Expanding the Toolbox of Metal–Phenolic Networks via Enzyme‐Mediated Assembly

Biomimetic Nanomodulator Regulates Oxidative and Inflammatory Stresses to Treat Sepsis-Associated Encephalopathy

Sepsis-associated encephalopathy (SAE) is a devastating complication of sepsis, affecting approximately 70% of patients with sepsis in intensive care units (ICU). Although the pathophysiological mechanisms remain elusive, sepsis is typically accompanied by systemic inflammatory response syndrome (SIRS) and hyper-oxidative conditions. Here, we introduce a biomimetic nanomodulator (mAOI NP) that specifically targets inflammation site and simultaneously regulates oxidative and inflammatory stresses. mAOI NPs are constructed using metal-coordinated polyphenolic antioxidants (tannic acid) and flavonoid quercetin, which are then coated with macrophage membrane to enhance pharmacokinetics and enable SAE targeting. In a cecal ligation and puncture (CLP)-induced severe sepsis model, mAOI NPs effectively mitigate oxidative stress by purging reactive oxygen species, repairing mitochondrial damage and activating the Nrf2/HO-1 signaling pathway; while polarizing M1 macrophages or microglia toward anti-inflammatory M2 subtype. mAOI NPs potently inhibit sepsis progress, prolong overall survival from 25 to 66% and enhance learning and memory capabilities in SAE mice. Further proteomics analysis reveals that mAOI NPs modulate neurodevelopment processes related to learning and memory formation while also exerting anti-inflammatory and antioxidative effects on brain tissue responses associated with SAE pathology. This study offers significant potential for improving patient outcomes and revolutionizing the treatment landscape for this devastating complication of sepsis.

Controlled Self-Assembly of Natural Polyphenols Driven by Multiple Molecular Interactions

Nature has exhibited a high degree of control over the structures and functions. Supramolecules have been utilized to mimic the subtle assembly in nature. However, sophisticated synthesis of molecular skeletons or programmable design of the driving forces raises great challenges in fabricating high-level superstructures in a controlled manner. Natural polyphenols show great promises as building blocks for a diverse of assemblies with controlled structures and functionalities. The intrinsically embedded phenolic groups (i. e., catechol and galloyl groups) are readily forming multiple molecular interactions, including coordination, hydrogen bonding, and π-π interactions with various materials of inorganic particles, organic compounds, synthetic polymers, and biomacromolecules, providing the self-assembled structures or nanocoating on surfaces. Subsequent assembly occurred by further bonding of polyphenols to construct supraparticles. To gain control over the self-assembly, the key lies in the interplay among the molecular interactions with one or two being dominant. In this Perspective, we introduce the representative polyphenol-based assemblies and their derived supraparticles to exhibit the effective harness of the controlled self-assembly by polyphenols.

Formation of Antifouling Brushes on Various Substrates Using a Melanin-Inspired Initiator Film

In this study, we developed a substrate-independent initiator film that can undergo surface-initiated polymerization to form an antifouling brush. Inspired by the melanogenesis found in nature, we synthesized a tyrosine-conjugated bromide initiator (Tyr-Br) that contains phenolic amine groups as the dormant coating precursor and α-bromoisobutyryl groups as the initiator. The resultant Tyr-Br was stable under ambient air conditions and underwent melanin-like oxidation only in the presence of tyrosinase to form an initiator film on various substrates. Subsequently, an antifouling polymer brush was formed using air-tolerant activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) of zwitterionic carboxybetaine. The entire surface coating procedure, including the initiator layer formation and ARGET ATRP, occurred under aqueous conditions and did not require organic solvents or chemical oxidants. Therefore, antifouling polymer brushes can be feasibly formed not only on experimentally preferred substrates (e.g., Au, SiO₂, and TiO₂) but also on polymeric substrates such as poly(ethylene terephthalate) (PET), cyclic olefin copolymer (COC), and nylon.

Modular Metal-Quinone Networks with Tunable Architecture and Functionality

Nanostructured materials with tunable structures and functionality are of interest in diverse areas. Herein, metal ions are coordinated with quinones through metal-acetylacetone coordination bonds to generate a class of structurally tunable, universally adhesive, hydrophilic, and pH-degradable materials. A library of metal-quinone networks (MQNs) is produced from five model quinone ligands paired with nine metal ions, leading to the assembly of particles, tubes, capsules, and films. Importantly, MQNs show bidirectional pH-responsive disassembly in acidic and alkaline solutions, where the quinone ligands mediate the disassembly kinetics, enabling temporal and spatial control over the release of multiple components using multilayered MQNs. Leveraging this tunable release and the inherent medicinal properties of quinones, MQN prodrugs with a high drug loading (>89 wt %) are engineered using doxorubicin for anti-cancer therapy and shikonin for the inhibition of the main protease in the SARS-CoV-2 virus.

Versatile Assembly of Metal-Phenolic Network Foams Enabled by Tannin-Cellulose Nanofibers

Metal-phenolic network (MPN) foams are prepared using colloidal suspensions of tannin-containing cellulose nanofibers (CNFs) that are ice-templated and thawed in ethanolic media in the presence of metal nitrates. The MPN facilitates the formation of solid foams by air drying, given the strength and self-supporting nature of the obtained tannin-cellulose nanohybrid structures. The porous characteristics and (dry and wet) compression strength of the foams are rationalized by the development of secondary, cohesive metal-phenolic layers combined with a hydrogen bonding network involving the CNF. The shrinkage of the MPN foams is as low as 6% for samples prepared with 2.5-10% tannic acid (or condensed tannin at 2.5%) with respect to CNF content. The strength of the MPN foams reaches a maximum at 10% tannic acid (using Fe^(III) ions), equivalent to a compressive strength 70% higher than that produced with tannin-free CNF foams. Overall, a straightforward framework is introduced to synthesize MPN foams whose physical and mechanical properties are tailored by the presence of tannins as well as the metal ion species that enable the metal-phenolic networking. Depending on the metal ion, the foams are amenable to modification according to the desired application.

Surface Coating with Naphthalene Trisulfonate/Hafnium(IV) Complexes: Versatility and Post-Functionalization

Naphthalene trisulfonate is found to have versatile surface coating capability when combined with hafnium(IV) ions, thereby forming complexes. Solid substrates such as titanium/titanium dioxide, glass, and nylon immersed in a solution of naphthalene trisulfonate and Hf^IV produces naphthalene trisulfonate/Hf^IV complex coating. The coating is not produced when the Hf^IV ions are absent or when naphthalene monosulfonate replaces naphthalene trisulfonate; this indicates the significance of Hf^IV ions and multiple sulfonates in this coating system. The versatile surface coating property of naphthalene trisulfonate/Hf^IV complexes is attributed to the coexistence of hydrophobic aromatic and hydrophilic side groups in naphthalene trisulfonate. Additionally, Hf^IV ion-mediated cross-linking reactions between naphthalene trisulfonate molecules induce molecular assembly, facilitating versatile surface coating. Post-functionalization of the coating is accomplished through additional Hf^IV-mediated coordinate bond formation; alginate and λ-carrageenan are successfully grafted onto the coating for nonbiofouling applications.

Mussel-inspired biomaterials: From chemistry to clinic

After several billions of years, nature still makes decisions on its own to identify, develop, and direct the most effective material for phenomena/challenges faced. Likewise, and inspired by the nature, we learned how to take steps in developing new technologies and materials innovations. Wet and strong adhesion by Mytilidae mussels (among which Mytilus edulis-blue mussel and Mytilus californianus-California mussel are the most well-known species) has been an inspiration in developing advanced adhesives for the moist condition. The wet adhesion phenomenon is significant in designing tissue adhesives and surgical sealants. However, a deep understanding of engaged chemical moieties, microenvironmental conditions of secreted proteins, and other contributing mechanisms for outstanding wet adhesion mussels are essential for the optimal design of wet glues. In this review, all aspects of wet adhesion of Mytilidae mussels, as well as different strategies needed for designing and fabricating wet adhesives are discussed from a chemistry point of view. Developed muscle-inspired chemistry is a versatile technique when designing not only wet adhesive, but also, in several more applications, especially in the bioengineering area. The applications of muscle-inspired biomaterials in various medical applications are summarized for future developments in the field.

Antifouling Surface Coating on Various Substrates by Inducing Tyrosinase-Mediated Oxidation of a Tyrosine-Conjugated Sulfobetaine Derivative

Inspired by the melanogenesis occurring in nature, we report tyrosinase-mediated antifouling surface coating by synthesizing a tyrosine-conjugated sulfobetaine derivative (Tyr-SB). Synthetic Tyr-SB contains zwitterionic sulfobetaine and tyrosine, whose phenolic amine group acts as a dormant coating precursor. In contrast to catecholamine derivatives, tyrosine derivatives are stable against auto-oxidation and are enzymatically oxidized only in the presence of tyrosinase to initiate melanin-like oxidation. When the surface of interest was applied during the course of Tyr-SB oxidation, a superhydrophilic poly(Tyr-SB) film was coated on the surfaces, thereby showing antifouling performance against proteins or adherent cells. Because the oxidation of Tyr-SB occurred under mild aqueous conditions (pH 6-7) without the use of any chemical oxidants, such as sodium periodate or ammonium persulfate, we anticipate that the coating method described herein will serve as a biocompatible tool in the field of biosensors, cell surface engineering, and medical devices, whose interfaces differ in chemistry.

Site-Selective Coordination Assembly of Dynamic Metal-Phenolic Networks

Coordination states of metal‐organic materials are known to dictate their physicochemical properties and applications in various fields. However, understanding and controlling coordination sites in metal‐organic systems is challenging. Herein, we report the synthesis of site‐selective coordinated metal‐phenolic networks (MPNs) using flavonoids as coordination modulators. The site‐selective coordination was systematically investigated experimentally and computationally using ligands with one, two, and multiple different coordination sites. Tuning the multimodal Fe coordination with catechol, carbonyl, and hydroxyl groups within the MPNs enabled the facile engineering of diverse physicochemical properties including size, selective permeability (20–2000 kDa), and pH‐dependent degradability. This study expands our understanding of metal‐phenolic chemistry and provides new routes for the rational design of structurally tailorable coordination‐based materials.

A green and highly efficient method to deliver hydrophilic polyphenols of Salvia miltiorrhiza and Carthamus tinctorius for enhanced anti-atherosclerotic effect via metal-phenolic network

Salvia miltiorrhiza and Carthamus tinctorius are traditional Chinese medicines that have been widely used for the treatment of cardiovascular disease. Salvianic acid A (SAA), salvianic acid B (SAB), protocatechuic aldehyde (PCA) and hydroxysafflor yellow A (HSYA) are the major hydrophilic polyphenols of Salvia miltiorrhiza and Carthamus tinctorius, all of which have been documented as active compounds for the prevention and treatment of atherosclerosis (AS). However, high aqueous solubility, low permeability and poor stability properties of the four hydrophilic polyphenols might influence their bioavailability and thus hinder their clinical potential. In this work, we introduced a green and highly efficient method for the efficient delivery of the four hydrophilic components via metal-phenolic network. The four coordination polymers of SAA, SAB, PCA and HSYA were successfully fabricated, and confirmed by UV-vis, FTIR, XPS, ICP-MS and dynamic light scattering analysis. We found all of them displayed potent antioxidant activity, good biocompatibility and stability. Impressively, the four coordination polymers showed remarkably enhanced anti-atherosclerotic effect compared with free drugs. Collectively, metal-phenolic network-based coordination polymer might show great potential for safe and efficient delivery of the hydrophilic polyphenols of Salvia miltiorrhiza and Carthamus tinctorius for anti-atherosclerotic therapy.

Coordination-driven Metal-polyphenolic Nanoparticles toward Effective Anticancer Therapy

Stabilization of bioactive components, especially for hydrophobic functional factors, is a promising approach for improving their biological activity. Here, a metal-phenolic coordination chemistry that synthesizes biocompatible and biodegradable thin-film based on tannic acid (TA) and trivalent metal ion (Fe³⁺ or Al³⁺ ) is addressed, and the results also demonstrate its use for encapsulating a hydrophobic drug (Nobiletin, NOB) and triggering drug release for cancer treatment both in vitro and in vivo. This assembled system provides drug-loaded nanoparticles (NPs) with small, but uniform, size (∼200 nm). It displays beneficial potential in enhancing colloidal stability and preventing premature drug leakage. Moreover, the metal-phenolic coating is found to possess high cell biocompatibility as a delivery vector for controlled drug delivery, while the final fabricated drug NPs have effective anti-tumor activity by both inducing higher tumor apoptosis and inhibiting tumor metastasis, which is superior to naked drug formulations. Overall, our findings propose an effective and straightforward way for coating hydrophobic drugs employing interfacial adhesion and assembly, which could be a highly promising vehicle for controlled-release biomedical applications for cancer therapy. This article is protected by copyright. All rights reserved.

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.

Nanostructured particles assembled from natural building blocks for advanced therapies

Advanced treatments based on immune system manipulation, gene transcription and regulation, specific organ and cell targeting, and/or photon energy conversion have emerged as promising therapeutic strategies against a range of challenging diseases. Naturally derived macromolecules (e.g., proteins, lipids, polysaccharides, and polyphenols) have increasingly found use as fundamental building blocks for nanostructured particles as their advantageous properties, including biocompatibility, biodegradability, inherent bioactivity, and diverse chemical properties make them suitable for advanced therapeutic applications. This review provides a timely and comprehensive summary of the use of a broad range of natural building blocks in the rapidly developing field of advanced therapeutics with insights specific to nanostructured particles. We focus on an up-to-date overview of the assembly of nanostructured particles using natural building blocks and summarize their key scientific and preclinical milestones for advanced therapies, including adoptive cell therapy, immunotherapy, gene therapy, active targeted drug delivery, photoacoustic therapy and imaging, photothermal therapy, and combinational therapy. A cross-comparison of the advantages and disadvantages of different natural building blocks are highlighted to elucidate the key design principles for such bio-derived nanoparticles toward improving their performance and adoption. Current challenges and future research directions are also discussed, which will accelerate our understanding of designing, engineering, and applying nanostructured particles for advanced therapies.

Development of Universal and Clickable Film by Mimicking Melanogenesis: On-Demand Oxidation of Tyrosine-Based Azido Derivative by Tyrosinase

In this study, we synthesized a tyrosine-based azido derivative (TBAD) that permits both substrate-independent surface coating and clickable film functionalization by mimicking natural melanogenesis. In contrast to catechol derivatives, which are generally susceptible to oxidation by air under ambient conditions, the monophenol-based TBAD remains stable under alkaline and neutral conditions, and is activated to oxidized quinone in situ by tyrosinase to initiate melanin-like polymerization. The resulting poly(TBAD) film can be formed on various substrates including noble metals, metal oxides, and synthetic polymers, which can undergo click reaction with terminal alkyne moieties on the entire surface or a specific region through Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The enzyme-mediated coating can rapidly form thin films (∼10 nm) and produce a uniform film morphology, which are important aspects in surface chemistry. This on-demand, clickable coating may become a significant tool for bioconjugation, soft lithography, and labeling techniques. This article is protected by copyright. All rights reserved.

Synthesis of Dithiocatechol-Pendant Polymers

Although the synthesis of thiophenol-pendant polymers was reported in the 1950s, the polymers generally suffered from oxidation and became insoluble in organic solvents, hampering detailed characterization and further applications. Dithiocatechol-pendant polymers, which have one additional ortho-thiol group than thiophenol-pendant polymers, have never been synthesized, despite their promise in various applications due to their analogous molecular structure with catechol-pendant polymers. Herein, we report the first synthesis of dithiocatechol-pendant polymers using a novel protection-deprotection strategy. We carefully examined the synthetic routes and identified the deprotection conditions that do not cause cross-linking of the dithiocatechol moieties. Because the resulting dithiocatechol-pendant polymers were soluble in common organic solvents (e.g., tetrahydrofuran and N,N-dimethylformamide), the polymers can be fully characterized by standard spectroscopic methods, providing valuable data for future researchers. We also showed that besides free-radical polymerization, reversible addition-fragmentation chain-transfer polymerization can also be adopted to synthesize dithiocatechol-pendant polymers. This work paves the way for the exploitation of dithiocatechol-containing polymers for the fabrication of novel functional materials.

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.

Sono-Fenton Chemistry Converts Phenol and Phenyl Derivatives into Polyphenols for Engineering Surface Coatings

We report a sono-Fenton strategy to mediate the supramolecular assembly of metal-phenolic networks (MPNs) as substrate-independent coatings using phenol and phenyl derivatives as building blocks. The assembly process is initiated from the generation of hydroxyl radicals (^. OH) using high-frequency ultrasound (412 kHz), while the metal ions synergistically participate in the production of additional ^. OH for hydroxylation/phenolation of phenol and phenyl derivatives via the Fenton reaction and also coordinate with the phenolic compounds for film formation. The coating strategy is applicable to various phenol and phenyl derivatives and different metal ions including Fe^II , Fe^III , Cu^II , and Co^II . In addition, the sono-Fenton strategy allows real-time control over the assembly process by turning the high-frequency ultrasound on or off. The properties of the building blocks are maintained in the formed films. This work provides an environmentally friendly and controllable method to expand the application of phenolic coatings for surface engineering.

Universal Surface Coating with a Non-Phenolic Molecule, Sulfonated Pyrene

Nature-inspired small molecules such as catecholamines and polyphenols have gained a great deal of attention because of the exceptional surface-coating property that is applicable to many diverse substrates. Many researchers have conducted studies to expand molecular pools with surface-coating properties, but previous reports have still been limited to phenolic molecules as surface-coating agents. In this study, we describe for the first time the material-independent coating properties of nonphenolic molecules, namely, sulfonated pyrenes with Zr^IV ions. Owing to the binding capability with several oxygen-containing ligands, Zr^IV can be used for the molecular assembly of sulfonated pyrenes. We also report on the mixing of multiple sulfonated pyrenes and Zr^IV results in cross-linked complexes that can coat diverse solid substrates. The resulting coating can serve as a platform for grafting functional polysaccharides.

Polyphenol-Containing Nanoparticles: Synthesis, Properties, and Therapeutic Delivery

Polyphenols, the phenolic hydroxyl group-containing organic molecules, are widely found in natural plants and have shown beneficial effects on human health. Recently, polyphenol-containing nanoparticles have attracted extensive research attention due to their antioxidation property, anticancer activity, and universal adherent affinity, and thus have shown great promise in the preparation, stabilization, and modification of multifunctional nanoassemblies for bioimaging, therapeutic delivery, and other biomedical applications. Additionally, the metal-polyphenol networks, formed by the coordination interactions between polyphenols and metal ions, have been used to prepare an important class of polyphenol-containing nanoparticles for surface modification, bioimaging, drug delivery, and disease treatments. By focusing on the interactions between polyphenols and different materials (e.g., metal ions, inorganic materials, polymers, proteins, and nucleic acids), a comprehensive review on the synthesis and properties of the polyphenol-containing nanoparticles is provided. Moreover, the remarkable versatility of polyphenol-containing nanoparticles in different biomedical applications, including biodetection, multimodal bioimaging, protein and gene delivery, bone repair, antibiosis, and cancer theranostics is also demonstrated. Finally, the challenges faced by future research regarding the polyphenol-containing nanoparticles are discussed.

Metal-phenolic network coatings for engineering bioactive interfaces

The surface modification of biomaterials is crucial for constructing bioactive interfaces capable of interacting with specific biomolecules, controlling cell behavior and regulating biological processes. Because of their excellent biocompatibility, facile preparation, pH-responsiveness and universal adhesion, surface coatings made from metal-phenolic network (MPN) have attracted extensive attention for handling interfacial properties and designing biomaterials in recent years. Different methods and technologies for assembling MPN coatings are summarized and compared in this paper, followed by highlighting the advantages of MPN coatings as bioactive interfaces for controlling biological process at the molecular, cellular, and tissue levels. Current challenges and prospects of MPN coatings for biomedical applications are also discussed.

Phenolic-enabled nanotechnology: versatile particle engineering for biomedicine

Phenolics are ubiquitous in nature and have gained immense research attention because of their unique physiochemical properties and widespread industrial use. In recent decades, their accessibility, versatile reactivity, and relative biocompatibility have catalysed research in phenolic-enabled nanotechnology (PEN) particularly for biomedical applications which have been a major benefactor of this emergence, as largely demonstrated by polydopamine and polyphenols. Therefore, it is imperative to overveiw the fundamental mechanisms and synthetic strategies of PEN for state-of-the-art biomedical applications and provide a timely and comprehensive summary. In this review, we will focus on the principles and strategies involved in PEN and summarize the use of the PEN synthetic toolkit for particle engineering and the bottom-up synthesis of nanohybrid materials. Specifically, we will discuss the attractive forces between phenolics and complementary structural motifs in confined particle systems to synthesize high-quality products with controllable size, shape, composition, as well as surface chemistry and function. Additionally, phenolic's numerous applications in biosensing, bioimaging, and disease treatment will be highlighted. This review aims to provide guidelines for new scientists in the field and serve as an up-to-date compilation of what has been achieved in this area, while offering expert perspectives on PEN's use in translational research.

Silanization of a Metal-Polyphenol Coating onto Diverse Substrates as a Strategy for Controllable Wettability with Enhanced Performance to Resist Acid Corrosion

Wettability is a crucial characteristic of materials that plays a vital role in surface engineering. Surface modification is the key to changing the wettability of materials, and a simple and universal modification approach is being extensively pursued by researchers. Recently, metal-phenolic networks (MPNs) have been widely studied because they impart versatility and functionality in surface modification. However, an MPN is not stable for long periods, especially under acidic conditions, and is susceptible to pollution by invasive species. Spurred by the versatility of MPNs and various functionalities achieved by silanization, we introduce a general strategy to fabricate functionally stable coatings with controllable surface wettability by combining the two methods. The formation process of MPN and silane-MPN coatings was characterized by spectroscopic ellipsometry (SE), UV-visible-near-infrared (UV-vis-NIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), water contact angle (WCA), etc. We found that the stability of the MPN was greatly enhanced after silanization, which is attributed to the cross-linking effect that occurs between silane and the MPN, namely, the cross-linking protection produced in this case. Additionally, the wettability of an MPN can be easily changed through our strategy. We trust that our strategy can further extend the applications of MPNs and points toward potential prospects in surface modification.

Self-Amplification of Tumor Oxidative Stress with Degradable Metallic Complexes for Synergistic Cascade Tumor Therapy

The ferroptosis effect has been illuminated with a clear Fenton reaction mechanism that converts endogenous hydrogen peroxide (H₂O₂) into highly oxidative hydroxyl radicals (·OH) in ROS-amplified tumor therapy. This ferroptosis-related oxidation effect was then further enhanced by the enzyme-like roles of cisplatin (CDDP). This CDDP-induced apoptosis was promoted in reverse by ferroptosis via the depletion of glutathione (GSH) and prevention of DNA damage repair. Here, we have developed degradable metallic complexes (PtH@FeP) containing an Fe(III)-polydopamine (FeP) core and HA-cross-linked CDDP (PtH) shell, exaggerating in situ toxic ROS production via the synergistic effect of CDDP and Fe(III). Taken together, the rationally designed PtH@FeP provided a new strategy for self-amplified synergistic chemotherapy/ferroptosis/photothermal therapy (PTT) antitumor effects with a reduced dosage that facilitates clinical safety.

A Clean and Tunable Mussel-Inspired Coating Technology by Enzymatic Deposition of Pseudo-Polydopamine (ψ-PDA) Thin Films from Tyramine

The tyrosinase-catalyzed oxidation of tyramine, leading to the deposition of pseudo-polydopamine (ψ-PDA) thin films, is disclosed herein as a superior technology for surface functionalization and coating at a neutral pH and at a low substrate concentration, compared to the standard autoxidative PDA coating protocols. Smooth ψ-PDA thin films of variable thickness up to 87 nm were obtained from 1 mM tyramine by varying tyrosinase concentrations (5-100 U/mL). Compared to the PDA films obtained by the similar enzymatic oxidation of 1 mM dopamine with tyrosinase (T-PDA), ψ-PDA displayed slower deposition kinetics, lower water contact angles in the range of 11°-28°, denoting higher hydrophilicity but similar UV-vis absorption profiles, as well as electrochemical properties and antioxidant activity. MALDI-MS analysis indicated for ψ-PDA a well defined pattern of peaks compatible with dopamine tetrameric structures degraded to a variable extent. The exposure to a tyramine solution of tyrosinase-loaded alginate spheres, or films deposited on glass or polyethylene, resulted in a rapid gel-confined ψ-PDA formation with no leakage or darkening of the solution, allowing the complete recovery and re-utilization of the unreacted tyramine. In contrast, an abundant PDA precipitation outside the gel was observed with dopamine under the same conditions. The ψ-PDA deposition by tyrosinase-catalyzed tyramine oxidation is thus proposed as a controllable and low-waste technology for selective surface functionalization and coating or for clean eumelanin particle production.

Zr(IV) Coordination Chemistry for Cell-Repellent Alginate Coatings: The Effect of Surface Functional Groups

Surface modification using alginic acid and its salt, alginate (Alg), has attracted much attention owing to its potential applications in various fields, including tissue engineering, drug delivery, antiplatelet surface preparation, and energy-storage technologies. In these applications, efficient immobilization of Alg on the solid surface is required because the delamination of the surface-bound Alg eventually leads to a significant decrease in its function. Therefore, much effort has been made to introduce Alg onto solid surfaces in a stable manner. Despite recent advances, existing methods for immobilizing Alg on surfaces have some limitations: (i) derivatization of Alg is typically also required and (ii) these methods only function under specific reaction conditions. Herein, we report a Zr(IV)-mediated strategy to immobilize Alg on solid surfaces. We demonstrate efficient Alg grafting onto carboxyl-, catechol-, polydopamine-, and tannic acid-functionalized surfaces via Zr(IV)-mediated cross-linking reactions. This strategy yields Alg multilayers that suppress fibroblast and platelet adhesion onto the solid surfaces. Furthermore, we show that the Alg multilayers can be selectively constructed on specific sites of solid surfaces. Given its ease of use and the wide selection of available carboxyl polymers, the current strategy is expected to be a useful tool for preparing functional polymer films for various applications.