Enzyme-Instructed Activation of Pro-protein Therapeutics In Vivo

Unnatural enzyme activation by a metal-responsive regulatory protein

As a result of calcium ion binding, the calcium-dependent regulatory protein calmodulin (CaM) undergoes a conformational change, enabling it to bind to and activate a variety of enzymes. However, the detoxification enzyme glutathione S-transferase (GST) is notably not among the enzymes activated by CaM. In this study, we demonstrate the feasibility of establishing, in vitro, an artificial regulatory link between CaM and GST using bifunctional chemical transducer (CT) molecules possessing binders for CaM and GST. We show that the CTs convert the constitutively active GST into a triggerable enzyme whose activity is unnaturally regulated by the CaM conformational state and consequently, by the level of calcium ions. The ability to reconfigure the regulatory function of CaM demonstrates a novel mode by which CTs could be employed to mediate artificial protein crosstalk, as well as a new means to achieve artificial control of enzyme activity by modulating the coordination of metal ions. Within this study, we also investigated the impact of covalent interaction between the CTs and the enzyme target. This investigation offers further insights into the mechanisms governing the function of CTs and the possibility of rendering them isoform specific.

Innovative Colorimetric NQO1 Detection Strategy via Substrate Competitive and Biomimetic Cascade Reactions with a Highly Active NADH Oxidase Mimic

NAD(P)H: quinone oxidoreductase-1 (NQO1) plays critical roles in antioxidation and abnormally overexpresses in tumors. Developing a fast and sensitive method of monitoring NQO1 will greatly promote cancer diagnosis in clinical practice. This study introduces a transformative colorimetric detection strategy for NQO1, harnessing an innovative competitive substrate mechanism between NQO1 and a new NADH oxidase (NOX) mimic, cobalt-nitrogen-doped carbon nanozyme (CoNC). This method ingeniously exploits the differential consumption of NADH in the presence of NQO1 to modulate the generation of H2O2 from CoNC catalysis, which is then quantified through a secondary, peroxidase-mimetic cascade reaction involving Prussian blue (PB) nanoparticles. This dual-stage reaction framework not only enhances the sensitivity of NQO1 detection, achieving a limit of detection as low as 0.67 μg mL-1, but also enables the differentiation between cancerous and noncancerous cells by their enzymatic activity profiles. Moreover, CoNC exhibits exceptional catalytic efficiency, with a specific activity reaching 5.2 U mg-1, significantly outperforming existing NOX mimics. Beyond mere detection, CoNC serves a dual role, acting as both a robust mimic of cytochrome c reductase (Cyt c) and a cornerstone for enzymatic regeneration, thereby broadening the scope of its biological applications. This study not only marks a significant step forward in the bioanalytical application of nanozymes but also sets the stage for their expanded use in clinical diagnostics and therapeutic monitoring.

Thioketal-Based Electrochemical Sensor Reveals Biphasic Effects of l-DOPA on Neuroinflammation

Neuroinflammation is linked closely to neurodegenerative diseases, with reactive oxygen species (ROS) exacerbating neuronal damage. Traditional electrochemical sensors show promise in targeting cellular ROS to understand their role in neuropathogenesis and assess therapies. Nevertheless, these sensors face challenges in mitigating the ROS oxidation overpotential. We herein introduce an ROS oxidation-independent nucleic acid sensor for in situ ROS analysis and therapeutic assessment. The sensor comprises ionizable and thioketal (TK)-based lipids with methylene blue-tagged nucleic acids on a glass carbon electrode. ROS exposure triggers cleavage within the sensor's thioketal moiety, detaching the nucleic acid from the electrode and yielding quantifiable results via square-wave voltammetry. Importantly, the sensor's low potential window minimizes interference, ensuring precise ROS measurements with high selectivity. Using this sensor, we unveil levodopa's dose-dependent biphasic effect on neuroinflammation: low doses alleviate oxidative stress, while high doses exacerbate it. The TK-based sensor offers a promising methodology for investigating neuroinflammation's pathogenesis and screening potential treatments, advancing neurodegenerative disease research.

New-generation advanced PROTACs as potential therapeutic agents in cancer therapy

Proteolysis-targeting chimeras (PROTACs) technology has garnered significant attention over the last 10 years, representing a burgeoning therapeutic approach with the potential to address pathogenic proteins that have historically posed challenges for traditional small-molecule inhibitors. PROTACs exploit the endogenous E3 ubiquitin ligases to facilitate degradation of the proteins of interest (POIs) through the ubiquitin-proteasome system (UPS) in a cyclic catalytic manner. Despite recent endeavors to advance the utilization of PROTACs in clinical settings, the majority of PROTACs fail to progress beyond the preclinical phase of drug development. There are multiple factors impeding the market entry of PROTACs, with the insufficiently precise degradation of favorable POIs standing out as one of the most formidable obstacles. Recently, there has been exploration of new-generation advanced PROTACs, including small-molecule PROTAC prodrugs, biomacromolecule-PROTAC conjugates, and nano-PROTACs, to improve the in vivo efficacy of PROTACs. These improved PROTACs possess the capability to mitigate undesirable physicochemical characteristics inherent in traditional PROTACs, thereby enhancing their targetability and reducing off-target side effects. The new-generation of advanced PROTACs will mark a pivotal turning point in the realm of targeted protein degradation. In this comprehensive review, we have meticulously summarized the state-of-the-art advancements achieved by these cutting-edge PROTACs, elucidated their underlying design principles, deliberated upon the prevailing challenges encountered, and provided an insightful outlook on future prospects within this burgeoning field.

Polyphenol-Assisted Biomineralization of Metal-Organic Framework Nanoparticles for Precision Delivery of Therapeutic Proteins to Cancer Cells

The delivery of proteins into the cytosol holds great promise for cell signaling manipulation and the development of precision medicine. However, this potency is challenged by achieving targeted and controlled delivery, specifically within diseased cells. In this study, we introduce a versatile and effective method for the precision delivery of therapeutic proteins to cancer cells by designing polyphenol-assisted biomineralization of zeolite imidazole framework-8 (ZIF-8). We demonstrate that by leveraging the strong noncovalent binding affinity of epigallocatechin gallate (EGCG) with both proteins and ZIF-8, our approach significantly enhances the biomineralization of ZIF-8, which in turn improves the efficiency of protein encapsulation and intracellular delivery. Moreover, the incorporation of EGCG within ZIF-8 enables controlled degradation of the nanoparticles and the selective release of the encapsulated proteins in cancer cells. This selective release is triggered by the oxidation of EGCG in response to the high levels of reactive oxygen species (ROS) found within cancer cells that destabilize the EGCG/ZIF-8 nanoparticles. We have further demonstrated the ability of EGCG/ZIF-8 to deliver a wide range of proteins into cancer cells, including bacterial virulence protein, to rewire cell signaling and prohibit tumor cell growth in a mouse xenograft model. Our strategy and findings underscore the potential of designing the EGCG/ZIF-8 interface for specific and controlled protein delivery for targeted cancer therapy.

Self-assembly of peptides in living cells for disease theranostics

The past few decades have witnessed substantial progress in biomedical materials for addressing health concerns and improving disease therapeutic and diagnostic efficacy. Conventional biomedical materials are typically created through an ex vivo approach and are usually utilized under physiological environments via transfer from preparative media. This transfer potentially gives rise to challenges for the efficient preservation of the bioactivity and implementation of theranostic goals on site. To overcome these issues, the in situ synthesis of biomedical materials on site has attracted great attention in the past few years. Peptides, which exhibit remarkable biocompability and reliable noncovalent interactions, can be tailored via tunable assembly to precisely create biomedical materials. In this review, we summarize the progress in the self-assembly of peptides in living cells for disease diagnosis and therapy. After a brief introduction to the basic design principles of peptide assembly systems in living cells, the applications of peptide assemblies for bioimaging and disease treatment are highlighted. The challenges in the field of peptide self-assembly in living cells and the prospects for novel peptide assembly systems towards next-generation biomaterials are also discussed, which will hopefully help elucidate the great potential of peptide assembly in living cells for future healthcare applications.

Therapeutic Peptides, Proteins and their Nanostructures for Drug Delivery and Precision Medicine

Peptide and protein nanostructures with tunable structural features, multifunctionality, biocompatibility and biomolecular recognition capacity enable development of efficient targeted drug delivery tools for precision medicine applications. In this review article, we present various techniques employed for the synthesis and self-assembly of peptides and proteins into nanostructures. We discuss design strategies utilized to enhance their stability, drug-loading capacity, and controlled release properties, in addition to the mechanisms by which peptide nanostructures interact with target cells, including receptor-mediated endocytosis and cell-penetrating capabilities. We also explore the potential of peptide and protein nanostructures for precision medicine, focusing on applications in personalized therapies and disease-specific targeting for diagnostics and therapeutics in diseases such as cancer.

Artificial Protein Crosstalk with a Molecule that Exchanges Binding Partners

Drawing inspiration from allosteric signaling enzymes, whose catalytic and regulatory units are non-covalently linked, we have devised a method to establish unnatural, effector-mediated enzyme activation within native cells. The feasibility of this approach is demonstrated by introducing a synthetic regulatory unit (sRU) onto glycogen synthase kinase 3 (GSK-3) through non-covalent means. Our study reveals that this synthetic regulator mediates an unnatural crosstalk between GSK-3 and lactate dehydrogenase A (LDHA), whose expression is regulated by cellular oxygen levels. Specifically, with this approach, the constitutively active GSK-3 is transformed into an activable enzyme, whereas LDHA is repurposed as an unnatural effector protein that controls the activity of the kinase, making it unnaturally dependent on the cell's hypoxic response. These findings demonstrate a step toward imitating the function of effector-regulated cell-signaling enzymes, which play a key biological role in mediating the response of cells to changes in their environment. In addition, at the proof-of-principle level, our results indicate the potential to develop a new class of protein inhibitors whose inhibitory effect in cells is dictated by the cell's environment and consequent protein expression profile.

Unleashing the Power of Proenzyme Delivery for Targeted Therapeutic Applications Using Biodegradable Lipid Nanoparticles

Proenzymes, functioning as inactive precursor forms of enzymes, hold significant promise for regulating essential biological processes. Their inherent property of latency, remaining inert until they arrive at the intended site of action, positions them as particularly promising candidates for the development of targeted therapeutics. Despite this potential, the therapeutic potential of proenzymes is challenged by designing proenzymes with excellent selectivity for disease cells. This limitation is further exacerbated by the inability of proenzymes to spontaneously cross the cell membrane, a biological barrier that impedes the cellular internalization of exogenous macromolecules. Therefore, efficacious intracellular delivery is paramount to unlocking the full therapeutic potency of proenzymes.In this Account, we first elucidate our recent advancements made in designing biodegradable lipid nanoparticles (LNPs) for the cell-specific delivery of biomacromolecules, including proteins and nucleic acids. Using a strategy of parallel synthesis, we have constructed an extensive library of ionizable lipids, each integrated with different biodegradable moieties. This combinatorial approach has led to the identification of LNPs that are particularly efficacious for the delivery of biomacromolecules specifically to tumor cells. This innovation capitalizes on the unique intracellular environment of cancer cells to control the degradation of LNPs, thereby ensuring the targeted release of therapeutics within tumor cells. Additionally, we discuss the structure-activity relationship governing the delivery efficacy of these LNPs and their applicability in regulating tumor cell signaling, specifically through the delivery of bacterial effector proteins.In the second segment, we aim to provide an overview of our recent contributions to the field of proenzyme design, where we have chemically tailored proteins to render them responsive to the unique milieu of tumor cells. Specifically, we elaborate on the chemical principles employed to modify proteins and DNAzymes, thereby priming them for activation in the presence of NAD(P)H:quinone oxidoreductase 1 (NQO1), an enzyme that is prevalently upregulated within tumor cells. We summarize the methodologies for intracellular delivery of these proenzymes using biodegradable LNPs, both in vitro and in vivo. The concomitant intracellular delivery and activation of proenzymes are examined in the context of enhanced therapeutic outcomes and targeted CRISPR/Cas9 genome editing.In conclusion, we offer a perspective on the chemical principles that could be leveraged to optimize LNPs for tissue-specific delivery of proenzymes. We also explore chemical strategies for the irreversible modulation of proenzyme activity within living cells and in vivo. Through this discussion, we provide insights into potential avenues for overcoming existing limitations and enhancing the delivery of proenzymes using LNPs, particularly for developing tumor-targeted therapies and genome editing applications.

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.

Stimuli-activatable PROTACs for precise protein degradation and cancer therapy

The proteolysis targeting chimeras (PROTACs) approach has attracted extensive attention in the past decade, which represents an emerging therapeutic modality with the potential to tackle disease-causing proteins that are historically challengeable for conventional small molecular inhibitors. PROTAC harnesses the endogenic E3 ubiquitin ligase to degrade protein of interest (POI) via ubiquitin-proteasome system in a cycle-catalytic manner. The event-driven pharmacology of PROTAC is poised to pursue those targets that are conventionally undruggable, which enormously extends the space of drug development. Furthermore, PROTAC has the potential to address drug resistance of small molecular inhibitors by degrading the whole POI. Nevertheless, PROTACs display high-efficiency and always-on properties to degrade POI, they may cause severe side effects due to an "on-target but off-tissue" protein degradation profile at the undesirable tissues and cells. Given that, the stimuli-activatable PROTAC prodrugs have been recently exploited to confine precise protein degradation of the favorable targets, which may conquer the adverse effects of PROTAC due to uncontrollable protein degradation. Herein, we summarized the cutting-edge advances of the stimuli-activatable PROTAC prodrugs. We also overviewed the progress of PROTAC prodrug-based nanomedicine to improve PROTAC delivery to the tumors and precise POI degradation in the targeted cells.

Intracellular delivery of therapeutic proteins. New advancements and future directions

Achieving the full potential of therapeutic proteins to access and target intracellular receptors will have enormous benefits in advancing human health and fighting disease. Existing strategies for intracellular protein delivery, such as chemical modification and nanocarrier-based protein delivery approaches, have shown promise but with limited efficiency and safety concerns. The development of more effective and versatile delivery tools is crucial for the safe and effective use of protein drugs. Nanosystems that can trigger endocytosis and endosomal disruption, or directly deliver proteins into the cytosol, are essential for successful therapeutic effects. This article aims to provide a brief overview of the current methods for intracellular protein delivery to mammalian cells, highlighting current challenges, new developments, and future research opportunities.

Intracellular delivery of bacterial effectors for cancer therapy using biodegradable lipid nanoparticles

Bacterial effector proteins are virulence factors that are secreted and mediate orthogonal post-translational modifications of proteins that are not found naturally in mammalian systems. They hold great promise for developing biotherapeutics by regulating malignant cell signaling in a specific and targeted manner. However, delivering bacterial effectors into disease cells poses a significant challenge to their therapeutic potential. In this study, we report on the design of a combinatorial library of bioreducible lipid nanoparticles containing disulfide bonds for highly efficient bacterial effector delivery and potential cancer therapy. A leading lipid, PPPDA-O16B, identified from the library, can encapsulate and deliver DNA plasmids into cells. The gene cargo is released in response to the reductive cellular environment that is upregulated in cancer cells, leading to enhanced gene delivery and protein expression efficiency. Furthermore, we demonstrate that PPPDA-O16B can deliver the bacterial effector protein, DUF5, to degrade mutant RAS and inactivate downstream MAPK signaling cascades to suppress cancer cell growth in vitro and in tumor-bearing mouse xenografts. This strategy of delivering bacterial effectors using biodegradable lipid nanoparticles can be expanded for cancer cell signaling regulation and antitumor studies.

Engineered bacteria combined with doxorubicin nanoparticles suppress angiogenesis and metastasis in murine melanoma models

Methods capable of distributing antitumour therapeutics uniformly throughout an entire tumour and that can suppress metastasis at the same time, would be of great significance in improving cancer treatment. Bacteria-mediated synergistic therapies have been explored for better specificity, temporal and spatial controllability, as well for providing regulation of the immune microenvironment, in order to provide improved cancer treatment. To achieve this goal, here we developed an engineered bacteria delivery system (GDOX@HSEc) using synthetic biology and interfacial chemistry technologies. The engineered bacteria were concurrently modified to express heparin sulfatase 1 (HSulf-1) inside (HSEc), to attach doxorubicin-loaded glycogen nanoparticles (GDOX NPs) on their surface. Here we demonstrate that HSEc can actively target and colonise tumour sites resulting in HSulf-1 overexpression, thereby suppressing angiogenesis and metastasis. Simultaneously, the GDOX NPs were able to penetrate into tumour cells, leading to intracellular DNA damage. Our results confirmed that a combination of biotherapy and chemotherapy using GDOX@HSEc resulted in significant melanoma suppression in murine models, with reduced side effects. This study provides a powerful platform for the simultaneous delivery of biomacromolecules and chemotherapeutic drugs to tumours, representing an innovative strategy potentially more effective in treating solid tumours. STATEMENT OF SIGNIFICANCE: An original engineered bacteria-based system (GDOX@HSEc) was developed using synthetic biology and interfacial chemistry technologies to concurrently produce naturally occurring heparin sulfatase 1 (HSulf-1) inside and anchor doxorubicin-loaded glycogen nanoparticles on the surface. GDOX@HSEc allowed for combined local delivery of chemotherapeutic agents along with the enzymes and immunostimulatory bacterial adjuvants, which resulted in a synergistic action in the inhibition of tumour growth and metastasis. The study provides a potential therapeutic approach that allows therapeutic agents to be distributed in a spatiotemporally controllable manner in tumours for combinatorial enhanced therapy.

Strategies for Conditional Regulation of Proteins

Design of the next-generation of therapeutics, biosensors, and molecular tools for basic research requires that we bring protein activity under control. Each protein has unique properties, and therefore, it is critical to tailor the current techniques to develop new regulatory methods and regulate new proteins of interest (POIs). This perspective gives an overview of the widely used stimuli and synthetic and natural methods for conditional regulation of proteins.

A DNA origami nanostructure embedded with NQO1-activated prodrugs for precision drug delivery

A rectangle DNA origami nanostructure equipped with doxorubicin-derived prodrugs targeting a tumor cell-specific enzyme (NQO1) is constructed. Combining the high prodrug payload of DNA origami and NQO1-activated chemotherapy, this nanosystem presents therapeutic selectivity for NQO1-overexpressing MCF-7 cells over healthy L02 cells, offering a potent strategy for precision cancer therapy.

Orthogonal Chemical Activation of Enzyme-Inducible CRISPR/Cas9 for Cell-Selective Genome Editing

The precision and therapeutic potential of CRISPR/Cas9 genome editing are greatly challenged by the less control over Cas9-mediated DNA cleavage. Herein, we introduce a conditional and cell-selective genome editing system controlled by disease-associated enzymes, termed enzyme-inducible CRISPR (eiCRISPR). eiCRISPR comprises Cas9 protein, a self-blocked inactive single-guide RNA (bsgRNA), and a chemically caged deoxyribozyme (DNAzyme) that activates bsgRNA and eiCRISPR in a controllable manner. We design chemical modifications of DNAzyme to suppress its ability to cleave the blocking region of bsgRNA, while the decaging of DNAzyme triggered by the tumor cell-overexpressed enzyme, for instance, NAD(P)H:quinone oxidoreductase (NQO1), restores the activity of bsgRNA and switches on eiCRISPR selectively for genome editing in cancer cells. Moreover, using a biodegradable lipid nanoparticle to deliver eiCRISPR in a tumor-bearing xenograft, we show that the in vivo activation of eiCRISPR enables the editing of human papillomavirus 18 E6 for potential cancer therapy. The strategy of postsynthetic and site-specific modification of DNAzyme is compatible with endogenous chemistries for regulating eiCRISPR for cell-selective genome editing and targeted gene therapy.

Self-amplified chain-shattering cinnamaldehyde-based poly(thioacetal) boosts cancer chemo-immunotherapy

The selective activation of stimuli-responsive polymers in the tumor microenvironment is a great concern to achieve intelligent cancer therapy, but most of them show inadequate response due to insufficient endogenous triggering agents. Herein, we rationally designed a reactive oxygen species (ROS)-responsive cinnamaldehyde (CA)-based poly(thioacetal), consisting of ROS-responsive thioacetal (TA) and ROS-generating agent CA, with self-amplified chain-shattering polymer degradation. The mechanism of self-amplified chain-shattering is that endogenous ROS as a triggering agent facilitates chain cleavage of TA with the release of CA, which in turn produces more ROS through mitochondrial dysfunction, resulting in an exponential polymer degradation cascade. The polymer can be further modified with anticancer drug doxorubicin (DOX) for cooperative amplification of oxidative stress and immunogenic cell death (ICD) of tumor cells, thereby boosting the effect of chemo-immunotherapy. The self-amplified chain-shattering polymer designed in this work holds great promise in developing stimuli-responsive polymers for efficient drug delivery. STATEMENT OF SIGNIFICANCE: This study presented an approach to utilize self-amplified chain-shattering cinnamaldehyde-based poly (thioacetal) as a drug delivery system to restrain tumor growth and boost chemo-immunotherapy. The endogenous ROS as a triggering agent initiates the chain cleavage with the release of CA, which in turn produces ROS through mitochondria dysfunction, resulting in an exponential polymer degradation cascade and rapid drug release.

Biodegradable Metal-Organic-Frameworks-Mediated Protein Delivery Enables Intracellular Cascade Biocatalysis and Pyroptosis In Vivo

Pyroptosis is a new type of regulated cell death that is of great interest for developing new strategies for treating cancers. This potential is however greatly limited by the low efficiency and selectivity of current strategies to regulate cancer cell pyroptosis. Herein, we report biodegradable metal-organic frameworks (MOFs) for intracellular delivery of glucose oxidase (GOx) that promotes cascade biocatalysis inside cells and selectively induces cancer cell pyroptosis. We show that the self-assembly of Cu²⁺ and 4,4'-azobisbenzoic acid along with GOx affords protein-encapsulated GOx@Cu MOF that efficiently delivers GOx into cells. In addition, the tumor-cell-overexpressed NAD(P)H quinone dehydrogenase 1 (NQO1) can trigger the reduction of 4,4'-azobisbenzoic acid and the degradation of GOx@Cu MOF, releasing GOx to catalyze glucose oxidation and produce excessive hydrogen peroxide (H₂O₂) intracellularly. Furthermore, released Cu²⁺ from Cu MOF could be reduced to Cu⁺ by intracellular glutathione (GSH), promoting Fenton-like reaction with H₂O₂ to continuously generate a hydroxyl radical that induces cancer cell pyroptosis and prohibits tumor cell growth. We anticipate the strategy of harnessing biodegradable MOFs for protein delivery, and intracellular biocatalysis provides a powerful approach to regulate tumor cell pyroptosis for advanced therapeutic development.

Reactive oxygen species-responsive branched poly (β-amino ester) with robust efficiency for cytosolic protein delivery

Protein therapy targeting the intracellular machinery holds great potentials for disease treatment, and therefore, effective cytosolic protein delivery technologies are highly demanded. Herein, we developed reactive oxygen species (ROS)-degradable, branched poly(β-amino ester) (PBAE) with built-in phenylboronic acid (PBA) in the backbone and terminal-pendent arginine for the efficient cytosolic protein delivery. The PBAE could form stable and cell-ingestible nanocomplexes (NCs) with proteins via electrostatic interaction, nitrogen-boronate (N-B) coordination, and hydrogen bonding, while it can be degraded into small segments by the over-produced H₂O₂ in tumor cells to enable cytoplasmic protein release. As thus, PBAE exhibited high efficiency in delivering varieties of proteins with distinct molecular weights (12.4-430 kDa) and isoelectric points (4.7-10.5) into tumor cells, including enzymes, toxins, and antibodies. Moreover, PBAE mediated efficient delivery of saporin into tumor cells in vivo, provoking pronounced anti-tumor outcomes. This study provides a robust and versatile platform for cytosolic protein delivery, and the elaborately tailored PBAE may find promising applications for protein-based biological research and disease management. STATEMENT OF SIGNIFICANCE: Cytosolic delivery of native proteins holds great therapeutic potentials, which however, is limited by the lack of robust delivery carriers that can simultaneously feature strong protein encapsulation yet effective intracellular protein release. Herein, ROS-degradable, branched poly(β-amino ester) (PBAE) with backbone-embedded phenylboronic acid (PBA) and terminal-pendent arginine was developed to synchronize these two processes. PBA and arginine moieties allowed PBAE to encapsulate proteins via N-B coordination, electrostatic interaction, hydrogen bonding, and salt bridging, while PBA could be oxidized by over-produced H₂O₂ inside cancer cells to trigger PBAE degradation and intracellular protein release. As thus, the top-performing PBAE mediated efficient cytosolic delivery of various proteins including enzymes, toxins, and antibodies. This study provides a powerful platform for cytosolic protein delivery, and may find promising utilities toward intracellular protein therapy against cancer and other diseases such as inflammation.

Endocytosis-Independent and Cancer-Selective Cytosolic Protein Delivery via Reversible Tagging with LAT1 substrate

Protein drugs targeting intracellular machineries have shown profound therapeutic potentials, but their clinical utilities are greatly hampered by the lack of efficient cytosolic delivery techniques. Existing strategies mainly rely on nanocarriers or conjugated cell-penetrating peptides (CPPs), which often have drawbacks such as materials complexity/toxicity, lack of cell specificity, and endolysosomal entrapment. Herein, a unique carrier-free approach is reported for mediating cancer-selective and endocytosis-free cytosolic protein delivery. Proteins are sequentially modified with 4-nitrophenyl 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) benzyl carbonate as the H₂ O₂ -responsive domain and 3,4-dihydroxy-l-phenylalanine as the substrate of l-type amino acid transporter 1 (LAT1). Thus, the pro-protein can be directly transported into tumor cells by overexpressed LAT1 on cell membranes, bypassing endocytosis and endolysosomal entrapment. In the cytosol, overproduced H₂ O₂ restores the protein structure and activity. Using this technique, versatile proteins are delivered into tumor cells with robust efficiency, including toxins, enzymes, CRISPR-Cas9 ribonucleoprotein, and antibodies. Furthermore, intravenously injected pro-protein of saporin shows potent anticancer efficacy in 4T1-tumor-bearing mice, without provoking systemic toxicity. Such a facile and versatile pro-protein platform may benefit the development of protein pharmaceuticals.

Hypoxia-Reinforced Antitumor RNA Interference Mediated by Micelleplexes with Programmed Disintegration

The performance of polycation-mediated siRNA delivery is often hurdled by the multiple systemic and cellular barriers that pose conflicting requirements for materials properties. Herein, micelleplexes (MPs) capable of programmed disintegration were developed to mediate efficient delivery of siRNA against XIAP (siXIAP) in a hypoxia-reinforced manner. MPs were assembled from azobenzene-crosslinked oligoethylenimine (AO), acid-transformable diblock copolymer PPDHP with conjugated photosensitizer, and siXIAP. AO efficiently condensed siXIAP via electrostatic interaction, and PPDHP rendered additional hydrophobic interaction with AO to stabilize the MPs against salt. The hydrophilic PEG corona enhanced the serum stability of MPs to prolong blood circulation and promote tumor accumulation. After internalization into cancer cells, the endolysosomal acidity triggered shedding of PPDHP, exposing AO to induce endolysosomal escape. Then, light irradiation generated lethal amount of ROS, and concurrently aggravated intracellular hypoxia level to degrade AO into low-molecular weight segments, release siXIAP, and potentiate the XIAP silencing efficiency. Thus, siXIAP-mediated pro-apoptosis cooperated with generated ROS to provoke pronounced anti-cancer efficacy against Skov-3 tumors in vitro and in vivo. This study provides a hypoxia-instructed strategy to overcome the multiple barriers against anti-cancer siRNA delivery in a programmed manner. STATEMENT OF SIGNIFICANCE: : The success of RNA interference (RNAi) heavily depends on delivery systems that can enable spatiotemporal control over siRNA delivery. Herein, we developed micelleplexes (MPs) constructed from hypoxia-degradable, azobenzene-crosslinked oligoethylenimine (AO) and acid-responsive, photosensitizer-conjugated diblock copolymer PPDHP, to mediate efficient anti-tumor siRNA (siXIAP) delivery via programmed disintegration. MPs possessed high salt/serum stability and underwent acid-triggered PPDHP detachment to promote endolysosomal escape. Then, light irradiation aggravated hypoxia to trigger AO degradation and intracellular siXIAP release, which cooperated with photodynamic therapy to eradicate tumor cells. This study presents a new example of hypoxia-degradable polycation to mediate hypoxia-reinforced RNAi, and it also renders an effective strategy to overcome the complicated extracellular/intracellular barriers against systemic siRNA delivery.

Design and synthesis of a deep tissue penetrating near-infrared two-photon fluorescence probe for the specific detection of NQO1

NAD(P)H:quinone oxidoreductase 1 (NQO1) is overexpressed in a broad range of human tumors but remains difficult to study. Herein, we report a novel two-photon fluorescent probe with NIR emission for NQO1 detection. The probe demonstrated superior analytical performance with a large Stokes shift and deep tissue penetration.

Massively parallel, computationally guided design of a proenzyme

Proteins have shown promise as therapeutics and diagnostics, but their effectiveness is limited by our inability to spatially target their activity. To overcome this limitation, we developed a computationally guided method to design inactive proenzymes or zymogens, which are activated through cleavage by a protease. Since proteases are differentially expressed in various tissues and disease states, including cancer, these proenzymes could be targeted to the desired microenvironment. We tested our method on the therapeutically relevant protein carboxypeptidase G2 (CPG2). We designed Pro-CPG2s that are inhibited by 80 to 98% and are partially to fully reactivatable following protease treatment. The developed methodology, with further refinements, could pave the way for routinely designing protease-activated protein-based therapeutics and diagnostics that act in a spatially controlled manner.

Confining the activity of a designed protein to a specific microenvironment would have broad-ranging applications, such as enabling cell type-specific therapeutic action by enzymes while avoiding off-target effects. While many natural enzymes are synthesized as inactive zymogens that can be activated by proteolysis, it has been challenging to redesign any chosen enzyme to be similarly stimulus responsive. Here, we develop a massively parallel computational design, screening, and next-generation sequencing-based approach for proenzyme design. For a model system, we employ carboxypeptidase G2 (CPG2), a clinically approved enzyme that has applications in both the treatment of cancer and controlling drug toxicity. Detailed kinetic characterization of the most effectively designed variants shows that they are inhibited by ∼80% compared to the unmodified protein, and their activity is fully restored following incubation with site-specific proteases. Introducing disulfide bonds between the pro- and catalytic domains based on the design models increases the degree of inhibition to 98% but decreases the degree of restoration of activity by proteolysis. A selected disulfide-containing proenzyme exhibits significantly lower activity relative to the fully activated enzyme when evaluated in cell culture. Structural and thermodynamic characterization provides detailed insights into the prodomain binding and inhibition mechanisms. The described methodology is general and could enable the design of a variety of proproteins with precise spatial regulation.

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

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

Integration of Palladium Nanoparticles with Surface Engineered Metal-Organic Frameworks for Cell-Selective Bioorthogonal Catalysis and Protein Activity Regulation

Bioorthogonal catalysis provides a powerful tool to perform non-natural chemical reactions in living systems to dissect complex intracellular processes. Its potency to precisely regulate cellular function, however, is limited by the lack of bioorthogonal catalysts with cell selectivity. Herein, we report that palladium nanoparticles deposited on metal-organic frameworks, Pd@UiO-66, are highly efficient for intracellular bioorthogonal catalysis. In addition, introducing a cancer cell-targeting aptamer, AS1411, onto Pd@UiO-66 enables a threefold enhancement of catalysis efficiency in cancer cells. Moreover, AS1411@Pd@UiO-66 is effective in activating chemically caged 4-hydroxytamoxifen to regulate the activity of a protein destabilizing domain, ER50, and therefore protein function selectively in cancer cells. We show that the control over the activity of a bacterial effector, OspF, using AS1411@Pd@UiO-66 inactivates mitogen-activated protein kinase (MAPK) signaling of cancer cells to selectively prohibit tumor cell growth. We believe that the strategy developed herein for cell-selective bioorthogonal catalysis can expand the chemical biology toolbox for spatiotemporal control of protein function for advanced therapeutic applications.

Research advances in NQO1-responsive prodrugs and nanocarriers for cancer treatment

NAD(P)H: quinine oxidoreductase (NQO1) is a class of flavoprotein enzymes commonly expressed in eukaryotic cells. It actively participates in the metabolism of various quinones and their in vivo bioactivation through electron reduction reactions. The expression level of NQO1 is highly upregulated in many solid tumor cells compared with that in normal cells. NQO1 has been considered a candidate molecular target because of its overexpression and bioactivity in different tumors. NQO1-responsive prodrugs and nanocarriers have recently been identified as effective objectives for achieving controlled drug release, reducing adverse reactions and improving clinical efficacy. This review systematically introduces the research advances in applying NQO1-responsive prodrugs and nanocarriers to cancer treatment. It also discusses the existing problems and the developmental prospects of these two antitumor drug delivery systems.

Tailoring Hyperbranched Poly(β-amino ester) as a Robust and Universal Platform for Cytosolic Protein Delivery

Cytosolic protein delivery is a prerequisite for protein-based biotechnologies and therapeutics on intracellular targets. Polymers that can complex with proteins to form nano-assemblies represent one of the most important categories of materials, because of the ease of nano-fabrication, high protein loading efficiency, no need for purification, and maintenance of protein bioactivity. Stable protein encapsulation and efficient intracellular liberation are two critical yet opposite processes toward cytosolic delivery, and polymers that can resolve these two conflicting challenges are still lacking. Herein, hyperbranched poly(β-amino ester) (HPAE) with backbone-embedded phenylboronic acid (PBA) is developed to synchronize these two processes, wherein PBA enhanced protein encapsulation via nitrogen-boronate (N-B) coordination while triggered polymer degradation and protein release upon oxidation by H₂ O₂ in cancer cells. Upon optimization of the branching degree, charge density, and PBA distribution, the best-performing A2-B3-C2-S₂ -P₂ is identified, which mediates robust delivery of various native proteins/peptides with distinct molecular weights (1.6-430 kDa) and isoelectric points (4.1-10.3) into cancer cells, including enzymes, toxins, antibodies, and CRISPR-Cas9 ribonucleoproteins (RNPs). Moreover, A2-B3-C2-S₂ -P₂ mediates effective cytosolic delivery of saporin both in vitro and in vivo to provoke remarkable anti-tumor efficacy. Such a potent and universal platform holds transformative potentials for protein pharmaceuticals.

Intracellular Enzyme-Responsive Profluorophore and Prodrug Nanoparticles for Tumor-Specific Imaging and Precise Chemotherapy

Responsive drug delivery systems possess great potential in disease diagnosis and treatment. Herein, we develop an activatable prodrug and fluorescence imaging material by engineering the endogenous NAD(P)H:quinone oxidoreductase-1 (NQO1) responsive linker. The as-prepared nanomaterials possess the NQO1-switched drug release and fluorescence enablement, which realizes the tumor-specific chemotherapy and imaging in living mice. The enzyme-sensitive prodrug nanoparticles exhibit selectively potent anticancer performance to NQO1-positive cancer and ignorable off-target toxicity. This work provides an alternative strategy for constructing smart prodrug nanoplatforms with precision, selectivity, and practicability for advanced cancer imaging and therapy.

Cytosolic delivery of CDK4/6 inhibitor p16 protein using engineered protein crystals for cancer therapy

The tumor suppressor p16 protein is an endogenous CDK4/6 inhibitor. Inactivation of its encoding gene is found in nearly half of human cancers. Restoration of p16 function via adenovirus-based gene delivery has been shown to be effective in suppressing aberrant cell growth in many types of cancer, however, the potential risk of insertional mutagenesis in genomic DNA remains a major concern. Thus, there has been great interest in developing efficient strategies to directly deliver proteins into cells as an alternative that can avoid such safety concerns while achieving a comparable therapeutic effect. Nevertheless, intracellular delivery of protein therapeutics remains a challenge. Our group has recently developed a protein delivery platform based on an engineered Pos3Aa protein that forms sub-micrometer-sized crystals in Bacillus thuringiensis cells. In this report, we describe the further development of this platform (Pos3AaTM) via rationally designed site-directed mutagenesis, and its resultant potency for the delivery of cargo proteins into cells. Pos3AaTM-based fusion protein crystals are shown to exhibit improved release of their cargo proteins as demonstrated using a model mCherry protein. Importantly, this Pos3AaTM platform is able to mediate the efficient intracellular delivery of p16 protein with significant endosomal escape, resulting in p16-mediated inhibition of CDK4/6 kinase activity and Rb phosphorylation, and as a consequence, significant cell cycle arrest and cell growth inhibition. These results validate the ability of these improved Pos3AaTM crystals to mediate enhanced cytosolic protein delivery and highlight the potential of using protein therapeutics as selective CDK4/6 inhibitors for cancer therapy. STATEMENT OF SIGNIFICANCE: Cytosolic delivery of bioactive therapeutic proteins capable of eliciting therapeutic benefit remains a significant challenge. We have previously developed a protein delivery platform based on engineered Pos3Aa protein crystals with excellent cell-permeability and endosomal escape properties. In this report, we describe the rational design of an improved Pos3Aa triple mutant (Pos3AaTM) with enhanced cargo release. We demonstrate that Pos3AaTM-mCherry-p16 fusion crystals can efficiently deliver p16 protein, a CDK4/6 inhibitor frequently inactivated in human cancers, into p16-deficient UM-SCC-22A cells, where it promotes significant G1 cell cycle arrest and cell growth inhibition. These results highlight the ability of the Pos3AaTM platform to promote potent cytosolic delivery of protein therapeutics, and the efficacy of p16 protein delivery as an effective strategy for treating cancer.

Multifunctional micro/nanomotors as an emerging platform for smart healthcare applications

Self-propelling micro- and nano-motors (MNMs) are emerging as a multifunctional platform for smart healthcare applications such as biosensing, bioimaging, and targeted drug delivery with high tissue penetration, stirring effect, and rapid drug transport. MNMs can be propelled and/or guided by chemical substances or external stimuli including ultrasound, magnetic field, and light. In addition, enzymatically powered MNMs and biohybrid micromotors have been developed using the biological components in the body. In this review, we describe emerging MNMs focusing on their smart propulsion systems, and diagnostic and therapeutic applications. Finally, we highlight several MNMs for in vivo applications and discuss the future perspectives of MNMs on their current limitations and possibilities toward further clinical applications.

A pH-Responsive Phase-Transition Polymer with High Serum Stability in Cytosolic Protein Delivery

Polymer-mediated intracellular protein delivery systems are important for the development of protein-based biotechnologies and therapeutics. However, intracellular delivery of cargo proteins in the presence of serum remains challenging due to competitive binding of serum proteins with the polymers. Here, we reported a dendrimer engineered with a high density of 4-diethylaminophenyl groups on the surface to address this issue. The dendrimer showed a pH-responsive phase-transition behavior and could assemble with cargo proteins into stable nanoparticles in serum solutions. It efficiently delivered cargo proteins into living cells, and exhibited a pH-responsive disassembly behavior after cell internalization. As a result, various cargo proteins were delivered into the cytosol of living cells with maintained bioactivity. This study provided a convenient and efficient strategy to design polymers with high serum-tolerance in cytosolic protein delivery.

DNAzyme-Catalyzed Cellular Oxidative Stress Amplification for Pro-protein Activation in Living Cells

The conditional control of protein function in response to the physiological change of cells is of great interest for studying protein function in biological settings and developing protein therapeutics. We report herein that catalase (CAT) DNAzyme can potentiate the generation of reactive oxygen species (ROS) in living cells by knocking down catalase expression, which could further activate a reactive oxygen species (ROS)-responsive pro-protein, RNase A-NBC, in situ. Using an optimized lipid nanoparticle delivery system to simultaneously introduce CAT DNAzyme and RNase A-NBC into cells, we show that the pro-protein, RNase A-NBC, could be activated in a significantly enhanced manner to prohibit tumor cell growth in different types of cancer cells. We believe the methodology of regulating pro-protein activity using DNAzyme biocatalysis to differentiate intracellular environment could further be extended to other functional proteins, and even fundamental investigations in living systems to develop pro-protein therapeutics.

Cytosolic protein delivery via metabolic glycoengineering and bioorthogonal click reactions

Cytosolic protein delivery holds great potential for the development of protein-based biotechnologies and therapeutics. Currently, cytosolic protein delivery is mainly achieved with the assistance of various carriers. Herein, we present a universal and effective strategy for carrier-free cytosolic protein delivery via metabolic glycoengineering and bioorthogonal click reactions. Ac₄ManNAz (AAM), an azido-modified N-acetylmannosamine analogue, was first employed to label tumor cell surfaces with abundant azido groups via glycometabolism. Then, proteins including RNase A, cytochrome C (Cyt C), and bovine serum albumin (BSA) were covalently modified with dibenzocyclooctyne (DBCO). Based on the highly efficient bioorthogonal click reactions between DBCO and azido, DBCO-modified proteins could be efficiently internalized by azido-labeled cancer cells. RNase A-DBCO could largely maintain its enzymatic activity and, thus, led to notable anti-tumor efficacy in HeLa and B16F10 cells in vitro and in B16F10 xenograft tumors in vivo. This study therefore provides a simple and powerful approach for carrier-free protein delivery and would have broad applicability in anti-tumor protein therapy.

Dynamic Continuum of Nanoscale Peptide Assemblies Facilitates Endocytosis and Endosomal Escape

Alkaline phosphatase (ALP) enables intracellular targeting by peptide assemblies, but how the ALP substrates enter cells remains elusive. Here we show that nanoscale phosphopeptide assemblies cluster ALP to enable caveolae-mediated endocytosis (CME) and endosomal escape. Specifically, fluorescent phosphopeptides undergo enzyme-catalyzed self-assembly to form nanofibers. Live cell imaging unveils that phosphopeptides nanoparticles, coincubated with HEK293 cells overexpressing red fluorescent protein-tagged tissue-nonspecific ALP (TNAP-RFP), cluster TNAP-RFP in lipid rafts to enable CME. Further dephosphorylation of the phosphopeptides produces peptidic nanofibers for endosomal escape. Inhibiting TNAP, cleaving the membrane anchored TNAP, or disrupting lipid rafts abolishes the endocytosis. Decreasing the transformation to nanofibers prevents the endosomal escape. As the first study establishing a dynamic continuum of nanoscale assemblies for cellular uptake, this work illustrates an effective design for enzyme-responsive supramolecular therapeutics and provides mechanism insights for understanding the dynamics of cellular uptake of proteins or exogenous peptide aggregates.

Intracellular delivery of therapeutic proteins through N-terminal site-specific modification

A versatile strategy for the intracellular delivery of functional proteins/antibodies was developed using N-terminal site-specific modification. Adopting orthogonal dual-labeling strategies, a cell-permeable RNase A prodrug was designed complementing N-terminal site-specific modification with lysine labeling. Upon successful cytosolic uptake, the prodrug showed reactive oxygen species (ROS)-dependent targeted cancer therapy.

Binary Prodrug of Dichloroacetic Acid and Doxorubicin with Enhanced Anticancer Activity

The inevitable challenge in conventional chemotherapy is to deliver the anticancer drugs to the dense population of tumors cells while minimizing the drug-associated side effects on the normal cells. Cancer cells' preference for glycolysis for energy production is well recognized. Intuitively, taking advantage of such cancer-associated metabolism would be a promising strategy for anticancer drug delivery with minimal side effects. In this investigation, we have designed a binary prodrug PDOX as a sequential drug delivery regimens to realize the combination therapy for cancer. As cancer cells exhibit abrupt metabolism with elevated pyruvate dehydrogenase kinase (PDK) activity, dichloroacetic acid (DCA, a well-known PDK inhibitor) was used in combination with anticancer drug doxorubicin (DOX). The designed molecular prodrug was activated selectively by cancer-associated esterase to deliver DCA and DOX, respectively, and induced synergetic effects. Hence, sequential targeted delivery of molecular prodrug PDOX offers a promising approach to overcome the offside drug toxicity, pharmacokinetics, and biodistribution of individuals and provide an alternative option for cancer treatment.

Hierarchical Self-assembly of Discrete Metal-Organic Cages into Supramolecular Nanoparticles for Intracellular Protein Delivery

Hierarchical self-assembly (HAS) is a powerful approach to create supramolecular nanostructures for biomedical applications. This potency, however, is generally challenged by the difficulty of controlling the HAS of biomacromolecules and the functionality of resulted HAS nanostructures. Herein, we report a modular approach for controlling the HAS of discrete metal-organic cages (MOC) into supramolecular nanoparticles, and its potential for intracellular protein delivery and cell-fate specification. The hierarchical coordination-driven self-assembly of adamantane-functionalized M12 L24 MOC (Ada-MOC) and the host-guest interaction of Ada-MOC with β-cyclodextrin-conjugated polyethylenimine (PEI-βCD) afford supramolecular nanoparticles in a controllable manner. HAS maintains high efficiency and orthogonality in the presence of protein, enabling the encapsulation of protein into the nanoparticles for intracellular protein delivery for therapeutic application and CRISPR/Cas9 genome editing.

Biomedical Micro-/Nanomotors: From Overcoming Biological Barriers to In Vivo Imaging

Self-propelled micro- and nanomotors (MNMs) have shown great potential for applications in the biomedical field, such as active targeted delivery, detoxification, minimally invasive diagnostics, and nanosurgery, owing to their tiny size, autonomous motion, and navigation capacities. To enter the clinic, biomedical MNMs request the biodegradability of their manufacturing materials, the biocompatibility of chemical fuels or externally physical fields, the capability of overcoming various biological barriers (e.g., biofouling, blood flow, blood-brain barrier, cell membrane), and the in vivo visual positioning for autonomous navigation. Herein, the recent advances of synthetic MNMs in overcoming biological barriers and in vivo motion-tracking imaging techniques are highlighted. The challenges and future research priorities are also addressed. With continued attention and innovation, it is believed that, in the future, biomedical MNMs will pave the way to improve the targeted drug delivery efficiency.

Cationic Lipid-based Intracellular Delivery of Bacterial Effectors for Rewiring Malignant Cell Signaling

The abundance of bacterial effectors have inspired us to explore their potential in rewiring malignant cell signaling. Their incapability for entering cells, however, hinders such application. Herein we developed a cationic lipid-based high throughput library screening platform for effective intracellular delivery of bacterial effectors. As the misregulated MAPK signaling is a hallmark of many types of cancer, we turned to the Shigella effector OspF which irreversibly inactivates ERK, the terminal component of MAPK cascade. We created a function-based screening assay to obtain AMPA-O16B lipid nanoparticles for effective OspF intracellular delivery, which inhibited the malignant MAPK signaling and tumor growth in vitro and in vivo. Furthermore, the optimized lipid nanoparticle formulation can deliver OspF to modulate the immunosuppressive responses in macrophages. Our work is a general strategy to explore the therapeutic potentials of naturally evolved bacterial effectors.

Endogenous Hydrogen Sulfide-Triggered MOF-Based Nanoenzyme for Synergic Cancer Therapy

The developing nanoparticle therapeutic agents triggered by tumor microenvironment are a feasible strategy for the substantial elevation of accuracy of diagnosis and the reduction of side effects in cancer treatments. Dysregulated H₂S production from the enzyme system of overexpressed cystathionine β-synthase has long been considered to act as an autocrine and paracrine factor for the tumor growth and proliferation of colon cancer. Herein, for the first time, an endogenous H₂S-activated copper metal-organic framework (Cu-MOF; HKUST-1) nanoenzyme has been demonstrated to synergistically mediate H₂S-activated near-infrared photothermal therapy and chemodynamic therapy in the effective treatment of colon cancer. This endogenous biomarker-triggered "turn-on" strategy to generate therapeutic agents in situ could largely simplify the constitution of nanomedicine by avoiding the cargo introduction and thus supply great promise for the precise treatments of colon cancer.