Intracellular Activation of Bioorthogonal Nanozymes through Endosomal Proteolysis of the Protein Corona

Designing intelligent bioorthogonal nanozymes: Recent advances of stimuli-responsive catalytic systems for biomedical applications

Bioorthogonal nanozymes have emerged as a potent tool in biomedicine due to their unique ability to perform enzymatic reactions that do not interfere with native biochemical processes. The integration of stimuli-responsive mechanisms into these nanozymes has further expanded their potential, allowing for controlled activation and targeted delivery. As such, intelligent bioorthogonal nanozymes have received more and more attention in developing therapeutic approaches. This review provides a comprehensive overview of the recent advances in the development and application of stimuli-responsive bioorthogonal nanozymes. By summarizing the design outlines for anchoring bioorthogonal nanozymes with stimuli-responsive capability, this review seeks to offer valuable insights and guidance for the rational design of these remarkable materials. This review highlights the significant progress made in this exciting field with different types of stimuli and the various applications. Additionally, it also examines the current challenges and limitations in the design, synthesis, and application of these systems, and proposes potential solutions and research directions. This review aims to stimulate further research toward the development of more efficient and versatile stimuli-responsive bioorthogonal nanozymes for biomedical applications.

Nanozymes and their biomolecular conjugates as next-generation antibacterial agents: A comprehensive review

Antimicrobial resistance (AMR), the ability of bacterial species to develop resistance against exposed antibiotics, has gained immense global attention in the past few years. Bacterial infections are serious health concerns affecting millions of people annually worldwide. Therefore, developing novel antibacterial agents that are highly effective and avoid resistance development is imperative. Among various strategies, recent developments in nanozyme technology have shown promising results as antibacterials in several antibiotic-sensitive and resistant bacterial species. Nanozymes offer several advantages over corresponding natural enzymes, such as inexpensive, stable, multifunctional, tunable catalytic properties. Although the use of nanozymes as antibacterial agents has provided promising results, the specific biomolecule-conjugated nanozymes have shown further improvement in catalytic performance and associated antibacterial efficacy. The exclusive design of functional nanozymes with theranostic potential is found to simultaneously inhibit the growth and image of AMR bacterial species. This review comprehensively summarizes the history of nanozymes, their classification, biomolecules conjugated nanozyme, and their mechanism of enzyme-mimetic activity and associated antibacterial activity in antibiotic-sensitive and resistant species. The future needs to effectively engineer the existing or new nanozymes to curb AMR have also been discussed.

Nanozymes with biomimetically designed properties for cancer treatment

Nanozymes, as a type of nanomaterials with enzymatic catalytic activity, have demonstrated tremendous potential in cancer treatment owing to their unique biomedical properties. However, the heterogeneity of tumors and the complex tumor microenvironment pose significant challenges to the in vivo catalytic efficacy of traditional nanozymes. Drawing inspiration from natural enzymes, scientists are now using biomimetic design to build nanozymes from the ground up. This approach aims to replicate the key characteristics of natural enzymes, including active structures, catalytic processes, and the ability to adapt to the tumor environment. This achieves selective optimization of nanozyme catalytic performance and therapeutic effects. This review takes a deep dive into the use of these biomimetically designed nanozymes in cancer treatment. It explores a range of biomimetic design strategies, from structural and process mimicry to advanced functional biomimicry. A significant focus is on tweaking the nanozyme structures to boost their catalytic performance, integrating them into complex enzyme networks similar to those in biological systems, and adjusting functions like altering tumor metabolism, reshaping the tumor environment, and enhancing drug delivery. The review also covers the applications of specially designed nanozymes in pan-cancer treatment, from catalytic therapy to improved traditional methods like chemotherapy, radiotherapy, and sonodynamic therapy, specifically analyzing the anti-tumor mechanisms of different therapeutic combination systems. Through rational design, these biomimetically designed nanozymes not only deepen the understanding of the regulatory mechanisms of nanozyme structure and performance but also adapt profoundly to tumor physiology, optimizing therapeutic effects and paving new pathways for innovative cancer treatment.

A non-metal single atom nanozyme for cutting off the energy and reducing power of tumors

Enzymes are considered safe and effective therapeutic tools for various diseases. With the increasing integration of biomedicine and nanotechnology, artificial nanozymes offer advanced controllability and functionality in medical design. However, several notable gaps, such as catalytic diversity, specificity and biosafety, still exist between nanozymes and their native counterparts. Here we report a non-metal single-selenium (Se)-atom nanozyme (SeSAE), which exhibits potent nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-mimetic activity. This novel single atom nanozyme provides a safe alternative to conventional metal-based catalysts and effectively cuts off the cellular energy and reduction equivalents through its distinctive catalytic function in tumors. In this study, we have demonstrated the substantial efficacy of SeSAE as an antitumor nanomedicine across diverse mouse models without discernible systemic adverse effects. The mechanism of the NADPH oxidase-like activity of the non-metal SeSAE was rationalized by density functional theory calculations. Furthermore, comprehensive elucidation of the biological functions, cell death pathways, and metabolic remodeling effects of the nanozyme was conducted, aiming to provide valuable insights into the development of single atom nanozymes with clinical translation potential.

Transition Metal Ru(II) Catalysts Immobilized Nanoreactors for Conditional Bioorthogonal Catalysis in Cells

Employing transition metal catalysts (TMCs) to perform bioorthogonal activation of prodrugs and pro-fluorophores in biological systems, particularly in a conditional fashion, remains a challenge. Here, we used a mesoporous organosilica nanoscaffold (RuMSN), which localizes Ru(II) conjugates on the pore wall, enabling the biorthogonal photoreduction reactions of azide groups. Due to easily adjustable surface charges and pore diameter, this efficiently engineering RuMSN catalyst, with abundant active sites on the inner pore well, could spontaneously repel or attract substrates with different molecular sizes and charges and thus ensure selective bioorthogonal catalysis. Depending on it, engineering RuMSN nanoreactors showed fascinating application scales from conditional bioorthogonal activation of prodrugs and pro-fluorophores in either intra- or extracellular localization to performing intracellular concurrent and tandem catalysis together with natural enzymes.

Protein Aggregation on Metal Oxides Governs Catalytic Activity and Cellular Uptake

Engineering of catalytically active inorganic nanomaterials holds promising prospects for biomedicine. Catalytically active metal oxides show applications in enhancing wound healing but have also been employed to induce cell death in photodynamic or radiation therapy. Upon introduction into a biological system, nanomaterials are exposed to complex fluids, causing interaction and adsorption of ions and proteins. While protein corona formation on nanomaterials is acknowledged, its modulation of nanomaterial catalytic efficacy is less understood. In this study, proteomic analyses and nano-analytic methodologies quantify and characterize adsorbed proteins, correlating this protein layer with metal oxide catalytic activity in vitro and in vivo. The protein corona comprises up to 280 different proteins, constituting up to 38% by weight. Enhanced complement factors and other opsonins on nanocatalyst surfaces lead to their uptake into macrophages when applied topically, localizing >99% of the nanomaterials in tissue-resident macrophages. Initially, the formation of the protein corona significantly reduces the nanocatalysts' activity, but this activity can be partially recovered in endosomal conditions due to the proteolytic degradation of the corona. Overall, the research reveals the complex relationship between physisorbed proteins and the catalytic characteristics of specific metal oxide nanoparticles, providing design parameters for optimizing nanocatalysts in complex biological environments.

Modular Fabrication of Bioorthogonal Nanozymes for Biomedical Applications

The incorporation of transition metal catalysts (TMCs) into nanoscaffolds generates nanocatalysts that replicate key aspects of enzymatic behavior. The TMCs can access bioorthogonal chemistry unavailable to living systems. These bioorthogonal nanozymes can be employed as in situ "factories" for generating bioactive molecules where needed. The generation of effective bioorthogonal nanozymes requires co-engineering of the TMC and the nanometric scaffold. This review presents an overview of recent advances in the field of bioorthogonal nanozymes, focusing on modular design aspects of both nanomaterial and catalyst and how they synergistically work together for in situ uncaging of imaging and therapeutic agents.

Surface Chemistry of Biologically Active Reducible Oxide Nanozymes

Reducible metal oxide nanozymes (rNZs) are a subject of intense recent interest due to their catalytic nature, ease of synthesis, and complex surface character. Such materials contain surface sites which facilitate enzyme-mimetic reactions via substrate coordination and redox cycling. Further, these surface reactive sites are shown to be highly sensitive to stresses within the nanomaterial lattice, the physicochemical environment, and to processing conditions occurring as part of their syntheses. When administered in vivo, a complex protein corona binds to the surface, redefining its biological identity and subsequent interactions within the biological system. Catalytic activities of rNZs each deliver a differing impact on protein corona formation, its composition, and in turn, their recognition, and internalization by host cells. Improving the understanding of the precise principles that dominate rNZ surface-biomolecule adsorption raises the question of whether designer rNZs can be engineered to prevent corona formation, or indeed to produce "custom" protein coronas applied either in vitro, and preadministration, or formed immediately upon their exposure to body fluids. Here, fundamental surface chemistry processes and their implications in rNZ material performance are considered. In particular, material structures which inform component adsorption from the application environment, including substrates for enzyme-mimetic reactions are discussed.

Modulation of Gold Nanoparticle Ligand Structure-Dynamic Relationships Probed Using Solution NMR

Ligand dynamics plays a critical role in the chemical and biological properties of gold nanoparticles (AuNPs). In this study, ligands featuring hydrophobic alkanethiol interiors and hydrophilic shells were used to systematically examine the effects of ligand headgroups on the ligand dynamics. Solution nuclear magnetic resonance (NMR) spectroscopy provided quantitative insight into the monolayer ligand dynamics. Notably, the introduction of hydrophobic moieties to the cationic headgroups significantly decreased ligand conformational mobility; however, variations in hydrophobicity among these moieties had a limited effect on this reduction. Further examination of ligand dynamics under various physiological conditions, including ionic strength and temperature, showed that ligands bound to the AuNP surface become less conformationally mobile with an increase in ionic strength or decreasing temperature. This exploration of ligand dynamics provides insight into designing nanoparticles tailored to specific biological applications.

Polarization of macrophages to an anti-cancer phenotype through in situ uncaging of a TLR 7/8 agonist using bioorthogonal nanozymes

Macrophages are plastic cells of the immune system that can be broadly classified as having pro-inflammatory (M1-like) or anti-inflammatory (M2-like) phenotypes. M2-like macrophages are often associated with cancers and can promote cancer growth and create an immune-suppressive tumor microenvironment. Repolarizing macrophages from M2-like to M1-like phenotype provides a crucial strategy for anticancer immunotherapy. Imiquimod is an FDA-approved small molecule that can polarize macrophages by activating toll-like receptor 7/8 (TLR 7/8) located inside lysosomes. However, the non-specific inflammation that results from the drug has limited its systemic application. To overcome this issue, we report the use of gold nanoparticle-based bioorthogonal nanozymes for the conversion of an inactive, imiquimod-based prodrug to an active compound for macrophage re-education from anti- to pro-inflammatory phenotypes. The nanozymes were delivered to macrophages through endocytosis, where they uncaged pro-imiquimod in situ. The generation of imiquimod resulted in the expression of pro-inflammatory cytokines. The re-educated M1-like macrophages feature enhanced phagocytosis of cancer cells, leading to efficient macrophage-based tumor cell killing.

Hydrous ruthenium oxide triggers template-free and spontaneous growth of metal nanostructures

Intrinsically conductive ruthenium oxide is an excellent material for energy storage and conversion. Herein, we present hydrous RuO2 (H-RuO2) as a potent reducing agent to achieve spontaneous growth of multiple noble metals at room temperature. Self-assembled gold and platinum, comprising small-sized nanoparticles, are generated on the surface of H-RuO2 without the need for additional templates. Structural analysis reveals that the disordered structure and the presence of oxygen vacancies trigger interfacial redox reactions between H-RuO2 and oxidative metal salts. The resulting integrated nanostructures, consisting of a metal oxide and different metals (H-RuO2@metal), are subsequently used to treat inflammatory bowel diseases. In addition to biomedical applications, our developed synthetic strategy, using reactive oxides to spontaneously generate multicomponent nanostructures, also holds great significance for other catalysis-based applications.

Target-Specific Bioorthogonal Reactions for Precise Biomedical Applications

Bioorthogonal chemistry is a promising toolbox for dissecting biological processes in the native environment. Recently, bioorthogonal reactions have attracted considerable attention in the medical field for treating diseases, since this approach may lead to improved drug efficacy and reduced side effects via in situ drug synthesis. For precise biomedical applications, it is a prerequisite that the reactions should occur in the right locations and on the appropriate therapeutic targets. In this minireview, we highlight the design and development of targeted bioorthogonal reactions for precise medical treatment. First, we compile recent strategies for achieving target-specific bioorthogonal reactions. Further, we emphasize their application for the precise treatment of different therapeutic targets. Finally, a perspective is provided on the challenges and future directions of this emerging field for safe, efficient, and translatable disease treatment.

Current Advances of Atomically Dispersed Metal-Centered Nanozymes for Tumor Diagnosis and Therapy

Nanozymes, which combine enzyme-like catalytic activity and the biological properties of nanomaterials, have been widely used in biomedical fields. Single-atom nanozymes (SANs) with atomically dispersed metal centers exhibit excellent biological catalytic activity due to the maximization of atomic utilization efficiency, unique metal coordination structures, and metal-support interaction, and their structure-activity relationship can also be clearly investigated. Therefore, they have become an emerging alternative to natural enzymes. This review summarizes the examples of nanocatalytic therapy based on SANs in tumor diagnosis and treatment in recent years, providing an overview of material classification, activity modulation, and therapeutic means. Next, we will delve into the therapeutic mechanism of SNAs in the tumor microenvironment and the advantages of synergistic multiple therapeutic modalities (e.g., chemodynamic therapy, sonodynamic therapy, photothermal therapy, chemotherapy, photodynamic therapy, sonothermal therapy, and gas therapy). Finally, this review proposes the main challenges and prospects for the future development of SANs in cancer diagnosis and therapy.

Progress in controllable bioorthogonal catalysis for prodrug activation

Bioorthogonal catalysis, a class of catalytic reactions that are mediated by abiotic metals and proceed in biological environments without interfering with native biochemical reactions, has gained ever-increasing momentum in prodrug delivery over the past few decades. Albeit great progress has been attained in developing new bioorthogonal catalytic reactions and optimizing the catalytic performance of transition metal catalysts (TMCs), the use of TMCs to activate chemotherapeutics at the site of interest in vivo remains a challenging endeavor. To translate the bioorthogonal catalysis-mediated prodrug activation paradigm from flasks to animals, TMCs with targeting capability and stimulus-responsive behavior have been well-designed to perform chemical transformations in a controlled manner within highly complex biochemical systems, rendering on-demand drug activation to mitigate off-target toxicity. Here, we review the recent advances in the development of controllable bioorthogonal catalysis systems, with an emphasis on different strategies for engineering TMCs to achieve precise control over prodrug activation. Furthermore, we outline the envisaged challenges and discuss future directions of controllable bioorthogonal catalysis for disease therapy.

Anti-inflammatory potential of platinum nanozymes: mechanisms and perspectives

Inflammation is a complex process of the body in response to pathogen infections or dysregulated metabolism, involving the recruitment and activation of immune system components. Repeated dangerous stimuli or uncontrolled immune effector mechanisms can result in tissue injury. Reactive Oxygen Species (ROS) play key roles in physiological cell signaling as well as in the destruction of internalized pathogens. However, aberrant ROS production and release have deleterious effects on the surrounding environment, making ROS regulation a priority to reduce inflammation. Most of the current anti-inflammatory therapies rely on drugs that impair the release of pro-inflammatory mediators. Nevertheless, increasing the enzymatic activity to reduce ROS levels could be an alternative or complementary therapeutic approach to decrease inflammation. Nanozymes are nanomaterials with high catalytic activity that mimic natural enzymes, allowing biochemical reactions to take place. Such functional particles typically show different and regenerable oxidation states or catalytically reactive surfaces offering long-term activity and stability. In this scenario, platinum-based nanozymes (PtNZs) exhibit broad and efficient catalytic functionalities and can reduce inflammation mainly through ROS scavenging, e.g. by catalase and superoxide dismutase reactions. Dose-dependent biocompatibility and immune compatibility of PtNZs have been shown in different cells and tissues, both in vitro and in vivo. Size/shape/surface engineering of the nanozymes could also potentiate their efficacy to act at different sites and/or steps of the inflammation process, such as cytokine removal or specific targeting of activated leukocytes. In the present review, we analyze key inflammation triggering processes and the effects of platinum nanozymes under exemplificative inflammatory conditions. We further discuss potential platinum nanozyme design and improvements to modulate and expand their anti-inflammatory action.

Biomimetic and bioorthogonal nanozymes for biomedical applications

Nanozymes mimic the function of enzymes, which drive essential intracellular chemical reactions that govern biological processes. They efficiently generate or degrade specific biomolecules that can initiate or inhibit biological processes, regulating cellular behaviors. Two approaches for utilizing nanozymes in intracellular chemistry have been reported. Biomimetic catalysis replicates the identical reactions of natural enzymes, and bioorthogonal catalysis enables chemistries inaccessible in cells. Various nanozymes based on nanomaterials and catalytic metals are employed to attain intended specific catalysis in cells either to mimic the enzymatic mechanism and kinetics or expand inaccessible chemistries. Each nanozyme approach has its own intrinsic advantages and limitations, making them complementary for diverse and specific applications. This review summarizes the strategies for intracellular catalysis and applications of biomimetic and bioorthogonal nanozymes, including a discussion of their limitations and future research directions.

Biodegradable nanoemulsion-based bioorthogonal nanocatalysts for intracellular generation of anticancer therapeutics

Bioorthogonal catalysis mediated by transition metal catalysts (TMCs) provides controlled in situ activation of prodrugs through chemical reactions that do not interfere with cellular bioprocesses. The direct use of 'naked' TMCs in biological environments can have issues of solubility, deactivation, and toxicity. Here, we demonstrate the design and application of a biodegradable nanoemulsion-based scaffold stabilized by a cationic polymer that encapsulates a palladium-based TMC, generating bioorthogonal nanocatalyst "polyzymes". These nanocatalysts enhance the stability and catalytic activity of the TMCs while maintaining excellent mammalian cell biocompatibility. The therapeutic potential of these nanocatalysts was demonstrated through efficient activation of a non-toxic prodrug into an active chemotherapeutic drug, leading to efficient killing of cancer cells.

Interfacing Nanomaterials with Biology through Ligand Engineering

Nanoparticles (NPs) have incredible potential in biology and biomedicine. Gold nanoparticles (AuNPs) have become a cornerstone of the nanomedicine revolution due to their ease of synthesis, inertness, and versatility. The widespread use of AuNPs can be traced to the development of accessible, bottom-up wet synthesis methods that emphasized the role of ligands in controlling the size, dispersity, and stability of colloids in solution. Decoration of AuNPs with organic ligands can be used to dictate the interactions of these nanomaterials with biosystems on multiple scales. The tunability of the AuNP ligand monolayer via covalent and noncovalent approaches allows the use of AuNPs in a broad range of biomedical fields.In this Account, we describe our use of AuNPs to answer a central question in the ligand engineering of colloidal nanoparticles: can we fabricate NPs that are nontoxic, modular, and functional in biological environments? We explored spherical AuNPs of different sizes and ligand structures, empirically exploring the AuNP-biomolecule interaction. We show here how the atom-by-atom control provided by organic synthesis can be used to create engineered ligands. Presenting these ligands on the surface of AuNPs creates multivalent constructs with unique and useful properties. Ligand design is a key feature of these AuNPs. We have developed ligands that have three distinct structural segments: 1) a hydrophobic alkanethiol interior that imparts stability; 2) a tetra(ethylene glycol) segment that creates a noninteracting tabula rasa surface; and 3) ligand headgroups that dictate how the AuNP interacts with the outside world. Our research into the design principles of ligands on AuNPs and their interactions with biological systems can be translated to other nanoparticle systems.This Account also summarizes the trajectory of ligand engineering in our laboratory and further afield. At the outset, experimental and theoretical fundamental studies were focused on the interactions between AuNPs and cellular components, such as proteins and lipid membranes. Understanding these behaviors provided the direction for investigating how ligands mediate the interface of AuNPs with mammalian and bacterial cells. In these experiments, it was particularly noteworthy that the ligand hydrophobicity and charge play a significant role in the uptake and toxicity of AuNPs. These revelations formed a basis for translating AuNPs to physiological environments. We present how we have integrated our synthetic abilities to construct AuNPs for biomedical applications, including delivery, bioorthogonal catalysis, antimicrobial and antitumor therapeutics, and biosensing.Overall, we hope that this Account will give the reader insight into how our research has evolved, changing AuNPs from synthetic curiosities into functional nanoplatforms for nanomedicine, all through the power of ligand design and synthesis.

Converting Nanotoxicity Data to Information Using Artificial Intelligence and Simulation

Decades of nanotoxicology research have generated extensive and diverse data sets. However, data is not equal to information. The question is how to extract critical information buried in vast data streams. Here we show that artificial intelligence (AI) and molecular simulation play key roles in transforming nanotoxicity data into critical information, i.e., constructing the quantitative nanostructure (physicochemical properties)-toxicity relationships, and elucidating the toxicity-related molecular mechanisms. For AI and molecular simulation to realize their full impacts in this mission, several obstacles must be overcome. These include the paucity of high-quality nanomaterials (NMs) and standardized nanotoxicity data, the lack of model-friendly databases, the scarcity of specific and universal nanodescriptors, and the inability to simulate NMs at realistic spatial and temporal scales. This review provides a comprehensive and representative, but not exhaustive, summary of the current capability gaps and tools required to fill these formidable gaps. Specifically, we discuss the applications of AI and molecular simulation, which can address the large-scale data challenge for nanotoxicology research. The need for model-friendly nanotoxicity databases, powerful nanodescriptors, new modeling approaches, molecular mechanism analysis, and design of the next-generation NMs are also critically discussed. Finally, we provide a perspective on future trends and challenges.

Catalytic Bioswitch of Platinum Nanozymes: Mechanistic Insights of Reactive Oxygen Species Scavenging in the Neurovascular Unit

Oxidative stress is known to be the cause of several neurovascular diseases, including neurodegenerative disorders, since the increase of reactive oxygen species (ROS) levels can lead to cellular damage, blood-brain barrier leaking, and inflammatory pathways. Herein, we demonstrate the therapeutic potential of 5 nm platinum nanoparticles (PtNPs) to effectively scavenge ROS in different cellular models of the neurovascular unit. We investigated the mechanism underlying the PtNP biological activities, analyzing the influence of the evolving biological environment during particle trafficking and disclosing a key role of the protein corona, which elicited an effective switch-off of the PtNP catalytic properties, promoting their selective in situ activity. Upon cellular internalization, the lysosomal environment switches on and boosts the enzyme-like activity of the PtNPs, acting as an intracellular "catalytic microreactor" exerting strong antioxidant functionalities. Significant ROS scavenging was observed in the neurovascular cellular models, with an interesting protective mechanism of the Pt-nanozymes along lysosomal-mitochondrial axes.

Bioorthogonal nanozymes for breast cancer imaging and therapy

Bioorthogonal catalysis via transition metal catalysts (TMCs) enables the generation of therapeutics locally through chemical reactions not accessible by biological systems. This localization can enhance the efficacy of anticancer treatment while minimizing off-target effects. The encapsulation of TMCs into nanomaterials generates "nanozymes" to activate imaging and therapeutic agents. Here, we report the use of cationic bioorthogonal nanozymes to create localized "drug factories" for cancer therapy in vivo. These nanozymes remained present at the tumor site at least seven days after a single injection due to the interactions between cationic surface ligands and negatively charged cell membranes and tissue components. The prodrug was then administered systemically, and the nanozymes continuously converted the non-toxic molecules into active drugs locally. This strategy substantially reduced the tumor growth in an aggressive breast cancer model, with significantly reduced liver damage compared to traditional chemotherapy.

Metal and Metal Oxides Nanoparticles and Nanosystems in Anticancer and Antiviral Theragnostic Agents

The development of antiviral treatment and anticancer theragnostic agents in recent decades has been associated with nanotechnologies, and primarily with inorganic nanoparticles (INPs) of metal and metal oxides. The large specific surface area and its high activity make it easy to functionalize INPs with various coatings (to increase their stability and reduce toxicity), specific agents (allowing retention of INPs in the affected organ or tissue), and drug molecules (for antitumor and antiviral therapy). The ability of magnetic nanoparticles (MNPs) of iron oxides and ferrites to enhance proton relaxation in specific tissues and serve as magnetic resonance imaging contrast agents is one of the most promising applications of nanomedicine. Activation of MNPs during hyperthermia by an external alternating magnetic field is a promising method for targeted cancer therapy. As therapeutic tools, INPs are promising carriers for targeted delivery of pharmaceuticals (either anticancer or antiviral) via magnetic drug targeting (in case of MNPs), passive or active (by attaching high affinity ligands) targeting. The plasmonic properties of Au nanoparticles (NPs) and their application for plasmonic photothermal and photodynamic therapies have been extensively explored recently in tumor treatment. The Ag NPs alone and in combination with antiviral medicines reveal new possibilities in antiviral therapy. The prospects and possibilities of INPs in relation to magnetic hyperthermia, plasmonic photothermal and photodynamic therapies, magnetic resonance imaging, targeted delivery in the framework of antitumor theragnostic and antiviral therapy are presented in this review.

Inorganic nanoparticles as scaffolds for bioorthogonal catalysts

Bioorthogonal transition metal catalysts (TMCs) transform therapeutically inactive molecules (pro-drugs) into active drug compounds. Inorganic nanoscaffolds protect and solubilize catalysts while offering a flexible design space for decoration with targeting elements and stimuli-responsive activity. These "drug factories" can activate pro-drugs in situ, localizing treatment to the disease site and minimizing off-target effects. Inorganic nanoscaffolds provide structurally diverse scaffolds for encapsulating TMCs. This ability to define the catalyst environment can be employed to enhance the stability and selectivity of the TMC, providing access to enzyme-like bioorthogonal processes. The use of inorganic nanomaterials as scaffolds TMCs and the use of these bioorthogonal nanozymes in vitro and in vivo applications will be discussed in this review.

Boosting Ferroptosis Therapy with Iridium Single-Atom Nanocatalyst in Ultralow Metal Content

Nanocatalysts are promising tumor therapeutics due to their ability to induce reactive oxygen species in the tumor microenvironment. Although increasing metal loading can improve catalytic activity, the quandary of high metal content versus potential systemic biotoxicity remains challenging. Here, a fully exposed active site strategy by site-specific anchoring of single iridium (Ir) atoms on the outer surface of a nitrogen-doped carbon composite (Ir single-atom catalyst (SAC)) is reported to achieve remarkable catalytic performance at ultralow metal content (≈0.11%). The Ir SAC exhibits prominent dual enzymatic activities to mimic peroxidase and glutathione peroxidase, which catalyzes the conversion of endogenous H2 O2 into •OH in the acidic TME and depletes glutathione (GSH) simultaneously. With an advanced support of GSH-trapping platinum(IV) and encapsulation with a red-blood-cell membrane, this nanocatalytic agent (Pt@IrSAC/RBC) causes intense lipid peroxidation that boosts tumor cell ferroptosis. The Pt@IrSAC/RBC demonstrates superior therapeutic efficacy in a mouse triple-negative mammary carcinoma model, resulting in complete tumor ablation in a single treatment session with negligible side effects. These outcomes may provide valuable insights into the design of nanocatalysts with high performance and biosafety for biomedical applications.

Biodegradable Antibacterial Bioorthogonal Polymeric Nanocatalysts Prepared by Flash Nanoprecipitation

Bioorthogonal activation of pro-dyes and prodrugs using transition-metal catalysts (TMCs) provides a promising strategy for imaging and therapeutic applications. TMCs can be loaded into polymeric nanoparticles through hydrophobic encapsulation to generate polymeric nanocatalysts with enhanced solubility and stability. However, biomedical use of these nanostructures faces challenges due to unwanted tissue accumulation of nonbiodegradable nanomaterials and cytotoxicity of heavy-metal catalysts. We report here the creation of fully biodegradable nanocatalysts based on an engineered FDA-approved polymer and the naturally existing catalyst hemin. Stable nanocatalysts were generated through kinetic stabilization using flash nanoprecipitation. The therapeutic potential of these nanocatalysts was demonstrated through effective treatment of bacterial biofilms through the bioorthogonal activation of a pro-antibiotic.

The protein corona from nanomedicine to environmental science

The protein corona spontaneously develops and evolves on the surface of nanoscale materials when they are exposed to biological environments, altering their physiochemical properties and affecting their subsequent interactions with biosystems. In this Review, we provide an overview of the current state of protein corona research in nanomedicine. We next discuss remaining challenges in the research methodology and characterization of the protein corona that slow the development of nanoparticle therapeutics and diagnostics, and we address how artificial intelligence can advance protein corona research as a complement to experimental research efforts. We then review emerging opportunities provided by the protein corona to address major issues in healthcare and environmental sciences. This Review details how mechanistic insights into nanoparticle protein corona formation can broadly address unmet clinical and environmental needs, as well as enhance the safety and efficacy of nanobiotechnology products.

Hybrid Nanosystems of Antibiotics with Metal Nanoparticles-Novel Antibacterial Agents

The appearance and increasing number of microorganisms resistant to the action of antibiotics is one of the global problems of the 21st century. Already, the duration of therapeutic treatment and mortality from infectious diseases caused by pathogenic microorganisms have increased significantly over the last few decades. Nanoscale inorganic materials (metals and metal oxides) with antimicrobial potential are a promising solution to this problem. Here we discuss possible mechanisms of pathogenic microorganisms' resistance to antibiotics, proposed mechanisms of action of inorganic nanoparticles on bacterial cells, and the possibilities and benefits of their combined use with antibacterial drugs. The prospects of using metal and metal oxide nanoparticles as carriers in targeted delivery systems for antibacterial compositions are also discussed.

Shortwave Infrared Fluorofluorophores for Multicolor In Vivo Imaging

Developing chemical tools to detect and influence biological processes is a cornerstone of chemical biology. Here we combine two tools which rely on orthogonality- perfluorocarbons and multiplexed shortwave infrared (SWIR) fluorescence imaging- to visualize nanoemulsions in real time in living mice. Drawing inspiration from fluorous and SWIR fluorophore development, we prepared two SWIR-emissive, fluorous-soluble chromenylium polymethine dyes. These are the most red-shifted fluorous fluorophores- "fluorofluorophores"-to date. After characterizing the dyes, their utility was demonstrated by tracking perfluorocarbon nanoemulsion biodistribution in vivo. Using an excitation-multiplexed approach to image two variables simultaneously, we gained insight into the importance of size and surfactant identity on biodistribution.

Protein encapsulation of nanocatalysts: A feasible approach to facilitate catalytic theranostics

Enzyme-mimicking nanocatalysts, also termed nanozymes, have attracted much attention in recent years. They are considered potential alternatives to natural enzymes due to their multiple catalytic activities and high stability. However, concerns regarding the colloidal stability, catalytic specificity, efficiency and biosafety of nanomaterials in biomedical applications still need to be addressed. Proteins are biodegradable macromolecules that exhibit superior biocompatibility and inherent bioactivities; hence, the protein modification of nanocatalysts is expected to improve their bioavailability to match clinical needs. The diversity of amino acid residues in proteins provides abundant functional groups for the conjugation or encapsulation of nanocatalysts. Moreover, protein encapsulation can not only improve the overall performance of nanocatalysts in biological systems, but also bestow materials with new features, such as targeting and retention in pathological sites. This review aims to report the recent developments and perspectives of protein-encapsulated catalysts in their functional improvements, modification methods and applications in biomedicine.

Nanoceria as an Electron Reservoir: Spontaneous Deposition of Metal Nanoparticles on Oxides and Their Anti-inflammatory Activities

Designing metal-metal oxide heteronanostructures with synergistic and superior activities (unattainable in the case of a single entity) is of great interest for a wide range of technological applications. Traditional synthetic strategies typically require reducing agents, stabilizing ligands, or high temperature reductive treatment to produce oxide-supported metals. Herein, a facile noble metal deposition strategy is developed to produce silver, gold, and platinum nanocrystals on the surface of hollow mesoporous cerium oxide nanospheres without any pretreatment. Unlike the galvanic replacement reaction, the developed protocol employs the innate reductive potential of CeO₂ to produce a high density of ultrafine noble metal nanocrystals homogeneously immobilized onto the surface of CeO₂ nanospheres. The multienzyme-like activities (i.e., superoxide dismutase-like and catalase-like) of CeO₂@metal nanostructures, originating from CeO₂ and metal nanoparticles, were effectively utilized for anti-inflammatory therapies in two in vivo models. This oxygen vacancy-mediated reduction strategy can be generalized to produce diverse metal-metal oxide nanostructures for a wide range of applications.

Bioorthogonal nanozymes: an emerging strategy for disease therapy

Transition metal catalysts (TMCs), capable of performing bioorthogonal reactions, have been engineered to trigger the formation of bioactive molecules in a controlled manner for biomedical applications. However, the widespread use of TMCs based biorthogonal reactions in vivo is still largely limited owing to their toxicity, poor stability, and insufficient targeting properties. The emergence of nanozymes (nanomaterials with enzyme-like activity), especially bioorthogonal nanozymes that combine the bioorthogonal catalytic activity of TMCs, the physicochemical properties of nanomaterials, and the enzymatic properties of classical nanozymes potentially provide opportunities to address these challenges. Thus, they can be used as multifunctional catalytic platforms for disease treatment and will be far-reaching. In this review, we first briefly recall the classical TMC-based bioorthogonal reactions. Furthermore, this review highlights the diverse strategies for manufacturing bioorthogonal nanozymes and their potential for therapeutic applications, with the goal of facilitating bioorthogonal catalysis in the clinic. Finally, we present challenges and the prospects of bioorthogonal nanozymes in bioorthogonal chemistry.

All-natural gelatin-based bioorthogonal catalysts for efficient eradication of bacterial biofilms

Bioorthogonal catalysis mediated by transition metal catalysts (TMCs) presents a versatile tool for in situ generation of diagnostic and therapeutic agents. The use of 'naked' TMCs in complex media faces numerous obstacles arising from catalyst deactivation and poor water solubility. The integration of TMCs into engineered inorganic scaffolds provides 'nanozymes' with enhanced water solubility and stability, offering potential applications in biomedicine. However, the clinical translation of nanozymes remains challenging due to their side effects including the genotoxicity of heavy metal catalysts and unwanted tissue accumulation of the non-biodegradable nanomaterials used as scaffolds. We report here the creation of an all-natural catalytic "polyzyme", comprised of gelatin-eugenol nanoemulsion engineered to encapsulate catalytically active hemin, a non-toxic iron porphyrin. These polyzymes penetrate biofilms and eradicate mature bacterial biofilms through bioorthogonal activation of a pro-antibiotic, providing a highly biocompatible platform for antimicrobial therapeutics.

Exporting Homogeneous Transition Metal Catalysts to Biological Habitats

The possibility of performing designed transition-metal catalyzed reactions in biological and living contexts can open unprecedented opportunities to interrogate and interfere with biology. However, the task is far from obvious, in part because of the presumed incompatibly between organometallic chemistry and complex aqueous environments. Nonetheless, in the past decade there has been a steady progress in this research area, and several transition-metal (TM)-catalyzed bioorthogonal and biocompatible reactions have been developed. These reactions encompass a wide range of mechanistic profiles, which are very different from those used by natural metalloenzymes. Herein we present a summary of the latest progress in the field of TM-catalyzed bioorthogonal reactions, with a special focus on those triggered by activation of multiple carbon-carbon bonds.

Macrophage-Encapsulated Bioorthogonal Nanozymes for Targeting Cancer Cells

Macrophages migrate to tumor sites by following chemoattractant gradients secreted by tumor cells, providing a truly active targeting strategy for cancer therapy. However, macrophage-based delivery faces challenges of cargo loading, control of release, and effects of the payload on the macrophage vehicle. We present a strategy that employs bioorthogonal "nanozymes" featuring transition metal catalysts (TMCs) to provide intracellular "factories" for the conversion of prodyes and prodrugs into imaging agents and chemotherapeutics. These nanozymes solubilize and stabilize the TMCs by embedding them into self-assembled monolayer coating gold nanoparticles. Nanozymes delivered into macrophages were intracellularly localized and retained activity even after prolonged (72 h) incubation. Significantly, nanozyme-loaded macrophages maintained their inherent migratory ability toward tumor cell chemoattractants, efficiently killing cancer cells in cocultures. This work establishes the potential of nanozyme-loaded macrophages for tumor site activation of prodrugs, providing readily tunable dosages and delivery rates while minimizing off-target toxicity of chemotherapeutics.

Degradable ZnS-Supported Bioorthogonal Nanozymes with Enhanced Catalytic Activity for Intracellular Activation of Therapeutics

Bioorthogonal catalysis using transition-metal catalysts (TMCs) provides a toolkit for the in situ generation of imaging and therapeutic agents in biological environments. Integrating TMCs with nanomaterials mimics key properties of natural enzymes, providing bioorthogonal "nanozymes". ZnS nanoparticles provide a platform for bioorthogonal nanozymes using ruthenium catalysts embedded in self-assembled monolayers on the particle surface. These nanozymes uncage allylated profluorophores and prodrugs. The ZnS core combines the non-toxicity and degradability with the enhancement of Ru catalysis through the release of thiolate surface ligands that accelerate the rate-determining step in the Ru-mediated deallylation catalytic cycle. The maximum rate of reaction (V_max) increases ∼2.5-fold as compared to the non-degradable gold nanoparticle analogue. The therapeutic potential of these bioorthogonal nanozymes is demonstrated by activating a chemotherapy drug from an inactive prodrug with efficient killing of cancer cells.

High-Throughput Colorimetric Analysis of Nanoparticle-Protein Interactions Based on the Enzyme-Mimic Properties of Nanoparticles

While an in-depth understanding of the biological behavior of engineered nanoparticles (NPs) is of great importance for their various applications, it remains challenging to quantitatively characterize NP-protein interactions in a simple and high-throughput manner. In the present work, we propose a new, colorimetric approach capable of quantitatively analyzing the adsorption of proteins onto the surface of NPs by their distinct peroxidase-mimic properties. Taking cationic AuNPs as an example, we demonstrate that this colorimetric method is capable of evaluating NP-protein interactions in a simple and high-throughput manner in multiwell plates. Important binding parameters (e.g., the binding affinity) of three different serum proteins (bovine serum albumin, transferrin, and lysozyme) as well as human serum to AuNPs with three different sizes (average diameters of 5, 10, and 15 nm) have been obtained. Based on a quantitative analysis of NP-protein interactions, we observe that the binding affinity and the inhibition efficiency of the nanozyme activity of AuNPs are strongly affected by the characteristics of proteins as well as the sizes of NPs. These results illustrate the great potential of the present colorimetric method as a simple, low-cost, and high-throughput platform for quantitatively investigating NP-protein interactions.

Chemical and Biophysical Signatures of the Protein Corona in Nanomedicine

An inconvenient hurdle in the practice of nanomedicine is the protein corona, a spontaneous collection of biomolecular species by nanoparticles in living systems. The protein corona is dynamic in composition and may entail improved water suspendability and compromised delivery and targeting to the nanoparticles. How much of this nonspecific protein ensemble is determined by the chemistry of the nanoparticle core and its surface functionalization, and how much of this entity is dictated by the biological environments that vary spatiotemporally in vivo? How do we "live with" and exploit the protein corona without significantly sacrificing the efficacy of nanomedicines in diagnosing and curing human diseases? This article discusses the chemical and biophysical signatures of the protein corona and ponders challenges ahead for the field of nanomedicine.

Supramolecular Shear-Thinning Glycopeptide Hydrogels for Injectable Enzyme Prodrug Therapy Applications

Transplantable catalytic reactors have attracted considerable attention as therapeutic biomedical materials. However, existing transplantable reactors such as biocatalytic films are limited by their invasiveness. Here, we report the fabrication of biocatalytic supramolecular hydrogels via self-assembly of amphiphilic glycopeptides. We show that the hydrogels have shear-thinning properties, demonstrating their potential to be administered using a syringe. Enzymes can be loaded into the hydrogels by simply adding enzyme solution, and the enzyme-loaded hydrogels can transform a prodrug into an anticancer drug that inhibits tumor cell growth. This study demonstrates the potential of these biocatalytic hydrogels as injectable therapeutic reactors for enzyme prodrug therapy.

Protein adsorption onto nanomaterials engineered for theranostic applications

The key role of biomolecule adsorption onto engineered nanomaterials for therapeutic and diagnostic purposes has been well recognized by the nanobiotechnology community, and our mechanistic understanding of nano-bio interactions has greatly advanced over the past decades. Attention has recently shifted to gaining active control of nano-bio interactions, so as to enhance the efficacy of nanomaterials in biomedical applications. In this review, we summarize progress in this field and outline directions for future development. First, we briefly review fundamental knowledge about the intricate interactions between proteins and nanomaterials, as unraveled by a large number of mechanistic studies. Then, we give a systematic overview of the ways that protein-nanomaterial interactions have been exploited in biomedical applications, including the control of protein adsorption for enhancing the targeting efficiency of nanomedicines, the design of specific protein adsorption layers on the surfaces of nanomaterials for use as drug carriers, and the development of novel nanoparticle array-based sensors based on nano-bio interactions. We will focus on particularly relevant and recent examples within these areas. Finally, we conclude this topical review with an outlook on future developments in this fascinating research field.

Synthesis of a cerium-based nanomaterial with superior oxidase-like activity for colorimetric determination of glutathione in food samples

Enzyme-like nanomaterials have received significant attention for their high stability and low cost. However, most nanomaterials require complicated synthesis processes, limiting the range of their potential applications. In this study, a novel cerium-based nanomaterial was fabricated in a facile manner from a mixture of dipicolinic acid (DPA), guanosine 5'-monophosphate (GMP), and cerium acetate under ambient conditions. The obtained nanomaterial, designated as DPA-Ce-GMP, exhibited superior oxidase-like activity owing to the mixed valence (Ce³⁺/Ce⁴⁺) of cerium ions. DPA-Ce-GMP efficiently catalyzed the oxidation of 3,3,5,5-tetramethylbenzidine (TMB), achieving a color reaction without requiring hydrogen peroxide. Thus, DPA-Ce-GMP was incorporated into a simple, rapid, and sensitive colorimetric sensor for glutathione (GSH) detection. Within this sensor, TMB oxidation is inhibited by the reducibility of GSH. The sensor exhibits a linear response over two concentration ranges (0.05-10 and 10-40 μM), and its detection limit is 17.1 nM (3σ/slope). The proposed sensor was successfully applied to GSH quantification in food samples. The developed sensor provides an efficient biomimic oxidase for GSH detection in real samples. Facile approach to prepare cerium-based nanomaterial with superior oxidase-like activity for colorimetric detection of glutathione in food samples.

Room-Temperature Harvesting Oxidase-Mimicking Enzymes with Exogenous ROS Generation in One Step

Despite the advantages of low cost, high stability, and activities, a majority of nanozymes rely on strict synthesis conditions and precise size/structure control, hindering the stable, bulk, and high-yield production that is necessary for general use. To facilitate the transition of nanozymes from benchtop to real-world applications, we herein present a one-step approach, which only needs mixing of two broad commercialized reagents at room temperature, to harvest gold nanoparticles-bovine serum albumin (BSA) nanocomposite (BSA-Au) with distinct oxidase-like activity and good stability in a broad range of harsh conditions. Density functional theory (DFT) calculations demonstrate the oxidase-like activity of BSA-Au stemming from thermodynamically and kinetically favored facets for O2 activation. The reactive oxygen species (ROS) generation of BSA-Au contributes to the catalytic activities and further enables water sterilization and antibacterial applications against superbugs. This one-step strategy promises great potential in bulk production of nanozyme for broad application beyond laboratory use.

Nanomaterial-based bioorthogonal nanozymes for biological applications

Bioorthogonal transformations are chemical reactions that use pathways which biological processes do not access. Bioorthogonal chemistry provides new approaches for imaging and therapeutic strategies, as well as tools for fundamental biology. Bioorthogonal catalysis enables the development of bioorthogonal "factories" for on-demand and in situ generation of drugs and imaging tools. Transition metal catalysts (TMCs) are widely employed as bioorthogonal catalysts due to their high efficiency and versatility. The direct application of TMCs in living systems is challenging, however, due to their limited solubility, instability in biological media and toxicity. Incorporation of TMCs into nanomaterial scaffolds can be used to enhance aqueous solubility, improve long-term stability in biological environment and minimize cytotoxicity. These nanomaterial platforms can be engineered for biomedical applications, increasing cellular uptake, directing biodistribution, and enabling active targeting. This review summarizes strategies for incorporating TMCs into nanomaterial scaffolds, demonstrating the potential and challenges of moving bioorthogonal nanocatalysts and nanozymes toward the clinic.

Click and Bioorthogonal Chemistry: The Future of Active Targeting of Nanoparticles for Nanomedicines?

Over the years, click and bioorthogonal reactions have been the subject of considerable research efforts. These high-performance chemical reactions have been developed to meet requirements not often provided by the chemical reactions commonly used today in the biological environment, such as selectivity, rapid reaction rate, and biocompatibility. Click and bioorthogonal reactions have been attracting increasing attention in the biomedical field for the engineering of nanomedicines. In this review, we study a compilation of articles from 2014 to the present, using the terms "click chemistry and nanoparticles (NPs)" to highlight the application of this type of chemistry for applications involving NPs intended for biomedical applications. This study identifies the main strategies offered by click and bioorthogonal chemistry, with respect to passive and active targeting, for NP functionalization with specific and multiple properties for imaging and cancer therapy. In the final part, a novel and promising approach for "two step" targeting of NPs, called pretargeting (PT), is also discussed; the principle of this strategy as well as all the studies listed from 2014 to the present are presented in more detail.

In situ activation of therapeutics through bioorthogonal catalysis

Bioorthogonal chemistry refers to any chemical reactions that can occur inside of living systems without interfering with native biochemical processes, which has become a promising strategy for modulating biological processes. The development of synthetic metal-based catalysts to perform bioorthogonal reactions has significantly expanded the toolkit of bioorthogonal chemistry for medicinal chemistry and synthetic biology. A wide range of homogeneous and heterogeneous transition metal catalysts (TMCs) have been reported, mediating different transformations such as cycloaddition reactions, as well as bond forming and cleaving reactions. However, the direct application of 'naked' TMCs in complex biological media poses numerous challenges, including poor water solubility, toxicity and catalyst deactivation. Incorporating TMCs into nanomaterials to create bioorthogonal nanocatalysts can solubilize and stabilize catalyst molecules, with the decoration of the nanocatalysts used to provide spatiotemporal control of catalysis. This review presents an overview of the advances in the creation of bioorthogonal nanocatalysts, highlighting different choice of nano-scaffolds, and the therapeutic and diagnostic applications.

Iridium-Triggered Allylcarbamate Uncaging in Living Cells

Designing a metal catalyst that addresses the major issues of solubility, stability, toxicity, cell uptake, and reactivity within complex biological milieu for bioorthogonal controlled transformation reactions is a highly formidable challenge. Herein, we report an organoiridium complex that is nontoxic and capable of the uncaging of allyloxycarbonyl-protected amines under biologically relevant conditions and within living cells. The potential applications of this uncaging chemistry have been demonstrated by the generation of diagnostic and therapeutic agents upon the activation of profluorophore and prodrug in a controlled fashion within HeLa cells, providing a valuable tool for numerous potential biological and therapeutic applications.

Nanozyme for tumor therapy: Surface modification matters

As the next generation of artificial enzymes, nanozymes have shown unique properties compared to its natural counterparts, such as stability in harsh environment, low cost, and ease of production and modification, paving the way for its biomedical applications. Among them, tumor catalytic therapy mediated by the generation of reactive oxygen species (ROS) has made great progress mainly from the peroxidase-like activity of nanozymes. Fe₃O₄ nanozymes, the earliest type of nanomaterial discovered to possess peroxidase-like activity, has consequently received wide attention for tumor therapy due to its ROS generation ability and tumor cell killing ability. However, inconsistent results of cytotoxicity were observed between different reports, and some even showed the scavenging of ROS in some cases. By collectively studying these inconsistent outcomes, we raise the question whether surface modification of Fe₃O₄ nanozymes, either through affecting peroxidase activity or by affecting the biodistribution and intracellular fate, play an important role in its therapeutic effects. This review will go over the fundamental catalytic mechanisms of Fe₃O₄ nanozymes and recent advances in tumor catalytic therapy, and discuss the importance of surface modification. Employing Fe₃O₄ nanozymes as an example, we hope to provide an outlook on the improvement of nanozyme-based antitumor activity.

Bioorthogonal strategies for the in vivo synthesis or release of drugs

The site-specific delivery of antitumor agents is a rapidly developing field that relies on prodrug activation and uncaging strategies. For this purpose, a wide range of homogeneous and heterogeneous biocompatible activators/catalysts have been developed to convert caged drugs with low toxicity and high stability in physiological settings into active substances in a bioorthogonal manner. The current methods allow for the site-specific delivery of activators and prodrugs to organelles, target cells, or tumors in living organisms. Here, we present an overview of the latest advances in catalytic drugs, highlighting the expanding toolbox of bioorthogonal activation strategies made possible by transition metals acting as activators or catalysts.