, creating synthetic nanoassemblies with specific physicochemical and morphological properties in living cells to interfere or couple with the natural organelle architectures has attracted great attention in precision therapeutics of cancers. In this review, we give an overview of the latest advances in the synthetic nanoassemblies for precise organelle regulation, including the formation mechanisms, triggering strategies, and biomedical applications in precision therapeutics. We summarize the emerging material systems, including polymers, peptides, and deoxyribonucleic acids (DNAs), and their respective intermolecular interactions for intercellular synthetic nanoassemblies, and highlight their design principles in constructing precursors that assemble into synthetic nanoassemblies targeting specific organelles in the complex cellular environment. We further showcase the developed intracellular synthetic nanoassemblies targeting specific organelles including mitochondria, the endoplasmic reticulum, lysosome, Golgi apparatus, and nucleus and describe their underlying mechanisms for organelle regulation and precision therapeutics for cancer. Last, the essential challenges in this field and prospects for future precision therapeutics of synthetic nanoassemblies are discussed. This review should facilitate the rational design of organelle-targeting synthetic nanoassemblies and the comprehensive recognition of organelles by materials and contribute to the deep understanding and application of the synthetic nanoassemblies for precision therapeutics.

Tyrosinase-Woven Melanin Nets for Melanoma Therapy through Targeted Mitochondrial Tethering and Enhanced Photothermal Treatment

Manipulating intracellular biological processes and organelles has emerged as a pivotal strategy to influence cellular physiological functions. Mitochondria, recognized as the powerhouse of cells, play a crucial role in tumorigenesis and progression. Inspired by the Nature's tyrosinase-catalyzed melanin formation within melanoma cells, here an approach is developed using a polysaccharide dually-functionalized with tyrosine and triphenylphosphine (TPP) for targeted mitochondria cross-linking in melanoma cells. This technique intricately weaves melanin nets within the cells, serving as a tether for the mitochondria and effectively decelerating tumor metabolism through nanoparticle-net transformation. Tyrosinase acts as the "needle", while the functionalized polysaccharide serves as the "string" successfully constructing nets within the cell. Furthermore, the tyrosinase-catalyzed cross-linking of tyrosine not only facilitates the production of artificial melanin but also enhances the photothermal conversion efficiency of melanoma cells, leading to decrease of the tumor growth. This study unveils a non-drug method for regulating organelle physiological activity and introduces photothermal treatment. This work not only sheds light on the manipulation of cellular functions but also holds promise for advancing cancer therapeutic strategies.

Chemical Reaction Steers Spatiotemporal Self-Assembly of Supramolecular Hydrogels

Supramolecular structures are widespread in living system, which are usually spatiotemporally regulated by sophisticated metabolic processes to enable vital biological functions. Inspired by living system, tremendous efforts have been made to realize spatiotemporal control over the self-assembly of supramolecular materials in synthetic scenario by coupling chemical reaction with molecular self-assembly process. In this review, we focused on the works related to supramolecular hydrogels that are regulated in space and time using chemical reaction. Firstly, we summarized how spatially controlled self-assembly of supramolecular hydrogels can be achieved via chemical reaction-instructed self-assembly, and the application of such a self-assembly methodology in biotherapy was discussed as well. Second, we reviewed dynamic supramolecular hydrogels dictated by chemical reaction networks that can evolve their structures and properties against time. Third, we discussed the recent progresses in the control of the self-assembly of supramolecular hydrogels in both space and time though a reaction-diffusion-coupled self-assembly approach. Finally, we provided a perspective on the further development of spatiotemporally controlled supramolecular hydrogels using chemical reaction in the future.

Self-Assembly in Living Cells: Bottom-Up Syntheses in Natural Factory

In situ self-assembly in living systems is referred to as the processes that regulate assembly by stimuli-responsive reactions at target sites under physiological conditions. Due to the advantages of precisely forming well-defined nanostructures at pathological lesions, in situ-formed assemblies with tailored bioactivity are promising for the development of next-generation biomedical agents. In this Perspective, we summarize the progress of in situ self-assembly of peptides in living cells with an emphasis on the state-of-the-art strategies regulating assembly processes, establishing complexity within assembly systems, and exploiting their applications in biomedicines. We also provide our forward conceiving perspectives on the challenges in the development of in situ assembly in living cells to demonstrate its great potential in creating biomaterials for healthcare in the future.

DNA Nanotechnology Targeting Mitochondria: From Subcellular Molecular Imaging to Tailor-Made Therapeutics

Mitochondria, one of the most important organelles, represent a crucial subcellular target for fundamental research and biomedical applications. Despite significant advances in the design of DNA nanotechnologies for a variety of bio-applications, the dearth of strategies that enable mitochondria targeting for subcellular molecular imaging and therapy remains an outstanding challenge in this field. In this Minireview, we summarize the recent progresses on the emerging design and application of DNA nanotechnology for mitochondria-targeted molecular imaging and tumor treatment. We first highlight the engineering of mitochondria-localized DNA nanosensors for in situ detection and imaging of diverse key molecules that are essential to maintain mitochondrial functions, including mitochondrial DNA and microRNA, enzymes, small molecules, and metal ions. Then, we compile the developments of DNA nanotechnologies for mitochondria-targeted anti-tumor therapy, including modularly designed DNA nanodevices for subcellular delivery of therapeutic agents, and programmed DNA assembly for mitochondrial interference. We will place an emphasis on clarification of the chemical principles of how DNA nanobiotechnology can be designed to target mitochondria for various biomedical applications. Finally, the remaining challenges and future directions in this emerging field will be discussed, hoping to inspire further development of advanced DNA toolkits for both academic and clinical research regarding mitochondria.

Subcellular targeting strategies for protein and peptide delivery

Cytosolic delivery of proteins and peptides provides opportunities for effective disease treatment, as they can specifically modulate intracellular processes. However, most of protein-based therapeutics only have extracellular targets and are cell-membrane impermeable due to relatively large size and hydrophilicity. The use of organelle-targeting strategy offers great potential to overcome extracellular and cell membrane barriers, and enables localization of protein and peptide therapeutics in the organelles. Although progresses have been made in the recent years, organelle-targeted protein and peptide delivery is still challenging and under exploration. We reviewed recent advances in subcellular targeted delivery of proteins/peptides with a focus on targeting mechanisms and strategies, and highlight recent examples of active and passive organelle-specific protein and peptide delivery systems. This emerging platform could open a new avenue to develop more effective protein and peptide therapeutics.

Bioorthogonal In Situ Polymerization of Dendritic Agents for Hijacking Lysosomes and Enhancing Antigen Presentation in Cancer Cells

A low-generation lysine dendrimer, SPr-G2, responds to intracellular glutathione to initiate bioorthogonal in situ polymerization, resulting in the formation of large assemblies in mouse breast cancer cells. The intracellular large assemblies of SPr-G2 can interact with lysosomes to induce lysosome expansion and enhance lysosomal membrane permeabilization, leading to major histocompatibility complex class I upregulation on tumor cell surfaces and ultimately tumor cell death. Moreover, the use of the SPr-G2 dendrimer to conjugate the chemotherapeutic drug, camptothecin (CPT), can boost the therapeutic potency of CPT. Excellent antitumor effects in vitro and in vivo are obtained from the combinational treatment of the SPr-G2 dendrimer and CPT. This combinational effect also enhances antitumor immunity through promoting activation of cytotoxic T cells in tumor tissues and maturation of dendritic cells. This study can shed new light on the development of peptide dendritic agents for cancer therapy.

From cells to subcellular organelles: Next-generation cancer therapy based on peptide self-assembly

Due to the editability, functionality, and excellent biocompatibility of peptides, in situ self-assembly of peptides in cells is a powerful strategy for biomedical applications. Subcellular organelle targeting of peptides assemblies enables more precise drug delivery, enhances selectivity to disease cells, and mitigates drug resistance, providing an effective strategy for disease diagnosis and therapy. This reviewer first introduces the triggering conditions, morphological changes, and intracellular locations of self-assembling peptides. Then, the functions of peptide assemblies are summarized, followed by a comprehensive understanding of the interactions between peptide assemblies and subcellular organelles. Finally, we provide a brief outlook and the remaining challenges in this field.

Nanofibers in Organelles: From Structure Design to Biomedical Applications

Nanofibers are one of the most important morphologies of molecular self-assemblies, the formation of which relies on the diverse intermolecular interactions of fibrous-forming units. In the past decade, rapid advances have been made in the biomedical application of nanofibers, such as bioimaging and tumor treatment. An important topic to be focused on is not only the nanofiber formation mechanism but also where it forms, because different destinations could have different influences on cells and its formation could be triggered by unique stimuli in organelles. It is therefore necessary and timely to summarize the nanofibers assembled in organelles. This minireview discusses the formation mechanism, triggering strategies, and biomedical applications of nanofibers, which may facilitate the rational design of nanofibers, improve our understanding of the relationship between nanofiber properties and organelle characteristics, allow a comprehensive recognition of organelles affected by materials, and enhance the therapeutic efficiency of nanofibers.

Organelle-Mediated Dissipative Self-Assembly of Peptides in Living Cells

Implementing dissipative assembly in living systems is meaningful for creation of living materials or even artificial life. However, intracellular dissipative assembly remains scarce and is significantly impeded by the challenges lying in precisely operating chemical reaction cycles under complex physiological conditions. Here, we develop organelle-mediated dissipative self-assembly of peptides in living cells fueled by GSH, via the design of a mitochondrion-targeting and redox-responsive hexapeptide. While the hexapeptide undergoes efficient redox-responsive self-assembly, the addition of GSH into the peptide solution in the presence of mitochondrion-biomimetic liposomes containing hydrogen peroxide allows for transient assembly of peptides. Internalization of the peptide by LPS-stimulated macrophages leads to the self-assembly of the peptide driven by GSH reduction and the association of the peptide assemblies with mitochondria. The association facilitates reversible oxidation of the reduced peptide by mitochondrion-residing ROS and thereby dissociates the peptide from mitochondria to re-enter the cytoplasm for GSH reduction. The metastable peptide-mitochondrion complexes prevent the thermodynamically equilibrated self-assembly, thus establishing dissipative assembly of peptides in stimulated macrophages. The entire dissipative self-assembling process allows for elimination of elevated ROS and decrease of pro-inflammatory cytokine expression. Creating dissipative self-assembling systems assisted by internal structures provides new avenues for the development of living materials or medical agents in the future.

Recent Advances in Biomedical Nanotechnology Related to Natural Products

Natural product processing via nanotechnology has opened the door to innovative and significant applications in medical fields. On one hand, plants-derived bioactive ingredients such as phenols, pentacyclic triterpenes and flavonoids exhibit significant pharmacological activities, on another hand, most of them are hydrophobic in nature, posing challenges to their use. To overcome this issue, nanoencapsulation technology is employed to encapsulate these lipophilic compounds and enhance their bioavailability. In this regard, various nano-sized vehicles, including degradable functional polymer organic compounds, mesoporous silicon or carbon materials, offer superior stability and retention for bioactive ingredients against decomposition and loss during delivery as well as sustained release. On the other hand, some naturally occurring polymers, lipids and even microorganisms, which constitute a significant portion of Earth's biomass, show promising potential for biomedical applications as well. Through nano-processing, these natural products can be developed into nano-delivery systems with desirable characteristics for encapsulation a wide range of bioactive components and therapeutic agents, facilitating in vivo drug transport. Beyond the presentation of the most recent nanoencapsulation and nano-processing advancements with formulations mainly based on natural products, this review emphasizes the importance of their physicochemical properties at the nanoscale and their potential in disease therapy.

Artificial Peptide-Protein Necrosomes Promote Cell Death

The presence of disordered region or large interacting surface within proteins significantly challenges the development of targeted drugs, commonly known as the "undruggable" issue. Here, we report a heterogeneous peptide-protein assembling strategy to selectively phosphorylate proteins, thereby activating the necroptotic signaling pathway and promoting cell necroptosis. Inspired by the structures of natural necrosomes formed by receptor interacting protein kinases (RIPK) 1 and 3, the kinase-biomimetic peptides are rationally designed by incorporating natural or D -amino acids, or connecting D -amino acids in a retro-inverso (DRI) manner, leading to one RIPK3-biomimetic peptide PR3 and three RIPK1-biomimetic peptides. Individual peptides undergo self-assembly into nanofibrils, whereas mixing RIPK1-biomimetic peptides with PR3 accelerates and enhances assembly of PR3. In particular, RIPK1-biomimetic peptide DRI-PR1 exhibits reliable binding affinity with protein RIPK3, resulting in specific cytotoxicity to colon cancer cells that overexpress RIPK3. Mechanistic studies reveal the increased phosphorylation of RIPK3 induced by RIPK1-biomimetic peptides, elucidating the activation of the necroptotic signaling pathway responsible for cell death without an obvious increase in secretion of inflammatory cytokines. Our findings highlight the potential of peptide-protein hybrid aggregation as a promising approach to address the "undruggable" issue and provide alternative strategies for overcoming cancer resistance in the future.

Acceptor engineering-facilitated versatile AIEgen for mitochondria-targeted multimodal imaging-guided cancer photoimmunotherapy

Photoimmunotherapy has been acknowledged to be an unprecedented strategy to obtain significantly improved cancer treatment efficacy. In this regard, the exploitation of high-performance multimodal phototheranostic agents is highly desired. Apart from tailoring electron donors, acceptor engineering is gradually rising as a deliberate approach in this field. Herein, we rationally designed a family of aggregation-induced emission (AIE)-active compounds with the same donors but different acceptors based on the acceptor engineering. Through finely adjusting the functional groups on electron acceptors, the electron affinity of electron acceptors and the conformation of the compounds were simultaneously modulated. It was found that one of the molecules (named DCTIC), bearing a moderately electrophilic electron acceptor and the best planarity, exhibited optimal phototheranostic properties in terms of light-harvesting ability, fluorescence emission, reactive oxygen species (ROS) production, and photothermal performance. For the purpose of amplified therapeutic outcomes, DCTIC was fabricated into tumor and mitochondria dual-targeted DCTIC nanoparticles (NPs), which afforded good performance in the fluorescence/photoacoustic/photothermal trimodal imaging-guided photodynamic/photothermal-synergized cancer immunotherapy with the combination of programmed cell death protein-1 (PD-1) antibody. Not only the primary tumors were totally eradicated, but efficient growth inhibition of distant tumors was also realized.

Targeting tumor energy metabolism via simultaneous inhibition of mitochondrial respiration and glycolysis using biodegradable hydroxyapatite nanorods

Tumor cells obtain energy supply from the unique metabolic pathways of mitochondrial respiration and glycolysis, which can be used interchangeably to produce adenosine triphosphate (ATP) for survival. To simultaneously block the two metabolic pathways and sharply cut off ATP supply, a multifunctional "nanoenabled energy interrupter" (called as HNHA-GC) was prepared by attaching glucose oxidase (GOx), hyaluronic acid (HA), and 10-hydroxycamptothecin (CPT) on the surface of degradable hydroxyapatite (NHA) nanorods. After targeted delivery of HNHA-GC to the tumor site by HA, the tumor-selective acid degradation of HNHA-GC as well as the subsequent deliveries of Ca²⁺, drug CPT, and GOx take place. The released Ca²⁺ and CPT induce mitochondrial dysfunction by Ca²⁺ overload and chemotherapy respectively, while the GOx-triggered glucose oxidation inhibits glycolysis by starvation therapy (exogenous effect). The generated H₂O₂ and released CPT increase the intracellular reactive oxygen (ROS) level. Moreover, the generated H⁺ and enhanced ROS promote Ca²⁺ overload by accelerating the degradation of HNHA-GC and preventing intracellular Ca²⁺ efflux, respectively (endogenous effect). As a result, the HNHA-GC displays a promising therapeutic modality for simultaneously cutting off mitochondrial and glycolytic ATP production through a combination of Ca²⁺ overload, chemotherapy, and starvation therapy.

Smart Metabolism Nanovalve Reprograms Cancer Energy Homeostasis for Maximizing Photometabolism Therapy

Better understanding of important roles of metabolic reprogramming in therapeutic resistance provides insights into advancing cancer treatment. Herein, we present a photoactive metabolic reprogramming strategy (termed as photometabolism therapy, PMT), in which photoregulation of mitochondria leads to cancer cell metabolic crisis, and consequently overcomes therapeutic resistance while improving treatment efficacy. In specific, a stimuli-responsive metabolism NanoValve is developed for improving cascade cancer therapy through blocking mitochondrial energy supply. NanoValve is composed of an onion-like architecture with a gold nanorod core, a mesoporous silica shell encapsulating photosensitizer chlorin e6 and oxygen-saturated perfluorocarbon, and cationic liposomal coating with MMP2-cleavable polyethylene glycol corona, which together initiate mitochondria-specific PMT. NanoValve selectively responds to tumor-overexpressed MMP2 and achieves size decrease and charge reversal, which consequently enhances tumor penetration, cancer cell uptake, endosome escape, and most critically, mitochondrial accumulation. Importantly, NanoValve-mediated phototherapy can strongly destruct mitochondrial energy metabolism, thereby minimizing therapy resistance. Particularly, perfluorocarbon supplies oxygen to further overcome the tumor hypoxia-associated therapeutic barrier and maximizes synergistic anticancer effects. In vivo studies show that NanoValve can effectively eliminate tumors without side effects, thereby dramatically prolonging the survival of tumor-bearing mice. Thus, NanoValve provides a modular PMT approach and has the potential of advancing the treatment of malignancy.

Persistent Endoplasmic Reticulum Stress Stimulated by Peptide Assemblies for Sensitizing Cancer Chemotherapy

Pharmacological targeting of endoplasmic reticulum (ER) stress represents one of important methods for disease therapy, which, however, is significantly suppressed by the ER homeostatic processe. Herein, a proof-of-concept strategy is reported for persistent stimulation of ER stress via preventing ER stress adaptation by utilizing multifunctional peptide assemblies. The strategy is established via creation of peptide assemblies with ER-targeting and chaperone glucose-regulated protein 78 (GRP78)-inhibiting functions. The peptides assemblies form well-defined nanofibers that are retrieved by ER organelles in human cervical cancer cell. The underlying mechanism studies unravel that the ER-accumulated peptide assemblies simultaneously stimulate ER stress and inhibit GRP78 refolding activity and thereby promoting endogenous protein aggregation. Combining the internalized peptide assemblies with the induced protein aggregates leads to the persistent stimulation of ER stress. The persistent ER stress induced by the peptide assemblies bestows their application in sensitizing cancer chemotherapy. Both in vitro and in vivo results confirm the enhanced cytotoxicity of drug toyocamycin against HeLa cells by peptide assemblies, thus efficiently inhibiting in vivo tumor growth. The strategy reported here discloses the fundamental keys for efficient promotion of ER stress, thus providing the guidance for development of ER-targeting-assisted cancer chemotherapy in the future.

Stimulus-Responsive Amino Acids Behind In Situ Assembled Bioactive Peptide Materials

In situ self-assembly of peptides into well-defined nanostructures represents one of versatile strategies for creation of bioactive materials within living cells with great potential in disease diagnosis and treatment. The intimate relationship between amino acid sequences and the assembling propensity of peptides has been thoroughly elucidated over the past few decades. This has inspired development of various controllable self-assembling peptide systems based on stimuli-responsive naturally occurring or non-canonical amino acids, including redox-, pH-, photo-, enzyme-responsive amino acids. This review attempts to summarize the recent progress achieved in manipulating in situ self-assembly of peptides by controllable reactions occurring to amino acids. We will highlight the systems containing non-canonical amino acids developed in our laboratory during the past few years, primarily including acid/enzyme-responsive 4-aminoproline, redox-responsive (seleno)methionine, and enzyme-responsive 2-nitroimidazolyl alanine. Utilization of the stimuli-responsive assembling systems in creation of bioactive materials will be specifically introduced to emphasize their advantages for addressing the concerns lying in disease theranostics. Eventually, we will provide the perspectives for the further development of stimulus-responsive amino acids and thereby demonstrating their great potential in development of next-generation biomaterials.

Morphological Transformation and In Situ Polymerization of Caspase-3 Responsive Diacetylene-Containing Lipidated Peptide Amphiphile for Self-Amplified Cooperative Antitumor Therapy

In order to artificially regulate cell behaviors, intracellular polymerization as an emerging chemical technique has attracted much attention. Yet, it is still a challenge to achieve effective intracellular polymerization to conquer tumors in the complex cellular environment. Herein, this work develops a tumor-targeting and caspase-3 responsive nanoparticle composed of a diacetylene-containing lipidated peptide amphiphile and mitochondria-targeting photosensitizer (C3), which undergoes nanoparticle-to-nanofiber transformation and efficient in situ polymerization triggered by photodynamic treatment and activation of caspase-3. The locational nanofibers on the mitochondria membranes lead to mitochondrial reactive oxygen species (mtROS) burst and self-amplified circulation, offering persistent high oxidative stress to induce cell apoptosis. This study provides a strategy for greatly enhanced antitumor therapeutic efficacy through mtROS burst and self-amplified circulation induced by intracellular transformation and in situ polymerization.

Ultrasmall Coordination Polymers for Alleviating ROS-Mediated Inflammatory and Realizing Neuroprotection against Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease globally, and there is currently no effective treatment for this condition. Excessive accumulation of reactive oxygen species (ROS) and neuroinflammation are major contributors to PD pathogenesis. Herein, ultrasmall nanoscale coordination polymers (NCPs) coordinated by ferric ions and natural product curcumin (Cur) were exploited, showing efficient neuroprotection by scavenging excessive radicals and suppressing neuroinflammation. In a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse PD model, such ultrasmall Fe-Cur NCPs with prolonged blood circulation and BBB traversing capability could effectively alleviate oxidative stress, mitochondrial dysfunction, and inflammatory condition in the midbrain and striatum to reduce PD symptoms. Thus, this study puts forth a unique type of therapeutics-based NCPs that could be used for safe and efficient treatment of PD with potential in clinical translation.

In Situ Self-Sorting Peptide Assemblies in Living Cells for Simultaneous Organelle Targeting

Self-sorting is a common phenomenon in eukaryotic cells and represents one of the versatile strategies for the formation of advanced functional materials; however, developing artificial self-sorting assemblies within living cells remains challenging. Here, we report on the GSH-responsive in situ self-sorting peptide assemblies within cancer cells for simultaneous organelle targeting to promote combinatorial organelle dysfunction and thereby cell death. The self-sorting system was created via the design of two peptides E3C16E6 and EVM^SeO derived from lipid-inspired peptide interdigitating amphiphiles and peptide bola-amphiphiles, respectively. The distinct organization patterns of the two peptides facilitate their GSH-induced self-sorting into isolated nanofibrils as a result of cleavage of disulfide-connected hydrophilic domains or reduction of selenoxide groups. The GSH-responsive in situ self-sorting in the peptide assemblies within HeLa cells was directly characterized by super-resolution structured illumination microscopy. Incorporation of the thiol and ER-targeting groups into the self-sorted assemblies endows their simultaneous targeting of endoplasmic reticulum and Golgi apparatus, thus leading to combinatorial organelle dysfunction and cell death. Our results demonstrate the establishment of the in situ self-sorting peptide assemblies within living cells, thus providing a unique platform for drug targeting delivery and an alternative strategy for modulating biological processes in the future.

Self-Amplifying Assembly of Peptides in Macrophages for Enhanced Inflammatory Treatment

Enzyme-regulated in situ self-assembly of peptides represents one versatile strategy in the creation of theranostic agents, which, however, is limited by the strong dependence on enzyme overexpression. Herein, we reported the self-amplifying assembly of peptides precisely in macrophages associated with enzyme expression for improving the anti-inflammatory efficacy of conventional drugs. The self-amplifying assembling system was created via coassembling an enzyme-responsive peptide with its derivative functionalized with a protein ligand. Reduction of the peptides by the enzyme NAD(P)H quinone dehydrogenase 1 (NQO1) led to the formation of nanofibers with high affinity to the protein, thereby facilitating NQO1 expression. The improved NQO1 level conversely promoted the assembly of the peptides into nanofibers, thus establishing an amplifying relationship between the peptide assembly and the NQO1 expression in macrophages. Utilization of the amplifying assembling system as vehicles for drug dexamethasone allowed for its passive targeting delivery to acute injured lungs. Both in vitro and in vivo studies confirmed the capability of the self-amplifying assembling system to enhance the anti-inflammatory efficacy of dexamethasone via simultaneous alleviation of the reactive oxygen species side effect and downregulation of proinflammatory cytokines. Our findings demonstrate the manipulation of the assembly of peptides in living cells with a regular enzyme level via a self-amplification process, thus providing a unique strategy for the creation of supramolecular theranostic agents in living cells.

Liposome-Based Nanoencapsulation of a Mitochondria-Stapling Photosensitizer for Efficient Photodynamic Therapy

Mitochondria-targeting photodynamic therapy (PDT) can block mitochondrial function and trigger the inherent proapoptotic cascade signal of mitochondria, which has been considered to have the potential to amplify the efficiency of PDT. However, the dynamic change of mitochondrial membrane potential (MMP) makes most cationic photosensitizers easily fall off from the mitochondria, which greatly limits the efficiency of PDT. Here, we have developed a smart liposome encapsulation method based on a mitochondria-stapling photosensitizer for efficient theranostic photodynamic therapy. The stapling photosensitizer can be covalently bound inside mitochondria via two reaction sites without a falloff effect, regardless of the change of MMP. As a result, the liposome-based nanophotosensitizer showed a high efficiency of PDT (IC₅₀ = 0.98 μM) under 630 nm light. At the same time, the nanophotosensitizer had fluorescence imaging-guided ability to monitor abnormal mitochondrial morphology during PDT. Importantly, the results of mice experiments also showed that the liposome-based nanophotosensitizer possessed excellent antitumor PDT activity because the released photosensitizer can stay inside mitochondria during the whole process of PDT.

Dynamic Assembly of DNA Nanostructures in Living Cells for Mitochondrial Interference

Constructing artificial dynamic architectures inside cells to rationally interfere with organelles is emerging as an efficient strategy to regulate the behaviors and fate of cells, thus providing new routes for therapeutics. Herein, we develop an intracellular K⁺-mediating dynamic assembly of DNA tetrahedrons inside cells, which realizes efficient mitochondrial interference and consequent regulation on the energy metabolism of living cells. In the designer DNA tetrahedron, one vertex was modified with triphenylphosphine (TPP) for mitochondrial targeting, and the other three vertexes were tethered with guanine-rich sequences that could realize K⁺-mediating formation of intermolecular G-quadruplexes, which consequently led to the assembly of DNA tetrahedrons to form aggregates in the cytoplasm. The DNA aggregates specially targeted mitochondria and served as a polyanionic barrier for substance communication, thus generating a significant inhibition effect on the aerobic respiration function of mitochondria and the associated glycolysis process, which consequently reduced the production of intracellular adenosine triphosphate (ATP). The lack of ATP impeded the formation of lamellipodium that was essential for the movement of cells, consequently resulting in a significant inhibitory effect on cell migration. Remarkably, the migration capacity was suppressed by as high as 50% for cancer cells. This work provides a new strategy for the manipulation of organelles via the endogenous molecule-mediating dynamic assembly of exogenous artificial architectures inside living cells, which is envisioned to have great potential in precise biomedicine.

Tracking Cell Viability for Adipose-Derived Mesenchymal Stem Cell-Based Therapy by Quantitative Fluorescence Imaging in the Second Near-Infrared Window

Cell survival rate determines engraftment efficiency in adipose-derived mesenchymal stem cell (ADSC)-based regenerative medicine. In vivo monitoring of ADSC viability to achieve effective tissue regeneration is a major challenge for ADSC therapy. Here, we developed an activated near-infrared II (NIR-II) fluorescent nanoparticle consisting of lanthanide-based down-conversion nanoparticles (DCNPs) and IR786s (DCNP@IR786s) for cell labeling and real-time tracking of ADSC viability in vivo. In dying ADSCs due to excessive ROS generation, absorption competition-induced emission of IR786s was destroyed, which could turn on the NIR-II fluorescent intensity of DCNPs at 1550 nm by 808 nm laser excitation. In contrast, the NIR-II fluorescent intensity of DCNPs was stable at 1550 nm by 980 nm laser excitation. This ratiometric fluorescent signal was precise and sensitive for tracking ADSC viability in vivo. Significantly, the nanoparticle could be applied to quantitively evaluate stem cell viability in real-time in vivo. Using this method, we successfully sought two small molecules including glutathione and dexamethasone that could improve stem cell engraftment efficiency and enhance ADSC therapy in a liver fibrotic mouse model. Therefore, we provide a potential strategy for real-time in vivo quantitative tracking of stem cell viability in ADSC therapy.

Combination of mitochondria impairment and inflammation blockade to combat metastasis

Targeted induction of mitochondria impairment has emerged as a promising strategy for anti-metastasis therapy. However, problems such as limited mitochondria targeting efficiency, undesired drug leakage and insufficient drug release inside mitochondria remain crucial challenges for mitochondria-targeting therapy. Here, we constructed an N-(2-hydroxypropyl) methacrylamide (HPMA) polymer based cationic system that could target to mitochondria and facilitate on demand drug release in response to excessive mitochondrial reactive oxygen species. Whereas, this drug delivery system is still challenged by limitations of (1) in vivo application, and (2) inflammatory tumor microenvironment (TME). On one aspect, to prolong blood circulation and increase tumor targeting, we designed a nanocomposite (PDT-NCs) that assembled from the cationic HPMA polymer and anionic hyaluronic acid via electrostatic interaction. On another aspect, a celecoxib loaded liposome (Lip-Cel) was further fabricated to alleviate inflammation in TME by downregulating various metastasis-associated factors. Ultimately, PDT-NCs and Lip-Cel led to a drastic improvement in the suppression of primary tumor growth and distant lung metastasis. Our work provided a generalizable approach of mitochondria dysfunction and inflammation blockade to combat metastatic tumors.

Adaptable peptide-based therapeutics modulating tumor microenvironment for combinatorial radio-immunotherapy

Radiotherapy is one of the conventional tumor treatments, while its abscopal therapeutic efficacy is severely hampered by the immunosuppressive tumor microenvironment. To address this challenge, we herein report on the morphology-adaptable peptide-based therapeutics for efficiently reversing the immunosuppression in the combinatorial radio-immunotherapy through simultaneous checkpoint blocking and induction of immunogenic cell death. The peptide-based therapeutics were created via co-assembling a pentapeptide containing a 4-amino proline residue with its derivatives containing IDO-1 inhibitor NLG919. The resulting therapeutics underwent pH-adaptable morphological transformation between nanofibrils and nanoparticles and released NLG919 upon GSH cleavage. In vivo studies confirmed that the pH-adaptable morphologies of the therapeutics facilitated their tumor accumulation and retention at tumor sites compared to morphology-persistent counterparts, thus resulting in efficient delivery of IDO-1 inhibitors. Simultaneously treating the tumor-bearing mice with the therapeutics and external γ-ray radiation boosted the tumor immunogenicity via inducing ICD cascade of the tumor cells and reverse the immunosuppressive tumor microenvironment due to the inhibition of IDO-1 for depletion of tryptophan. Our findings strongly demonstrate that the morphology-adaptable peptide-based therapeutics exhibit the capability to reverse the immunosuppressive tumor microenvironment during irradiation, thus providing a new strategy for the combinatorial radio-immunotherapy.

Noncanonical Amino Acids for Hypoxia-Responsive Peptide Self-Assembly and Fluorescence

Design of endogenous stimuli-responsive amino acids allows for precisely modulating proteins or peptides under a biological microenvironment and thereby regulating their performance. Herein we report a noncanonical amino acid 2-nitroimidazol-1-yl alanine and explore its functions in creation of the nitroreductase (NTR)-responsive peptide-based supramolecular probes for efficient hypoxia imaging. On the basis of the reduction potential of the nitroimidazole unit, the amino acid was synthesized via the Mitsunobu reaction between 2-nitroimidazole and a serine derivate. We elucidated the relationship between the NTR-responsiveness of the amino acid and the structural feature of peptides involving a series of peptides. This eventually facilitates development of aromatic peptides undergoing NTR-responsive self-assembly by rationally optimizing the sequences. Due to the intrinsic role of 2-nitroimidazole in the fluorescence quench, we created a morphology-transformable supramolecular probe for imaging hypoxic tumor cells based on NTR reduction. We found that the resulting supramolecular probes penetrated into solid tumors, thus allowing for efficient fluorescence imaging of tumor cells in hypoxic regions. Our findings demonstrate development of a readily synthesized and versatile amino acid with exemplified properties in creating fluorescent peptide nanostructures responsive to a biological microenvironment, thus providing a powerful toolkit for synthetic biology and development of novel biomaterials.