Self-Assembling Ability Determines the Activity of Enzyme-Instructed Self-Assembly for Inhibiting Cancer Cells

Programming two-component peptide self-assembly by tuning the hydrophobic linker

Molecular self-assembly enables the formation of intricate networks through non-covalent interactions, serving as a key strategy for constructing structures ranging from molecules to macroscopic forms. While zero-dimensional and one-dimensional nanostructures have been widely achieved, two-dimensional nanostrip structures present unique advantages in biomedical and other applications due to their high surface area and potential for functionalization. However, their efficient design and precise regulation remain challenging. This study systematically explores how different hydrophobic amino acid linkers impact the microscopic morphology in two-component co-assembly systems with strong electrostatic interactions. The introduction of the AA linker resulted in distinctive 2D nanostrips, which stacked to form bilayer sheets, whereas VV, LL, and NleNle linkers formed one-dimensional fibers. In contrast, GG and PP linkers did not produce stable aggregates. Our findings highlight the role of intermolecular interactions in the development of 2D assemblies, providing new insights into the design and application of 2D materials.

In situ peptide assembly for cell membrane rewiring in tumor therapy

Peptide assembly on the cell membrane is capable of endowing cells with novel biological properties that are distinct from their original states, thereby playing a pivotal role in the regulation of diverse cellular biological events. In practical biomedical scenarios, in order to make peptide assembly more precisely meet the requirements of cells at different physiological stages and conditions to achieve desired effects of cell function regulation, it becomes particularly crucial to conduct precise in situ spatiotemporal control of peptide assembly on the cell membrane, thus attracting great attentions. Particularly for tumor treatment, this artificially manipulated cell surface engineering can achieve excellent anti-tumor effects by altering the cell membrane structure, influencing receptor clustering or interfering with relevant signal pathways. Of note, membrane-anchoring peptides play a key role in these processes. In this review, we focus on three main types of membrane-anchoring peptides, elaborating in detail on how their assembly regulation mechanisms influence the cell membrane remodeling effect, and further exert therapeutic effects on tumors. On this basis, we further introduce a variety of tumor treatment strategies combined with in situ peptide assembly on the cell membrane, and discuss the current opportunities and challenges in this field, aiming to present the overall research panorama and trend of in situ peptide self-assembly on the cell membrane for efficient tumor treatment.

Recent Advances in Therapeutic Peptides: Innovations and Applications in Treating Infections and Diseases

Peptides have become a powerful frontier in modern medicine, offering a promising therapeutic solution for various diseases and advancing rapidly in pharmaceutical development. These small amino acid chains, with their innovative design, have attracted significant attention due to their versatility and high receptor specificity, which minimizes off-target effects, along with enhanced therapeutic efficacy, biodegradability, low toxicity, and minimal immunogenicity. They are being explored for use in several clinical domains, like metabolic diseases, immunomodulation, and cancer. Furthermore, antimicrobial peptides (AMPs) have grown to be a promising strategy to combat the worldwide challenge of antibiotic resistance, demonstrating promising results against multidrug-resistant organisms. Both natural and engineered peptides have been discovered and investigated, whereas numerous others are progressing toward clinical trials in a number of therapeutic domains. Recent improvements with surface modification, such as peptide engineering, peptide cyclization, PEGylation, and the utilization of synthetic amino acids to enhance their pharmacokinetic profiles and overcome the inherent disadvantages of these peptides have made it possible for the area to continue to advance. Moreover, their therapeutic potential has been further enhanced by innovative delivery methods, such as self-assembling peptides, nanocarriers, and alternate routes of administration. This Review critically states the potential of peptides as versatile therapeutics along with their modifications and advancements to drive the significant progress to treat infections and chronic diseases, along with their potential benefits and challenges.

Synthesis of Abiotic Supramolecular Polymers Inside Living Cells via Organocatalysis-Mediated Self-Assembly

Cells execute mesmerizing functions using supramolecular polymers (SPs) formed through the self-assembly of biological precursors. Integration of the vast array of synthetic SPs with living cells would offer a powerful way to remold cellular functions and bridge the gap between synthetic materials and the biological realm, yet remains a challenge because of the lack of robust abiotic SP systems that can be triggered to self-assemble inside cells. Here, we report how fully abiotic SPs can be synthesized inside living cells via an organocatalysis-responsive self-assembly strategy, and how the in situ-generated SPs are capable of interfering and can interfere with cellular functions. The incorporation of a nucleophilic organocatalyst (CAT) into living cells accelerates the intracellular conversion of hydrazide (H) and aldehyde-derived precursors (A) to hydrazone-based monomers (HA3) that locally self-assemble into SPs. Interestingly, the in situ-generated SPs possess ignorable effects on cell viability and proliferation but remarkably hinder cell migration. Furthermore, the presence of SPs is found to retard intracellular diffusion and alter the organization of the actin cytoskeleton, both of which are suggested to be responsible for the hindered cellular migration. In considering the vastly wide range of synthetic SPs, tremendous non-natural cellular functionalities can be obtained by in situ-synthesizing SPs.

Intrinsically Disordered Peptide Nanofibers from a Structured Motif Within Proteins

Intrinsically disordered regions (IDRs) are ubiquitous in proteins, orchestrating complex cellular signaling through higher-order protein assemblies. However, the properties and functions of intrinsically disordered peptide (IDP) assemblies are largely underexplored. This work unveiled a facile strategy for engineering IDP assemblies. We demonstrate that conjugating a structured motif derived from a protein's phosphorylation site to a self-assembling tripeptide unexpectedly yields self-assembled nanofibers with intrinsic disorder. Specifically, by using a glycine linker to attach a pentapeptide derived from a phosphorylation site within a random coil region of SRC kinase to the C-terminus of a widely used self-assembling enabler, we generated a phosphorylated octapeptide. The octapeptide exhibits cell compatibility and forms a hydrogel upon dephosphorylation of the phosphooctapeptide. Cryo-electron microscopy (cryo-EM) structural analysis of the nanofibers reveals that the peptides adopt two types of helical arrangements but exhibit intrinsic disorder at the periphery of the nanofibers. The hydrogels exhibit decreased protein adsorption with increasing peptide concentration. This study represents the first instance of a structured random coil within a protein transitioning into an intrinsically disordered state within self-assembled peptide nanofibers, expanding the pool of peptide sequences for IDPs and providing valuable insights for the engineering of peptide nanofibers with intrinsic disorder for the development of cell-compatible biomaterials.

Mechanistic Insights into the Apoptosis of Cancer Cells Induced by a Kinase-Responsive Peptide Amphiphile

Organelle targeting is a useful approach in drug development for cancer therapy. Peptide amphiphiles are good candidates for targeting specific organelles because they can be engineered into a wide range of molecular structures, enabling customization for specific functional needs. We have developed a peptide amphiphile, C16-(EY)3, that can respond to tyrosine kinase activity and undergo phosphorylation inside cancer cells. C16-(EY)3 selectively induced apoptosis in cancer cells that overexpressed tyrosine kinase. The self-assembly of peptide amphiphiles on the endoplasmic reticulum (ER) membrane reduced the ER membrane fluidity and triggered ER stress. The mechanism of the cancer cell death induced by C16-(EY)3 was shown to involve phosphorylation by tyrosine kinase, ER stress induction, and the subsequent activation of caspase-4, -12, and -9, which ultimately triggered apoptosis through the activation of caspase-3 and -7. In vivo studies further validated the antitumor efficacy of C16-(EY)3, as transcutaneous administration of the peptide amphiphile inhibited tumor growth in mice. This study elucidated the mechanism of apoptosis induced by the peptide amphiphile, indicating the potential of peptide amphiphiles as organelle-targeting cancer therapeutics and providing a novel strategy for the development of selective and potent anticancer drugs.

Organelle-Specific Smart Supramolecular Materials for Bioimaging and Theranostics Application

In cellular environments, certain synthetic molecules can form nanostructures via self-assembly, impacting molecular imaging, and biomedical applications. Control over the formation of these self-assembled nanostructures in subcellular organelle is challenging. By the action of stimuli, either present in the cellular environment or applied externally, in situ generation of molecular precursors can lead to accumulation and supramolecular nanostructure formation, resulting in efficient bioimaging. Here, we summarize smart fluorophore-based ordered nanostructure preparation at specific organelles for efficient bioimaging and therapeutic application towards cancer theranostics. We also present challenges and an outlook regarding intercellular self-assembly for theranostics application. Altogether, smart nanostructured materials with fluorescence read-outs at specific subcellular compartments would be beneficial in synthetic biology and precision therapeutics.

Enzymatic self-assembly of short peptides for cell spheroid formation

Cell spheroids, including organoids, serve as a valuable link between in vitro systems and in vivo animal models, offering powerful tools for studying cell biology in a three-dimensional environment. However, existing methods for generating cell spheroids are time consuming or difficult to scale up for large-scale production. Our recent study has revealed that transcytotic peptide assemblies, which transform from nanoparticles to nanofibers by enzymatic reactions, can create an intercellular fibril/gel, accelerating cell spheroid formation from a 2D cell culture or a cell suspension. While this finding presents an alternative approach for generating cell spheroids, the specific structural features required for efficient cell spheroid formation remain unclear. Based on our observation that a phosphotetrapeptide with a biphenyl cap at its N-terminus enables cell spheroid formation, we produced 10 variants of the original peptide. The variants explored modifications to the peptide backbone, length, electronic properties of the biphenyl capping group, and the type of phosphorylated amino acid residue. We then evaluated their ability for inducing cell spheroid formation. Our analysis revealed that, among the tested molecules, peptides with C-terminal phosphotyrosine, low critical micelle concentration, and dephosphorylation-guided nanoparticle to nanofiber morphological transition were the most effective in inducing the formation of cell spheroids. This work represents the first example to correlate the thermodynamic properties (e.g., self-assembling ability) and kinetic behavior (e.g., enzymatic dephosphorylation) of peptides with the efficacy of controlling intercellular interaction, thus offering valuable insights into using enzymatic self-assembly to generate peptide assemblies for biological applications.

Cell-Free Nonequilibrium Assembly for Hierarchical Protein/Peptide Nanopillars

Cells contain intricate protein nanostructures, but replicating them outside of cells presents challenges. One such example is the vertical fibronectin pillars observed in embryos. Here, we demonstrate the creation of cell-free vertical fibronectin pillar mimics using nonequilibrium self-assembly. Our approach utilizes enzyme-responsive phosphopeptides that assemble into nanotubes. Enzyme action triggers shape changes in peptide assemblies, driving the vertical growth of protein nanopillars into bundles. These bundles, with peptide nanotubes serving as a template to remodel fibronectin, can then recruit collagen, which forms aggregates or bundles depending on their types. Nanopillar formation relies on enzyme-catalyzed nonequilibrium self-assembly and is governed by the concentrations of enzyme, protein, peptide, the structure of the peptide, and peptide assembly morphologies. Cryo-EM reveals unexpected nanotube thinning and packing after dephosphorylation, indicating a complex sculpting process during assembly. Our study demonstrates a cell-free method for constructing intricate, multiprotein nanostructures with directionality and composition.

Alkaline Phosphatase-Instructed Peptide Assemblies for Imaging and Therapeutic Applications

Self-assembly, a powerful strategy for constructing highly stable and well-ordered supramolecular structures, widely exists in nature and in living systems. Peptides are frequently used as building blocks in the self-assembly process due to their advantageous characteristics, such as ease of synthesis, tunable mechanical stability, good biosafety, and biodegradability. Among the initiators for peptide self-assembly, enzymes are excellent candidates for guiding this process under mild reaction conditions. As a crucial and commonly used biomarker, alkaline phosphatase (ALP) cleaves phosphate groups, triggering a hydrophilicity-to-hydrophobicity transformation that induces peptide self-assembly. In recent years, ALP-instructed peptide self-assembly has made breakthroughs in biological imaging and therapy, inspiring the development of self-assembly biomaterials for diagnosis and therapeutics. In this review, we highlight the most recent advancements in ALP-instructed peptide assemblies and provide perspectives on their potential impact. Finally, we briefly discuss the ongoing challenges for future research in this field.

Clustering of the Membrane Protein by Molecular Self-Assembly Downregulates the Signaling Pathway for Cancer Cell Inhibition

This work reports a cyclic peptide appended self-assembled scaffold that recognizes the membrane protein EGFR and arrests the EGFR signaling through multivalent interactions by assembly-induced aggregation. When incubated with cells, the oligomers of PAD-1 first recognize the overexpressed EGFR on cancer cell membranes for arresting EGFR, which then initiates cellular uptake through endocytosis. The accumulation of PAD-1 and EGFR in the lysosome results in the formation of nanofibers, leading to the lysosomal membrane permeabilization (LMP). These processes disrupt the homeostasis of EGFR and inhibit the downstream signaling transduction of EGFR for cancer cell survival. Moreover, LMP induced the release of protein aggregates that could generate endoplasmic reticulum (ER) stress, resulting in cancer cell death selectively. In vivo studies indicate the efficient antitumor efficiency of PAD-1 in tumor-bearing mice. As a first example, this work provides an alternative strategy for controlling protein behavior for tuning cellular events in living cells.

Copper-Induced Supramolecular Peptide Assemblies for Multi-Pathway Cell Death and Tumor Inhibition

Although self-assembly has emerged as an effective tool for fabricating biomaterials, achieving precise control over the morphologies and functionalities of the resultant assemblies remains an ongoing challenge. Inspired by the copper peptide naturally present in human plasma, in this study, we designed a synthetic precursor, FcGH. FcGH can self-assemble via two distinct pathways: spontaneous and Cu2+-induced. These two assembly pathways enabled the formation of assemblies with tunable morphologies by adjusting the amount of added Cu2+. We found that the nanoparticles formed by Cu2+-induced self-assembly exhibited a significantly higher cellular uptake efficiency than the wormlike fibers formed spontaneously. Moreover, this Cu2+-induced assembly process occurred spontaneously at a 1 : 1 molar ratio of Cu2+ to FcGH, avoiding the excessive use of Cu2+ and a tedious preparation procedure. By co-assembling with 10-hydroxycamptothecin (HCPT)-conjugated FcGH, Cu2+-induced supramolecular nanodrugs elicited multiple cell death modalities in cancer cells with elevated immunogenicity, enhancing the therapeutic effect compared to free HCPT. This study highlights Cu2+-induced self-assembly as an efficient tool for directing the assembly of nanodrugs and for synergistic tumor therapy.

In Situ Forming, Enzyme-Responsive Peptoid-Peptide Hydrogels: An Advanced Long-Acting Injectable Drug Delivery System

Long-acting drug delivery systems are promising platforms to improve patient adherence to medication by delivering drugs over sustained periods and removing the need for patients to comply with oral regimens. This research paper provides a proof-of-concept for the development of a new optimized in situ forming injectable depot based on a tetrabenzylamine-tetraglycine-d-lysine-O-phospho-d-tyrosine peptoid-D-peptide formulation ((NPhe)4GGGGk(AZT)y(p)-OH). The chemical versatility of the peptoid-peptide motif allows low-molecular-weight drugs to be precisely and covalently conjugated. After subcutaneous injection, a hydrogel depot forms from the solubilized peptoid-peptide-drug formulation in response to phosphatase enzymes present within the skin space. This system is able to deliver clinically relevant concentrations of a model drug, the antiretroviral zidovudine (AZT), for 35 days in Sprague-Dawley rats. Oscillatory rheology demonstrated that hydrogel formation began within ∼30 s, an important characteristic of in situ systems for reducing initial drug bursts. Gel formation continued for up to ∼90 min. Small-angle neutron scattering data reveal narrow-radius fibers (∼0.78-1.8 nm) that closely fit formation via a flexible cylinder elliptical model. The inclusion of non-native peptoid monomers and D-variant amino acids confers protease resistance, enabling enhanced biostability to be demonstrated in vitro. Drug release proceeds via hydrolysis of an ester linkage under physiological conditions, releasing the drug in an unmodified form and further reducing the initial drug burst. Subcutaneous administration of (NPhe)4GGGGk(AZT)y(p)-OH to Sprague-Dawley rats resulted in zidovudine blood plasma concentrations within the 90% maximal inhibitory concentration (IC90) range (30-130 ng mL-1) for 35 days.

Self-assembling peptides induced by eyes absent enzyme to boost the efficacy of doxorubicin therapy in drug-resistant breast cancer cells

Enzyme-induced self-assembly (EISA) is a recently developed nanotechnology technique in which small molecules are induced by cellular enzymes self-assembling into nanostructures inside cancer cells. This technique can boost the efficacy of chemotherapy drugs by avoiding drug efflux, inhibiting the cells' DNA repair mechanisms, and targeting the mitochondria. In this work, we study the self-assembly of a short peptide and its fluorescence analogue induced by Eyes absent (EYA) tyrosine phosphatases to boost the efficacy of doxorubicin (DOX) therapy in drug-resistant types of breast cancer cells, MDA-MB-231 and MCF-7. The peptides Fmoc-FF-YP and NBD-FF-YP were synthesized with the solid-phase peptide synthesis (SPPS) method and analyzed with HPLC and MALDI-TOF. Dynamic light scattering was used to determine the size distribution of peptides exposed to the EYA enzyme in vitro. The presence of EYA enzymes in breast cancer cells was confirmed using the western blotting assay. The intracellular location of the peptide self-assembly was studied by imaging fluorescence NBD-tagged peptides. The efficacy of the peptide alone and with DOX was determined against MCF-7 and MDA-MB-231 using MTT and LIVE-DEAD assays. Nucleus and cytoplasm F-actin (Phalloidin) staining was used to determine cell morphology changes in response to the combination therapy of peptides/DOX. At an optimal concentration, the peptides are not toxic to the cells; however, they boost the efficacy of DOX against drug-resistant breast cancer cells. We used state-of-the-art computer-aided techniques to predict the molecular structure of peptides and their interactions with EYA. This study demonstrates an approach for incorporating non-cytotoxic components into DOX combination therapy, thereby avoiding increased systemic burden or adverse effects.

Enzyme-Instructed Self-Assembly of Peptides Induced by Tyrosine Phosphatase in Breast Cancer Cells

Enzyme induced self-assembly (EISA) leverages the expression of locally diseased enzymes within tumors to facilitate the self-assembly of small molecules into larger nanostructures capable of targeting cancer cells. Eye absent (EYA) is a tyrosine phosphatase enzyme found to be overexpressed in specific types of drug-resistant breast cancer cells. Utilizing this overexpression, we propose the synthesis of small peptides that can undergo self-assembly induced by the EYA tyrosine phosphatase. Our research demonstrates the presence of the EYA protein in Triple-Negative Breast Cancer cells by using the western blot. We then study the interaction between EYA's Tyr-phosphatase and the peptides P1and P2, and validate the successful intracellular self-assembly of fluorescence-tagged peptides in TNBC cells. These findings are reinforced by viability assays demonstrating the efficacy of the combination therapy of peptides and anticancer drugs for decreasing viability of TNBC cells. This paves the way for investigations into the discovery of new therapeutics for breast cancers.

Peptide Stereochemistry Effects from pKa-Shift to Gold Nanoparticle Templating in a Supramolecular Hydrogel

The divergent supramolecular behavior of a series of tripeptide stereoisomers was elucidated through spectroscopic, microscopic, crystallographic, and computational techniques. Only two epimers were able to effectively self-organize into amphipathic structures, leading to supramolecular hydrogels or crystals, respectively. Despite the similarity between the two peptides' turn conformations, stereoconfiguration led to different abilities to engage in intramolecular hydrogen bonding. Self-assembly further shifted the pKa value of the C-terminal side chain. As a result, across the pH range 4-6, only one epimer predominated sufficiently as a zwitterion to reach the critical molar fraction, allowing gelation. By contrast, the differing pKa values and higher dipole moment of the other epimer favored crystallization. The four stereoisomers were further tested for gold nanoparticle (AuNP) formation, with the supramolecular hydrogel being the key to control and stabilize AuNPs, yielding a nanocomposite that catalyzed the photodegradation of a dye. Importantly, the AuNP formation occurred without the use of reductants other than the peptide, and the redox chemistry was investigated by LC-MS, NMR, and infrared scattering-type near field optical microscopy (IR s-SNOM). This study provides important insights for the rational design of simple peptides as minimalistic and green building blocks for functional nanocomposites.

Enzymatic Dimerization-Induced Self-Assembly of Alanine-Tyramine Conjugates into Versatile, Uniform, Enzyme-Loaded Organic Nanoparticles

Herein, we report a novel enzymatic dimerization-induced self-assembly (e-DISA) procedure that converts alanine-tyramine conjugates into highly uniform enzyme-loaded nanoparticles (NPs) or nanocontainers by the action of horseradish peroxidase (HRP) in an aqueous medium under ambient conditions. The NP formation was possible with both enantiomers of alanine, and the average diameter could be varied from 150 nm to 250 nm (with a 5-12 % standard deviation of as-prepared samples) depending on the precursor concentration. About 60 % of the added HRP enzyme was entrapped within the NPs and was subsequently utilized for post-synthetic modification of the NPs with phenolic compounds such as tyramine or tannic acid. One-pot multi-enzyme entrapment of glucose oxidase (GOx) and peroxidase (HRP) within the NPs was also achieved. These GOx-HRP loaded NPs allowed multimodal detection of glucose, including that present in human saliva, with a limit of detection (LoD) of 740 nM through fluorimetry. The NPs exhibited good cytocompatibility and were stable to changes in pH (acidic to basic), temperature, ultrasonication, and even the presence of organic solvent (EtOH) to a certain extent, since they are stabilized by intermolecular hydrogen bonding, π-π, and CH-π interactions. The proposed e-DISA procedure can be widely expanded through the design of diverse enzyme-responsive precursors.

Therapeutic Supramolecular Polymers: Designs and Applications

The self-assembly of low-molecular-weight building motifs into supramolecular polymers has unlocked a new realm of materials with distinct properties and tremendous potential for advancing medical practices. Leveraging the reversible and dynamic nature of non-covalent interactions, these supramolecular polymers exhibit inherent responsiveness to their microenvironment, physiological cues, and biomolecular signals, making them uniquely suited for diverse biomedical applications. In this review, we intend to explore the principles of design, synthesis methodologies, and strategic developments that underlie the creation of supramolecular polymers as carriers for therapeutics, contributing to the treatment and prevention of a spectrum of human diseases. We delve into the principles underlying monomer design, emphasizing the pivotal role of non-covalent interactions, directionality, and reversibility. Moreover, we explore the intricate balance between thermodynamics and kinetics in supramolecular polymerization, illuminating strategies for achieving controlled sizes and distributions. Categorically, we examine their exciting biomedical applications: individual polymers as discrete carriers for therapeutics, delving into their interactions with cells, and in vivo dynamics; and supramolecular polymeric hydrogels as injectable depots, with a focus on their roles in cancer immunotherapy, sustained drug release, and regenerative medicine. As the field continues to burgeon, harnessing the unique attributes of therapeutic supramolecular polymers holds the promise of transformative impacts across the biomedical landscape.

Enzyme-Instructed Intracellular Peptide Assemblies

Higher-order or supramolecular protein assemblies, usually regulated by enzymatic reactions, are ubiquitous and essential for cellular functions. This evolutionary fact has provided a rigorous scientific foundation, as well as an inspiring blueprint, for exploring supramolecular assemblies of man-made molecules that are responsive to biological cues as a novel class of therapeutics for biomedicine. Among the emerging man-made supramolecular structures, peptide assemblies, formed by enzyme reactions or other stimuli, have received most of the research attention and advanced most rapidly.In this Account, we will review works that apply enzyme-instructed self-assembly (EISA) to generate intracellular peptide assemblies for developing a new kind of biomedicine, especially in the field of novel cancer nanomedicines and modulating cell morphogenesis. As a versatile and cell-compatible approach, EISA can generate nondiffusive peptide assemblies locally; thus, it provides a unique approach to target subcellular organelles with exceptional cell selectivity. We have arranged this Account in the following way: after introducing the concept, simplicity, and uniqueness of EISA, we discuss the EISA-formed intracellular peptide assemblies, including artificial filaments, in the cell cytosol. Then, we describe the representative examples targeting subcellular organelles, such as mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and the nucleus, by enzyme-instructed intracellular peptide assemblies for potential cancer therapeutics. After that, we highlight the recent exploration of the transcytosis of peptide assemblies for controlling cell morphogenesis. Finally, we provide a brief outlook of enzyme-instructed intracellular peptide assemblies. This Account aims to illustrate the promise of EISA-generated intracellular peptide assemblies in understanding diseases, controlling cell behaviors, and developing new therapeutics from a class of less explored molecular entities, which are substrates of enzymes and become building blocks of self-assembly after the enzymatic reactions.

Peptide-drug co-assembling: A potent armament against cancer

Cancer is still one of the major problems threatening human health and the therapeutical efficacies of available treatment choices are often rather low. Due to their favorable biocompatibility, simplicity of modification, and improved therapeutic efficacy, peptide-based self-assembled delivery systems have undergone significant evolution. Physical encapsulation and covalent conjugation are two common approaches to load drugs for peptide assembly-based delivery, which are always associated with drug leaks in the blood circulation system or changed pharmacological activities, respectively. To overcome these difficulties, a more elegant peptide-based assembly strategy is desired. Notably, peptide-mediated co-assembly with drug molecules provides a new method for constructing nanomaterials with improved versatility and structural stability. The co-assembly strategy can be used to design various nanostructures for cancer therapy, such as nanotubes, nanofibrils, hydrogels, and nanovesicles. Recently, these co-assembled nanostructures have gained tremendous attention for their unique superiorities in tumor therapy. This article describes the classification of assembled peptides, driving forces for co-assembly, and specifically, the design methodologies for various drug molecules in co-assembly. It also highlights recent research on peptide-mediated co-assembled delivery systems for cancer therapy. Finally, it summarizes the pros and cons of co-assembly in cancer therapy and offers some suggestions for conquering the challenges in this field.

Peptides Targeting HER2-Positive Breast Cancer Cells and Applications in Tumor Imaging and Delivery of Chemotherapeutics

Breast cancer represents the most common cancer type and one of the major leading causes of death in the female worldwide population. Overexpression of HER2, a transmembrane glycoprotein related to the epidermal growth factor receptor, results in a biologically and clinically aggressive breast cancer subtype. It is also the primary driver for tumor detection and progression and, in addition to being an important prognostic factor in women diagnosed with breast cancer, HER2 is a widely known therapeutic target for drug development. The aim of this review is to provide an updated overview of the main approaches for the diagnosis and treatment of HER2-positive breast cancer proposed in the literature over the past decade. We focused on the different targeting strategies involving antibodies and peptides that have been explored with their relative outcomes and current limitations that need to be improved. The review also encompasses a discussion on targeted peptides acting as probes for molecular imaging. By using different types of HER2-targeting strategies, nanotechnology promises to overcome some of the current clinical challenges by developing novel HER2-guided nanosystems suitable as powerful tools in breast cancer imaging, targeting, and therapy.

Cell spheroid creation by transcytotic intercellular gelation

Cell spheroids bridge the discontinuity between in vitro systems and in vivo animal models. However, inducing cell spheroids by nanomaterials remains an inefficient and poorly understood process. Here we use cryogenic electron microscopy to determine the atomic structure of helical nanofibres self-assembled from enzyme-responsive D-peptides and fluorescent imaging to show that the transcytosis of D-peptides induces intercellular nanofibres/gels that potentially interact with fibronectin to enable cell spheroid formation. Specifically, D-phosphopeptides, being protease resistant, undergo endocytosis and endosomal dephosphorylation to generate helical nanofibres. On secretion to the cell surface, these nanofibres form intercellular gels that act as artificial matrices and facilitate the fibrillogenesis of fibronectins to induce cell spheroids. No spheroid formation occurs without endo- or exocytosis, phosphate triggers or shape switching of the peptide assemblies. This study-coupling transcytosis and morphological transformation of peptide assemblies-demonstrates a potential approach for regenerative medicine and tissue engineering.

Peptide Assemblies for Cancer Therapy

Supramolecular assemblies made by the self-assembly of peptides are finding an increasing number of applications in various fields. While the early exploration of peptide assemblies centered on tissue engineering or regenerative medicine, the recent development has shown that peptide assemblies can act as supramolecular medicine for cancer therapy. This review covers the progress of applying peptide assemblies for cancer therapy, with the emphasis on the works appeared over the last five years. We start with the introduction of a few seminal works on peptide assemblies, then discuss the combination of peptide assemblies with anticancer drugs. Next, we highlight the use of enzyme-controlled transformation or shapeshifting of peptide assemblies for inhibiting cancer cells and tumors. After that, we provide the outlook for this exciting field that promises new kind of therapeutics for cancer therapy.

In situ stimulus-responsive self-assembled nanomaterials for drug delivery and disease treatment

The individual motifs that respond to specific stimuli for the self-assembly of nanomaterials play important roles. In situ constructed nanomaterials are formed spontaneously without human intervention and have promising applications in bioscience. However, due to the complex physiological environment of the human body, designing stimulus-responsive self-assembled nanomaterials in vivo is a challenging problem for researchers. In this article, we discuss the self-assembly principles of various nanomaterials in response to the tissue microenvironment, cell membrane, and intracellular stimuli. We propose the applications and advantages of in situ self-assembly in drug delivery and disease diagnosis and treatment, with a focus on in situ self-assembly at the lesion site, especially in cancer. Additionally, we introduce the significance of introducing exogenous stimulation to construct self-assembly in vivo. Based on this foundation, we put forward the prospects and possible challenges in the field of in situ self-assembly. This review uncovers the relationship between the structure and properties of in situ self-assembled nanomaterials and provides new ideas for innovative drug molecular design and development to solve the problems in the targeted delivery and precision medicine.

Intra-Lysosomal Peptide Assembly for the High Selectivity Index against Cancer

Lysosomes remain powerful organelles and important targets for cancer therapy because cancer cell proliferation is greatly dependent on effective lysosomal function. Recent studies have shown that lysosomal membrane permeabilization induces cell death and is an effective way to treat cancer by bypassing the classical caspase-dependent apoptotic pathway. However, most lysosome-targeted anticancer drugs have very low selectivity for cancer cells. Here, we show intra-lysosomal self-assembly of a peptide amphiphile as a powerful technique to overcome this problem. We designed a peptide amphiphile that localizes in the cancer lysosome and undergoes cathepsin B enzyme-instructed supramolecular assembly. This localized assembly induces lysosomal swelling, membrane permeabilization, and damage to the lysosome, which eventually causes caspase-independent apoptotic death of cancer cells without conventional chemotherapeutic drugs. It has specific anticancer effects and is effective against drug-resistant cancers. Moreover, this peptide amphiphile exhibits high tumor targeting when attached to a tumor-targeting ligand and causes significant inhibition of tumor growth both in cancer and drug-resistant cancer xenograft models.

Cell membrane-specific self-assembly of peptide nanomedicine induces tumor immunogenic death to enhance cancer therapy

Immunogenic cell death (ICD), as an unusual cell death pattern, mediates cancer cells to release a series of damage-associated molecular patterns (DAMPs), and is widely used in the field of cancer immunotherapy. Injuring the cell membrane can serve as a novel ICD initiation strategy. In this study, a peptide nanomedicine (PNpC) is designed using the fragment CM11 of cecropin, which is effective in disrupting cell membranes because of its α-helical structure. PNpC self-assembles in situ in the presence of high levels of alkaline phosphatase (ALP) on the tumor cell membrane, transforming from nanoparticles to nanofibers, which reduces the cellular internalization of the nanomedicine and increases the interaction between CM11 and tumor cell membranes. Both in vitro and in vivo results indicate that PNpC plays a significant role in killing tumor cells by triggering ICD. The ICD induced by the destruction of the cancer cell membrane is accompanied by the release of DAMPs, which promotes the maturation of DCs and facilitates the presentation of tumor-associated antigens (TAA), resulting in the infiltration of CD8+ T cells. We believe that PNpC can trigger ICD while killing cancer cells, providing a new reference for cancer immunotherapy.

Molecularly Stimuli-Responsive Self-Assembled Peptide Nanoparticles for Targeted Imaging and Therapy

Self-assembly has emerged as an extensively used method for constructing biomaterials with sizes ranging from nanometers to micrometers. Peptides have been extensively investigated for self-assembly. They are widely applied owing to their desirable biocompatibility, biodegradability, and tunable architecture. The development of peptide-based nanoparticles often requires complex synthetic processes involving chemical modification and supramolecular self-assembly. Stimuli-responsive peptide nanoparticles, also termed "smart" nanoparticles, capable of conformational and chemical changes in response to stimuli, have emerged as a class of promising materials. These smart nanoparticles find a diverse range of biomedical applications, including drug delivery, diagnostics, and biosensors. Stimuli-responsive systems include external stimuli (such as light, temperature, ultrasound, and magnetic fields) and internal stimuli (such as pH, redox environment, salt concentration, and biomarkers), facilitating the generation of a library of self-assembled biomaterials for biomedical imaging and therapy. Thus, in this review, we mainly focus on peptide-based nanoparticles built by self-assembly strategy and systematically discuss their mechanisms in response to various stimuli. Furthermore, we summarize the diverse range of biomedical applications of peptide-based nanomaterials, including diagnosis and therapy, to demonstrate their potential for medical translation.

Peptide Self-Assembled Nanocarriers for Cancer Drug Delivery

The design of novel cancer drug nanocarriers is critical in the framework of cancer therapeutics. Nanomaterials are gaining increased interest as cancer drug delivery systems. Self-assembling peptides constitute an emerging novel class of highly attractive nanomaterials with highly promising applications in drug delivery, as they can be used to facilitate drug release and/or stability while reducing side effects. Here, we provide a perspective on peptide self-assembled nanocarriers for cancer drug delivery and highlight the aspects of metal coordination, structure stabilization, and cyclization, as well as minimalism. We review particular challenges in nanomedicine design criteria and, finally, provide future perspectives on addressing a portion of the challenges via self-assembling peptide systems. We consider that the intrinsic advantages of such systems, along with the increasing progress in computational and experimental approaches for their study and design, could possibly lead to novel classes of single or multicomponent systems incorporating such materials for cancer drug delivery.

Self-Assembly, Bioactivity, and Nanomaterials Applications of Peptide Conjugates with Bulky Aromatic Terminal Groups

The self-assembly and structural and functional properties of peptide conjugates containing bulky terminal aromatic substituents are reviewed with a particular focus on bioactivity. Terminal moieties include Fmoc [fluorenylmethyloxycarbonyl], naphthalene, pyrene, naproxen, diimides of naphthalene or pyrene, and others. These provide a driving force for self-assembly due to π-stacking and hydrophobic interactions, in addition to the hydrogen bonding, electrostatic, and other forces between short peptides. The balance of these interactions leads to a propensity to self-assembly, even for conjugates to single amino acids. The hybrid molecules often form hydrogels built from a network of β-sheet fibrils. The properties of these as biomaterials to support cell culture, or in the development of molecules that can assemble in cells (in response to cellular enzymes, or otherwise) with a range of fascinating bioactivities such as anticancer or antimicrobial activity, are highlighted. In addition, applications of hydrogels as slow-release drug delivery systems and in catalysis and other applications are discussed. The aromatic nature of the substituents also provides a diversity of interesting optoelectronic properties that have been demonstrated in the literature, and an overview of this is also provided. Also discussed are coassembly and enzyme-instructed self-assembly which enable precise tuning and (stimulus-responsive) functionalization of peptide nanostructures.

Cancer-Responsive Multifunctional Nanoplatform Based on Peptide Self-Assembly for Highly Efficient Combined Cancer Therapy by Alleviating Hypoxia and Improving the Immunosuppressive Microenvironment

Hypoxia, as a main feature of the tumor microenvironment, has greatly limited the efficacy of photodynamic therapy (PDT), as well as its clinical application. Here, a multifunctional composite nanoplatform, the peptide/Ce6/MnO₂ nanocomposite (RKCM), has been constructed to alleviate tumor hypoxia and increase the efficacy of PDT using rationally designed peptide fibrils to encapsulate chlorin e6 (Ce6) inside and to mineralize MnO₂ nanoparticles on the surface. As a result, RKCM significantly improved the PDT efficacy by increasing reactive oxygen species (ROS) generation, decreasing tumor cell viability, and inhibiting tumor growth and metastasis. Besides, decreased HIF-1α expression and increased immune-activated cell infiltration were also observed in RKCM/laser treatment xenograft. Mechanically, (1) Ce6 can induce singlet oxygen (¹O₂) generation under laser irradiation to give photodynamic therapy (PDT); (2) MnO₂ can react with H₂O₂ in situ to supply additional O₂ to alleviate tumor hypoxia; and (3) the released Mn²⁺ ions can induce a Fenton-like reaction to generate ^•OH for chemical dynamic therapy (CDT). Moreover, RKCM/laser treatment also presented with an abscopal effect to block the occurrence of lung metastasis by remolding the pre-metastasis immune microenvironment. With these several aspects working together, the peptide/Ce6/MnO₂ nanoplatform can achieve highly efficient tumor therapy. Such a strategy based on peptide self-assembly provides a promising way to rationally design a cancer-responsive multifunctional nanoplatform for highly efficient combined cancer therapy by alleviating hypoxia and improving the immune microenvironment.

Intracellular Enzyme-Instructed Self-Assembly of Peptides (IEISAP) for Biomedical Applications

Despite the remarkable significance and encouraging breakthroughs of intracellular enzyme-instructed self-assembly of peptides (IEISAP) in disease diagnosis and treatment, a comprehensive review that focuses on this topic is still desirable. In this article, we carefully review the advances in the applications of IEISAP, including the development of various bioimaging techniques, such as fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, positron-emission tomography imaging, radiation imaging, and multimodal imaging, which are successfully leveraged in visualizing cancer tissues and cells, bacteria, and enzyme activity. We also summarize the utilization of IEISAP in disease treatments, including anticancer, antibacterial, and antiinflammation applications, among others. We present the design, action modes, structures, properties, functions, and performance of IEISAP materials, such as nanofibers, nanoparticles, nanoaggregates, and hydrogels. Finally, we conclude with an outlook towards future developments of IEISAP materials for biomedical applications. It is believed that this review may foster the future development of IEISAP with better performance in the biomedical field.

In Situ Synthesis of an Anticancer Peptide Amphiphile Using Tyrosine Kinase Overexpressed in Cancer Cells

Cell-selective killing using molecular self-assemblies is an emerging concept for cancer therapy. Reported molecular self-assemblies are triggered by hydrolysis of well-designed molecules inside or outside cancer cells. This hydrolysis can occur in cancer and normal cells because of the abundance of water in living systems. Here, we report the in situ synthesis of a self-assembling molecule using a tyrosine kinase overexpressed in cancer cells. We designed a tyrosine-containing peptide amphiphile (C16-E4Y) that is transformed into a phosphorylated peptide amphiphile (C16-E4pY) by the overexpressed tyrosine kinase. Phosphorylation of C16-E4Y promoted self-assembly to form nanofibers in cancer cells. C16-E4Y exhibited selective cytotoxicity toward cancer cells overexpressing the tyrosine kinase. Self-assembled C16-E4pY induced endoplasmic reticulum stress that caused apoptotic cell death. Animal experiments revealed that C16-E4Y has antitumor activity. These results show that an enzyme overexpressed in cancer cells is available for intracellular synthesis of an antitumor self-assembling drug that is cell-selective.

Self-assembly hydrogels of therapeutic agents for local drug delivery

Advanced drug delivery systems are of vital importance to enhance therapeutic efficacy. Among various recently developed formulations, self-assembling hydrogels composed of therapeutic agents have shown promising potential for local drug delivery owing to their excellent biocompatibility, high drug-loading efficiency, low systemic toxicity, and sustained drug release behavior. In particular, therapeutic agents self-assembling hydrogels with well-defined nanostructures are beneficial for direct delivery to the target site via injection, not only improving drug availability, but also extending their retention time and promoting cellular uptake. In brief, the self-assembly approach offers better opportunities to improve the precision of pharmaceutical treatment and achieve superior treatment efficacies. In this review, we intend to cover the recent developments in therapeutic agent self-assembling hydrogels. First, the molecular structures, self-assembly mechanisms, and application of self-assembling hydrogels are systematically outlined. Then, we summarize the various self-assembly strategies, including the single therapeutic agent, metal-coordination, enzyme-instruction, and co-assembly of multiple therapeutic agents. Finally, the potential challenges and future perspectives are discussed. We hope that this review will provide useful insights into the design and preparation of therapeutic agent self-assembling hydrogels.

Protease-Responsive Peptide-Conjugated Mitochondrial-Targeting AIEgens for Selective Imaging and Inhibition of SARS-CoV-2-Infected Cells

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a serious threat to human health and lacks an effective treatment. There is an urgent need for both real-time tracking and precise treatment of the SARS-CoV-2-infected cells to mitigate and ultimately prevent viral transmission. However, selective triggering and tracking of the therapeutic process in the infected cells remains challenging. Here, we report a main protease (Mpro)-responsive, mitochondrial-targeting, and modular-peptide-conjugated probe (PSGMR) for selective imaging and inhibition of SARS-CoV-2-infected cells via enzyme-instructed self-assembly and aggregation-induced emission (AIE) effect. The amphiphilic PSGMR was constructed with tunable structure and responsive efficiency and validated with recombinant proteins, cells transfected with Mpro plasmid or infected by SARS-CoV-2, and a Mpro inhibitor. By rational construction of AIE luminogen (AIEgen) with modular peptides and Mpro, we verified that the cleavage of PSGMR yielded gradual aggregation with bright fluorescence and enhanced cytotoxicity to induce mitochondrial interference of the infected cells. This strategy may have value for selective detection and treatment of SARS-CoV-2-infected cells.

Intracellular Crowding by Bio-Orthogonal Hydrogel Formation Induces Reversible Molecular Stasis

To survive extreme conditions, certain animals enter a reversible protective stasis through vitrification of the cytosol by polymeric molecules such as proteins and polysaccharides. In this work, synthetic gelation of the cytosol in living cells is used to induce reversible molecular stasis. Through the sequential lipofectamine-mediated transfection of complementary poly(ethylene glycol) macromers into mammalian cells, intracellular crosslinking occurs through bio-orthogonal strain-promoted azide-alkyne cycloaddition click reactions. This achieves efficient polymer uptake with minimal cell death (99% viable). Intracellular crosslinking decreases DNA replication and protein synthesis, and increases the quiescent population by 2.5-fold. Real-time tracking of single cells containing intracellular crosslinked polymers identifies increases in intermitotic time (15 h vs 19 h) and decreases in motility (30 µm h-1  vs 15 µm h-1 ). The cytosol viscosity increases threefold after intracellular crosslinking and results in disordered cytoskeletal structure in addition to the disruption of cellular coordination in a scratch assay. By incorporating photodegradable nitrobenzyl moieties into the polymer backbone, the effects of intracellular crosslinking are reversed upon exposure to light, thereby restoring proliferation (80% phospho-Rb+ cells), protein translation, and migration. Reversible intracellular crosslinking provides a novel method for dynamic manipulation of intracellular mechanics, altering essential processes that determine cellular function.

Constructing ECM-like Structure on the Plasma Membrane via Peptide Assembly to Regulate the Cellular Response

This feature article introduces the design of self-assembling peptides that serve as the basic building blocks for the construction of extracellular matrix (ECM)-like structure in the vicinity of the plasma membrane. By covalently conjugating a bioactive motif, such as membrane protein binding ligand or enzymatic responsive building block, with a self-assembling motif, especially the aromatic peptide, a self-assembling peptide that retains bioactivity is obtained. Instructed by the target membrane protein or enzyme, the bioactive peptides self-assemble into ECM-like structure exerting various stimuli to regulate the cellular response via intracellular signaling, especially mechanotransduction. By briefly summarizing the properties and applications (e.g., wound healing, controlling cell motility and cell fate) of these peptides, we intend to illustrate the basic requirements and promises of the peptide assembly as a true bottom-up approach in the construction of artificial ECM.

Supramolecular nanomedicines through rational design of self-assembling prodrugs

Advancements in the development of nanomaterials have led to the creation of a plethora of functional constructs as drug delivery vehicles to address many dire medical needs. The emerging prodrug strategy provides an alternative solution to create nanomedicines of extreme simplicity by directly using the therapeutic agents as molecular building blocks. This Review outlines different prodrug-based drug delivery systems, highlights the advantages of the prodrug strategy for therapeutic delivery, and demonstrates how combinations of different functionalities - such as stimuli responsiveness, targeting propensity, and multidrug conjugation - can be incorporated into designed prodrug delivery systems. Furthermore, we discuss the opportunities and challenges facing this rapidly growing field.

Strategies of engineering nanomedicines for tumor retention

The retention of therapeutic agents in solid tumors at sufficient concentration and duration is crucial for their antitumor effects. Given the important contribution of nanomedicines to oncology, we herein summarized two major strategies of nanomedicines for tumor retention, such as transformation- and interactions-mediated strategies. The transformation-mediated retention strategy was achieved by enlarging particle size of nanomedicines or modulating the morphology into fibrous structures, while the interactions-mediated retention strategy was accomplished by modulating nanomedicines to promote their interactions with versatile cells or components in tumors. Moreover, we provide some considerations and perspectives of tumor-retaining nanomedicines for effective cancer therapy.

Biomimetic Heterodimerization of Tetrapeptides to Generate Liquid Crystalline Hydrogel in A Two-Component System

Anisotropic structures made by hierarchical self-assembly and crystallization play an essential role in the living system. However, the spontaneous formation of liquid crystalline hydrogel of low molecular weight organic molecules with controlled properties remains challenging. This work describes a rational design of tetrapeptide without N-terminal modification and chemical conjugation that utilizes intermolecular interactions to drive the formation of nanofiber bundles in a two-component system, which could not be accessed by a single component. The diameter of nanofibers can be simply controlled by varying the enantiomer of electrostatic pairs. Mutation of lysine (K) to arginine (R) results in an over 30-fold increase of mechanical property. Mechanistic studies using different techniques unravel the mechanism of self-assembly and formation of anisotropic liquid crystalline domains. All-atom molecular dynamics simulations reveal that the mixture of heterochiral peptides self-assembles into a nanofiber with a larger width compared to the homochiral assemblies due to the different stacking pattern and intermolecular interactions. The intermolecular interactions show an obvious increase by substituting the K with R, facilitating a more stable assembly and further altering the assembly mechanics and bulk material properties. Moreover, we also demonstrated that the hydrogel properties can be easily controlled by incorporating a light-responsive group. This work provides a method to generate the liquid crystalline hydrogel from isotropic monomers.

Enzymatic noncovalent synthesis of peptide assemblies generates multimolecular crowding in cells for biomedical applications

Enzymatic noncovalent synthesis enables the spatiotemporal control of multimolecular crowding in cells, thus offering a unique opportunity for modulating cellular functions. This article introduces some representative enzymes and molecular building blocks for generating peptide assemblies as multimolecular crowding in cells, highlights the relevant biomedical applications, such as anticancer therapy, molecular imaging, trafficking proteins, genetic engineering, artificial intracellular filaments, cell morphogenesis, and antibacterial, and briefly discusses the promises of ENS as a multistep molecular process in biology and medicine.

Dynamic supramolecular self-assembly of platinum(ii) complexes perturbs an autophagy-lysosomal system and triggers cancer cell death

Self-assembly of platinum(ii) complexes to form supramolecular structures/nanostructures due to intermolecular ligand π-π stacking and metal-ligand dispersive interactions is widely used to develop functional molecular materials, but the application of such non-covalent molecular interactions has scarcely been explored in medical science. Herein is described the unprecedented biological properties of platinum(ii) complexes relevant to induction of cancer cell death via manifesting such intermolecular interactions. With conjugation of a glucose moiety to the planar platinum(ii) terpyridyl scaffold, the water-soluble complex [Pt(tpy)(C[triple bond, length as m-dash]CArOGlu)](CF₃SO₃) (1a, tpy = 2,2':6',2''-terpyridine, Glu = glucose) is able to self-assemble into about 100 nm nanoparticles in physiological medium, be taken up by lung cancer cells via energy-dependent endocytosis, and eventually transform into other superstructures distributed in endosomal/lysosomal and mitochondrial compartments apparently following cleavage of the glycosidic linkage. Accompanying the formation of platinum-containing superstructures are increased autophagic vacuole formation, lysosomal membrane permeabilization, and mitochondrial membrane depolarization, as well as anti-tumor activity of 1a in a mouse xenograft model. These findings highlight the dynamic, multi-stage extracellular and intracellular supramolecular self-assembly of planar platinum(ii) complexes driven by modular intermolecular interactions with potential anti-cancer application.

Recent advances in peptide-based nanomaterials for targeting hypoxia

Hypoxia is a prominent feature of many severe diseases such as malignant tumors, ischemic strokes, and rheumatoid arthritis. The lack of oxygen has a paramount impact on angiogenesis, invasion, metastasis, and chemotherapy resistance. The potential of hypoxia as a therapeutic target has been increasingly recognized over the last decade. In order to treat these disease states, peptides have been extensively investigated due to their advantages in safety, target specificity, and tumor penetrability. Peptides can overcome difficulties such as low drug/energy delivery efficiency, hypoxia-induced drug resistance, and tumor nonspecificity. There are three main strategies for targeting hypoxia through peptide-based nanomaterials: (i) using peptide ligands to target cellular environments unique to hypoxic conditions, such as cell surface receptors that are upregulated in cells under hypoxic conditions, (ii) utilizing peptide linkers sensitive to the hypoxic microenvironment that can be cleaved to release therapeutic or diagnostic payloads, and (iii) a combination of the above where targeting peptides will localize the system to a hypoxic environment for it to be selectively cleaved to release its payload, forming a dual-targeting system. This review focuses on recent developments in the design and construction of novel peptide-based hypoxia-targeting nanomaterials, followed by their mechanisms and potential applications in diagnosis and treatment of hypoxic diseases. In addition, we address challenges and prospects of how peptide-based hypoxia-targeting nanomaterials can achieve a wider range of clinical applications.

Spatiotemporal Control over Chemical Assembly in Living Cells by Integration of Acid-Catalyzed Hydrolysis and Enzymatic Reactions

Spatiotemporal control of chemical assembly in living cells remains challenging. We have now developed an efficient and general platform to precisely control the formation of assemblies in living cells. We introduced an O-[bis(dimethylamino)phosphono]tyrosine protection strategy in the self-assembly motif as the Trojan horse, whereby the programmed precursors resist hydrolysis by phosphatases on and inside cells because the unmasking of the enzymatic cleavage site occurs selectively in the acidic environment of lysosomes. After demonstrating the multistage self-assembly processes in vitro by liquid chromatography/mass spectrometry (LC-MS), cryogenic electron microscopy (Cryo-EM), and circular dichroism (CD), we investigated the formation of site-specific self-assembly in living cells using confocal laser scanning microscopy (CLSM), LC-MS, and biological electron microscopy (Bio-EM). Controlling chemical assembly in living systems spatiotemporally may have applications in supramolecular chemistry, materials science, synthetic biology, and chemical biology.