Recent advances in the synthesis of catechol-derived (bio)polymers for applications in energy storage and environment

Coacervate-Derived Assembly of Poly(ethylene glycol) Nanoparticles for Combinational Tumor Therapy

Coacervates have garnered significant attention as potential drug carriers. However, the instability resulting from their intrinsic membrane-free nature restricts the application of coacervates in drug delivery. Herein, the engineering of poly(ethylene glycol) nanoparticles (PEG NPs) is reported using coacervates composed of PEG and polyphenols as the templates, where PEG is subsequently cross-linked based on different chemistries (e.g., thiol-disulfide exchange, click chemistry, and Schiff base reaction). The reported assembly strategy avoids the template removal process and the resultant PEG NPs exhibit excellent stability in the physiological environment compared to coacervates. The presence of polyphenols in PEG NPs enables the loading of various cargos including metal ions (i.e., Ru, Gd, Mn, Fe) and drug molecules (i.e., doxorubicin), which demonstrates their promise in magnetic resonance imaging and combinational tumor therapy. This work provides a promising strategy to promote the development of coacervate-derived NPs as a drug delivery system for biomedical applications.

Ni(II)-Directed Supramolecular Metallogel: Stimuli Responsiveness and Semiconducting Device Fabrication

Metal-organic gels (MOGs) are a type of supramolecular complex that have become highly intriguing due to their synergistic combination of inorganic and organic elements. We report the synthesis and characterization of a Ni-directed supramolecular gel using chiral amino acid L-DOPA (3,4-dihydroxy phenylalanine) containing ligand, which coordinates with Ni(II) to form metal-organic gels with exceptional properties. The functional Ni(II)-gel was synthesized by heating nickel(II) acetate hexahydrate and the L-DOPA containing ligand in DMSO at 70 °C. The rheological tests have verified the gel with its mechanical stability, while a SEM image has shown a spherical aggregate morphology. The gel is photo-responsive in nature and exhibits gel to sol transformation upon adsorption of toxic gases like NH3 or H2S. Notably, electrical conductivity of the gel was observed in electronic metal-semiconductor (MS) junctions' devices with a measured conductivity of 0.9×10-6 Sm-1. These devices also exhibited Schottky barrier diode characteristics, underscoring the multifunctional potential of the Ni(II)-gel.

Zwitterionic modified and freeze-thaw reinforced foldable hydrogel as intraocular lens for posterior capsule opacification prevention

Posterior capsule opacification (PCO) is a predominant postoperative complication, often leading to visual impairment due to the aberrant proliferation and adhesion of lens epithelial cells (LECs) and protein precipitates subsequent to intraocular lens (IOL) implantation. To address this clinical issue, a foldable and antifouling sharp-edged IOL implant based on naturally-derived cellulose hydrogel is synthesized. The mechanical strength and transparency of the hydrogel is enhanced via repeated freeze-thaw (FT) cycles. The incorporated zwitterionic modifications can remarkably prevent the incidence of PCO by exhibiting proteins repulsion and cell anti-adhesion properties. The graft of dopamine onto both the haptic and the periphery of the posterior surface ensures the adhesion of the hydrogel to the posterior capsule and impedes the migration of LECs without compromising transparency. In in vivo study, the zwitterionic modified foldable hydrogel exhibits uveal and capsular biocompatibility synchronously with no signs of inflammatory response and prevent PCO formation, better than that of commercialized and PEG-modified IOL. With foldability, endurability, antifouling effect, and adhesive to posterior capsule, the reported hydrogel featuring heterogeneous surface design displays great potential to eradicate PCO and attain post-operative efficacy after cataract surgery.

Preparation strategies of mussel-inspired chitosan-based biomaterials for hemostasis

Chitosan (CS) has been extensively studied in wound care for its intrinsic hemostatic and antibacterial properties. However, CS has limiting hemostasis applications on account of its drawbacks such as poor adhesion in humid environments and water solubility at neutral pH. CS-based biomaterials, inspired by mussel-adhesive proteins, serve as a suggested platform by biomedical science. The reports show that the mussel-inspired CS-based hemostatic structure has negligible toxicity and excellent adhesiveness. Biomedicine has witnessed significant progress in the development of these hemostatic materials. This review summarizes the methods for the modification of CS by mussel-inspired chemistry. Moreover, the general method for preparation of mussel-inspired CS-based biomaterials is briefly discussed in this review. This work is expected to give a better understanding of opportunities and challenges of the mussel-inspired strategy for the functionalization of CS-based biomaterials in hemostasis and wound healing. This review is hoped to provide an important perspective on the preparation of mussel-inspired CS-based hemostatic materials.

Bioadhesive-Inspired Ionomer for Membrane Electrode Assembly Interface Reinforcement in Fuel Cells

Anion exchange membrane fuel cells promise a sustainable and ecofriendly energy conversion pathway yet suffer from insufficient performance and durability. Drawing inspiration from mussel foot adhesion proteins for the first time, we herein demonstrate catechol-modified ionomers that synergistically reinforce the membrane electrode assembly interface and triple-phase boundary inside catalyst layers. The resulting ionomers present exceptional alkaline stability with only slight ionic conductivity declines after treatment in 2 M NaOH aqueous solution at 80 °C for 2500 h. Adopting catechol-modified ionomer as both anion exchange membrane and binder achieves a single-cell performance increase of 34%, and more importantly, endows fuel cell operation at a current density of 0.4 A cm-2 for over 300 h with negligible performance degradation (with a cell voltage decay rate of 0.03 mV h-1). Combining theoretical and experimental investigations, we reveal the molecular adhesion mechanism between the catechol-modified ionomer and Pt catalyst and illuminate the effect on the catalyst layer microstructure. Of fundamental interest, this bioadhesive-inspired strategy is critical to enabling knowledge-driven ionomer design and is promising for diverse membrane electrode assembly configurational applications.

Trends in polysaccharide-based hydrogels and their role in enhancing the bioavailability and bioactivity of phytocompounds

Over the years, polysaccharides such as chitosan, alginate, hyaluronic acid, k-carrageenan, xanthan gum, carboxymethyl cellulose, pectin, and starch, alone or in combination with proteins and/or synthetic polymers, have been used to engineer an extensive portfolio of hydrogels with remarkable features. The application of polysaccharide-based hydrogels has the potential to alleviate challenges related to bioavailability, solubility, stability, and targeted delivery of phytocompounds, contributing to the development of innovative and efficient drug delivery systems and functional food formulations. This review highlights the current knowledge acquired on the preparation, features and applications of polysaccharide/phytocompounds hydrogel-based hybrid systems in wound management, drug delivery, functional foods, and food industry. The structural, functional, and biological requirements of polysaccharides and phytocompounds on the overall performance of such hybrid systems, and their impact on the application domains are also discussed.

Self-Assembled Chiral Film Based on Melanin Polymers

Chirality plays a fundamental role in natural phenomena, yet its manifestation on solid surfaces remains relatively unexplored. In this study, we investigate the formation of chiroptical melanin-based self-assembled films on quartz substrates, leveraging mussel-inspired surface chemistry. Water-soluble porphyrins serve as molecular synthons, facilitating the spontaneous formation of hetero-aggregates in phosphate-buffered saline containing L- or D-DOPA. Spectroscopic analysis reveals chiral transfer from DOPA enantiomers to porphyrin hetero-aggregates, followed by the disruption of these latter and subsequent generation of chiral melanin structures in solution. Quartz substrates inserted into these solutions spontaneously accumulate homogeneous melanin-like films over days, demonstrating the feasibility of self-assembly. The resulting films exhibit characteristic UV/Vis and CD spectra, with distinct signals indicating successful chiral induction. Interestingly, the AFM characterizations reveal a distinct surface morphology, and in addition, some thermal and mechanical properties have been taken into account. Overall, this study sheds light on the formation, stability, and chiroptical properties of melanin-based films, paving the way for their application in various fields.

Deep eutectic supramolecular polymer functionalized MXene for enhancing mechanical properties, photothermal conversion, and bacterial inactivation of cellulose textiles

Two-dimensional (2D) transition metal carbides (Ti3C2Tx MXene) have gained significant attention for their potential in constructing diverse functional materials, However, MXene is easily oxidized and weakly bound to the cellulose matrix, which pose challenges in developing MXene-decorated non-woven fabric with strong bonding and stable thermal management properties. Herein, we successfully prepared deep eutectic supramolecular polymer (DESP) functionalized MXene to address these issues. MXene can be wrapped with DESP to be insulated from water and protected from being oxidized. Subsequently, we achieved an efficient in-situ deposition of DESP-functionalized MXene onto fibers through a combination of dip coating and photopolymerization technique. The resulting nonwoven fabric (CNs-DESP@M) exhibited excellent photothermal conversion properties along with rapid thermal response and functional stability. Interestingly, the interface bonding between MXene and the fiber surface was significantly enhanced due to the abundant pyrogallol groups in DESP, resulting in the composite textile exhibiting commendable mechanical properties (2.68 MPa). Moreover, the as-prepared textile demonstrates outstanding bactericidal efficacy against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The multifunctional textile, created through a facile and efficient approach, demonstrates remarkable potential for applications in smart textiles, catering to the diverse needs of individuals in the future.

A review of cellulose-based catechol-containing functional materials for advanced applications

With the increment in global energy consumption and severe environmental pollution, it is urgently needed to explore green and sustainable materials. Inspired by nature, catechol groups in mussel adhesion proteins have been successively understood and utilized as novel biomimetic materials. In parallel, cellulose presents a wide class of functional materials rating from macro-scale to nano-scale components. The cross-over among both research fields alters the introduction of impressive materials with potential engineering properties, where catechol-containing materials supply a general stage for the functionalization of cellulose or cellulose derivatives. In this review, the role of catechol groups in the modification of cellulose and cellulose derivatives is discussed. A broad variety of advanced applications of cellulose-based catechol-containing materials, including adhesives, hydrogels, aerogels, membranes, textiles, pulp and papermaking, composites, are presented. Furthermore, some critical remaining challenges and opportunities are studied to mount the way toward the rational purpose and applications of cellulose-based catechol-containing materials.

Tannin-albumin particles as stable carriers of medicines

Background: The effectiveness of a drug is dependent on its accumulation at the site of therapeutic action, as well as its time in circulation. The aim of the research was the creation of stable albumin/tannin (punicalagin, punicalin) particles, which might serve for the delivery of medicines. Methods: Numerous chromatographic and analytical methods, docking analyses and in vivo testing were applied and used. Results: Stable tannin-albumin/medicine particles with a diameter of ∼100 nm were obtained. The results of in vivo experiments proved that tannin-albumin particles are more stable than albumin particles. Conclusion: Based on the experiments and docking analyses, these stable particles can carry an extended number of medicines, with diverse chemical structures.

Advancements and Perspectives toward Lignin Valorization via O-Demethylation

Lignin represents the largest aromatic carbon resource in plants, holding significant promise as a renewable feedstock for bioaromatics and other cyclic hydrocarbons in the context of the circular bioeconomy. However, the methoxy groups of aryl methyl ethers, abundantly found in technical lignins and lignin-derived chemicals, limit their pertinent chemical reactivity and broader applicability. Unlocking the phenolic hydroxyl functionality through O-demethylation (ODM) has emerged as a valuable approach to mitigate this need and enables further applications. In this review, we provide a comprehensive summary of the progress in the valorization of technical lignin and lignin-derived chemicals via ODM, both catalytic and non-catalytic reactions. Furthermore, a detailed analysis of the properties and potential applications of the O-demethylated products is presented, accompanied by a systematic overview of available ODM reactions. This review primarily focuses on enhancing the phenolic hydroxyl content in lignin-derived species through ODM, showcasing its potential in the catalytic funneling of lignin and value-added applications. A comprehensive synopsis and future outlook are included in the concluding section of this review.

Development of Biocompatible Mussel-Inspired Cellulose-Based Underwater Adhesives

Conventional adhesives have poor underwater adhesion and harm to human health and the environment during their use, which largely limits their practical applications. Herein, we synthesized cellulose-based adhesives with underwater adhesion and biocompatibility by grafting N-(3,4-dihydroxyphenethyl)methacrylamide into the cellulose chain via atom transfer radical polymerization (ATRP). FTIR, 1H NMR, and XPS analyses ensured the successful preparation of the cellulose-based adhesive polymers. The different properties of the prepared adhesives, including swelling ratio, adhesion strength, and biocompatibility are examined. Results found that the lap shear strength is enhanced by increasing the catechol content. When catechol content is 27.2 mol %, cellulose-based adhesive with the addition of Fe3+ possesses a strong lap shear strength of 2.13 MPa in a dry environment, 0.10 MPa underwater, and 0.16 MPa under seawater for iron substrate, respectively. In addition, the cell culture test demonstrated that the prepared adhesives have outstanding biocompatibility. The cellulose-based adhesives with underwater adhesion and biocompatibility have potential applications in biomedicine, electronic engineering, and construction fields.

Designing Composite Stimuli-Responsive Hydrogels for Wound Healing Applications: The State-of-the-Art and Recent Discoveries

Effective wound treatment has become one of the most important challenges for healthcare as it continues to be one of the leading causes of death worldwide. Therefore, wound care technologies significantly evolved in order to provide a holistic approach based on various designs of functional wound dressings. Among them, hydrogels have been widely used for wound treatment due to their biocompatibility and similarity to the extracellular matrix. The hydrogel formula offers the control of an optimal wound moisture level due to its ability to absorb excess fluid from the wound or release moisture as needed. Additionally, hydrogels can be successfully integrated with a plethora of biologically active components (e.g., nanoparticles, pharmaceuticals, natural extracts, peptides), thus enhancing the performance of resulting composite hydrogels in wound healing applications. In this review, the-state-of-the-art discoveries related to stimuli-responsive hydrogel-based dressings have been summarized, taking into account their antimicrobial, anti-inflammatory, antioxidant, and hemostatic properties, as well as other effects (e.g., re-epithelialization, vascularization, and restoration of the tissue) resulting from their use.

Development of a Stretchable and Water-Resistant Hydrogel with Antibacterial and Antioxidant Dual Functions for Wound Healing in Movable Parts

The treatment of wounds that develop on moving parts of the body, such as joints, is considered a challenge due to poor mechanical matching and secondary injury caused by continuous motion and inflammation. Herein, a stretchable, multifunctional hydrogel dressing utilizing the dual cross-linking of chitosan (CS) and acrylic acid (AA) and modified with caffeic acid (CA) and aloin (Alo) was developed. Mechanical testing demonstrated that the hydrogel possessed excellent stretching capability (of approximately 869%) combined with outstanding adhesion (about 56 kPa), contributing to its compatibility with moving parts and allowing complete coverage of wound sites without limiting joint and organ motion. Bioinformatics analysis confirmed that use of the hydrogel resulted in upregulated expression of multiple genes related to angiogenesis and cell proliferation. Furthermore, antibacterial testing indicated that the dressing suppressed the growth of Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA), providing a better microenvironment for wound healing. An in vivo wound defect model on movable skin verified that the wound healing observed with the hydrogel dressing was superior to that observed with a commercially available dressing. Taken together, the results suggest that a stretchable multifunctional hydrogel dressing represents a promising alternative wound dressing with therapeutic potential for superior healing, especially for moving parts of the body.

Acrylate monomer polymerization triggered by iron oxide magnetic nanoparticles and catechol containing microgels

Phenol and its derivatives are the most used polymerization inhibitors for vinyl-based monomers. Here, we reported a novel catalytic system composed of mussel inspired adhesive moiety, catechol, in combination with iron oxide nanoparticles (IONPs) to generate hydroxyl radical (•OH) at pH 7.4. Catechol-containing microgel (DHM) was prepared by copolymerizing dopamine methacrylamide (DMA) and N-hydroxyethyl acrylamide (HEAA), which generated superoxide (•O2-) and hydrogen peroxide (H2O2) as a result of catechol oxidation. In the presence of IONPs, the generated reactive oxygen species were further converted to •OH, which initiated free radical polymerization of various water-soluble acrylate-based monomers including neutral (acrylamide, methyl acrylamide, etc.), anionic (2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt), cationic ([2-(methacryloyloxy)ethyl]trimethylammonium chloride), and zwitterionic (2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide) monomers. Compared with the typical free radical initiating systems, the reported system does not require the addition of extra initiators for polymerization. During the process of polymerization, a bilayer hydrogel was formed in situ and exhibited the ability to bend during the process of swelling. The incorporation of IONPs significantly enhanced magnetic property of the hydrogel and the combination of DHM and IONPs also improved the mechanical properties of these hydrogels.

Catechol-Based Porous Organic Polymers for Effective Removal of Phenolic Pollutants from Water

Phenolic pollutants released from industrial activities seriously damage natural freshwater resources, and their elimination or reduction to safe levels is an urgent challenge. In this study, three catechol-based porous organic polymers, CCPOP, NTPOP, and MCPOP, were prepared using sustainable lignin biomass-derived monomers for the adsorption of phenolic contaminants in water. CCPOP, NTPOP, and MCPOP showed good adsorption performance for 2,4,6-trichlorophenol (TCP) with theoretical maximum adsorption capacities of 808.06 mg/g, 1195.30 mg/g, and 1076.85 mg/g, respectively. In addition, MCPOP maintained a stable adsorption performance after eight consecutive cycles. These results indicate that MCPOP is a potential material for the effective treatment of phenol pollutants in wastewater.

Mussel-inspired nanoparticle composite hydrogels for hemostasis and wound healing

Uncontrolled hemorrhage caused by trauma can easily lead to death. Efficient and safe hemostatic materials are an urgent and increasing need for hemostatic research. Following a trauma, wound healing is induced by various cellular mechanisms and proteins. Hemostatic biomaterials that can not only halt bleeding quickly but also provide an environment to promote wound healing have been the focus of research in recent years. Mussel-inspired nanoparticle composite hydrogels have been propelling the development of hemostatic materials owing to their unique advantages in adhesion, hemostasis, and bacteriostasis. This review summarizes the hemostatic and antimicrobial fundamentals of polydopamine (PDA)-based nanomaterials and emphasizes current developments in hemorrhage-related PDA nanomaterials. Moreover, it briefly discusses safety concerns and clinical application problems with PDA hemostatic nanomaterials.

Advances of Mussel-Inspired Nanocomposite Hydrogels in Biomedical Applications

Hydrogels, with 3D hydrophilic polymer networks and excellent biocompatibilities, have emerged as promising biomaterial candidates to mimic the structure and properties of biological tissues. The incorporation of nanomaterials into a hydrogel matrix can tailor the functions of the nanocomposite hydrogels to meet the requirements for different biomedical applications. However, most nanomaterials show poor dispersion in water, which limits their integration into the hydrophilic hydrogel network. Mussel-inspired chemistry provides a mild and biocompatible approach in material surface engineering due to the high reactivity and universal adhesive property of catechol groups. In order to attract more attention to mussel-inspired nanocomposite hydrogels, and to promote the research work on mussel-inspired nanocomposite hydrogels, we have reviewed the recent advances in the preparation of mussel-inspired nanocomposite hydrogels using a variety of nanomaterials with different forms (nanoparticles, nanorods, nanofibers, nanosheets). We give an overview of each nanomaterial modified or hybridized by catechol or polyphenol groups based on mussel-inspired chemistry, and the performances of the nanocomposite hydrogel after the nanomaterial's incorporation. We also highlight the use of each nanocomposite hydrogel for various biomedical applications, including drug delivery, bioelectronics, wearable/implantable biosensors, tumor therapy, and tissue repair. Finally, the challenges and future research direction in designing mussel-inspired nanocomposite hydrogels are discussed.

Electrochemical detection and quantification of catechol based on a simple and sensitive poly(riboflavin) modified carbon nanotube paste electrode

In the present research work, selective and sensitive catechol (CT) detection and quantification were shown in the presence of resorcinol (RS) in 0.2 M phosphate buffer (PB) solution by preparing a low-cost, simple, and green carbon nanotube paste electrode (CNTPE) surface activated with electropolymerized riboflavin (PRF). The morphological, conductivity, and electrochemical features of the modified electrode (PRFMCNTPE) and bare carbon nanotube paste electrode (BCNTPE) materials were analyzed using electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FE-SEM), cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The PRF-activated electrode displays outstanding sensitivity, stability, selectivity, reproducibility, and repeatability for the redox feature of CT with improved electrochemical current and declined electrochemical potential compared to BCNTPE. The peak currents of CT are correlated to the different CT concentrations (CV method: 6.0-60.0 μM & DPV method: 0.5-7.0 μM), and the obtained detection limit (DL) and quantification limit (QL) are found to be 0.025 μM and 0.085 μM (CV method) and 0.0039 μM and 0.0132 μM (DPV method), respectively. The prepared PRFMCNTPE material was advantageous for the examination of CT in environmentally important tap water sample as a real-time application.

Multifunctional Ionic Polymers from Deep Eutectic Monomers Based on Polyphenols

Herein we report a novel family of deep eutectic monomers and the corresponding polymers, made of (meth)acrylic ammonium salts and a series of biobased polyphenols bearing catechol or pyrogallol motifs. Phenolic chemistry allows modulating molecular interactions by tuning the ionic polymer properties from soft adhesive to tough materials. For instance, pyrogallol and hydrocaffeic acid-derived ionic polymers showed outstanding adhesiveness (>1 MPa), while tannic acid/gallic acid polymers with dense hydrogen bond distribution afforded ultratough elastomers (stretchability ≈1000% and strength ≈3 MPa). Additionally, phenolic polymeric deep eutectic solvents (polyDES) featured metal complexation ability, antibacterial properties, and fast processability by digital light 3D printing.

Dual-Crosslinked Degradable Elastomeric Networks With Self-Healing Properties: Bringing Multi(catechol) Star-Block Copolymers into Play

In the biomedical field, degradable chemically crosslinked elastomers are interesting materials for tissue engineering applications, since they present rubber-like mechanical properties matching those of soft tissues and are able to preserve their three-dimensional (3D) structure over degradation. Their use in biomedical applications requires surgical handling and implantation that can be a source of accidental damages responsible for the loss of properties. Therefore, their inability to be healed after damage or breaking can be a major drawback. In this work, biodegradable dual-crosslinked networks that exhibit fast and efficient self-healing properties at 37 °C are designed. Self-healable dual-crosslinked (chemically and physically) elastomeric networks are prepared by two methods. The first approach is based on the mix of hydrophobic poly(ethylene glycol)-poly(lactic acid) (PEG-PLA) star-shaped copolymers functionalized with either catechol or methacrylate moieties. In the second approach, hydrophobic bifunctional PEG-PLA star-shaped copolymers with both catechol and methacrylate on their structure are used. In the two systems, the supramolecular network is responsible for the self-healing properties, thanks to the dynamic dissociation/reassociation of the numerous hydrogen bonds between the catechol groups, whereas the covalent network ensures mechanical properties similar to pure methacrylate networks. The self-healable materials display mechanical properties that are compatible with soft tissues and exhibit linear degradation because of the chemical cross-links. The performances of networks from mixed copolymers versus bifunctional copolymers are compared and demonstrate the superiority of the latter. The biocompatibility of the materials is also demonstrated, confirming the potential of these degradable and self-healable elastomeric networks to be used for the design of temporary medical devices.

Synthesis of Thermoresponsive, Catechol-Rich Poly(ethylene glycol) Brush Polymers for Attenuating Cellular Oxidative Stress

Herein, we report a platform to integrate customizable quantities of catechol units into polymers by reacting caffeic acid carbonic anhydride with polymers having pendant amine groups. Brush poly(ethylene glycol)-caffeamide (PEG-CAF) copolymers based on oligo(ethylene glycol)methyl ether methacrylate (OEGMA₅₀₀) were obtained with a catechol content of approximately 30, 40, and 50 mol % (vs OEGMA content). Owing to the hydrophobicity of the introduced CAF groups, the catechol copolymers exhibited cloud points in the range of 23-46 °C and were used to fabricate thermoresponsive Fe^III metal-phenolic network capsules. Polymers with the highest CAF content (50 mol %) proved most effective for attenuating reactive oxygen species levels in vitro, in co-cultured fibroblasts, and breast cancer cells, even in the presence of an exogenous oxidant source. The reported approach to synthesize customizable catechol materials could be generalized to other amine-functional polymers, with potential biomedical applications such as adhesives or stimuli-responsive drug delivery systems.

Combination wound healing using polymer entangled porous nanoadhesive hybrids with robust ROS scavenging and angiogenesis properties

Nanoadhesives can achieve tight wound closure by connecting biomacromolecules from both sides. However, previously developed adhesive systems suffered from suboptimal wound healing efficiency due to the lack of interparticle cohesion, sufficient reactive oxygen species (ROS)-scavenging sites, and angiogenesis consideration. Herein, we developed a polymer entangled porous nanoadhesive system to address the above challenge by synergy of three functional components. Firstly, hybrid mesoporous silica nanoparticles with highly integrated polydopamine (MS-PDA) were prepared by templated synthesis. The entangling between PVA polymer and MS-PDA contributed to much stronger cohesion between nanoparticles, which led to 75% larger adhesion strength. As confirmed by in vitro and in vivo evaluations, the highly exposed catechol groups boosted the scavenging activity of ROS (1.8-4.1 fold enhancement as compared with nonporous counterpart). Consequently, more macrophages exhibited anti-inflammatory phenotype, leading to 2-2.6 fold lower pro-inflammatory cytokine levels. Moreover, the sustained release of bioactive SiO₄^4- by the disintegration of nanoparticles contributed to ∼3-fold higher expression of VEGF and enhanced new blood vessel formation, as well as better wound repair. This platform can provide a new paradigm for developing multifunctional nanoadhesive systems in treating skin wounds. STATEMENT OF SIGNIFICANCE: PVA polymer entangled mesoporous nanoadhesives of polydopamine (PDA)/silica hybrids with the combination of excellent wound closure effect, boosted ROS-scavenging activity, and significant angiogenesis ability were developed for improving the suboptimal skin wound healing efficiency. This strategy not only greatly advances our ability to rationally integrate repairing elements in nanoadhesives for manipulating combined processes of interfacial events during wound healing, but also offers general implications toward application of polymers to reinforce the adhesion strength in nanoadhesive systems. In addition, our findings on the impacts of pore effects mediated ROS species conversion and polymer entanglement may also trigger great interests and facilitate the development/broad application of therapeutic adhesives.

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.

Natural Deep Eutectic Solvents Based on Choline Chloride and Phenolic Compounds as Efficient Bioadhesives and Corrosion Protectors

Natural deep eutectics solvents (NADES), owing to their high solvation capacity and nontoxicity, are actively being sought for many technological applications. Herein, we report a series of novel NADES based on choline chloride and plant-derived polyphenols. Most of the obtained phenolic NADES have a wide liquid range and high thermal stability above 150 °C. Among them, small-sized polyphenols, like pyrogallol, vanillyl alcohol, or gentisic acid, lead to low-viscosity liquids with ionic conductivities in the order of 10^-3 S cm^-1 at room temperature. Interestingly, polyphenols possess valuable properties as therapeutic agents, antioxidants, adhesives, or redox-active compounds, among others. Thus, we evaluated the potential of these novel NADES for two applications: bioadhesives and corrosion protection. The mixture of choline chloride-vanillyl alcohol (2:3 mol ratio) and gelatin resulted in a highly adhesive viscoelastic liquid (adhesive stress ≈ 135 kPa), affording shear thinning behavior. Furthermore, choline chloride-tannic acid (20:1) showed an extraordinary ability to coordinate iron ions, reaching excellent corrosion inhibitive efficiencies in mild steel protection.

Facile anchoring mussel adhesive mimic tentacles on biodegradable polymer cargo carriers via self-assembly for microplastic-free cosmetics

Enhancing the deposition of fragrance delivery systems contained in personal care products on target surfaces is crucial for increasing the longevity of scent, efficiently utilizing expensive functional compounds and limiting the generation of microplastics in domestic waste water. In this work, we designed and synthesized a new type of biomimetic macromolecules, chitosan-graft-L-lysine-L-DOPA (C-L-D), as a versatile biodegradable adhesion promoter to facilitate the deposition of biodegradable fragrance carriers on diverse surfaces including hair, cotton and skin. The C-L-D has hyperbranched chain architecture with many oligopeptide adhesive tentacles, each being a simple mimic of mussel adhesive proteins. It also exhibits unique amphiphilic characteristic. As a result, it could be facilely anchored on cargo-loaded poly(lactic-co-glycolic acid) nanoparticle surface via self-assembly in the particle preparation process. The C-L-D-modified nanoparticles show significantly higher deposition efficiencies than polyvinyl alcohol- and chitosan-coated particles when deposited on the target surfaces in different aqueous media as the lysine and DOPA units are capable of providing multi-noncovalent interactions, including electrostatic, polar, hydrophobic interactions, and bidentate hydrogen bonds, with the target surfaces, and possibly also inducing oxidative cross-linking. A much higher retention rate of the C-L-D-modified nanoparticles on cotton surface is also observed after washing with a soap solution, which could be attributed to the significant role played by bidentate hydrogen bonds. These findings suggest that C-L-D is a versatile biodegradable adhesion promoter and has the potential to be applied for various personal care applications and beyond.

Optimization of the Elasticity and Adhesion of Catechol- or Dopamine-Loaded Gelatin Gels under Oxidative Conditions

The synthesis of surgical adhesives is based on the need to design glues that give rise to strong and fast bonds without cytotoxic side effects. A recent trend in surgical adhesives is to use gel-forming polymers modified with catechol groups, which can undergo oxidative crosslinking reactions and are strongly adhesive to all kinds on surfaces in wet conditions. We previously showed that blending gelatin with catechol can yield strong adhesion when the catechol is oxidized by a strong oxidant. Our previous work was limited to the study of the variation in the sodium periodate concentration. In this article, for an in-depth approach to the interactions between the components of the gels, the influence of the gelatin, the sodium periodate and dopamine/(pyro)catechol concentration on the storage (G') and loss (G″) moduli of the gels, as well as their adhesion on steel, have been studied by shear rheometry. The hydrogels were characterized by infrared and UV-Vis spectroscopy and the size of their pores visualized by digital microscopy and SEM after freeze drying but without further additives. In terms of adhesion between two stainless steel plates, the optimum was obtained for a concentration of 10% w/v in gelatin, 10 mM in sodium periodate, and 20 mM in phenolic compounds. Below these values, it is likely that crosslinking has not been maximized and that the oxidizing environment is weakening the gelatin. Above these values, the loss in adhesiveness may result from the disruption of the alpha helixes due to the large number of phenolic compounds as well as the maintenance of an oxidizing environment. Overall, this investigation shows the possibility to design strongly adhesive hydrogels to metal surfaces by blending gelatin with polyphenols in oxidative conditions.

Toward bioinspired polymer adhesives: activation assisted via HOBt for grafting of dopamine onto poly(acrylic acid)

The design of bioinspired polymers has long been an area of intense study, however, applications to the design of concrete admixtures for improved materials performance have been relatively unexplored. In this work, we functionalized poly(acrylic acid) (PAA), a simple analogue to polycarboxylate ether admixtures in concrete, with dopamine to form a catechol-bearing polymer (PAA-g-DA). Synthetic routes using hydroxybenzotriazole (HOBt) as an activating agent were examined for their ability in grafting dopamine to the PAA backbone. Previous literature using the traditional coupling reagent 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) to graft dopamine to PAA were found to be inconsistent and the sensitivity of EDC coupling reactions necessitated a search for an alternative. Additionally, HOBt allowed for greater control over per cent functionalization of the backbone, is a simple, robust reaction, and showed potential for scalability. This finding also represents a novel synthetic pathway for amide bond formation between dopamine and PAA. Finally, we performed preliminary adhesion studies of our polymer on rose granite specimens and demonstrated a 56% improvement in the mean adhesion strength over unfunctionalized PAA. These results demonstrate an early study on the potential of PAA-g-DA to be used for improving the bonds within concrete.

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.

Fabrication of Functional Polycatechol Nanoparticles

While low-dimensional (1D and 2D) polycatechol materials have been widely described for a range of biomedical and surface engineering applications, very few examples have been explored that focus on the construction of functional polycatechol nanoparticles. Herein, we report the facile fabrication of a series of polycatechol nanoparticles via a general and robust strategy based on the one-step oxidation reaction. IO₃^--induced catechol redox chemistry could facilitate the precise size control of the resulting nanoparticles and also allow the successful transfer and amplification of microscopic monomer function into macroscopic polycatechol material properties. The ease, facileness, and controllability of such a one-step fabrication process could highly promote the development of polycatechol nanomaterials for various applications.

Barium 5-(tert-butyl)-2,3-dihydroxybenzenesulfonate

Catechols and their derivatives attract great scientific interest due to the broad spectrum of their functional properties, including complexation, redox behavior, association ability and antioxidant activity. Because of the low molecular mass and two-electron redox process, they are considered to be a promising energy storage compound in different types of electrochemical power sources, such as metal-ion batteries or redox flow batteries. Herein, we report a preparation of the sterically hindered sulfonated catechol, namely the barium salt of 5-(tert-butyl)-2,3-dihydroxybenzenesulfonic acid, by the direct sulfonation of 4-tert-butylcatechol, by concentrated sulfuric acid. The proposed procedure is green and atom-economic, providing the desired product in high yield after simple purification. The solvent-free procedure is inexpensive and highly scalable, which enables direct industrial production of the title product. The resulting product was characterized by the 1H and 13C nuclear magnetic resonance (NMR) and ESI-high resolution mass spectrometry (ESI-HRMS).

Polyphenol-based hydrogels: Pyramid evolution from crosslinked structures to biomedical applications and the reverse design

As a kind of nature-derived bioactive materials, polyphenol-based hydrogels possess many unique and outstanding properties such as adhesion, toughness, and self-healing due to their specific crosslinking structures, which have been widely used in biomedical fields including wound healing, antitumor, treatment of motor system injury, digestive system disease, oculopathy, and bioelectronics. In this review, starting with the classification of common polyphenol-based hydrogels, the pyramid evolution process of polyphenol-based hydrogels from crosslinking structures to derived properties and then to biomedical applications is elaborated, as well as the efficient reverse design considerations of polyphenol-based hydrogel systems are proposed. Finally, the existing problems and development prospects of these hydrogel materials are discussed. It is hoped that the unique perspective of the review can promote further innovation and breakthroughs of polyphenol-based hydrogels in the future.

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Polyphenol-based hydrogels combine advantages of polyphenols with common hydrogels.

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Cognition of such hydrogels underwent from structures to properties to applications.

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Various crosslinked structures of such hydrogels can derive outstanding properties.

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Such hydrogels can be widely used in biomedicine due to the outstanding properties.

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Reverse design thought from applications to properties to structures is promising.

Antimicrobial Peptides and Macromolecules for Combating Microbial Infections: From Agents to Interfaces

Bacterial resistance caused by the overuse of antibiotics and the shelter of biofilms has evolved into a global health crisis, which drives researchers to continuously explore antimicrobial molecules and strategies to fight against drug-resistant bacteria and biofilm-associated infections. Cationic antimicrobial peptides (AMPs) are considered to be a category of potential alternative for antibiotics owing to their excellent bactericidal potency and lesser likelihood of inducing drug resistance through their distinctive antimicrobial mechanisms. In this review, the hitherto reported plentiful action modes of AMPs are systematically classified into 15 types and three categories (membrane destructive, nondestructive membrane disturbance, and intracellular targeting mechanisms). Besides natural AMPs, cationic polypeptides, synthetic polymers, and biopolymers enable to achieve tunable antimicrobial properties by optimizing their structures. Subsequently, the applications of these cationic antimicrobial agents at the biointerface as contact-active surface coatings and multifunctional wound dressings are also emphasized here. At last, we provide our perspectives on the development of clinically significant cationic antimicrobials and related challenges in the translation of these materials.

Oxidative control over the morphology of Cu3(HHTP)2, a 2D conductive metal–organic framework

The morphology of electrically conductive metal–organic frameworks strongly impacts their performance in applications such as energy storage and electrochemical sensing. However, identifying the appropriate conditions needed to achieve a specific nanocrystal size and shape can be a time-consuming, empirical process. Here we show how partial ligand oxidation dictates the morphology of Cu₃(HHTP)₂ (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene), a prototypical 2D conductive metal–organic framework. Using organic quinones as the chemical oxidant, we demonstrate that partial oxidation of the ligand prior to metal binding alters the nanocrystal aspect ratio by over 60-fold. Systematically varying the extent of initial ligand oxidation leads to distinct rod, block, and flake-like morphologies. These results represent an important advance in the rational control of Cu₃(HHTP)₂ morphology and motivate future studies into how ligand oxidation impacts the nucleation and growth of 2D conductive metal–organic frameworks.

The morphology of a copper-based 2D conductive metal–organic framework can be tuned via controlled ligand oxidation. Using quinone oxidants, we show how partial ligand oxidation prior to metal binding alters the nanocrystal aspect ratio by >60-fold.

Novel Digital Light Processing Printing Strategy Using a Collagen-Based Bioink with Prospective Cross-Linker Procyanidins

Three-dimensional (3D) bioink plays a vital role in the construction of tissues and organs by 3D bioprinting. Collagen has outstanding biocompatibility and is widely used in the field of tissue engineering. However, due to poor mechanical properties and slow self-assembly, it is challenging to manufacture high-precision 3D bioprinted collagen scaffolds. Herein, a novel digital light processing (DLP) bioink which can satisfy the printing of complex structures has been developed. This photocurable bioink is based on collagen and supplemented with a small amount of procyanidins (PA) as a cross-linking agent. The low concentration of collagen gives the bioink good fluidity and excellent biocompatibility, and a small amount of PA increases the cross-linking density of the system to obtain better mechanical properties. Using commercial digital light processing (DLP) printers, this collagen-based ink can effectively print structures with micrometer resolution, and the fidelity of the 3D structures can reach above 90%. Cells were able to be loaded in the bioink and distributed uniformly in the collagen scaffold in an unscathed way. This photocurable collagen bioink has broad application potential in DLP 3D bioprinting.

Surface-Initiated, Catechol-Containing Polymer Films for Effective Chelation of Aluminum Ions

We present a new route for obtaining surface-tethered polymer films containing pendant catechol functional groups via surface-initiated activators regenerated by electron-transfer atom-transfer radical polymerization (SI-ARGET ATRP) of glycidyl methacrylate (GMA) and post-polymerization modification of the resulting poly(glycidyl methacrylate) (pGMA) films with dopamine. This method enables a high degree of functionalization of pGMA films with catechol groups at a controlled level, depending on the duration of the post-polymerization modification reaction. The dopamine-pGMA films readily absorbs Al³⁺ and Zn²⁺ ions, as verified by quartz crystal microbalance with dissipation (QCM-D) under continuous flow conditions, and demonstrates a four-fold molar selectivity to Al³⁺ over Zn²⁺. The ions desorb from the films upon rinsing with pure deionized (DI) water, which regenerates the catechol sites in the dopamine-pGMA film. Subsequent exposure to metal ions after rinsing steps yields reproducible levels of loading.

Oriented in situ immobilization of a functional tyrosinase on microcrystalline cellulose effectively incorporates DOPA residues in bioengineered mussel adhesive protein

BACKGROUND

Catechol-containing polymers such as mussel adhesive proteins (MAPs) are attractive as biocompatible adhesive biomaterials, and the catecholic amino acid 3,4-dihydroxyphenyl-L-alanine (DOPA) is considered a key molecule in underwater mussel adhesion. Tyrosinases can specifically convert tyrosine to DOPA without any cofactors. However, their catalytic properties still need to be adjusted to minimize unwanted DOPA oxidation via their diphenolase activity and catechol instability at neutral and basic pH values in the reaction products.

METHODS AND RESULTS

In this work, we constructed a novel functional tyrosinase, mTyr-CNK_CBM, by fusion of mTyr-CNK with a cellulose-binding motif (CBM) for oriented in situ immobilization on microcrystalline cellulose via the C-terminal CBM without any additional purification steps. mTyr-CNK_CBM showed optimal catalytic activity at pH 4.5-6.5 and room temperature and had a high monophenolase/diphenolase activity ratio (V_max mono/V_max di = 2.08 at pH 6 and 25°C). mTyr-CNK_CBM exhibited 2.17-fold higher (as a unimmobilized free enzyme) and similarly high (upon immobilization) in vitro DOPA modification of a bioengineered MAP compared to a commercially available mushroom tyrosinase. Moreover, the immobilized mTyr-CNK_CBM showed long-term storability and improved reusability.

CONCLUSIONS

These results clearly demonstrate a strong potential for practical use of immobilized mTyr-CNK_CBM as a monophenol monooxygenase in preparing biocompatible DOPA-tethered biomaterials and other catechol-containing polymers.