In vivo biocompatibility and immunogenicity of metal-phenolic gelation

Multifunctional calcium polyphenol networks reverse the hostile microenvironment of trauma for preventing postoperative peritoneal adhesions

Abdominal adhesions, a commonly observed complication of abdominal surgery, have a high incidence and adversely affect patients' physical and mental health. The primary causes of abdominal adhesions are intraoperative trauma, acute inflammatory response, bleeding, and foreign body infection. Because most current treatment approaches for abdominal adhesions are limited, improved and novel postoperative anti-adhesion regimens are urgently needed. In this study, we developed calcium polyphenol network (CaPN) microspheres based on the self-assembly of the natural triphenolic compound gallic acid and Ca2+ in solution. The physicochemical properties of CaPNs, including their hemostatic, antibacterial, antioxidant, and anti-inflammatory activities, were investigated in vitro. Bleeding and cecal-abdominal wall adhesion models were established to observe the hemostatic activity of CaPNs and their preventive effect on postoperative abdominal wall adhesion in vivo. The results showed that CaPNs significantly reduced inflammation, oxidative stress, fibrosis, and abdominal adhesion formation and had good hemostatic and antibacterial properties. Our findings suggest a novel strategy for the prevention of postoperative adhesions.

Recent Advances of Metal-Polyphenol Coordination Polymers for Biomedical Applications

Nanomedicine has provided cutting-edge technologies and innovative methods for modern biomedical research, offering unprecedented opportunities to tackle crucial biomedical issues. Nanomaterials with unique structures and properties can integrate multiple functions to achieve more precise diagnosis and treatment, making up for the shortcomings of traditional treatment methods. Among them, metal-polyphenol coordination polymers (MPCPs), composed of metal ions and phenolic ligands, are considered as ideal nanoplatforms for disease diagnosis and treatment. Recently, MPCPs have been extensively investigated in the field of biomedicine due to their facile synthesis, adjustable structures, and excellent biocompatibility, as well as pH-responsiveness. In this review, the classification of various MPCPs and their fabrication strategies are firstly summarized. Then, their significant achievements in the biomedical field such as biosensing, drug delivery, bioimaging, tumor therapy, and antibacterial applications are highlighted. Finally, the main limitations and outlooks regarding MPCPs are discussed.

Direct synthesis of amorphous coordination polymers and metal–organic frameworks

Coordination polymers (CPs) and their subset, metal-organic frameworks (MOFs), can have porous structures and hybrid physicochemical properties that are useful for diverse applications. Although crystalline CPs and MOFs have received the most attention to date, their amorphous states are of growing interest as they can be directly synthesized under mild conditions. Directly synthesized amorphous CPs (aCPs) can be constructed from a wider range of metals and ligands than their crystalline and crystal-derived counterparts and demonstrate numerous unique material properties, such as higher mechanical robustness, increased stability and greater processability. This Review examines methods for the direct synthesis of aCPs and amorphous MOFs, as well as their properties and characterization routes, and offers a perspective on the opportunities for the widespread adoption of directly synthesized aCPs.

Engineering metal‐phenolic networks for enhancing cancer therapy by tumor microenvironment modulation

The complicated tumor microenvironment (TME) is featured by low pH values, high redox status, and hypoxia, which greatly supports the genesis, development, and metastasis of tumors, leading to drug resistance and clinical failure. Moreover, a lot of immunosuppressive cells infiltrate in such TME, resulting in depressing immunotherapy. Therefore, the development of TME-responsive nanoplatforms has shown great significance in enhancing cancer therapeutics. Metal-phenolic networks (MPNs)-based nanosystems, which self-assemble via coordination of phenolic materials and metal ions, have emerged as excellent TME theranostic nanoplatforms. MPNs have unique properties including fast preparation, tunable morphologies, pH response, and biocompatibility. Besides, functionalization and surface modification can endow MPNs with specific functions for application requirements. Here, the representative engineering strategies of various polyphenols are first introduced, followed by the introduction of the engineering mechanisms of polyphenolic nanosystems, fabrication, and distinct properties of MPNs. Then, their advances in TME modulation are highlighted, such as antiangiogenesis, hypoxia relief, combination therapy sensitization, and immunosuppressive TME reversion. Finally, we will discuss the challenges and future perspectives of MPNs-based nanosystems for enhancing cancer therapy. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Assembly of surface-independent polyphenol/liquid gallium composite nanocoatings

The development of functional nanocoatings using natural compounds is a hallmark of sustainable strategies in the field of green synthesis. Herein, we report a surface-independent nanocoating strategy using natural polyphenols and gallium-based room temperature liquid metal nanoparticles. The nanocoating matrix is composed of tannic acid, crosslinked with group (IV) transition metal ions. Liquid gallium nanoparticles are incorporated into the coatings as a gallium ion releasing depot. The coating deposition is rapid and can be applied to a range of substrates including glass, plastics, paper, and metal surfaces, owing to the versatile adhesive nature of the catechol/gallol functional groups of tannic acid. The coating thickness can be controlled from 100 to 700 nm and the content of liquid gallium nanoparticles can be modulated. This enables the tunable release behaviour of gallium ions into the surrounding from the composite coatings. The coatings are highly biocompatible and display antioxidant and antibacterial properties that can be useful for diverse applications.

Self-assembly hydrogels of therapeutic agents for local drug delivery

Advanced drug delivery systems are of vital importance to enhance therapeutic efficacy. Among various recently developed formulations, self-assembling hydrogels composed of therapeutic agents have shown promising potential for local drug delivery owing to their excellent biocompatibility, high drug-loading efficiency, low systemic toxicity, and sustained drug release behavior. In particular, therapeutic agents self-assembling hydrogels with well-defined nanostructures are beneficial for direct delivery to the target site via injection, not only improving drug availability, but also extending their retention time and promoting cellular uptake. In brief, the self-assembly approach offers better opportunities to improve the precision of pharmaceutical treatment and achieve superior treatment efficacies. In this review, we intend to cover the recent developments in therapeutic agent self-assembling hydrogels. First, the molecular structures, self-assembly mechanisms, and application of self-assembling hydrogels are systematically outlined. Then, we summarize the various self-assembly strategies, including the single therapeutic agent, metal-coordination, enzyme-instruction, and co-assembly of multiple therapeutic agents. Finally, the potential challenges and future perspectives are discussed. We hope that this review will provide useful insights into the design and preparation of therapeutic agent self-assembling hydrogels.

Recent Advances in the Development and Antimicrobial Applications of Metal-Phenolic Networks

Due to the abuse of antibiotics and the emergence of multidrug resistant microorganisms, medical devices, and related biomaterials are at high risk of microbial infection during use, placing a heavy burden on patients and healthcare systems. Metal-phenolic networks (MPNs), an emerging organic-inorganic hybrid network system developed gradually in recent years, have exhibited excellent multifunctional properties such as anti-inflammatory, antioxidant, and antibacterial properties by making use of the coordination between phenolic ligands and metal ions. Further, MPNs have received widespread attention in antimicrobial infections due to their facile synthesis process, excellent biocompatibility, and excellent antimicrobial properties brought about by polyphenols and metal ions. In this review, different categories of biomaterials based on MPNs (nanoparticles, coatings, capsules, hydrogels) and their fabrication strategies are summarized, and recent research advances in their antimicrobial applications in biomedical fields (e.g., skin repair, bone regeneration, medical devices, etc.) are highlighted.

Photocurrent and Gelation Properties of Polyphenol-Modified Titanium-Oxo Compounds

Organic-inorganic hybrid metal-polyphenols as stable structural modules have gained extensive interest due to their diverse applications. However, titanium-oxo compounds (TOCs) with large molecular polyphenols have been less explored, and they were expected to be different from small polyphenols with isolated metal ions. Herein, 4-methyl-esculetin (Mesc), a catechol derivative, was selected to construct three TOCs, namely, [Ti₁₇O₂₄(Mesc)₄(OⁱPr)₁₆] (1), [Ti₁₂O₁₄(OⁱPr)₁₈][Ti₁₆O₁₄(Mesc)₁₂(OⁱPr)₁₄] (2), and [Ti₃O(Mesc)₂(OAc)₂(OⁱPr)₄] (3). These compounds were structurally characterized. Photocurrent responses were evaluated using the compound-sensitized TiO₂ electrodes. It was found that the current densities of 1-3 electrodes are in the order of 1 ≫ 3 > 2, which relates to the ligand-to-TiO core and ligand-to-ligand charge transfers (LMCT and LLCT, respectively). Density functional theory calculations showed that the lowest band gap of 1 originates from its LLCT. Compound 1 reacted with polyphenol tannin (TA) to form a fully transparent and robust gel (1-TA), and the gelation properties were investigated. Using the gel as a nano-TiO₂ fixing agent, solar cell electrodes were prepared by a low-temperature wet method. The photocurrent responsive behavior of the 1-TA/TiO₂ electrode was compared with that of the 1-sensitized traditional high-temperature-treated TiO₂ electrode. Although the current density of the former is somewhat lower than that of the traditional electrode, the low-temperature wet preparation of the 1-TA/TiO₂ electrode is more energy-efficient and sustainable.

Metal Ion-Directed Functional Metal-Phenolic Materials

Metal ions are ubiquitous in nature and play significant roles in assembling functional materials in fields spanning chemistry, biology, and materials science. Metal-phenolic materials are assembled from phenolic components in the presence of metal ions through the formation of metal-organic complexes. Alkali, alkali-earth, transition, and noble metal ions as well as metalloids interacting with phenolic building blocks have been widely exploited to generate diverse hybrid materials. Despite extensive studies on the synthesis of metal-phenolic materials, a comprehensive summary of how metal ions guide the assembly of phenolic compounds is lacking. A fundamental understanding of the roles of metal ions in metal-phenolic materials engineering will facilitate the assembly of materials with specific and functional properties. In this review, we focus on the diversity and function of metal ions in metal-phenolic material engineering and emerging applications. Specifically, we discuss the range of underlying interactions, including (i) cation-π, (ii) coordination, (iii) redox, and (iv) dynamic covalent interactions, and highlight the wide range of material properties resulting from these interactions. Applications (e.g., biological, catalytic, and environmental) and perspectives of metal-phenolic materials are also highlighted.

Metal Phenolic Nanodressing of Porous Polymer Scaffolds for Enhanced Bone Regeneration via Interfacial Gating Growth Factor Release and Stem Cell Differentiation

Porous polymer scaffolds are essential materials for tissue engineering because they can be easily processed to deliver stem cells or bioactive factors. However, scaffolds made of synthetic polymers normally lack a bioactive cell-material interface and undergo a burst release of growth factors, which may hinder their further application in tissue engineering. In this paper, a metal-phenolic network (MPN) was interfacially constructed on the pore surface of a porous poly(dl-lactide) (PPLA) scaffold. Based on the molecular gating property of the MPN supramolecular structure, the PPLA@MPN scaffold achieved the sustained release of the loaded molecules. In addition, the MPN coating provided a bioactive interface, thus encouraging the migration and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). The PPLA@MPN scaffolds exhibited enhanced bone regeneration in a rat femoral defect model in vivo compared to PPLA, which is ascribed to the combined effect of sustained bone morphogenetic protein-2 (BMP-2) release and the osteogenic ability of MPN. This nanodressing technique provides a viable and straightforward strategy for enhancing the performance of porous polymer scaffolds in bone tissue engineering.

Deconstruction and Reassembly of Renewable Polymers and Biocolloids into Next Generation Structured Materials

This review considers the most recent developments in supramolecular and supraparticle structures obtained from natural, renewable biopolymers as well as their disassembly and reassembly into engineered materials. We introduce the main interactions that control bottom-up synthesis and top-down design at different length scales, highlighting the promise of natural biopolymers and associated building blocks. The latter have become main actors in the recent surge of the scientific and patent literature related to the subject. Such developments make prominent use of multicomponent and hierarchical polymeric assemblies and structures that contain polysaccharides (cellulose, chitin, and others), polyphenols (lignins, tannins), and proteins (soy, whey, silk, and other proteins). We offer a comprehensive discussion about the interactions that exist in their native architectures (including multicomponent and composite forms), the chemical modification of polysaccharides and their deconstruction into high axial aspect nanofibers and nanorods. We reflect on the availability and suitability of the latter types of building blocks to enable superstructures and colloidal associations. As far as processing, we describe the most relevant transitions, from the solution to the gel state and the routes that can be used to arrive to consolidated materials with prescribed properties. We highlight the implementation of supramolecular and superstructures in different technological fields that exploit the synergies exhibited by renewable polymers and biocolloids integrated in structured materials.

A tris-oxovanadium pyrogallate complex: synthesis, structure, and magnetic and electronic properties

With the aim of identifying new cation-phenolate complexes, we herein investigated the reactivity of pyrogallol (H₃pgal) with vanadium salts. A trimetallic anionic complex was identified, and found to be formed under a broad set of reaction conditions. This complex, with the formula V₃O₃(pgal)₃^3-, consists of three oxovanadium(IV) units connected together by three pyrogallate ligands to afford a bowl-shaped species presenting a pseudo 3-fold symmetry axis. Its crystal structure is reported, as well as its characterisation by a broad set of techniques, including powder X-ray diffraction, thermogravimetric analysis, infrared and Raman spectroscopy, and solid state UV-visible diffuse reflectance. Its redox activity both in solution and in the solid state is described, together with its magnetic behavior. Finally, the relevance of this trimetallic unit in the field of phenolic-based biocoatings and Metal Organic Framework (MOF) synthesis is briefly discussed.

Structurally Dynamic Hydrogels for Biomedical Applications: Pursuing a Fine Balance between Macroscopic Stability and Microscopic Dynamics

Owing to their unique chemical and physical properties, hydrogels are attracting increasing attention in both basic and translational biomedical studies. Although the classical hydrogels with static networks have been widely reported for decades, a growing number of recent studies have shown that structurally dynamic hydrogels can better mimic the dynamics and functions of natural extracellular matrix (ECM) in soft tissues. These synthetic materials with defined compositions can recapitulate key chemical and biophysical properties of living tissues, providing an important means to understanding the mechanisms by which cells sense and remodel their surrounding microenvironments. This review begins with the overall expectation and design principles of dynamic hydrogels. We then highlight recent progress in the fabrication strategies of dynamic hydrogels including both degradation-dependent and degradation-independent approaches, followed by their unique properties and use in biomedical applications such as regenerative medicine, drug delivery, and 3D culture. Finally, challenges and emerging trends in the development and application of dynamic hydrogels are discussed.

Metal-phenolic networks: facile assembled complexes for cancer theranostics

In recent years, metal-phenolic networks (MPNs) have attracted increasing attention for the engineering of multi-functional platforms because of their easy fabrication processes, excellent physicochemical properties, outstanding biocompatibility, and promising theranostic applications. In this review, we summarize recent progress in the design, synthesis, shape-control, biocompatibility evaluation, and potential theranostic applications of MPNs, especially for cancer theranostics. First, we provide an overview of various MPN systems, relevant self-assembly procedures, and shape-controllable preparation. The in vitro and in vivo biocompatibility evaluation of MPNs is also discussed, including co-incubation viability, adhesion, bio-distribution, and inflammation. Finally, we highlight the significant achievements of various MPNs for cancer theranostics, such as tumor imaging, drug delivery, photothermal therapy, radiotherapy, and chemo- and photo-dynamic therapy. This review provides a comprehensive background on the design and controllable synthesis, in vitro and in vivo biocompatibility evaluation, applications of MPNs as cancer theranostic agents, and presents an overview of the most up-to-date achievements in this field.

Supramolecular engineering of hydrogels for drug delivery

Supramolecular binding motifs are increasingly employed in the design of biomaterials. The ability to rationally engineer specific yet reversible associations into polymer networks with supramolecular chemistry enables injectable or sprayable hydrogels that can be applied via minimally invasive administration. In this review, we highlight two main areas where supramolecular binding motifs are being used in the design of drug delivery systems: engineering network mechanics and tailoring drug-material affinity. Throughout, we highlight many of the established and emerging chemistries or binding motifs that are useful for the design of supramolecular hydrogels for drug delivery applications.

Metal-phenolic networks for cancer theranostics

Metal-phenolic networks (MPNs) have shown promising potential in biomedical applications since they provide a rapid, simple and robust way to construct multifunctional nanoplatforms. As a novel nanomaterial self-assembled from metal ions and polyphenols, MPNs can be prepared to assist the theranostics of cancer owing to their bio-adhesiveness, good biocompatibility, versatile drug loading, and stimuli-responsive profile. This Critical Review aims to summarize recent progress in MPN-based nanoplatforms for multimodal tumor therapy and imaging. First, the advantages of MPNs as drug carriers are summarized. Then, various tumor therapeutic modalities based on MPNs are introduced. Next, MPN-based theranostic systems are reviewed. In terms of in vivo applications, specific attention is paid to their biosafety, biodistribution, as well as excretion. Finally, some problems and limitations of MPNs are discussed, along with a future perspective on the field.

Medical Applications Based on Supramolecular Self-Assembled Materials From Tannic Acid

Polyphenol, characterized by various phenolic rings in the chemical structure and an abundance in nature, can be extracted from vegetables, grains, chocolates, fruits, tea, legumes, and seeds, among other sources. Tannic acid (TA), a classical polyphenol with a specific chemical structure, has been widely used in biomedicine because of its outstanding biocompatibility and antibacterial and antioxidant properties. TA has tunable interactions with various materials that are widely distributed in the body, such as proteins, polysaccharides, and glycoproteins, through multimodes including hydrogen bonding, hydrophobic interactions, and charge interactions, assisting TA as important building blocks in the supramolecular self-assembled materials. This review summarizes the recent immense progress in supramolecular self-assembled materials using TA as building blocks to generate different materials such as hydrogels, nanoparticles/microparticles, hollow capsules, and coating films, with enormous potential medical applications including drug delivery, tumor diagnosis and treatment, bone tissue engineering, biofunctional membrane material, and the treatment of certain diseases. Furthermore, we discuss the challenges and developmental prospects of supramolecular self-assembly nanomaterials based on TA.