Coating process and stability of metal-polyphenol film

Use of Interfacial Interactions and Complexation of Carbon Dots to Construct Ultra-Robust and Efficient Photothermal Film From Micro-Carbonized Polysaccharides

Solar energy conversion technologies, particularly solar-driven photothermal conversion, are both clean and manageable. Although much progress has been made in designing solar-driven photothermal materials, significant challenges remain, not least the photobleaching of organic dyes. To tackle these issues, micro-carbonized polysaccharide chains, with carbon dots (CDs) suspended from the chains, are conceived, just like grapes or tomatoes hanging from a vine. Carbonization of sodium carboxymethyl cellulose (CMC) produces just such a structure (termed CMC-g-CDs), which is used to produce an ultra-stable, robust, and efficient solar-thermal film by interfacial interactions within the CMC-g-CDs. The introduction of the CDs into the matrix of the photothermal material effectively avoided the problem of photobleaching. Manipulating the interfacial interactions (such as electrostatic interactions, van der Waals interactions, π-π stacking, and hydrogen bonding) between the CDs and the polymer chains markedly enhances the mechanical properties of the photothermal film. The CMC-g-CDs are complexed with Fe3+ to eliminate leakage of the photothermal reagent from the matrix and to solve the problem of poor water resistance. The resulting film (CMC-g-CDs-Fe) has excellent prospects for practical application as a photothermal film.

Subtle distinction in molecular structure of flavonoids leads to vastly different coating efficiency and mechanism of metal-polyphenol networks with excellent antioxidant activities

Metal-polyphenol networks (MPNs) are of immense scientific interest because of their simple and rapid process to deposit on various substrates or particles with different shapes. However, there are rare reports on the effect of polyphenol molecular structure on coating efficiency and mechanism of MPNs. Herein, three typical flavonoid polyphenols, catechin (Cat), epigallocatechin (EGC) and procyanidin (PC), with the same skeleton (C6-C3-C6) but subtle distinction in molecular structure, were selected to build MPN coatings with ferric ions (Fe3+). And various techniques combined with the density functional theory (DFT) were applied to deeply reveal the roles of coordinative phenolic hydroxyl groups as well as noncovalent interactions (hydrogen bonding and π - π stacking) in the formation of flavonoid-based MPNs. We found that more accessible numbers of coordinative phenolic hydroxyl groups, the higher coating efficiency. In these flavonoid-based MPNs, the single-complex is the predominant during the coordinative modes between phenolic hydroxyl and Fe3+, not the previously reported mono-complex, bis-complex and/or tris-complex. Besides coordinative interaction, noncovalent interactions also contribute to MPNs formation, and hydrogen bonds prevail in the noncovalent interaction compared with π-π stacking. And these engineered MPN coatings can endow the substrate with excellent antioxidant activities. This study contributes to in-depth understanding the building mechanism of flavonoid-based MPNs, and increasing coating efficiency by choosing proper polyphenols.

Protection and Restoration of Damaged Hair via a Polyphenol Complex by Promoting Mechanical Strength, Antistatic, and Ultraviolet Protection Properties

In this study, we developed a hair-coating polyphenol complex (PPC) that showed ultraviolet (UV) protection properties, antistatic features, and the capability to enhance the mechanical strength of damaged hair. PPCs prepared with different ratios of tannic acid (TA), gallic acid (GA), and caffeic acid (CA) simultaneously increased the self-recovery of damaged hair by protecting the cuticle. PPC prevented light from passing through the damaged hair during exposure to UV radiation. Moreover, surfaces coated with PPC1 (TA:GA:CA, 100:20:0.5) exhibited a higher conductivity than surfaces coated with PPCs with other ratios of TA, GA, and CA, with a resistance of 0.72 MΩ. This influenced the antistatic performance of the surface, which exhibited no electrical attraction after being subjected to an electrostatic force. Additionally, damaged hair exhibited a significant increase in durability and elasticity after coating with a PPC1-containing shampoo, with a tensile strain of up to 2.06× post-treatment, indicating the recovery of the damaged cuticle by the PPC complex. Furthermore, PPC1-containing shampoo prevented damage by scavenging excess reactive oxygen species in the hair. The combination effect promoted by the natural PPC offers new insights into hair treatment and paves the way for further exploration of hair restoration technology.

Metal-Phenolic Film Coated Quartz Crystal Microbalance as a Selective Sensor for Methanol Detection in Alcoholic Beverages

The facile real-time monitoring of methyl content in fermented beverages is of fundamental significance in the alcohol and restaurant industry, since as little as 4 mL of methanol entering the blood may cause intoxication or blindness. So far, the practical applicability of available methanol sensors, including the piezoresonance analogs, is somewhat limited to laboratory use due to the complexity and bulkiness of the measuring equipment involving multistep procedures. This article introduces a hydrophobic metal-phenolic film-coated quartz crystal microbalance (MPF-QCM) as a novel streamlined detector of methanol in alcoholic drinks. Unlike other QCM-based alcohol sensors, our device operates under saturated vapor pressure conditions, permitting rapid detection of methyl fractions up to seven times below the tolerable levels in spirits (e.g., whisky) while effectively suppressing the cross-sensitivity to interfering chemical compounds such as water, petroleum ether or ammonium hydroxide. Furthermore, the good surface adhesion of metal-phenolic complexes endows the MPF-QCM with superior long-term stability, contributing to the repeatable and reversible physical sorption of the target analytes. These features, combined with the lack of mass flow controllers, valves and connecting pipes delivering the gas mixture, outline the likelihood for future design of a portable MPF-QCM prototype suitable to point-of-use analysis in drinking establishments.

One-Step Assembly of Versatile Multifunctional Coatings Based on Host-Guest and Polyphenol Chemistry

Developing a facile, efficient, and versatile polyphenol coating strategy and exploring its novel applications are of great significance in the fields of material surfaces and interfaces. Herein, a one-step assembly strategy for constructing novel tannic acid (TA) coatings via a solvent evaporation method is reported using TA and polycyclodextrin (PCD) particles (TPP). TPP with a high phenolic group activity of 88% integrates the advantages of host-guest and polyphenol chemistry. The former can drive TPP dynamically assemble into a large and collective aggregation activated by high temperature or density, and the latter provides excellent adhesion properties to substrates (0.9 mg cm^-2 ). TPP can assemble into a coating (TPC) rapidly on various substrates within 1 h at 37 °C while with a high availability of feed TPP (≈90%). The resulting TPC is not only high-temperature steam-sensitive for use as an anti-fake mask but also pH-sensitive for transforming into a free-standing film under physiological conditions. Moreover, various metal ions and functional particles can incorporate into TPC to extend its versatile properties including antibacterial activity, enhanced stability, and conductivity. This work expands the polyphenol coating strategy and builds up a one-step and efficient preparation platform of polyphenol coating for multiapplication prospects in various fields.

Separation Performance of Membranes Containing Ultrathin Surface Coating of Metal-Polyphenol Network

Metal-polyphenol networks (MPNs) are being used as versatile coatings for regulating membrane surface chemistry and for the formation of thin separation layers. The intrinsic nature of plant polyphenols and their coordination with transition metal ions provide a green synthesis procedure of thin films, which enhance membrane hydrophilicity and fouling resistance. MPNs have been used to fabricate tailorable coating layers for high-performance membranes desirable for a wide range of applications. Here, we present the recent progress of the use of MPNs in membrane materials and processes with a special focus on the important roles of tannic acid-metal ion (TA-Mⁿ⁺) coordination for thin film formation. This review introduces the most recent advances in the fabrication techniques and the application areas of TA-Mⁿ⁺ containing membranes. In addition, this paper outlines the latest research progress of the TA-metal ion containing membranes and summarizes the role of MPNs in membrane performance. The impact of fabrication parameters, as well as the stability of the synthesized films, is discussed. Finally, the remaining challenges that the field still faces and potential future opportunities are illustrated.

Roles and gains of coordination chemistry in nanofiltration membrane: A review

The nanofiltration (NF) membranes with the specific separation accuracy for molecules with the size of 0.5-2 nm have been applied in various industries. However, the traditional polymeric NF membranes still face problems like the trade-off effect, organic solvent consumption, and weak durability in harsh conditions. The participation of coordination action or metal-organic coordination compounds (MOCs) brings the membrane with uniform pores, better antifouling properties, and high hydrophilicity. Some of the aqueous-phase reactions also help to introduce a green fabrication process to NF membranes. This review critically summarizes the recent research progress in coordination chemistry relevant NF membranes. The participation of coordination chemistry was classified by the various functions in NF membranes like additives, interlayers, selective layers, coating layers, and cross-linkers. Then, the effect and mechanism of the coordination chemistry on the performance of NF membranes are discussed in depth. Perspectives are given for the further promotion that coordination chemistry can make in NF processes. This review also provides comprehensive insight and constructive guidance on high-performance NF membranes with coordination chemistry.

Enhancing Stability of Tannic Acid-FeIII Nanofiltration Membrane for Water Treatment: Intercoordination by Metal-Organic Framework

Tannic acid (TA)-Fe^III nanofiltration (NF) membrane has been demonstrated to possess more favorable removal of trace organic contaminants (TrOCs) over the conventional polyamide NF membrane. However, the drawback of acid instability severely hinders the practical application of TA-Fe^III NF membrane in the treatment of (weak) acidic wastewater containing TrOCs (e.g., pharmaceutical wastewater, surface water, and drinking water). Herein, we introduced the MIL-101(Cr) nanoparticle, a kind of metal-organic framework (MOF), into the TA-Fe^III selective layer to enhance the membrane acid stability. The acid-tolerance parameter of MIL-101(Cr)-stabilized TA-Fe^III membrane (TA-Fe^III-MOF membrane, 12,000 ppm/s^-1) was two orders of magnitude larger than that of the TA-Fe^III membrane (50 ppm/s^-1), and the TA-Fe^III-MOF membrane can withstand acid treatment at pH = 4 for more than 30 days. Meanwhile, the TA-Fe^III-MOF membrane displayed increased water permeance from 9.5 to 12.7 L/(m²·h·bar) after the MOF addition, without compromising the selectivity. The enhanced acid stability for the TA-Fe^III-MOF membrane was ascribed to an intercoordination mechanism, where Fe^III centers (from TA-Fe^III complex) coordinated with -COOH groups (from terephthalic acid of MOF) and Cr^III centers (from MOF) coordinated with -OH groups (from TA of TA-Fe^III complex), which was verified by the density functional theory calculation. This study highlights a new approach for the development of a TA-Fe^III-based NF membrane with markedly enhanced acid stability, which is important for its real application in wastewater treatment and water reuse.

Material priority engineered metal-polyphenol networks: mechanism and platform for multifunctionalities

Engineering the surface of materials with desired multifunctionalities is an effective way to fight against multiple adverse factors during tissue repair process. Recently, metal-polyphenol networks (MPNs) have gained increasing attention because of their rapid and simple deposition process onto various substrates (silicon, quartz, gold and polypropylene sheets, etc.). However, the coating mechanism has not been clarified, and multifunctionalized MPNs remain unexplored. Herein, the flavonoid polyphenol procyanidin (PC) was selected to form PC-MPN coatings with Fe³⁺, and the effects of different assembly parameters, including pH, molar ratio between PC and Fe³⁺, and material priority during coating formation, were thoroughly evaluated. We found that the material priority (addition sequence of PC and Fe³⁺) had a great influence on the thickness of the formed PC-MPNs. Various surface techniques (e.g., ultraviolet–visible spectrophotometry, quartz crystal microbalance, X-ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy) were used to investigate the formation mechanism of PC-MPNs. Then PC-MPNs were further engineered with multifunctionalities (fastening cellular attachment in the early stage, promoting long-term cellular proliferation, antioxidation and antibacterial activity). We believe that these findings could further reveal the coating formation mechanism of MPNs and guide the future design of MPN coatings with multifunctionalities, thereby greatly broadening their application prospects, such as in sensors, environments, drug delivery, and tissue engineering.

Systematic Approach to Mimic Phenolic Natural Polymers for Biofabrication

In nature, phenolic biopolymers are utilized as functional tools and molecular crosslinkers to control the mechanical properties of biomaterials. Of particular interest are phenolic proteins/polysaccharides from living organisms, which are rich in catechol and/or gallol groups. Their strong underwater adhesion is attributed to the representative phenolic molecule, catechol, which stimulates intermolecular and intramolecular crosslinking induced by oxidative polymerization. Significant efforts have been made to understand the underlying chemistries, and researchers have developed functional biomaterials by mimicking the systems. Owing to their unique biocompatibility and ability to transform their mechanical properties, phenolic polymers have revolutionized biotechnologies. In this review, we highlight the bottom-up approaches for mimicking polyphenolic materials in nature and recent advances in related biomedical applications. We expect that this review will contribute to the rational design and synthesis of polyphenolic functional biomaterials and facilitate the production of related applications.

Synergistic Anti-inflammatory Coating "Zipped Up" on Polypropylene Hernia Mesh

Violent inflammation has impeded worry-free application of polypropylene (PP) hernia meshes. Efficient anti-inflammatory coatings are urgently needed to alter the situation. Here, we present a zipper-like, two-layer coating with an intermediate antioxidant layer (I) and an outer antifouling layer (II) to endow PP meshes with synergistic anti-inflammatory effects. The controllable antioxidant ability of layer I was obtained by modulating the assembly cycle of the metal-phenolic network (MPN) composed of tannic acid (TA) and Fe3+. Polyzwitterionic (PMAD) brush-based layer II was generated upon multiple interactions between the catechol side groups of PMAD and layer I. To consolidate the entire assembly architecture, aryloxy radical coupling was initiated through alkali-catalyzed oxidation. The reaction is similar to a "zipping up" process to construct covalent bonds in the I-II interface and layer I by coupling adjacent catechol groups, which facilely achieved grafting and cross-linking. The obtained coating (PMAD-TA/Fe) did not affect the original properties of the PP mesh and remained stable during cyclic tensile testing or degradation. Most importantly, the excellent antioxidant and antifouling capacities enabled PMAD-TA/Fe-PP to exhibit desirable anti-inflammatory effects and reduce collagen deposition when compared with the bare material. The synergistic anti-inflammatory coating eliminates a major hindrance in the design of biocompatible meshes, and its potential application in developing medical implants with low immunogenicity is promising.

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.

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.

Stem cell spheroid engineering with osteoinductive and ROS scavenging nanofibers for bone regeneration

Stem cell spheroids have been widely investigated to accelerate bone tissue regeneartion. However, the directed differentiation of stem cells into osteoblastic lineage and the prevention of cells from damage by reactive oxygen species (ROS) remain challenge. Here, we developed osteoinductive and ROS scavenging extracellular matrix (ECM)-mimicking synthetic fibers based on epigallocatechin gallate (EGCG) coating. They were then utilized to fabricate engineered spheroids with human adipose-derived stem cells (hADSCs) for bone tissue regeneation. The EGCG-mineral fibers (EMF) effectively conferred osteoinductive and ROS scavenging signals on the hADSCs within spheroids, demonstrating relative upregulation of antioxidant genes (SOD-1 (25.8±2.1) and GPX-1 (3.3±0.1) and greater level of expression of osteogenic markers, RUNX2 (5.8±0.1) and OPN (5.9±0.1), compared to hADSCs in the spheroids without EMF. The in vitro overexpression of osteogenic genes from hADSCs was achieved from absence of osteogenic supplenments. Furthermore, in vivo transplantation of hADSCs spheroids with the EMF significantly promoted calvarial bone regeneration (48.39±9.24%) compared to that from defect only (17.38±6.63%), suggesting that the stem cell spheroid biofabrication system with our novel mineralization method described here is a promising tool for bone tissue regeneration.

Tannin-Based Hybrid Materials and Their Applications: A Review

Tannins are eco-friendly, bio-sourced, natural, and highly reactive polyphenols. In the past decades, the understanding of their versatile properties has grown substantially alongside a continuously broadening of the tannins' application scope. In particular, recently, tannins have been increasingly investigated for their interaction with other species in order to obtain tannin-based hybrid systems that feature advanced and/or novel properties. Furthermore, in virtue of the tannins' chemistry and their high reactivity, they either physicochemically or physically interact with a wide variety of different compounds, including metals and ceramics, as well as a number of organic species. Such hybrid or hybrid-like systems allow the preparation of various advanced nanomaterials, featuring improved performances compared to the current ones. Consequently, these diverse-shaped materials have potential use in wastewater treatment or catalysis, as well as in some novel fields such as UV-shielding, functional food packaging, and biomedicine. Since these kinds of tannin-based hybrids represent an emerging field, thus far no comprehensive overview concerning their potential as functional chemical building blocks is available. Hence, this review aims to provide a structured summary of the current state of research regarding tannin-based hybrids, detailed findings on the chemical mechanisms as well as their fields of application.

A Facile Approach to Increasing the Foliage Retention of Pesticides Based on Coating with a Tannic Acid/Fe3+ Complex

The effective utilization of many conventional pesticide formulations is less than 30%, which can increase the environmental impact of these substances. This degree of waste could be reduced by improving the adhesion of pesticides to foliage. In the present work, a complex comprising tannic acid (TA) and Fe3+ ions was used to encapsulate azoxystrobin and avermectin water dispersible granule (WDG) formulations (termed Az-WDG-TA and Av-WDG-TA) to improve adhesion. The treated pesticides exhibited improved photostability as well as sustained continuous release behavior. The retention proportions of the Az-WDG-TA and Av-WDG-TA on cucumber and lettuce foliage were improved by more than 50%. The ability of solutions of these materials to wet foliage was also enhanced after coating, such that the toxicity of Av-WDG-TA to aphids and the antifungal activity of Az-WDG-TA to Fusarium oxysporum were increased by nearly 50%. Given the low cost of TA and Fe3+ compounds and the simple synthesis process, this method represents a promising means of producing foliage-adhesive pesticide formulations with increased retention and bioavailability.

Layered self-assemblies for controlled drug delivery: A translational overview

Self-assembly is a prominent phenomenon observed in nature. Inspired by this thermodynamically favorable approach, several natural and synthetic materials have been investigated to develop functional systems for various biomedical applications, including drug delivery. Furthermore, layered self-assembled systems provide added advantages of tunability and multifunctionality which are crucial for controlled and targeted drug release. Layer-by-layer (LbL) deposition has emerged as one of the most popular, well-established techniques for tailoring such layered self-assemblies. This review aims to provide a brief overview of drug delivery applications using LbL deposition, along with a discussion of associated scalability challenges, technological innovations to overcome them, and prospects for commercial translation of this versatile technique. Additionally, alternative self-assembly techniques such as metal-phenolic networks (MPNs) and Liesegang rings are also reviewed in the context of their recent utilization for controlled drug delivery. Blending the sophistication of these self-assembly phenomena with material science and technological advances can provide a powerful tool to develop smart drug carriers in a scalable manner.

Mg-Phenolic Network Strategy for Enhancing Corrosion Resistance and Osteocompatibility of Degradable Magnesium Alloys

Magnesium-based alloys are the most widely used materials for degradable metallic implants and have considerable potential for bone applications owing to their excellent stimulating effect on osteogenesis. However, their high corrosion rate limits their structural stability and causes oxygen deficiency and an excessive increase in the pH around the defect area during bone healing. Magnesium oxides, which are the main corrosion products of Mg, are nontoxic materials with useful effects on new bone formation and pH neutralization. Metal-phenolic networks were introduced recently as a cost-effective and efficient surface modifier and were fabricated by deposition of nanosized metal oxides on different types of substrates using the chemical reaction between phenolic groups and metallic ions. In this study, magnesium oxide films were formed successfully on a Mg-based substrate using Mg-phenolic networks. The effects of various coating parameters on the surface morphology, corrosion resistance, degradation behavior, wettability, and osteocompatibility of degradable metallic materials after surface modification with Mg-phenolic networks were thoroughly investigated for the first time. The results showed that the initial concentration of Mg ions was the main parameter affecting the corrosion resistance, which was almost as much as 3 times that of uncoated samples. Additionally, cytotoxicity and viability assessment and observation of the morphological changes in bonelike cells showed that the in vitro osteocompatibility was significantly enhanced by coatings with Mg concentrations of 2.4-3.6 mg mL-1. Finally, in vivo animal studies using the rat calvarial defect model confirmed that the proposed coating method mitigated the formation of gas cavities around the implantation area by reducing the corrosion rate of the Mg-based implant. The nanosized metal oxides produced by the Mg-phenolic network significantly improved the biodegradability and osteocompatibility of Mg alloys, suggesting a potential approach to advancing the clinical application of Mg alloys.

Porous Inorganic and Hybrid Systems for Drug Delivery: Future Promise in Combatting Drug Resistance and Translation to Botanical Applications

BACKGROUND

Porous micro- and nanoparticles have the capacity to encapsulate a large quantity of therapeutics, making them promising delivery vehicles for a variety of applications. This review aims to highlight the latest development of inorganic and hybrid (inorganic/ organic) particles for drug delivery with an additional emphasis on combatting drug resistant cancer. We go one step further and discuss delivery applications beyond medicinal delivery, as there is generally a translation from medicinal delivery to botanic delivery after a short lag time.

METHODS

We undertook a search of relevant peer-reviewed publications. The quality of the relevant papers was appraised using standard tools. The characteristics of the papers are described herein, and the relevant material and therapeutic properties are discussed.

RESULTS

We discuss 4 classes of porous particles in terms of drug delivery and theranostics. We specifically focus on silica, calcium carbonate, metal-phenolic network, and metalorganic framework particles. Other relevant biomedically relevant applications are discussed and we highlight outstanding therapeutic results in the relevant literature.

CONCLUSION

The findings of this review confirm the importance of studying and utilizing porous particles for therapeutic delivery. Moreover, we show that the properties of porous particles that make them promising for medicinal drug delivery also make them promising candidates for agro-industrial applications.

Surface-Initiated ARGET ATRP of Antifouling Zwitterionic Brushes Using Versatile and Uniform Initiator Film

In this study, we developed a uniform initiator layer that can be formed on various surfaces, and formed site-selectively, for the subsequent antifouling polymer brush formation. Initially, metal-organic films composed of tannic acid (TA) and Fe^III ions (TA-Fe^III) were formed on various surfaces, followed by functionalization with an aryl azide-based initiator (ABI) under photoreaction. In particular, combination with a photolithographic technique enabled the presentation of initiators only on the intended region within a single-surface platform. A resultant initiator film (TF-ABI) was formed under mild reaction conditions and meets the uniformity and transparency requirements concurrently. Subsequently, we showed that TF-ABI can be further utilized to form a polymer brush by proceeding with surface-initiated polymerization using a zwitterionic monomer, namely, sulfobetaine acrylamide (SBAA). Instead of applying a classical, yet air-sensitive atom transfer radical polymerization (ATRP) technique, we utilized an activator regenerated by electron transfer (ARGET) ATRP under air conditions without a cumbersome deoxygenation step. Overall, our initiator layer allowed the antifouling poly(SBAA) brush to be used on various surfaces, and enabled their pattern generation.

Supramolecular-Based Regenerable Coating Layer of a Thin-Film Composite Nanofiltration Membrane for Simultaneously Enhanced Desalination and Antifouling Properties

A high-performance nanofiltration (NF) membrane with simultaneously improved desalination and antifouling properties while maintaining regeneration ability is highly desirable in water treatment. Surface modification is an effective approach to enhance the performance of NF membranes. In the present study, a multifunctional thin-film composite NF membrane (Fe-TFC) was fabricated via coating a regenerable ferric ion-tannic acid (Fe^III-TA) layer on the nascent polyamide membrane surface. The Fe-TFC membrane exhibited enhanced hydrophilicity, smaller pore size, and lower negative charge compared with the control membrane. The salt rejections and selectivity of divalent to monovalent ions were greatly improved with only a slight decrease in water permeability due to the presence of the coating layer. Meanwhile, dynamic fouling tests with humic acid demonstrated that the Fe-TFC membrane possessed an enhanced antifouling property and excellent flux recovery rate. After coating, the normalized water flux and flux recovery of the Fe-TFC membrane increased from 0.02 to 0.26 and 32.1 to 76.4% at the end of five cycles of fouling tests, respectively. In addition, the resultant membrane exhibited excellent durability and stability under harsh conditions for ∼10 days. Interestingly, the fouled coating layer can be easily removed by HCl cleaning and regenerated through an in situ strategy. Consequently, the regenerated membranes presented stable antifouling properties and desalination performance after several times of regeneration. It was demonstrated that the unique feature of Fe^III-TA networks enables the coating layer to act as a protective layer for the underlying polyamide membrane, leading to the high performance of the composite membrane. This study provides a new insight for surface functionalization and easy regeneration of the TFC nanofiltration membrane in water treatment technology.

Metal Ion-Chelated Tannic Acid Coating for Hemostatic Dressing

Tannic acid (TA), a high-molecular-weight polyphenol, is used as a hemostasis spray and unguent for trauma wound remedy in traditional medical treatment. However, the use of tannic acid on a large-area wound would lead to absorption poisoning. In this work, a TA coating was assembled on a quartz/silicon slide, or medical gauze, via chelation interaction between TA and Fe3+ ions and for further use as a hemostasis dressing. Protein adsorption on the TA coating was further investigated by fluorescence signal, ellipsometry analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The adsorbed bovine serum albumin (BSA), immunoglobulin G (IgG) and fibrinogen (Fgn) on the TA coating was in the manner of monolayer saturation adsorption, and fibrinogen showed the largest adsorption. Furthermore, we found the slight hemolysis of the TA coating caused by the lysed red blood cells and adsorption of protein, especially the clotting-related fibrinogen, resulted in excellent hemostasis performance of the TA coating in the blood clotting of an animal wound. Thus, this economic, environmentally friendly, flexible TA coating has potential in medical applications as a means of preparing novel hemostasis materials.

Silicic Acid-Mediated Formation of Tannic Acid Nanocoatings

Tannic acid (TA) adheres to a broad variety of different materials and forms versatile surface coatings for technical and biological applications. In mild alkaline conditions, autoxidation processes occur and a firm monolayer is formed. Up to now, thicker coatings are obtained in only a cross-linked multilayer fashion. This study presents an alternative method to form continuous TA coatings using orthosilicic acid (Si_aq). Adsorption kinetics and physical properties of TA coatings in the presence of Si_aq were determined using a quartz-crystal microbalance and nanoplasmonic spectroscopy. An in situ TA layer thickness of 200 nm was obtained after 24 h in solutions supplemented with 80 μM Si_aq. Dry-state measurements indicated a highly hydrated layer in situ. Furthermore, chemical analysis by Fourier transform infrared spectroscopy revealed possible complexation of TA by Si_aq, whereas UV-vis spectroscopy did not indicate an interaction of Si_aq in the autoxidation process of TA. Investigation of additional metalloid ions showed that germanic acid was also able to initiate a continuous coating formation of TA, whereas boric acid prevented the polymerization process. In comparison to that of TA, the coating formation of pyrogallol (PG) and gallic acid (GA) was not affected by Si_aq. PG formed continuous coatings also without Si_aq, whereas GA formed only a monolayer in the presence of Si_aq. However, Si_aq induced a continuous layer formation of ellagic acid. These results indicate the specific importance of orthosilicic acid in the coating formation of polyphenolic molecules with multiple ortho-dihydroxy groups and open new possibilities to deposit TA on interfaces.

Protein Adsorption and Coordination-Based End-Tethering of Functional Polymers on Metal-Phenolic Network Films

Metal-phenolic network (MPN) coatings have generated increasing interest owing to their biologically inspired nature, facile fabrication, and near-universal adherence, especially for biomedical applications. However, a key issue in biomedicine is protein fouling, and the adsorption of proteins on tannic acid-based MPNs remains to be comprehensively studied. Herein, we investigate the interaction of specific biomedically relevant proteins in solution (e.g., bovine serum albumin (BSA), immunoglobulin G (IgG), fibrinogen) and complex biological media (serum) using layer-by-layer-assembled tannic acid/Fe^III MPN films. When Fe^III was the outermost layer, galloyl-modified poly(2-ethyl-2-oxazoline) (P(EtOx)-Gal) could be grafted to the films through coordination bonds. Protein fouling and bacterial adhesion were greatly suppressed after functionalization with P(EtOx)-Gal and the mass of adsorbed protein was reduced by 79%. Interestingly, larger proteins adsorbed more on both the MPNs and P(EtOx)-functionalized MPNs. This study provides fundamental information on the interactions of MPNs with single proteins, mixtures of proteins as encountered in serum, and the noncovalent, coordination-based, functionalization of MPN films.

Iron(III)-Tannic Molecular Nanoparticles Enhance Autophagy effect and T1 MRI Contrast in Liver Cell Lines

Herein, a new molecular nanoparticle based on iron(III)-tannic complexes (Fe–TA NPs) is presented. The Fe–TA NPs were simply obtained by mixing the precursors in a buffered solution at room temperature, and they exhibited good physicochemical properties with capability of inducing autophagy in both hepatocellular carcinoma cells (HepG2.2.15) and normal rat hepatocytes (AML12). The Fe–TA NPs were found to induce HepG2.2.15 cell death via autophagic cell death but have no effect on cell viability in AML12 cells. This is possibly due to the much higher uptake of the Fe–TA NPs by the HepG2.2.15 cells via the receptor-mediated endocytosis pathway. As a consequence, enhancement of the T₁ MRI contrast was clearly observed in the HepG2.2.15 cells. The results demonstrate that the Fe–TA NPs could provide a new strategy combining diagnostic and therapeutic functions for hepatocellular carcinoma. Additionally, because of their autophagy-inducing properties, they can be applied as autophagy enhancers for prevention and treatment of other diseases.

Multiligand Metal-Phenolic Assembly from Green Tea Infusions

The synthesis of hybrid functional materials using the coordination-driven assembly of metal-phenolic networks (MPNs) is of interest in diverse areas of materials science. To date, MPN assembly has been explored as monoligand systems (i.e., containing a single type of phenolic ligand) where the phenolic components are primarily obtained from natural sources via extraction, isolation, and purification processes. Herein, we demonstrate the fabrication of MPNs from a readily available, crude phenolic source-green tea (GT) infusions. We employ our recently introduced rust-mediated continuous assembly strategy to prepare these GT MPN systems. The resulting hollow MPN capsules contain multiple phenolic ligands and have a shell thickness that can be controlled through the reaction time. These multiligand MPN systems have different properties compared to the analogous MPN systems reported previously. For example, the Young's modulus (as determined using colloidal-probe atomic force microscopy) of the GT MPN system presented herein is less than half that of MPN systems prepared using tannic acid and iron salt solutions, and the disassembly kinetics are faster (∼50%) than other, comparable MPN systems under identical disassembly conditions. Additionally, the use of rust-mediated assembly enables the formation of stable capsules under conditions where the conventional approach (i.e., using iron salt solutions) results in colloidally unstable dispersions. These differences highlight how the choice of phenolic ligand and its source, as well as the assembly protocol (e.g., using solution-based or solid-state iron sources), can be used to tune the properties of MPNs. The strategy presented herein expands the toolbox of MPN assembly while also providing new insights into the nature and robustness of metal-phenolic interfacial assembly when using solution-based or solid-state metal sources.

Galloyl groups-regulated fibrinogen conformation: Understanding antiplatelet adhesion on tannic acid coating

Fibrinogen (Fgn) has been identified as the key protein in the process of biomaterial-induced platelet adhesion. We have recently reported a facile and effective method for constructing platelet-repellent surface using a natural polyphenol component tannic acid (TA). However, the mechanism by which the TA surface repels platelets was not fully understood. To address this issue, we investigated the adsorption of Fgn (amount and conformation) on four TA-functionalized surfaces with different amounts of galloyl groups and the potential for platelet adherence on these surfaces. The experimental results indicated that the four TA-functionalized surfaces adsorbed a similar amount of Fgn, but the conformation and bioactivity of the adsorbed Fgn and the subsequent platelet adherence were quite different among the surfaces. The TA surface with the most galloyl groups induced minimal changes in the conformation of Fgn, a result of the α and γ chains of the adsorbed Fgn being highly inactive on the surface, thus leading to an outstanding antiplatelet adhesion performance. With a decreased amount of galloyl groups, the activity of the α chain in the adsorbed Fgn remained unchanged, but the activity of the γ chain and the extent of platelet adhesion gradually increased. This work provided a new concept for controlling platelet adhesion on solid materials, and we envision that the TA film could have potential applications in the development of new blood-contacting biomaterials in the future.

STATEMENT OF SIGNIFICANCE

Reducing platelet adhesion on material surfaces is of tremendous scientific interest in the field of blood-contacting biomaterials, but it remains a big challenge due to the highly adhesive nature of the platelets. In this study, we demonstrated for the first time that tannic acid surface with abundant galloyl groups could induce minimal conformational changes of fibrinogen, eventually leading to an outstanding antiplatelet adhesion effect. In addition, the platelet adhesion response could be easily controlled through regulating the amount of galloyl groups on the surface. This work provided a new strategy for controlling platelet adhesion on solid materials, which was totally different from existing methods such as construction of physically patterned surfaces, modification of inert hydrophilic polymers or appending bioactive moieties to target surfaces.

Facile Oriented Immobilization of Histidine-Tagged Proteins on Nonfouling Cobalt Polyphenolic Self-Assembly Surfaces

In this study, a completely green and facile protocol to oriented immobilization of histidine-tagged (His-tagged) proteins based on plant polyphenolic tannic acid (TA) is described. This is the first time that TA has been applied as ionic chelators to immobilize His-tagged proteins. To reduce the nonspecific interactions between the TA and immobilized proteins, we assembled nonfouling zwitterionic poly(sulfobetaine methacrylate) (PSBMA) on the TA surface. The use of PSBMA could maintain the high activity of the His-tagged proteins and inhibit the adsorption of untagged protein to the TA surface. Subsequently, the obtained TA/PSBMA film was further chelated with Co^II for specific binding to a His-tagged protein. As Co^III is more stable and inert than Co^II, the chelated Co^II was oxidized to Co^III. Using this approach, His-tagged Chitinase was anchored to TA/PSBMA/Co^III film as a catalyst for the hydrolysis of chitin. The loading capacity of the film for the His-tagged Chitinase can reach ∼4.0 μg/cm². Moreover, the oriented immobilized Chitinase had high catalytic activity and excellent thermal and storage stability as well as being more resistant to proteolytic digestion by papain. This low-cost and green protein-oriented immobilization strategy may serve as a versatile platform for a range of applications, such as biomaterials, biocatalysis, sensors, drug delivery, and so on.

Rust-Mediated Continuous Assembly of Metal-Phenolic Networks

The use of natural compounds for preparing hybrid molecular films-such as surface coatings made from metal-phenolic networks (MPNs)-is of interest in areas ranging from catalysis and separations to biomedicine. However, to date, the film growth of MPNs has been observed to proceed in discrete steps (≈10 nm per step) where the coordination-driven interfacial assembly ceases beyond a finite time (≈1 min). Here, it is demonstrated that the assembly process for MPNs can be modulated from discrete to continuous by utilizing solid-state reactants (i.e., rusted iron objects). Gallic acid etches iron from rust and produces chelate complexes in solution that continuously assemble at the interface of solid substrates dispersed in the system. The result is stable, continuous growth of MPN films. The presented double dynamic process-that is, etching and self-assembly-provides new insights into the chemistry of MPN assembly while enabling control over the MPN film thickness by simply varying the reaction time.

Bio-inspired Ni2+-polyphenol hydrophilic network to achieve unconventional high-flux nanofiltration membranes for environmental remediation

A Ni²⁺-polyphenol network was synthesized as a hydrophilic coating to achieve highly efficient nanofiltration membranes with an unconventional high flux for dye wastewater remediation.

A Novel Platelet-Repellent Polyphenolic Surface and Its Micropattern for Platelet Adhesion Detection

Surface patterning provides a powerful tool to the diagnosis of platelet adhesion. However, the current methodologies of constructing platelet-patterned surfaces require laborious and complicated steps. Herein, a novel and simple platelet-repellent surface was reported by metal (Fe³⁺ ions)-polyphenol (tannic acid, TA) coordination interaction. The platelet-repellent effect was significantly better than that of poly(ethylene glycol) (PEG) in a long-term. Moreover, the platelet-repellent behavior could extend to other polyphenols-functionalized surfaces. On the basis of these observations, a TA-based micropattern was fabricated in situ by one-step microcontact printing for well-defined platelet adhesion, which can effectively avoid the traditional introduction of inert hydrophilic polymers and bioactive ligands. Afterward, the TA-based micropattern was applied to monitor the adhesion of defective platelets treated with an antiplatelet drug (tirofiban). This work provided a facile, versatile, and environmentally friendly strategy to construct platelet-repellent polyphenolic surfaces and their micropattern. We expect that this simple micropattern could act as a low-cost and label-free platform for biomaterials and biosensors, and could be widely used in the clinical diagnoses of platelet adhesive functions and the evaluation of antiplatelet therapies.