Bioorthogonal nanozymes for breast cancer imaging and therapy

Nanosonosensitizer Optimization for Enhanced Sonodynamic Disease Treatment

Low-intensity ultrasound-mediated sonodynamic therapy (SDT), which, by design, integrates sonosensitizers and molecular oxygen to generate therapeutic substances (e.g., toxic hydroxyl radicals, superoxide anions, or singlet oxygen) at disease sites, has shown enormous potential for the effective treatment of a variety of diseases. Nanoscale sonosensitizers play a crucial role in the SDT process because their structural, compositional, physicochemical, and biological characteristics are key determinants of therapeutic efficacy. In particular, advances in materials science and nanotechnology have invigorated a series of optimization strategies for augmenting the therapeutic efficacy of nanosonosensitizers. This comprehensive review systematically summarizes, discusses, and highlights state-of-the-art studies on the current achievements of nanosonosensitizer optimization in enhanced sonodynamic disease treatment, with an emphasis on the general design principles of nanosonosensitizers and their optimization strategies, mainly including organic and inorganic nanosonosensitizers. Additionally, recent advancements in optimized nanosonosensitizers for therapeutic applications aimed at treating various diseases, such as cancer, bacterial infections, atherosclerosis, and autoimmune diseases, are clarified in detail. Furthermore, the biological effects of the improved nanosonosensitizers for versatile SDT applications are thoroughly discussed. The review concludes by highlighting the current challenges and future opportunities in this rapidly evolving research field to expedite its practical clinical translation and application.

Bioorthogonal chemistry-based prodrug strategies for enhanced biosafety in tumor treatments: current progress and challenges

Cancer is a significant global health challenge, and while chemotherapy remains a widely used treatment, its non-specific toxicity and broad distribution can lead to systemic side effects and limit its effectiveness against tumors. Therefore, the development of safer chemotherapy alternatives is crucial. Prodrugs hold great promise, as they remain inactive until they reach the cancer site, where they are selectively activated by enzymes or specific factors, thereby reducing side effects and improving targeting. However, subtle differences in the microenvironments between tumors and normal tissue may still result in unintended cytotoxicity. Bioorthogonal reactions, known for their selectivity and precision without interfering with natural biochemical processes, are gaining attention. When combined with prodrug strategies, these reactions offer the potential to create highly effective chemotherapy drugs. This review examines the safety and efficacy of prodrug strategies utilizing various bioorthogonal reactions in cancer treatment.

Nanozymes in cancer immunotherapy: metabolic disruption and therapeutic synergy

Over the past decade, there has been a growing emphasis on investigating the role of immunotherapy in cancer treatment. However, it faces challenges such as limited efficacy, a diminished response rate, and serious adverse effects. Nanozymes, a subset of nanomaterials, demonstrate boundless potential in cancer catalytic therapy for their tunable activity, enhanced stability, and cost-effectiveness. By selectively targeting the metabolic vulnerabilities of tumors, they can effectively intensify the destruction of tumor cells and promote the release of antigenic substances, thereby eliciting immune clearance responses and impeding tumor progression. Combined with other therapies, they synergistically enhance the efficacy of immunotherapy. Hence, a large number of metabolism-regulating nanozymes with synergistic immunotherapeutic effects have been developed. This review summarizes recent advancements in cancer immunotherapy facilitated by nanozymes, focusing on engineering nanozymes to potentiate antitumor immune responses by disturbing tumor metabolism and performing synergistic treatment. The challenges and prospects in this field are outlined. We aim to provide guidance for nanozyme-mediated immunotherapy and pave the way for achieving durable tumor eradication.

Engineering of bioorthogonal polyzymes through polymer sidechain design

Synthetic polymer scaffolds can encapsulate transition metal catalysts (TMCs) to provide bioorthogonal nanocatalysts. These 'polyzymes' catalyze the in situ generation of therapeutic agents without disrupting native biological processes. The design and modification of polymer scaffolds in these polyzymes can enhance the catalytic performance of TMCs in biological environments. In this study, we explore the hydrophobic design space of an oxanorborneneimide-based polymer by varying the length of its carbon side chain to engineer bioorthogonal polyzymes. Activity studies indicate that modulating the hydrophobicity of the polymer scaffold can be used to enhance the catalyst loading efficacy, catalytic activity, and serum stability of polyzymes. These findings provide insight into the structural elements contributing to improving polymeric nanocatalysts for a variety of applications.

A Synergistic Chemoimmunotherapy System Leveraging PD-L1 Blocking and Bioorthogonal Prodrug Activation

Novel strategies to facilitate tumor-specific drug delivery and restore immune attacks remain challenging in overcoming the current limitations of chemoimmunotherapy. An antitumor chemoimmunotherapy system comprising bioorthogonal reaction-ready group tetrazine (TZ) modified with an anti-PD-L1 antibody (αPD-L1TZ) and TZ-activatable prodrug vinyl ether-doxorubicin (DOX-VE) for self-reinforced anti-tumor chemoimmunotherapy is proposed. The αPD-L1TZ effectively disrupts the PD-L1/PD-1 interaction and activates the DOX prodrug in situ through the bioorthogonal click reaction of TZ and VE. Conversely, the activated DOX upregulates PD-L1 on the surface of tumor cells, facilitating tumor accumulation of αPD-L1TZ and enhancing DOX-VE activation. Furthermore, the activated DOX-induced immunogenic cell death of tumor cells, substantially improving the response efficiency of αPD-L1 in an immune-suppressive tumor microenvironment. Thus, PD-L1 blocking and bioorthogonal in situ prodrug activation synergistically enhance the antitumor efficacy of the chemoimmunotherapy system. Therefore, the system significantly enhances αPD-L1 tumor accumulation and prodrug activation and induces a robust immunological memory effect to prevent tumor recurrence and metastasis. Thus, a feasible chemoimmunotherapy combination regimen is presented.

Transition-Metal-Based Nanozymes: Synthesis, Mechanisms of Therapeutic Action, and Applications in Cancer Treatment

Cancer, as one of the leading causes of death worldwide, drives the advancement of cutting-edge technologies for cancer treatment. Transition-metal-based nanozymes emerge as promising therapeutic nanodrugs that provide a reference for cancer therapy. In this review, we present recent breakthrough nanozymes for cancer treatment. First, we comprehensively outline the preparation strategies involved in creating transition-metal-based nanozymes, including hydrothermal method, solvothermal method, chemical reduction method, biomimetic mineralization method, and sol-gel method. Subsequently, we elucidate the catalytic mechanisms (catalase (CAT)-like activities), peroxidase (POD)-like activities), oxidase (OXD)-like activities) and superoxide dismutase (SOD)-like activities) of transition-metal-based nanozymes along with their activity regulation strategies such as morphology control, size manipulation, modulation, composition adjustment and surface modification under environmental stimulation. Furthermore, we elaborate on the diverse applications of transition-metal-based nanozymes in anticancer therapies encompassing radiotherapy (RT), chemodynamic therapy (CDT), photodynamic therapy (PDT), photothermal therapy (PTT), sonodynamic therapy (SDT), immunotherapy, and synergistic therapy. Finally, the challenges faced by transition-metal-based nanozymes are discussed alongside future research directions. The purpose of this review is to offer scientific guidance that will enhance the clinical applications of nanozymes based on transition metals.

A Nanorobotics-Based Approach of Breast Cancer in the Nanotechnology Era

We are living in an era of advanced nanoscience and nanotechnology. Numerous nanomaterials, culminating in nanorobots, have demonstrated ingenious applications in biomedicine, including breast cancer (BC) nano-theranostics. To solve the complicated problem of BC heterogeneity, non-targeted drug distribution, invasive diagnostics or surgery, resistance to classic onco-therapies and real-time monitoring of tumors, nanorobots are designed to perform multiple tasks at a small scale, even at the organelles or molecular level. Over the last few years, most nanorobots have been bioengineered as biomimetic and biocompatible nano(bio)structures, resembling different organisms and cells, such as urchin, spider, octopus, fish, spermatozoon, flagellar bacterium or helicoidal cyanobacterium. In this review, readers will be able to deepen their knowledge of the structure, behavior and role of several types of nanorobots, among other nanomaterials, in BC theranostics. We summarized here the characteristics of many functionalized nanodevices designed to counteract the main neoplastic hallmark features of BC, from sustaining proliferation and evading anti-growth signaling and resisting programmed cell death to inducing angiogenesis, activating invasion and metastasis, preventing genomic instability, avoiding immune destruction and deregulating autophagy. Most of these nanorobots function as targeted and self-propelled smart nano-carriers or nano-drug delivery systems (nano-DDSs), enhancing the efficiency and safety of chemo-, radio- or photodynamic therapy, or the current imagistic techniques used in BC diagnosis. Most of these nanorobots have been tested in vitro, using various BC cell lines, as well as in vivo, mainly based on mice models. We are still waiting for nanorobots that are low-cost, as well as for a wider transition of these favorable effects from laboratory to clinical practice.

Controlled Bio-Orthogonal Catalysis Using Nanozyme-Protein Complexes via Modulation of Electrostatic Interactions

Bio-orthogonal chemistry provides a powerful tool for drug delivery systems due to its ability to generate therapeutic agents in situ, minimizing off-target effects. Bio-orthogonal transition metal catalysts (TMCs) with stimuli-responsive properties offer possibilities for controllable catalysis due to their spatial-, temporal-, and dosage-controllable properties. In this paper, we fabricated a stimuli-responsive bio-orthogonal catalysis system based on an enhanced green fluorescent protein (EGFP)-nanozyme (NZ) complex (EGFP-NZ). Regulation of the catalytic properties of the EGFP-NZ complex was directly achieved by modulating the ionic strength of the solution. The dielectric screening introduced by salt ions allows the dissociation of the EGFP-NZ complex, increasing the access of substrate to the active site of the NZs and concomitantly increasing nanozyme activity. The change in catalytic rate of the NZ/EGFP = 1:1 complex was positively correlated with salt concentration from 0 mM to 150 mM.

Dumbbell-shaped bimetallic AuPd nanoenzymes for NIR-II cascade catalysis-photothermal synergistic therapy

The noble metal NPs that are currently applied to photothermal therapy (PTT) have their photoexcitation location mainly in the NIR-I range, and the low tissue penetration limits their therapeutic effect. The complexity of the tumor microenvironment (TME) makes it difficult to inhibit tumor growth completely with a single therapy. Although TME has a high level of H2O2, the intratumor H2O2 content is still insufficient to catalyze the generation of sufficient hydroxide radicals (‧OH) to achieve satisfactory therapeutic effects. The AuPd-GOx-HA (APGH) was obtained from AuPd bimetallic nanodumbbells modified by glucose oxidase (GOx) and hyaluronic acid (HA) for photothermal enhancement of tumor starvation and cascade catalytic therapy in the NIR-II region. The CAT-like activity of AuPd alleviates tumor hypoxia by catalyzing the decomposition of H2O2 into O2. The GOx-mediated intratumoral glucose oxidation on the one hand can block the supply of energy and nutrients essential for tumor growth, leading to tumor starvation. On the other hand, the generated H2O2 can continuously supply local O2, which also exacerbates glucose depletion. The peroxidase-like activity of bimetallic AuPd can catalyze the production of toxic ‧OH radicals from H2O2, enabling cascade catalytic therapy. In addition, the high photothermal conversion efficiency (η = 50.7 %) of APGH nanosystems offers the possibility of photothermal imaging-guided photothermal therapy. The results of cell and animal experiments verified that APGH has good biosafety, tumor targeting, and anticancer effects, and is a precious metal nanotherapeutic system integrating glucose starvation therapy, nano enzyme cascade catalytic therapy, and PTT therapy. This study provides a strategy for photothermal-cascade catalytic synergistic therapy combining both exogenous and endogenous processes. STATEMENT OF SIGNIFICANCE: AuPd-GOx-HA cascade nanoenzymes were prepared as a potent cascade catalytic therapeutic agent, which enhanced glucose depletion, exacerbated tumor starvation and promoted cancer cell apoptosis by increasing ROS production through APGH-like POD activity. The designed system has promising photothermal conversion ability in the NIR-II region, simultaneously realizing photothermal-enhanced catalysis, PTT, and catalysis/PTT synergistic therapy both in vitro and in vivo. The present work provides an approach for designing and developing catalytic-photothermal therapies based on bimetallic nanoenzymatic cascades.

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.

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.

Quantitative imaging of the sub-organ distributions of nanomaterials in biological tissues via laser ablation inductively coupled plasma mass spectrometry

Nanomaterials have been employed in many biomedical applications, and their distributions in biological systems can provide an understanding of their behavior in vivo. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) can be used to determine the distributions of metal-based NMs in biological systems. However, LA-ICP-MS has not commonly been used to quantitatively measure the cell-specific or sub-organ distributions of nanomaterials in tissues. Here, we describe a new platform that uses spiked gelatin standards with control tissues on top to obtain an almost perfect tissue mimic for quantitative imaging purposes. In our approach, gelatin is spiked with both nanomaterial standards and an internal standard to improve quantitation and image quality. The value of the developed approach is illustrated by determining the sub-organ distributions of different metal-based and metal-tagged polymeric nanomaterials in mice organs. The LA-ICP-MS images reveal that the chemical and physical properties of the nanomaterials cause them to distribute in quantitatively different extents in spleens, kidneys, and tumors, providing new insight into the fate of nanomaterials in vivo. Furthermore, we demonstrate that this approach enables quantitative co-localization of nanomaterials and their cargo. We envision this method being a valuable tool in the development of nanomaterial drug delivery systems.

A narrative review: progress in transition metal-mediated bioorthogonal catalysis for the treatment of solid tumors

Background and Objective

Transition metals are commonly used catalysts in bioorthogonal chemistry and have attracted extensive attention in biochemistry because of their efficient catalytic performance. In recent years, transition metal-mediated cycloaddition reactions, bond cleavage, and formation reactions are being actively explored for tumor treatment. However, the direct application of transition metals in complex biological environments has several problems, including poor solubility, toxicity, and easy inactivation. The combination of transition metals and nanomaterials can solve those problems by playing a bioorthogonal catalytic role in tumor treatment. In this review, we summarize some research on the application of transition metals modified by nanomaterials in tumor therapy and discuss the potential and challenges of transition metal-mediated bioorthogonal therapy in comprehensive tumor therapy.

Methods

English literature on transition metal in cancer treatment was searched in PubMed and Web of Science. The main search terms were "cancer treatment", "bioorthogonal reaction", "transition metal", "bioorthogonal catalysis", etc.

Key Content and Findings

This review summarizes research on several major transition metals that can be used for bioorthogonal catalysis with the assistance of nanomaterials in anti-tumor therapy. In addition, bioorthogonal catalysis is a new supplement to antitumor therapy. We have compiled the potential challenges of the clinical application of transition metal-based nanocatalysts, which lays the foundation for future research related to medicinal chemistry and targeted cancer therapy.

Conclusions

Most of the transition metals still have a lot of room for exploration in cancer treatment research. We still need more research to confirm the feasibility of in vivo and clinical trials.

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.