Recent advances in MOF-based nanozymes: Synthesis, activities, and bioapplications

Nanozymes have garnered considerable research interest for their unique capacity to bridge nanotechnology and biology. Current studies predominantly concentrate on exploring nanozymes with diverse catalytic activities and their potential applications across various disciplines. Among them, nanoscale metal-organic frameworks (MOFs) are promising nanomaterials for constructing nanozymes. In this review, we firstly introduce the general construction strategies for MOF-based nanozymes. In addition, we also classify the MOF-based nanozymes in detail based on their catalytic performance. Thirdly, the recent research progress of MOF-based nanozymes in the field of biosensing, cancer therapy, antibacterial infection, and antioxidation are also comprehensively reviewed. Finally, we discuss the current challenges and future perspectives of MOF-based nanozymes, with the aim of assisting in their construction and maximizing their potential in bioapplications. It is hoped that we could provide scientists in materials science and biomedical research with valuable and comprehensive information, fostering advancements in interdisciplinary fields.

Biomimetic Integrated Nanozyme for Flare and Recurrence of Gouty Arthritis

Flare and multiple recurrences pose significant challenges in gouty arthritis. Traditional treatments provide temporary relief from inflammation but fail to promptly alleviate patient pain or effectively prevent subsequent recurrences. It should also be noted that both anti-inflammation and metabolism of uric acid are necessary for gouty arthritis, calling for therapeutic systems to achieve these two goals simultaneously. In this study, we propose a biomimetic integrated nanozyme, HMPB-Pt@MM, comprising platinum nanozyme and hollow Prussian blue. It demonstrates anti-inflammatory properties by eliminating reactive oxygen species and reducing infiltration of inflammatory macrophages. Additionally, it rapidly targets inflamed ankles through the camouflage of macrophage membranes. Furthermore, HMPB-Pt@MM exhibits urate oxidase-like capabilities, continuously metabolizing locally elevated uric acid concentrations, ultimately inhibiting multiple recurrences of gouty arthritis. In summary, HMPB-Pt@MM integrates ROS clearance with uric acid metabolism, offering a promising platform for the treatment of gouty arthritis.

Boosting Enzyme Activity in Enzyme Metal-Organic Framework Composites

Enzymes, as highly efficient biocatalysts, excel in catalyzing diverse reactions with exceptional activity and selective properties under mild conditions. Nonetheless, their broad applications are hindered by their inherent fragility, including low thermal stability, limited pH tolerance, and sensitivity to organic solvents and denaturants. Encapsulating enzymes within metal-organic frameworks (MOFs) can protect them from denaturation in these harsh environments. However, this often leads to a compromised enzyme activity. In recent years, extensive research efforts have been dedicated to enhancing enzymatic activity within MOFs, leading to the development of new enzyme-MOF composites that not only preserve their catalytic potential but also outperform their free counterparts. This Review provides a comprehensive review on recent developments in enzyme-MOF composites with a specific emphasis on their enhanced enzymatic activity compared to free enzymes.

Protein-guided biomimetic nanomaterials: a versatile theranostic nanoplatform for biomedical applications

Over the years, bioinspired mineralization-based approaches have been applied to synthesize multifunctional organic-inorganic nanocomposites. These nanocomposites can address the growing demands of modern biomedical applications. Proteins, serving as vital biological templates, play a pivotal role in the nucleation and growth processes of various organic-inorganic nanocomposites. Protein-mineralized nanomaterials (PMNMs) have attracted significant interest from researchers due to their facile and convenient preparation, strong physiological activity, stability, impressive biocompatibility, and biodegradability. Nevertheless, few comprehensive reviews have expounded on the progress of these nanomaterials in biomedicine. This article systematically reviews the principles and strategies for constructing nanomaterials using protein-directed biomineralization and biomimetic mineralization techniques. Subsequently, we focus on their recent applications in the biomedical field, encompassing areas such as bioimaging, as well as anti-tumor, anti-bacterial, and anti-inflammatory therapies. Furthermore, we discuss the challenges encountered in practical applications of these materials and explore their potential in future applications. This review aspired to catalyze the continued development of these bioinspired nanomaterials in drug development and clinical diagnosis, ultimately contributing to the fields of precision medicine and translational medicine.

Recent Progress and Prospect of Metal-Organic Framework-Based Nanozymes in Biomedical Application

A nanozyme is a nanoscale material having enzyme-like properties. It exhibits several superior properties, including low preparation cost, robust catalytic activity, and long-term storage at ambient temperatures. Moreover, high stability enables repetitive use in multiple catalytic reactions. Hence, it is considered a potential replacement for natural enzymes. Enormous research interest in nanozymes in the past two decades has made it imperative to look for better enzyme-mimicking materials for biomedical applications. Given this, research on metal-organic frameworks (MOFs) as a potential nanozyme material has gained momentum. MOFs are advanced hybrid materials made of inorganic metal ions and organic ligands. Their distinct composition, adaptable pore size, structural diversity, and ease in the tunability of physicochemical properties enable MOFs to mimic enzyme-like activities and act as promising nanozyme candidates. This review aims to discuss recent advances in the development of MOF-based nanozymes (MOF-NZs) and highlight their applications in the field of biomedicine. Firstly, different enzyme-mimetic activities exhibited by MOFs are discussed, and insights are given into various strategies to achieve them. Modification and functionalization strategies are deliberated to obtain MOF-NZs with enhanced catalytic activity. Subsequently, applications of MOF-NZs in the biosensing and therapeutics domain are discussed. Finally, the review is concluded by giving insights into the challenges encountered with MOF-NZs and possible directions to overcome them in the future. With this review, we aim to encourage consolidated efforts across enzyme engineering, nanotechnology, materials science, and biomedicine disciplines to inspire exciting innovations in this emerging yet promising field.

Alkaline Phosphatase Relieves Colitis in Obese Mice Subjected to Forced Exercise via Its Anti-Inflammatory and Intestinal Microbiota-Shaping Properties

Intestinal alkaline phosphatase (IAP) is an enzyme that plays a protective role in the gut. This study investigated the effect of IAP treatment on experimental colitis in mice subjected to forced exercise on a high-fat diet. C57BL/6 mice with TNBS colitis were fed a high-fat diet and subjected to forced treadmill exercise with or without IAP treatment. Disease activity, oxidative stress, inflammatory cytokines, and gut microbiota were assessed. Forced exercise exacerbated colitis in obese mice, as evidenced by increased disease activity index (DAI), oxidative stress markers, and proinflammatory adipokines and cytokines. IAP treatment significantly reduced these effects and promoted the expression of barrier proteins in the colonic mucosa. Additionally, IAP treatment altered the gut microbiota composition, favoring beneficial Verrucomicrobiota and reducing pathogenic Clostridia and Odoribacter. IAP treatment ameliorates the worsening effect of forced exercise on murine colitis by attenuating oxidative stress, downregulating proinflammatory biomarkers, and modulating the gut microbiota. IAP warrants further investigation as a potential therapeutic strategy for ulcerative colitis.

Orally-administered nanomedicine systems targeting colon inflammation for the treatment of inflammatory bowel disease: latest advances

Inflammatory bowel disease (IBD) is a chronic and idiopathic condition that results in inflammation of the gastrointestinal tract, leading to conditions such as ulcerative colitis and Crohn's disease. Commonly used treatments for IBD include anti-inflammatory drugs, immunosuppressants, and antibiotics. Fecal microbiota transplantation is also being explored as a potential treatment method; however, these drugs may lead to systemic side effects. Oral administration is preferred for IBD treatment, but accurately locating the inflamed area in the colon is challenging due to multiple physiological barriers. Nanoparticle drug delivery systems possess unique physicochemical properties that enable precise delivery to the target site for IBD treatment, exploiting the increased permeability and retention effect of inflamed intestines. The first part of this review comprehensively introduces the pathophysiological environment of IBD, covering the gastrointestinal pH, various enzymes in the pathway, transport time, intestinal mucus, intestinal epithelium, intestinal immune cells, and intestinal microbiota. The second part focuses on the latest advances in the mechanism and strategies of targeted delivery using oral nanoparticle drug delivery systems for colitis-related fields. Finally, we present challenges and potential directions for future IBD treatment with the assistance of nanotechnology.

SOD mineralized zeolitic imidazole framework-8 for the treatment of chemotherapy-related acute kidney injury

Acute kidney injury (AKI), a prevalent and fatal adverse event, seriously affects cancer patients undergoing chemotherapy. The most important pathological mechanism of AKI is oxidative stress from reactive oxygen species (ROS). Currently, ROS scavenging is a promising strategy to manage the risk of chemotherapy-induced AKI. Herein, we successfully synthesized SOD@ZIF-8 nanoparticles by biomimetic mineralization, which were taken up by cells and could improve cell viability by limiting oxidative stress damage, as found in in vitro studies. Moreover, SOD@ZIF-8 nanoparticles exhibit broad-spectrum antioxidant properties in addition to significant renal accumulation in AKI mice, preventing clinically related cisplatin-induced AKI in murine models. AKI alleviation in the model was validated by measuring blood serum, staining kidney tissue, and related biomarkers. SOD@ZIF-8 nanoparticle therapeutic efficiency exceeds NAC, a small molecular antioxidant functioning through free radical scavenging. The results suggest SOD@ZIF-8 nanoparticles as a potential therapeutic option for AKI and other ROS-related disorders.

Liposome-embedded SOD attenuated DSS-induced ulcerative colitis in mice by ameliorating oxidative stress and intestinal barrier dysfunction

Oxidative stress is generally considered inseparable from the development and exacerbation of ulcerative colitis (UC). Therefore, reducing oxidative stress has become a possible way to alleviate UC. In this study, the therapeutic effects of different doses of liposome-embedded superoxide dismutase (L-SOD) on mice with DSS-induced UC were systematically investigated. The results showed that L-SOD significantly attenuated the signs of colitis in mice, including colonic shortening, diarrhoea, bloody stools, and histopathological changes. L-SOD ameliorated DSS-induced oxidative damage, increased SOD, catalase (CAT), and glutathione (GSH) activities, and decreased malondialdehyde (MDA) levels. In addition, L-SOD ameliorated the inflammatory response by inhibiting the expression of myeloperoxidase (MPO) and pro-inflammatory cytokines and protected barrier function by promoting the expression of the tight junction proteins occludin and ZO-1 in the colon. Importantly, the results demonstrated a bell-shaped distribution of therapeutic effects relative to the administered dose, with an optimal dose of 150 000 U kg^-1. These results indicate that L-SOD has great potential as an ingredient in functional foods for the prevention and mitigation of UC.

Enzyme Immobilization on Metal Organic Frameworks: the Effect of Buffer on the Stability of the Support

Metal organic frameworks (MOFs) have been used to encapsulate an array of enzymes in a rapid and facile manner; however, the stability of MOFs as supports for enzymes has not been examined in detail. This study examines the stability of MOFs with different compositions (Fe-BTC, Co-TMA, Ni-TMA, Cu-TMA, and ZIF-zni) in buffered solutions commonly used in enzyme immobilization and biocatalysis. Stability was assessed via quantification of the release of metals by inductively coupled plasma optical emission spectroscopy. The buffers used had varied effects on different MOF supports, with incubation of all MOFs in buffers resulting in the release of metal ions to varying extents. Fe-BTC was completely dissolved in citrate, a buffer that has a profound destabilizing effect on all MOFs analyzed, precluding its use with MOFs. MOFs were more stable in acetate, potassium phosphate, and Tris HCl buffers. The results obtained provide a guide for the selection of an appropriate buffer with a particular MOF as a support for the immobilization of an enzyme. In addition, these results identify the requirement to develop methods of improving the stability of MOFs in aqueous solutions. The use of polymer coatings was evaluated with polyacrylic acid (PAA) providing an improved level of stability. Lipase was immobilized in Fe-BTC with PAA coating, resulting in a stable biocatalyst with retention of activity in comparison to the free enzyme.