Enzyme-Instructed Peptide Assemblies Selectively Inhibit Bone Tumors

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.

Recent progress in quantitative analysis of self-assembled peptides

Self-assembled peptides have been among the important biomaterials due to its excellent biocompatibility and diverse functions. Over the past decades, substantial progress and breakthroughs have been made in designing self-assembled peptides with multifaceted biomedical applications. The techniques for quantitative analysis, including imaging-based quantitative techniques, chromatographic technique and computational approach (molecular dynamics simulation), are becoming powerful tools for exploring the structure, properties, biomedical applications, and even supramolecular assembly processes of self-assembled peptides. However, a comprehensive review concerning these quantitative techniques remains scarce. In this review, recent progress in techniques for quantitative investigation of biostability, cellular uptake, biodistribution, self-assembly behaviors of self-assembled peptide etc., are summarized. Specific applications and roles of these techniques are highlighted in detail. Finally, challenges and outlook in this field are concluded. It is believed that this review will provide technical guidance for researchers in the field of peptide-based materials and pharmaceuticals, and facilitate related research for newcomers in this field.

Microfluidic-Assisted Self-Assembly of Molecular Hydrogelator at Water-Water Interfaces for Continuous Fabrication of Supramolecular Microcapsules

Control over the self-assembly of small molecules at specific areas is of great interest for many high-tech applications, yet remains a formidable challenge. Here, how the self-assembly of hydrazone-based molecular hydrogelators can be specifically triggered at water-water interfaces for the continuous fabrication of supramolecular microcapsules by virtue of the microfluidic technique is demonstrated. The non-assembling hydrazide- and aldehyde-based hydrogelator precursors are distributed in two immiscible aqueous polymer solutions, respectively, through spontaneous phase separation. In the presence of catalysts, hydrazone-based hydrogelators rapidly form and self-assemble into hydrogel networks at the generated water-water interfaces. Relying on the microfluidic technique, microcapsules bearing a shell of supramolecular hydrogel are continuously produced. The obtained microcapsules can effectively load enzymes, enabling localized enzymatic growth of supramolecular fibrous supramolecular structures, reminiscent of the self-assembly of biological filaments within living cells. This work may contribute to the development of biomimetic supramolecular carriers for applications in biomedicine and fundamental research, for instance, the construction of protocells.

Smart Molecular Imaging and Theranostic Probes by Enzymatic Molecular In Situ Self-Assembly

Enzymatic molecular in situ self-assembly (E-MISA) that enables the synthesis of high-order nanostructures from synthetic small molecules inside a living subject has emerged as a promising strategy for molecular imaging and theranostics. This strategy leverages the catalytic activity of an enzyme to trigger probe substrate conversion and assembly in situ, permitting prolonging retention and congregating many molecules of probes in the targeted cells or tissues. Enhanced imaging signals or therapeutic functions can be achieved by responding to a specific enzyme. This E-MISA strategy has been successfully applied for the development of enzyme-activated smart molecular imaging or theranostic probes for in vivo applications. In this Perspective, we discuss the general principle of controlling in situ self-assembly of synthetic small molecules by an enzyme and then discuss the applications for the construction of "smart" imaging and theranostic probes against cancers and bacteria. Finally, we discuss the current challenges and perspectives in utilizing the E-MISA strategy for disease diagnoses and therapies, particularly for clinical translation.

An in-situ peptide-antibody self-assembly to block CD47 and CD24 signaling enhances macrophage-mediated phagocytosis and anti-tumor immune responses

Targeted immunomodulation for reactivating innate cells, especially macrophages, holds great promise to complement current adaptive immunotherapy. Nevertheless, there is still a lack of high-performance therapeutics for blocking macrophage phagocytosis checkpoint inhibitors in solid tumors. Herein, a peptide-antibody combo-supramolecular in situ assembled CD47 and CD24 bi-target inhibitor (PAC-SABI) is described, which undergoes biomimetic surface propagation on cancer cell membranes through ligand-receptor binding and enzyme-triggered reactions. By simultaneously blocking CD47 and CD24 signaling, PAC-SABI enhances the phagocytic ability of macrophages in vitro and in vivo, promoting anti-tumor responses in breast and pancreatic cancer mouse models. Moreover, building on the foundation of PAC-SABI-induced macrophage repolarization and increased CD8+ T cell tumor infiltration, sequential anti-PD-1 therapy further suppresses 4T1 tumor progression, prolonging survival rate. The in vivo construction of PAC-SABI-based nano-architectonics provides an efficient platform for bridging innate and adaptive immunity to maximize therapeutic potency.

Enzymatic control of intermolecular interactions for generating synthetic nanoarchitectures in cellular environment

Nanoarchitectonics, as a technology to arrange nano-sized structural units such as molecules in a desired configuration, requires nano-organization, which usually relies on intermolecular interactions. This review briefly introduces the development of using enzymatic reactions to control intermolecular interactions for generating artificial nanoarchitectures in a cellular environment. We begin the discussion with the early examples and uniqueness of enzymatically controlled self-assembly. Then, we describe examples of generating intracellular nanostructures and their relevant applications. Subsequently, we discuss cases of forming nanostructures on the cell surface via enzymatic reactions. Following that, we highlight the use of enzymatic reactions for creating intercellular nanostructures. Finally, we provide a summary and outlook on the promises and future direction of this strategy. Our aim is to give an updated introduction to the use of enzymatic reaction in regulating intermolecular interactions, a phenomenon ubiquitous in biology but relatively less explored by chemists and materials scientists. Our goal is to stimulate new developments in this simple and versatile approach for addressing societal needs.

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.

Accelerating Cellular Uptake with Unnatural Amino Acid for Inhibiting Immunosuppressive Cancer Cells

Targeting immunosuppressive metastatic cancer cells is a key challenge in therapy. We recently have shown that a rigid-rod aromatic, pBP-NBD, that responds to enzymes and kill immunosuppressive metastatic osteosarcoma (mOS) and castration resistant prostate cancer (CRPC) cells in mimetic bone microenvironment. However, pBP-NBD demonstrated moderate efficacy against CRPC cells. To enhance activity, we incorporated the unnatural amino acid L- or D-4,4'-biphenylalanine (L- or D-BiP) into pBP-NBD, drastically increasing cellular uptake and CRPC inhibition. Specifically, we inserted BiP into pBP-NBD to target mOS (Saos2 and SJSA1) and CRPC (VCaP and PC3) cells with overexpressed phosphatases. Our results show that the D-peptide backbone with an aspartate methyl diester at the C-terminal offers the highest activity against these immunosuppressive mOS and CRPC cells. Importantly, imaging shows that the peptide assemblies almost instantly enter the cells and accumulate primarily within the endoplasmic reticulum of Saos2, SJSA1, and PC3 cells and at the lysosomes of VCaP cells. By using BiP to boost cellular uptake and self-assembly within cancer cells, this work illustrates an unnatural hydrophobic amino acid as a versatile and effective residue to boost endocytosis of synthetic peptides for intracellular self-assembly.

Immunomodulatory Peptides for Tumor Treatment

Peptides exhibit various biological activities, including biorecognition, cell targeting, and tumor penetration, and can stimulate immune cells to elicit immune responses for tumor immunotherapy. Peptide self-assemblies and peptide-functionalized nanocarriers can reduce the effect of various biological barriers and the degradation by peptidases, enhancing the efficiency of peptide delivery and improving antitumor immune responses. To date, the design and development of peptides with various functionalities have been extensively reviewed for enhanced chemotherapy; however, peptide-mediated tumor immunotherapy using peptides acting on different immune cells, to the knowledge, has not yet been summarized. Thus, this work provides a review of this emerging subject of research, focusing on immunomodulatory anticancer peptides. This review introduces the role of peptides in the immunomodulation of innate and adaptive immune cells, followed by a link between peptides in the innate and adaptive immune systems. The peptides are discussed in detail, following a classification according to their effects on different innate and adaptive immune cells, as well as immune checkpoints. Subsequently, two delivery strategies for peptides as drugs are presented: peptide self-assemblies and peptide-functionalized nanocarriers. The concluding remarks regarding the challenges and potential solutions of peptides for tumor immunotherapy are presented.

Emerging potential approaches in alkaline phosphatase (ALP) activatable cancer theranostics

Alkaline phosphatase (ALP) is known as one of the most crucial members of the phosphatase family and encompasses the enormous ability to hydrolyze the phosphate group in various biomolecules; by this, it regulates several events in the pool of biological medium. Owing to its overexpression in various cancer cells, recently, its potential has evolved as a prominent biomarker in cancer research. In this article, we have underlined the recent advances (2019 onwards) of alkaline phosphatase in the arena of emerging cancer theranostics. Herein, we mainly focused on phosphate-locked molecular systems such as peptides, prodrugs, and aggregation-induced emission (AIE)-based molecules. When these theranostics encounter cancer cell-overexpressed ALP, it results in the hydrolysis of the phosphate group, which leads to the release of highly cytotoxic agents along with turn-on fluorophore/pre-existing fluorophore.

Enzyme-Directed and Organelle-Specific Sphere-to-Fiber Nanotransformation Enhances Photodynamic Therapy in Cancer Cells

Employing responsive nanoplatforms as carriers for photosensitizers represents an effective strategy to overcome the challenges associated with photodynamic therapy (PDT), including poor solubility, low bioavailability, and high systemic toxicity. Drawing inspiration from the morphology transitions in biological systems, a general approach to enhance PDT that utilizes enzyme-responsive nanoplatforms is developed. The transformation of phosphopeptide/photosensitizer co-assembled nanoparticles is first demonstrated into nanofibers when exposed to cytoplasmic enzyme alkaline phosphatase. This transition is primarily driven by alkaline phosphatase-induced changes of the nanoparticles in the hydrophilic and hydrophobic balance, and intermolecular electrostatic interactions within the nanoparticles. The resulting nanofibers exhibit improved ability of generating reactive oxygen species (ROS), intracellular accumulation, and retention in cancer cells. Furthermore, the enzyme-responsive nanoplatform is expanded to selectively target mitochondria by mitochondria-specific enzyme sirtuin 5 (SIRT5). Under the catalysis of SIRT5, the succinylated peptide/photosensitizer co-assembled nanoparticles can be transformed into nanofibers specifically within the mitochondria. The resulting nanofibers exhibit excellent capability of modulating mitochondrial activity, enhanced ROS formation, and significant anticancer efficacy via PDT. Consequently, the enzyme-instructed in situ fibrillar transformation of peptide/photosensitizers co-assembled nanoparticles provides an efficient pathway to address the challenges associated with photosensitizers. It is envisaged that this approach will further expand the toolbox for enzyme-responsive biomaterials for cancer therapy.

Self-assembly of peptide nanomaterials at biointerfaces: molecular design and biomedical applications

Self-assembly is an important strategy for constructing ordered structures and complex functions in nature. Based on this, people can imitate nature and artificially construct functional materials with novel structures through the supermolecular self-assembly pathway of biological interfaces. Among the many assembly units, peptide molecular self-assembly has received widespread attention in recent years. In this review, we introduce the interactions (hydrophobic interaction, hydrogen bond, and electrostatic interaction) between peptide nanomaterials and biological interfaces, summarizing the latest advancements in multifunctional self-assembling peptide materials. We systematically demonstrate the assembly mechanisms of peptides at biological interfaces, such as proteins and cell membranes, while highlighting their application potential and challenges in fields like drug delivery, antibacterial strategies, and cancer therapy.

Assessment of the Enzymatic Dephosphorylation Kinetics in the Assemblies of a Phosphopentapeptide that Forms Intranuclear Nanoribbons

Although the formation of peptide assemblies catalyzed by alkaline phosphatase (ALP) has received increasing attention in inhibiting cancer cells, the detailed enzyme kinetics of the dephosphorylation of the corresponding phosphopeptide assemblies have yet to be determined. We recently discovered that assemblies from a phosphopentapeptide can form intracellular nanoribbons that kill induced pluripotent stem cells or osteosarcoma cells, but the kinetics of enzymatic dephosphorylation remain unknown. Thus, we chose to examine the enzyme kinetics of the dephosphorylation of the phosphopentapeptide [NBD-LLLLpY (1)] from concentrations below to above its critical micelle concentration (CMC). Our results show that the phosphopeptide exhibits a CMC of 75 μM in phosphate saline buffer, and the apparent Vmax and Km values of alkaline phosphatase catalyzed dephosphorylation are approximately 0.24 μM/s and 5.67 mM, respectively. Despite dephosphorylation remaining incomplete at 60 min in all the concentrations tested, dephosphorylation of the phosphopeptide at concentrations of 200 μM or above mainly results in nanoribbons, dephosphorylation at concentrations of CMC largely produces nanofibers, and dephosphorylation below the CMC largely generates nanoparticles. Moreover, the formation of nanoribbons correlates with the intranuclear accumulation of the pentapeptide. By providing the first examination of the enzymatic kinetics of phosphopeptide assemblies, this work further supports the notion that the assemblies of phosphopentapeptides can act as a new functional entity for controlling cell fates.

Uncovering supramolecular chirality codes for the design of tunable biomaterials

In neurodegenerative diseases, polymorphism and supramolecular assembly of β-sheet amyloids are implicated in many different etiologies and may adopt either a left- or right-handed supramolecular chirality. Yet, the underlying principles of how sequence regulates supramolecular chirality remains unknown. Here, we characterize the sequence specificity of the central core of amyloid-β 42 and design derivatives which enable chirality inversion at biologically relevant temperatures. We further find that C-terminal modifications can tune the energy barrier of a left-to-right chiral inversion. Leveraging this design principle, we demonstrate how temperature-triggered chiral inversion of peptides hosting therapeutic payloads modulates the dosed release of an anticancer drug. These results suggest a generalizable approach for fine-tuning supramolecular chirality that can be applied in developing treatments to regulate amyloid morphology in neurodegeneration as well as in other disease states.

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.

Cascade In Situ Self-Assembly and Bioorthogonal Reaction Enable the Enrichment of Photosensitizers and Carbonic Anhydrase Inhibitors for Pretargeted Cancer Theranostics

We report here a tumor-pretargted theranostic approach for multimodality imaging-guided synergistic cancer PDT by cascade alkaline phosphatase (ALP)-mediated in situ self-assembly and bioorthogonal inverse electron demand Diels-Alder (IEDDA) reaction. Using the enzymatic catalysis of ALP that continuously catalyses the dephosphorylation and self-assembly of trans-cyclooctene (TCO)-bearing P-FFGd-TCO, a high density of fluorescent and magnetic TCO-containing nanoparticles (FMNPs-TCO) can be synthesized and retained on the membrane of tumor cells. They can act as 'artificial antigens' amenable to concurrently capture lately administrated tetrazine (Tz)-decorated PS (775NP-Tz) and carbonic anhydrase (CA) inhibitor (SA-Tz) via the fast IEDDA reaction. This two-step pretargeting process can further induce FMNPs-TCO regrowth into microparticles (FMNPs-775/SA) directly on tumor cell membranes, which is analyzed by bio-SEM and fluorescence imaging. Thus, efficient enrichment of both SA-Tz and 775NP-Tz in tumors can be achieved, allowing to alleviate hypoxia by continuously inhibiting CA activity and improving PDT of tumors. Findings show that subcutaneous HeLa tumors could be completely eradicated and no tumor recurred after irradiation with an 808 nm laser (0.33 W cm-2 , 10 min). This pretargeted approach may be applied to enrich other therapeutic agents in tumors to improve targeted therapy.

Facile Preparation of Carbohydrate-Containing Adjuvants Based on Self-Assembling Glycopeptide Conjugates

Carbohydrates are intriguing biomolecules possessing diverse biological activities, including immune stimulating capability. However, their biomedical applications have been limited by their complex and heterogeneous structures. In this study, we have utilized a self-assembling glycopeptide conjugate (GPC) system to produce uniform nanoribbons appending homogeneous oligosaccharides with multivalency. This system successfully translates the nontrivial structural differences of oligomannoses into varied binding affinities to C-type lectin receptors (CLRs). We have shown that GPCs could promote the CLR-mediated endocytosis of ovalbumin (OVA) antigen, and two mannotriose-modified peptides F3m2 and F3m5 exhibit potent activity in inducing antigen-presenting cell maturation, as indicated by increased CD86 and MHCII expression. In vivo studies demonstrated that GPCs, combined with OVA antigen, significantly enhanced OVA-specific antibody production. Specifically, F3m2 and F3m5 exhibited the highest immunostimulatory effects, eliciting both Th1- and Th2-biased immune responses and promoting differentiation of CD4+ and CD8+  T cells. These findings highlight the potential of GPCs as vaccine adjuvants, and showcase their versatility in exploiting the biological functions of carbohydrates.

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.

A Dual-Mechanism Targeted Bioorthogonal Prodrug Therapy

Bioorthogonal prodrug therapies offer an intriguing two-component system that features enhanced circulating stability and controlled activation on demand. Current strategies often deliver either the prodrug or its complementary activator to the tumor with a monomechanism targeted mechanism, which cannot achieve the desired antitumor efficacy and safety profile. The orchestration of two distinct and orthogonal mechanisms should overcome the hierarchical heterogeneity of solid tumors to improve the delivery efficiency of both components simultaneously for bio-orthogonal prodrug therapies. We herein developed a dual-mechanism targeted bioorthogonal prodrug therapy by integrating two orthogonal, receptor-independent tumor-targeting strategies. We first employed the endogenous albumin transport system to generate the in situ albumin-bound, bioorthogonal-caged doxorubicin prodrug with extended plasma circulation and selective accumulation at the tumor site. We then employed enzyme-instructed self-assembly (EISA) to specifically enrich the bioorthogonal activators within tumor cells. As each targeted delivery mode induced an intrinsic pharmacokinetic profile, further optimization of the administration sequence according to their pharmacokinetics allowed the spatiotemporally controlled prodrug activation on-target and on-demand. Taken together, by orchestrating two discrete and receptor-independent targeting strategies, we developed an all-small-molecule based bioorthogonal prodrug system for dual-mechanism targeted anticancer therapies to maximize therapeutic efficacy and minimize adverse drug reactions for chemotherapeutic agents.

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.

Stimuli-Responsive PROTACs for Controlled Protein Degradation

Proteolysis Targeting Chimeras (PROTACs) represent a promising therapeutic modality to address undruggable and resistant issues in drug discovery. However, potential on-target toxicity remains clinically challenging. We developed a generalized caging strategy to synthesize a series of stimuli-responsive PROTACs (sr-PROTACs) with diverse molecular blocks bearing robust and cleavable linkers, presenting "turn on" features in manipulating protein degradation. By leveraging pathological cues, such as elevated ROS, phosphatase, H2 S, or hypoxia, and external triggers, such as ultraviolet light, X-Ray, or bioorthogonal reagents, we achieved site-specific activation and traceless release of original PROTACs through de-caging and subsequent self-immolative cleavage, realizing selective uptake and controlled protein degradation in vitro. An in vivo study revealed that two sr-PROTACs with phosphate- and fluorine-containing cages exhibited high solubility and long plasma exposure, which were specifically activated by tumor overexpressing phosphatase or low dosage of X-Ray irradiation in situ, leading to efficient protein degradation and potent tumor remission. With more reactive biomarkers to be screened from clinical practice, our caging library could provide a general tool to design activatable PROTACs, prodrugs, antibody-drug conjugates, and smart biomaterials for personalized treatment, tissue engineering or regenerative medicine.

Hierarchical Assembly of Intrinsically Disordered Short Peptides

The understanding on how short peptide assemblies transit from disorder to order remains limited due to the lack of atomistic structures. Here we report cryo-EM structure of the nanofibers short intrinsically disordered peptides (IDPs). Upon lowering pH or adding calcium ions, the IDP transitions from individual nanoparticles to nanofibers containing an aromatic core and a disordered periphery comprised of 2 to 5 amino acids. Protonating the phosphate or adding more metal ions further assembles the nanofibers into filament bundles. The assemblies of the IDP analogs with controlled chemistry, such as phosphorylation site, hydrophobic interactions, and sequences indicate that metal ions interact with the flexible periphery of the nanoparticles of the IDPs to form fibrils and enhance the interfibrillar interactions to form filament bundles. Illustrating that an IDP self-assembles from disorder to order, this work offers atomistic molecular insights to understand assemblies of short peptides driven by noncovalent interactions.

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.

Evaluating Alkaline Phosphatase-Instructed Self-Assembly of d-Peptides for Selectively Inhibiting Ovarian Cancer Cells

Cancer is a major public health concern requiring novel treatment approaches. Enzyme-instructed self-assembly (EISA) provides a unique approach for selectively inhibiting cancer cells. However, the structure and activity correlation of EISA remains to be explored. This study investigates new EISA substrates of alkaline phosphatase (ALP) to hinder ovarian cancer cells. Analogues 2-8 were synthesized by modifying the amino acid residues of a potent EISA substrate 1 that effectively inhibits the growth of OVSAHO, a high-grade serous ovarian cancer (HGSOC) cell line. The efficacy of 2-8 against OVSAHO was assessed, along with the combination of substrate 1 with clinically used drugs. The results reveal that substrate 1 displays the highest cytotoxicity against OVSAHO cells, with an IC50 of around 8 μM. However, there was limited synergism observed between substrate 1 and the tested clinically used drugs. These findings indicate that EISA likely operates through a distinct mechanism that necessitates further elucidation.

A Cascade-Targeted Enzyme-Instructed Peptide Self-Assembly Strategy for Cancer Immunotherapy through Boosting Immunogenic Cell Death

Immunogenic cell death (ICD) approaches by encumbering mitochondrial functions provide great promise for the treatment of malignant tumors, but these kinds of ICD strategies are still in their infancy. Here, one multifunctional drug-loaded, cascade-targeted, and enzyme-instructed self-assembling peptide nanomedicine (Comp. 4) for ICD-based cancer therapy is constructed. Comp. 4 consists of 1) lonidamine (LND) that specifically interferes with mitochondrial functions; 2) a programmed death ligand 1 (PD-L1) binding peptide sequence (NTYYEDQG) and a mitochondria-specific motif (triphenylphosphonium, TPP) that can sequentially control the cell membrane and mitochondria targeting capacities, respectively; and 3) a -G^D F^D Fp^D Y- assembly core to in situ organize peptide assemblies responsive to alkaline phosphatase (ALP). Comp. 4 demonstrates noticeable structural and morphological transformations in the presence of ALP and produces peptide assemblies in mouse colon cancer cells (CT26) with high expressions of both ALP and PD-L1. Moreover, the presence of PD-L1- and mitochondria-specific motifs can assist Comp. 4 for effective endocytosis and endosomal escape, forming peptide assemblies and delivering LND into mitochondria. Consequently, Comp. 4 shows superior capacities to in vivo induce abundant mitochondrial oxidative stress, provoke robust ICD responses, and produce an immunogenic tumor microenvironment, successfully inhibiting CT26 tumor growth by eliciting a systemic ICD-based antitumor immunity.

Apoptosis-Amplified Assembly of Porphyrin Nanofiber Enhances Photodynamic Therapy of Oral Tumor

Oral squamous cell carcinoma (OSCC) is the most common oral cancer, having high recurrence and metastasis features. In addition to surgery, photodynamic therapy (PDT) is considered as another effective approach for OSCC treatment. The water solubility of currently available PDT photosensitizers (PSs) is poor, lowering their singlet oxygen (¹O₂) yield and consequent PDT efficiency. Strategies of PS assembly have been reported to increase ¹O₂ yield, but it is still possible to further enhance PDT efficiency. In this work, we utilized apoptosis to amplify the assembly of porphyrin nanofibers for enhanced PDT of OSCC. A water-soluble porphyrin derivative, Ac-Asp-Glu-Val-Asp-Asp-TPP (Ac-DEVDD-TPP), was designed for this purpose. Upon caspase-3 (Casp3, an activated enzyme during apoptosis) cleavage and laser irradiation, Ac-DEVDD-TPP was converted to D-TPP, which spontaneously self-assembled into porphyrin nanofibers, accompanied by 1.4-fold and 2.1-fold ¹O₂ generations in vitro and in cells, respectively. The as-formed porphyrin nanofiber induced efficient cell apoptosis and pyroptosis. In vivo experiments demonstrated that, compared with the scrambled control compound Ac-DEDVD-TPP, Ac-DEVDD-TPP led to 6.2-fold and 1.3-fold expressions of Casp3 in subcutaneous and orthotopic oral tumor models, respectively, and significantly suppressed the tumors. We envision that our strategy of apoptosis-amplified porphyrin assembly might be applied for OSCC treatment in the clinic in the near future.

The Recent Advance of Cell-Penetrating and Tumor-Targeting Peptides as Drug Delivery Systems Based on Tumor Microenvironment

Cancer has become the primary reason for industrial countries death. Although first-line treatments have achieved remarkable results in inhibiting tumors, they could have serious side effects because of insufficient selectivity. Therefore, specific localization of tumor cells is currently the main desire for cancer treatment. In recent years, cell-penetrating peptides (CPPs), as a kind of promising delivery vehicle, have attracted much attention because they mediate the high-efficiency import of large quantities of cargos in vivo and vitro. Unfortunately, the poor targeting of CPPs is still a barrier to their clinical application. In order to solve this problem, researchers use the various characteristics of tumor microenvironment and multiple receptors to improve the specificity toward tumors. This review focuses on the characteristics of the tumor microenvironment, and introduces the development of strategies and peptides based on these characteristics as drug delivery system in the tumor-targeted therapy.

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.

Enzymatic Nanosphere-to-Nanofiber Transition and Autophagy Inducer Release Promote Tumor Chemotherapy

Chemotherapy has remained an effective and predominant cancer treatment for the past decades, but is hampered by its low response rate and severe systemic toxicity. Combination chemotherapies are proposed to address these issues, yet their therapeutic outcomes are still far from satisfactory. Thus, it is urgent to develop novel strategies to promote tumor chemosensitivity while reducing toxic side effects of chemotherapeutics. Herein, employing a rationally designed peptide conjugate Nap-Phe-Phe-Lys(SA-AZD8055)-Tyr(H₂ PO₃ )-OH (Nap-AZD-Yp), a novel approach of simultaneous intracellular nanofiber formation and autophagy inducer release is proposed for selectively sensitizing tumor to chemotherapy. Upon sequential catalyses of alkaline phosphatase and carboxylesterase, Nap-AZD-Yp undergoes nanosphere-to-nanofiber transition accompanied by autophagy inducer AZD8055 release in cancer cells. Cell experiments show enhanced endocytosis of anticancer drug doxorubicin and inhibition of cell migration due to the intracellular nanofiber formation. The released AZD8055 further activates excessive autophagy of cancer cells, sensitizing them to chemotherapy. Animal experiment results suggest Nap-AZD-Yp can significantly enhance the therapeutic effects of doxorubicin on tumors while mitigate its toxic adverse effects on normal tissues. It is anticipated that the "smart" concept in this work c be widely employed to develop novel combinational therapies for the treatment of cancers and other diseases in near future.

Enzyme-instructed morphology transformation of mitochondria-targeting peptide for the selective eradication of osteosarcoma

The treatment of osteosarcoma involves an adjuvant therapy that combines surgery and chemotherapy. However, considering that children are the main victims of osteosarcoma, replacing such a harsh treatment with a soft but powerful method that ensures a complete cure while having no adverse effects is highly desirable. To achieve this aim, we have developed a supramolecular therapeutic strategy based on morphology-transformable mitochondria-targeting peptides for the eradication of osteosarcoma with enhanced selectivity and reduced side effects. A newly designed micelle-forming amphiphilic peptide, l-Mito-FFYp, consisting of a phosphate substrate for the biomarker enzyme of osteosarcoma alkaline phosphatase (ALP), disassembles in response to the ALP enzyme in the cell membrane to generate positively charged l-Mito-FFY molecules, which diffuse inside the targeted cell and self-assemble to form nanostructures specifically inside the mitochondria to induce cell apoptosis.

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.

Enzyme-manipulated hydrogelation of small molecules for biomedical applications

Enzyme-manipulated hydrogelation based on self-assembly of small molecules is an attractive methodology for development of functional biomaterials. Upon the catalysis of enzymes, small-molecular precursors are converted into assemblable building blocks, which arrange into high-ordered nanofibers via non-covalent interactions at the molecular level, and further trap water to form hydrogels at the macroscopic level. Such approach has numerous advantages of region- and enantioselectivity, and mild reaction conditions for encapsulation of biomedications or cells that are fragile to environmental change. In addition to the common applications as drug reservoirs or cell scaffolds, the utilization of endogenous enzymes as stimuli to initiate self-assembly in the living cells and tissue is considered as an intelligent spatiotemporally controllable hydrogelation strategy for biomedical applications. The enzyme-instructed in situ self-assembly and hydrogelation can modulate the cell behavior, and even present therapeutic bioactivities, which provides a new perspective in the field of disease treatment. In this review, we categorize distinct enzymatic stimuli and elaborate substrate design, catalytic characteristics, and mechanisms of self-assembly and hydrogelation. The biomedical applications in drug delivery, tissue engineering, bioimaging, and in situ gelation-produced bioactivity are outlined. Advantages and limitations regarding the state-of-the-art enzyme-driven hydrogelation technologies and future perspectives are also discussed. STATEMENT OF SIGNIFICANCE: Hydrogel is a semi-solid soft material containing a large amount of water. Due to the features of adjustable flexibility, extremely porous architecture, and the high similarity of structure to natural extracellular matrices, the hydrogel has broad application prospects in biomedicine. In recent 20 years, enzyme-manipulated hydrogelation based on self-assembly of small molecules has developed rapidly as an attractive methodology for the construction of functional biomaterials. Upon the catalysis of enzymes, small-molecular precursors are converted into assemblable building blocks, which arrange into high-ordered nanofibers via non-covalent interactions at the molecular level, and further trap water to form hydrogels at the macroscopic level. This review summarized the characteristics of enzymatic hydrogel, as well as the traditional application and emerging prospect of enzyme-instructed self-assembly and hydrogelation.

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.

Peptide nano-blanket impedes fibroblasts activation and subsequent formation of pre-metastatic niche

There is evidence to suggest that the primary tumor induces the formation of a pre-metastatic niche in distal organs by stimulating the production of pro-metastatic factors. Given the fundamental role of the pre-metastatic niche in the development of metastases, interruption of its formation would be a promising strategy to take early action against tumor metastasis. Here we report an enzyme-activated assembled peptide FR17 that can serve as a “flame-retarding blanket” in the pre-metastatic niche specifically to extinguish the “fire” of tumor-supportive microenvironment adaption. We show that the in-situ assembled peptide nano-blanket inhibits fibroblasts activation, suppressing the remodeling of the metastasis-supportive host stromal tissue, and reversing vascular destabilization and angiogenesis. Furthermore, we demonstrate that the nano-blanket prevents the recruitment of myeloid cells to the pre-metastatic niche, regulating the immune-suppressive microenvironment. We show that FR17 administration effectively inhibits the formation of the pulmonary pre-metastatic niche and postoperative metastasis, offering a therapeutic strategy against pre-metastatic niche formation.

Primary tumors “spread the spark” by establishing a pre-metastatic niche. Here the authors develop an in-situ assembled peptide FR17 to serve as a “flame-retarding blanket” to extinguish the “fire” of the pre-metastatic microenvironment.

Self-Assembled Peptide Habitats to Model Tumor Metastasis

Metastatic tumours are complex ecosystems; a community of multiple cell types, including cancerous cells, fibroblasts, and immune cells that exist within a supportive and specific microenvironment. The interplay of these cells, together with tissue specific chemical, structural and temporal signals within a three-dimensional (3D) habitat, direct tumour cell behavior, a subtlety that can be easily lost in 2D tissue culture. Here, we investigate a significantly improved tool, consisting of a novel matrix of functionally programmed peptide sequences, self-assembled into a scaffold to enable the growth and the migration of multicellular lung tumour spheroids, as proof-of-concept. This 3D functional model aims to mimic the biological, chemical, and contextual cues of an in vivo tumor more closely than a typically used, unstructured hydrogel, allowing spatial and temporal activity modelling. This approach shows promise as a cancer model, enhancing current understandings of how tumours progress and spread over time within their microenvironment.

Supramolecular Self-Assembly in Living Cells

Supramolecular interactions rely on non-covalent forces, such as hydrophobic effects, hydrogen-bonding, and electrostatic interactions, which govern many intracellular biological pathways. In cellulo supramolecular self-assembly is mainly based on host-guest interactions, changes in pH, enzymes, and polymerization-induced self-assembly to accurately induce various unnatural reactions without disturbing natural biological processes. This process can produce synthetic biocompatible macromolecules to control cell properties and regulate biological functions, such as cell proliferation and differentiation. This Minireview focuses on the latest reports in the field of in cellulo supramolecular self-assembly and anticipates future advances regarding its activation in response to internal and external stimuli, such as pH changes, reactive oxygen species, and enzymes, as well as external light illumination.

Intracellular Self-Assembly of Peptides to Induce Apoptosis against Drug-Resistant Melanoma

Biosynthesis has been a diverse toolbox to develop bioactive molecules and materials, especially for fabricating modified peptides and their assemblies induced by enzymes. Although desired chemical structures and nanoarchitectures have been achieved, the subsequent interferences of peptide assemblies with organelles and the cellular pathways still remain unsolved important challenges. Herein, we developed a new tripeptide, phenylalanine-phenylalanine-tyrosine (Phe-Phe-Tyr, or FFY), which can be intracellularly oxidized and in situ self-assemble into nanoparticles with excellent interference capability with microtubules and ultimately reverse the drug resistance of melanoma. With the catalysis of tyrosinase, FFY was first oxidized to a melanin-like FFY dimer (mFFY) with a diquinone structure for further self-assembling into mFFY assemblies, which could inhibit the self-polymerization of tubulin to induce severe G2/M arrest (13.9% higher than control). Afterward, mitochondrial dysfunction was also induced for overproduction of cleaved caspase 3 (3.1 times higher than control) and cleaved PARP (6.3 times higher), achieving a high level of resistant reversing without chemotherapeutic drugs. In vivo studies showed that the resistant melanoma tumor volumes were reduced by 87.4% compared to control groups after FFY treatment by peritumoral injections. Overall, this tyrosinase-induced tripeptide assembly has been demonstrated with effective intrinsic apoptosis against drug-resistant melanoma, providing a new insight into utilizing biomolecules to interfere with organelles to activate certain apoptosis pathways for treatment of drug-resistant cancer.

Ca2+ accelerates peptide fibrillogenesis via a heterogeneous secondary nucleation pathway

A binding-induced fibrillogenesis (BIF) peptide mimics the fibrillogenesis of fibronectin, forming fibrous networks for disease theranostics. However, the mechanism of fast fibrillogenesis of the BIF peptide remains unclear. In this study, the fibrillogenesis processes of the BIF peptide in the absence and presence of receptors, i.e. Ca²⁺, are carefully studied. The BIF peptide, lauric acid-FFVLK-HSDVHK (LAFH) can self-assemble into nanoparticles (NPs) in solution and further transform into a fibrous structure, the fibrillogenesis of which could be accelerated by the addition of Ca²⁺. In detail, the fibrillogenesis of LAFH NPs without Ca²⁺ is achieved through a nucleation-elongation mechanism, in which homogeneous secondary nucleation is involved, followed by detachment of the newly formed fibers from pre-formed nanofibers (NFs). The fibrillogenesis of LAFH NPs in the presence of Ca²⁺ starts with an Ostwald ripening process, followed by a heterogeneous secondary nucleation, in which LAFH NPs bind to pre-formed LAFH NFs via Ca²⁺. The phenomenon of heterogeneous secondary nucleation including the attachment and shape change of LAFH NPs on pre-formed LAFH NFs is first revealed by TEM observation. These findings contribute to the understanding of the fast BIF process, supporting the mechanism study at the cellular level.

Enzyme-Instructed Self-Assembly of Peptides: From Concept to Representative Applications

Enzyme-instructed self-assembly, integrating enzymatic reaction and molecular self-assembly, has drawn noticeable attention over the last decade with the intension of being used in valuable applications. Recent advances in the field allow it possible to spatiotemporally control peptide self-assembly in cellular milieu, broadening the potential applications of peptide assemblies to cancer therapy and subcellular delivery. In this minireview, the concept of enzyme-instructed self-assembly of peptide, containing enzymatic trigger and spatiotemporal control, is described. Representative applications in cells are also discussed, followed by outlook on the field of enzyme-instructed self-assembly.

Supramolecular Nanomedicines of In-Situ Self-Assembling Peptides

Nanomedicines provide distinct clinical advantages over traditional monomolecular therapeutic and diagnostic agents. Supramolecular nanomedicines made from in-situ self-assembling peptides have emerged as a promising strategy in designing and fabricating nanomedicines. In-situ self-assambly (SA) allows the combination of nanomedicines approach with prodrug approach, which exhibited both advantages of these strategies while addressed the problems of both and thus receiving more and more research attention. In this review, we summarized recently designed supramolecular nanomedicines of in-situ SA peptides in the manner of applications and design principles, and the interaction between the materials and biological environments was also discussed.

Synthesis and bioactivity of pyrrole-conjugated phosphopeptides

Here we report the synthesis and effect on the cell viability of pyrrole-conjugated phosphopeptides. Encouraged by the selective inhibition of cancer cells by a naphthyl-capped phosphopeptide (Nap-ffpy, 1), we conjugated the heteroaromatic dipyrrole or tripyrrole motif at the N-terminal of short peptides containing phosphotyrosine or phosphoserine and examined the bioactivity of the resulting phosphopeptides (2-10). Although most of the phosphopeptides exhibit comparable activities with that of 1 against HeLa cells at 200 μM, they, differing from 1, are largely compatible with HeLa cells at 400 μM. Enzymatic dephosphorylation of 2-10, at 400 μM is unable to induce a dramatic morphological transition of the peptide assemblies observed in the case of 1. These results suggest that a heteroaromatic motif at the N-terminal of peptides likely disfavors the formation of extensive nanofibers or morphological changes during enzymatic self-assembly, thus provide useful insights for the development of phosphopeptides as substrates of phosphatases for controlling cell fate.

Research progress on self-assembled nanodrug delivery systems

In recent years, nanodrug delivery systems have attracted increasing attention due to their advantages, such as the high drug loading, low toxicity and side effects, improved bioavailability, long half-life, well...

Microbial Lipopeptide Supramolecular Self-Assemblies as a Methuosis-Like Cell Death Inducer with In Vivo Antitumor Activity

Discovering new drugs and improving action mechanisms is a promising strategy to overcome chemotherapy ineffectiveness caused by cancer cell apoptosis resistance. Natural products (like cyclic lipopeptides, CLPs) are potential sources of nonapoptotic cell death inducers and can form diverse supramolecular structures, closely relating to their bioactivities. Herein, it is found for the first time that fatty chain is the key to maintain self-assembled form and antitumor activity of microbial-derived amphiphilic CLP bacillomycin Lb (B-Lb). Compared with B-Lb analogues assemblies without antitumor activity, B-Lb supramolecular self-assemblies (including nanomicelles, nanofibers, giant micrometer rods) can be generated in a multilevel and cross-scale manner and served as a methuosis-like cell death inducer triggered by cytoplasmic vacuolation through macropinocytosis in MDA-MB-231-Luc and MCF-7 cells and in vivo tumor-bearing mice. This study will promote constructing of customized CLP micro-/nanostructures with multipurposes and functions, and boost designing of new antitumor drugs as nonapoptotic cell death modulators based on structure-activity relationship.

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.

Molecular engineering of organic-based agents for in situ bioimaging and phototherapeutics

In situ monitoring of the location and transportation of bioactive molecules is essential for deciphering diverse biological events in the field of biomedicine. In addition, obtaining the in situ information of lesions will provide a clear perspective for surgeons to perform precise resection in clinical surgery. Notably, delivering drugs or operating photodynamic therapy/photothermal therapy in situ by labeling the lesion regions of interest can improve treatment and reduce side effects in vivo. In various advanced imaging and therapy modalities, optical theranostic agents based on organic small molecules can be conveniently modified as needed and can be easily internalized into cells/lesions in a non-invasive manner, which are prerequisites for in situ bioimaging and precision treatment. In this tutorial review, we first summarize the in situ molecular immobilization strategies to retain small-molecule agents inside cells/lesions to prevent their diffusion in living organisms. Emphasis will be focused on introducing the application of these strategies for in situ imaging of biomolecules and precision treatment, particularly pertaining to why targeting therapy in situ is required.

Phosphobisaromatic motifs enable rapid enzymatic self-assembly and hydrogelation of short peptides

Enzyme-instructed self-assembly (EISA) and hydrogelation is a versatile approach for generating soft materials. Most of the substrates for alkaline phosphatase catalysed EISA utilize phosphotyrosine (pTyr) as the enzymatic trigger for EISA and hydrogelation. Here we show the first example of phosphonaphthyl (pNP) and phosphobiphenyl (pBP) motifs acting as faster enzymatic triggers than phosphotyrosine for EISA and hydrogelation. This work illustrates novel enzyme triggers for rapid enzymatic self-assembly and hydrogelation.

Enzymatically Forming Intranuclear Peptide Assemblies for Selectively Killing Human Induced Pluripotent Stem Cells

Tumorigenic risk of undifferentiated human induced pluripotent stem cells (iPSCs), being a major obstacle for clinical application of iPSCs, requires novel approaches for selectively eliminating undifferentiated iPSCs. Here, we show that an l-phosphopentapeptide, upon the dephosphorylation catalyzed by alkaline phosphatase (ALP) overexpressed by iPSCs, rapidly forms intranuclear peptide assemblies made of α-helices to selectively kill iPSCs. The phosphopentapeptide, consisting of four l-leucine residues and a C-terminal l-phosphotyrosine, self-assembles to form micelles/nanoparticles, which transform into peptide nanofibers/nanoribbons after enzymatic dephosphorylation removes the phosphate group from the l-phosphotyrosine. The concentration of ALP and incubation time dictates the morphology of the peptide assemblies. Circular dichroism and FTIR indicate that the l-pentapeptide in the assemblies contains a mixture of an α-helix and aggregated strands. Incubating the l-phosphopentapeptide with human iPSCs results in rapid killing of the iPSCs (=<2 h) due to the significant accumulation of the peptide assemblies in the nuclei of iPSCs. The phosphopentapeptide is innocuous to normal cells (e.g., HEK293 and hematopoietic progenitor cell (HPC)) because normal cells hardly overexpress ALP. Inhibiting ALP, mutating the l-phosphotyrosine from the C-terminal to the middle of the phosphopentapeptides, or replacing l-leucine to d-leucine in the phosphopentapeptide abolishes the intranuclear assemblies of the pentapeptides. Treating the l-phosphopentapeptide with cell lysate of normal cells (e.g., HS-5) confirms the proteolysis of the l-pentapeptide. This work, as the first case of intranuclear assemblies of peptides, not only illustrates the application of enzymatic noncovalent synthesis for selectively targeting nuclei of cells but also may lead to a new way to eliminate other pathological cells that express a high level of certain enzymes.