Catechol Groups Research Articles

NIR-activated catechol-functionalized nanodiamond nanofibers for accelerating on-demand MRSA and E. coli biofilm eradication.

The rise of antibiotic resistance has made bacterial infections a persistent global health issue. In particular, extracellular polymeric substances (EPS) secreted by bacteria limit the effectiveness of conventional antibiotics, making biofilm removal challenging. To address this, we created ND@PDA nanoparticles by coating the surface of nanodiamonds (ND) with polydopamine (PDA). These nanoparticles were then integrated into polyvinyl alcohol to fabricate PVA/ND@PDA nanofiber scaffolds, resulting in an innovative platform with enhanced photothermal, antibacterial and antibiofilm properties. Upon exposure to near-infrared (NIR) light, the scaffolds exhibited a significant photothermal activity, oxidative stress and effectively damaging key bacterial components, such as biofilm, bacterial membranes, and proteins. Additionally, the catechol groups in PDA provided strong cell adhesion and high biocompatibility on the nanofiber surface. Our research proposes a platform that not only effectively addresses antibiotic-resistant infections but also contributes to advancements in wound healing therapies by enabling controlled antibacterial action with minimal toxicity.

Polydopamine-Mediated Nanofillers Reinforced Zwitterion Hydrogel Electrodes for Supercapacitors in Bioelectronics.

Supercapacitors that can function when in direct contact with human tissue are of paramount importance for wearable bioelectronics but face mismatching with biological tissue and its movement. Herein, we developed a zwitterion hydrogel elastomer electrode-based all-hydrogel supercapacitor (AHSC) characterized by good energy storage properties, bioadhesion, body movement-matching mechanical properties, and biocompatibility. These functions were realized by integrating a [2-(methacryloyloxy)ethyl]dimethyl-(3-propylsulfonate)ammonium hydroxide (DMAPS) and hydroxyethyl acrylate (HEA)-copolymerized zwitterion hydrogel electrode (DMAPS-HEA) with redox-active nanofillers. This hydrogel electrode endowed AHSC with body movement-matching mechanical properties and biocompatibility. Redox-active nanofillers were designed with the structure of a reduced graphene oxide (rGO)-anchored cobalt/nickel bimetallic metal-organic framework (Co/Ni MOF) using polydopamine (PDA). The Co/Ni MOF contributes to the high energy storage performance. rGO enhances the conductivity, whereas PDA introduces catechol groups, contributing to the bioadhesion. This AHSC serves as a flexible alternative to traditional rigid and low-tissue-affinity power supply devices in bioelectronics.

Synergistic anion–π interactions in peptidomimetic polyethers

Anion-π interactions are crucial in various biological processes, such as enzyme catalysis and ion transport. Despite their significance, the exploitation of anion-π interactions in synthetic polymer systems remains underexplored. This study investigates anion-π interactions using chemically well-defined peptidomimetics guided by the composition of mussel foot proteins. Specifically, polyether-based polymers were designed utilizing two functional epoxide monomers-catechol acetonide glycidyl ether and 4,4-dimethyl-2-oxazoline glycidyl ether-to mimic the key amino acids 3,4-dihydroxyphenylalanine and aspartic acid, respectively. A surface forces apparatus was employed to study the anion-π interaction between the polymers, considering the effects of relative monomer composition and pH conditions. The maximum cohesion energy of 15.0 mJ/m2 was observed at an equimolar monomer composition at pH 7. Incorporating a phenyl group instead of the catechol group and introducing competing anions confirmed the dominant role of anion-π interactions. This study highlights the significance of anion-π interactions, posing a high potential in the design and synthesis of functional materials.

Engineering Protein-Based Lipid-Binding Nanovesicles via Catechol-Amine-Derived Coacervation with Their Underlying Interfacial Mechanisms.

The development of nonphospholipid nanovesicles has garnered tremendous attention as a viable alternative to traditional liposomal nanovesicles. Protein/peptide-based nanovesicles have demonstrated their potential to reduce immunogenicity while enhancing bioactivity. However, a fundamental understanding of how proteinaceous vesicles interact with lipids and cell membranes remains elusive. In this study, we engineered a series of protamine-based nonphospholipid nanovesicles by modulating intramolecular catechol-amine interactions. By grafting trihydroxybenzene (GA) and catechol (CA) groups onto the protamine (Prot), a salt-triggered coacervation was observed in an alkaline environment with the size of as-prepared vesicles ranging from 200 to 1200 nm. The bonding affinity to lipid interfaces followed the order of Prot-CA-Fe3+(25 μM) > Prot-CA-Fe3+(10 μM) > Prot-CA > original Prot with the underlying nanomechanics investigated by the lipid bubble force measurement. Direct quantification of interactions between the nanovesicles and living human gingival fibroblasts was performed by using surface charge difference mapping. Introducing trace amounts of Fe3+ (at 10 and 25 μM) enhanced vesicle-lipid interactions via the synergy of catechol-amine interactions and Fe3+-induced complexation. This work provides improved valuable insights into the interactions between nanovesicles and cell membranes, offering an energetic paradigm for modulating cell-target delivery processes via intramolecular short-range interactions.

Development and in vitro assessment of injectable, adhesive, and self-healing chitosan-based hydrogels for treatment of spinal cord injury.

Injured spinal cords have a limited ability to regenerate because of the inhibitory environment formed in situ that affects neuronal regrow. Ensuring stable contact between the injuried nerves to support neural regeneration in the lesion microenvironment remains a significant challenge. To address this challenge, we have engineered a new injectable and adhesive hydrogel to treat spinal cord injuries. This hydrogel was produced by functionalizing chitosan with catechol groups and crosslinking it with different amounts of β-glycerophosphate to obtain adhesive hydrogels with tunable mechanical properties. The softest hydrogel (G'~300Pa) demonstrated strong adhesion to different biological soft tissues, including porcine skin (adhesion strength of 3.4±0.9kPa) and spinal cord, as well as injectability and self-healing abilities, making it ideal for a minimally invasive administration in difficult-to-reach areas. Additionally, this composition promoted the attachment, viability, proliferation, and the expression of neuronal marker β-III tubulin (Tuj-1) by the neuroblastoma SH-SY5Y cells. Moreover, SH-SY5Y cells cultured on the hydrogel modulated its mechanical properties (G'~3500Pa). In summary, we propose a material that is compatible with different therapies for soft tissue healing, including repairing injured nerve tissue.

Catechol-grafted chitosan-based antioxidant hydrogel with rapid self-healing property for wound healing.

Chronic wounds, particularly those with non-healing ulcers, show high levels of oxidant stress, such as excessive reactive oxygen species (ROS), which delays the healing process. Bacterial infections in wounds increase the need for antibiotics, which brings up serious concerns regarding antibiotic resistance. The innovative antibiotic-free strategies to endow the hydrogels with antibacterial and antioxidant features including the grafting of ROS-scavenging moieties onto the hydrogel structure are in high demand for wound management. Herein, an antibacterial and antioxidant hydrogel with rapid self-healing performance was fabricated via the dynamic borate ester cross-linkages between catechol-grafted chitosan (CS-CA) and polyvinyl alcohol in the presence of borax with the incorporation of ellagic acid (EA). Benefiting from the catechol groups from EA and CS-CA, the resulting hydrogel exhibited desirable adhesive property, excellent antioxidant and intensified antibacterial dual functions. Furthermore, the hydrogel demonstrated remarkable biocompatibility and pH-responsive behavior for the controlled release of EA, attributed to the reversible characteristics of borate ester linkages. Notably, these multifunctional hydrogels exhibited substantial regenerative capabilities in wound healing, as evidenced by in vivo assessments conducted on a full-thickness skin defect model, highlighting their considerable potential as wound dressings for effective wound management.

Organogermanium: Potential beneficial effects on the cardiovascular system.

Organogermanium, especially poly-trans-[(2-carboxyethyl)germasesquioxane] (Ge-132), has been known to enhance immune-modulatory activities. However, the invivo and invitro evidence accumulated over the last 20 years reveals that Ge-132 has unique but underappreciated multi-functional properties that have a potential positive effect for the cardiovascular system. A hydrolysate of Ge-132, monomeric 3-(trihydroxygermyl)propanoic acid, forms a complex with a vicinal diol structure (i.e., having two adjacent hydroxyl groups such as the cis-diol and catechol groups) that exists in ribose (e.g., adenosine triphosphate), catecholamine (e.g., adrenaline), and saccharide (e.g., glucose). Additionally, Ge-132 enhances macrophage phagocytosis and the heme catabolic pathway by upregulating key enzymes that are responsible for producing cytoprotective molecules such as biliverdin and bilirubin during the process. These multi-functional properties exert pleiotropic physiological effects after an oral intake of Ge-132 such as anti-oxidation, anti-inflammation, anti-hypertensive, anti-glycation, and erythrocyte lifecycle enhancement, all of which appear to assist the cardiovascular system. Of those effects, the effects on the lifecycle of erythrocyte may have an important implication for maintaining optimal vascular function, augmenting the availability of oxygen by enhancing the elimination of senescent, and damaged erythrocytes as well as promoting erythropoiesis. Human studies are warranted to determine whether these beneficial effects observed in previous studies are translated into humans.

Mussel-Like Silk Fibroin Hydrogel With Skin Compliance Soft Electrode for Wearable Devices.

Flexible wearable electronic devices, capable of real-time physiological monitoring for personalized health management, are increasingly recognized for their convenience, comfort, and customization potential. Despite advancements, challenges persist for soft electrodes due to the skin's complex surface, biocompatibility demands, and modulus mismatch. In response, a mussel-inspired polydopamine-nanoclay-silk fibroin hydrogel (DA-C-SFH) is introduced, synthesized via a two-step process. The initial polydopamine oxidation introduces free catechol groups through polydopamine-incorporated nanoclay, followed by integration with silk fibroin, refining the fibroin network at the mesoscopic scale. This DA-C-SFH exhibits low modulus, high elasticity, adhesive properties, and biocompatibility, enabling conformal skin adhesion. It effectively detects subtle signals, such as pulse waves, and serves as a soft epidermal electrode, capable of recording various electrophysiological signals, including electrocardiograms and electromyograms, thus underscoring its potential in medical electronics and health monitoring applications.

PH-Regulated catechol-modified sodium alginate hydrogel with anti-freezing and high toughness for wearable strain sensor.

Hydrogel-based flexible electronic devices have garnered significant attention due to their excellent mechanical properties, high electrical conductivity, and signal sensitivity. Nevertheless, internal water molecules crystallize inevitably at low temperatures, impairing the performance of hydrogels. Designing anti-freezing and tough hydrogels to meet long-term stability requirements is extremely challenging. A double physically crosslinked PVA/SA-g-DA/Fe3+ hydrogel was fabricated using a two-step method. The coordination mode between catechol groups and ferric ions was modified by adjusting pH of soaking solution, subsequently regulating antifreeze performance and mechanical properties of the hydrogels. The obtained PVA/SA-g-DA/Fe3+ hydrogel is stretchable, tough, and has a remarkable freeze tolerance (-42.21 °C). The hydrogels can be assembled into a strain sensor to monitor various human activities accurately at normal and low temperatures. This study proposes a strategy for designing hydrogels for supporting signal detection in cold environments.

Robust-adhesion and high-mechanical strength hydrogel for efficient wet tissue adhesion.

Bioadhesive hydrogels show great promise in wound closure due to their minimally invasive nature and ease of use. However, they typically exhibit poor wet adhesion and mechanical properties on wet tissues. Herein, a ready-to-use bioadhesive hydrogel (denoted as PAA-NHS/C-CS) with rapidly robust adhesion and high mechanical strength is developed via a simple one-pot UV crosslinking polymerization of acrylic acid (AA), catechol-functionalized chitosan (C-CS), and acrylic acid N-hydroxysuccinimide ester (AA-NHS ester). Benefitting from the hydrogen bonds and electrostatic attractions formed between PAA-NHS and C-CS, the as-prepared hydrogel exhibits high tensile strength (∼630 kPa), fracture strain (∼1950%), and toughness (∼4250 kJ m-3) in the fully swollen state. Besides, the noncovalent interactions and covalent crosslinking formed between the dual adhesive moieties (the NHS ester and catechol groups) and the tissue surface endow the hydrogel with high shear strength (∼160 kPa), interfacial toughness (∼630 J m-2), and burst pressure (∼447 mmHg) on wet porcine skin. By integrating the high mechanical properties, rapid robust adhesion, and operational convenience, the as-prepared PAA-NHS/C-CS hydrogel shows great promise in wound closure.

Biomimetic Janus Particles Induced In Situ Interfacial Remineralization for Dentin Hypersensitivity

AbstractDentin hypersensitivity (DH), caused by the exposure of dentin tubules, is a common complaint of dental patients. Although occlusion of the exposed tubules is the primary treatment approach, the complex oral environment, and multiple simultaneous requirements often hinder its implementation. In this study, strawberry‐shaped hemispheric Janus particles (JPs) are synthesized, and their use in the treatment of DH is evaluated in vitro and in an animal model. The hemispheric side of the JPs is modified with polymers of quaternary ammonium salts (QASs) to form a superhydrophobic coating with antibiofilm properties, while the flat side is modified with catechol groups able to form strong bonds with dentin. Even after 1 h of ultrasonication or 1000 rounds of thermal cycling, the dentin tubules are completely occluded by the JPs. Moreover, biofilm formation is not observed, and the area of living bacteria is less than 1% compared to the blank control and sodium fluoride (NaF)‐treated groups. In a rat model, the dentin tubules in the fixed specimens are completely occluded at day 3, much earlier than the occlusion obtained with commonly used NaF. These results demonstrate that JPs can provide a novel approach to the treatment of DH.

Pendant Catechol Group Improves the Performance of Iron Porphyrin CO2 Reduction Catalysts

Pendant Catechol Group Improves the Performance of Iron Porphyrin CO₂ Reduction Catalysts

An effective drug-free hydrogel for accelerating the whole healing process of bacteria-infected wounds.

Wound healing is a dynamic and complex process involving hemostasis, inflammation, fibroblast proliferation, and tissue remodeling. This process is highly susceptible to bacterial infection, which often leads to impaired and delayed wound repair. While antibiotic therapy remains the primary clinical approach for treating bacteria-infected wounds, its widespread use poses a significant risk of developing bacterial resistance. Here, a novel drug-free hydrogel was fabricated using polysaccharides and humic acid (HU) to facilitate the healing of bacteria-infected wounds. Specifically, hyaluronic acid (HA) was modified via oxidation with sodium periodate, introducing aldehyde groups along its main chains. Pectin (PT) was grafted with amino groups on its side chains through an amidation reaction with ethylenediamine. HU, a natural organic compound with hemostatic, antioxidant, antibacterial, anti-inflammatory, and photothermal properties, was reduced using sodium borohydride to generate an increased number of phenolic hydroxyl and catechol groups. The resulting hydrogel, called HA-PT/HUOH, was prepared by integrating these three chemically modified biomaterials through dynamic Schiff base cross-linking and hydrogen bonding. The HA-PT/HUOH hydrogel showed excellent injectability, strong bioadhesiveness, rapid self-healing capabilities, and potent photothermal performance. Both in vitro and in vivo studies demonstrated that HA-PT/HUOH significantly accelerated the healing of bacteria-infected wounds by modulating the entire wound-healing process. This included enhancing hemostasis, bacteriostasis, antioxidation, anti-inflammatory responses, fibroblast proliferation, and tissue remodeling. In summary, this multifunctional drug-free hydrogel presents a highly promising solution as a wound dressing for clinical application.

Interplay between conformational flexibility, intermolecular H-bonding and 3d-metal cation extraction ability in a series of thiacalix[4]arene lower rim disubstituted Schiff base derivatives.

The rational design of organic ligands with the aim to control their binding abilities towards different metal ions can be considered as one of the key concepts in supramolecular coordination chemistry. Regarding the macrocyclic compounds of thiacalix[4]arene family, this can be achieved via the targeted modulation of macrocyclic platform rigidity as well as the proper choice of appended binding sites. Four macrocyclic salen-type ligands based on lower rim disubstituted thiacalix[4]arene derivatives, adopted in a cone conformation, bearing highly coordinating iminophenolic or catecholic groups and two -CH2- moieties as spacers but presenting different abilities to form H-bonds, were chosen to elucidate the interplay between the conformational flexibility of the macrocyclic ligands, propensity to participate in the intermolecular H-bonding and the extraction ability of 3d-metal cations. X-ray diffraction analysis, theoretical DFT calculations, IR and Raman spectroscopies, and dynamic light scattering (DLS) studies performed in combination with liquid-liquid metal extraction study revealed that compounds 4, and 6, based on a thiacalix[4]arene macrocyclic platform, display a higher extraction ability towards all studied 3d-metal ions, caused by enhanced conformational flexibility. This is in good accordance with the ability of 6 to form H-bonded supramolecular assemblies in solution and crystalline phases due to recognition between the catecholic moieties.

Photocontrolled RAFT Polymerization for the Preparation of Catechol‐Functionalized Surfaces

ABSTRACTIn nature, there are numerous compounds bearing catechol groups that demonstrate various useful properties, such as adhesion and antioxidant capacity. This inspired us to apply catechol functional group‐containing polymers on a surface for adhesive properties. Herein, we report the preparation of catechol‐functionalized polymeric surfaces by photo‐induced electron transfer‐reversible addition‐fragmentation chain transfer (PET‐RAFT) polymerization using a “grafting‐from” approach using surface anchored RAFT agents. The polymerization of tert‐butoxycarbonyl (Boc)‐protected vinyl catechol, derived from naturally abundant caffeic acid, was investigated under visible light irradiation, which showed good control over molecular weights especially under green light irradiation. The catechol‐bearing polymeric surfaces were readily obtained after concise thermal deprotection, which was revealed by the changes in the surface properties evaluated by contact angles. This study proposes a straightforward route to catechol‐modified surface using functional and sustainable materials in coating applications.

Strategically Designed Ternary Nanohybrids of Titanate Nanosheet and Polydopamine-Coated Carbon Nanotubes for Highly Efficient Enrichment of Uranium(VI).

A strategically designed ternary nanohybrid (TNS-PDA/CNT), consisting of titanate nanosheet (TNS) and polydopamine-modified multiwalled carbon nanotube (PDA/CNT composite), was synthesized by the facile hydrothermal method and wet impregnation method for removal of U(VI) from aqueous solution and were characterized by transmission electron microscopy (TEM), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), Raman spectroscopy, Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS). TNSs were introduced into the PDA/CNT composite, which effectively averted the agglomeration of the CNT and further exposed more adsorption sites. PDA thin layer exposing more active sites was conducive to enhance adsorption capacity and kinetic. The adsorption process was largely influenced by pH values and weakly affected by ionic strength, indicating that the adsorption process was controlled by inner-sphere surface complexes because of TNS-PDA/CNT with multiple functional groups, including imine, catechol, amine, and hydroxyl groups. The isotherm data could be well described by the Langmuir model, and the monolayer maximum adsorption was determined to be 309.60 mg/g at pH = 5.0 and temperature = 45 °C. Thermodynamic parameters (ΔG° < 0, ΔS° > 0, and ΔH° < 0) showed that the nature of adsorption was endothermic and spontaneous. By XRD, FT-IR, and XPS analyses, the adsorption mechanism mainly involved surface complexation and ion exchange. In summary, the TNS-PDA/CNT materials are fully qualified as a satisfactory adsorbent for the purification and recovery of U(VI) from wastewater.

Linear phenolic polymers with amide stabilized catechol moieties.

Phenolic polymers with catechol groups easily undergo oxidative crosslinking. Through the incorporation of pendant amide groups, the thermal stability of linear phenolic polymers with catechol moieties was significantly improved with maintained antioxidation performance and solubility in THF after storing at 80 °C for 96 hours.

Sustained Release of Curcumin from Cur-LPs Loaded Adaptive Injectable Self-Healing Hydrogels.

Biological tissue defects are typically characterized by various shaped defects, and they are prone to inflammation and the excessive accumulation of reactive oxygen species. Therefore, it is still urgent to develop functional materials which can fully occupy and adhere to irregularly shaped defects by injection and promote the tissue repair process using antioxidant and anti-inflammatory mechanisms. Herein, in this work, phenylboronic acid modified oxidized hyaluronic acid (OHAPBA) was synthesized and dynamically crosslinked with catechol group modified glycol chitosan (GCHCA) and guar gum (GG) into a hydrogel loaded with curcumin liposomes (Cur-LPs) which were relatively uniformly distributed around 180 nm. The hydrogel possessed rapid gelation within 30 s, outstanding injectability and tissue-adaptive properties with self-healing properties, and the ability to adhere to biological tissues and adapt to tissue movement. Moreover, good biocompatibility and higher DPPH scavenging efficiency were illustrated in the hydrogel. And a more sustainable release of curcumin from Cur-LPs-loaded hydrogels, which could last for 10 days, was achieved to improve the bioavailability of curcumin. Finally, they might be injected to fully occupy and adhere to irregularly shaped defects and promote the tissue repair process by antioxidant mechanisms and the sustained release of curcumin for anti-inflammation. And the hydrogel would have potential application as candidates in tissue defect repair.

Two birds with one stone: Mussel-inspired anchoring strategy enabling full-spectrum utilization and superior carriers transfer capacity for efficient photocatalytic degradation and antibacterial

Antibiotic pollution that often leads to the increases in the prevalence of resistance represents unneglectable risks to human health. Photocatalysis shows great potential in addressing the antibiotic pollution issue. However, developing photocatalysts integrating full-spectrum photocatalysis and self-adaptive antibacterial performances still remains challenges due to the limited utilization rate of light and carrier transfer capacity. Herein, a mussel-inspired anchoring strategy was employed to fabricate polydopamine coated Hydrothermal carbon carbide ZIF-8ZnO (PDA@HTCC/ZIF-8ZnO) heterojunction photocatalyst. The PDA coating was used as a transition layer to promote the heterogeneous nucleation of ZIF-8 on HTCC. Benefiting from the interfacial connections formed by metal coordination interactions between catechol groups of PDA coating and metal sites of ZIF-8, the carrier transfer capacity of PDA@HTCC/ZIF-8ZnO was improved and the range of light that can be utilized for the PDA@HTCC/ZIF-8ZnO was broadened. Therefore, the PDA@HTCC/ZIF-8ZnO heterojunction presented outstanding full-spectrum photocatalytic degradation and antibacterial performances. The full-spectrum degradation efficiency of tetracycline by PDA@HTCC/ZIF-8ZnO reached 98.7 % in 50 min. Moreover, the antimicrobial efficacy of PDA@HTCC/ZIF-8ZnO against E. coli exceeded 90 % under both light and dark conditions. The promotion effect of PDA transition layer on electrons transfer has been confirmed by DFT calculations. Under light irradiation, PDA@HTCC/ZIF-8ZnO gradually degrades tetracycline through demethylation, deamination, decarboxylation reactions, and ring-opening reactions, ultimately generating CO2 and H2O. This innovative strategy benefits the future heterojunction photocatalysts design for efficient solution of antibiotics pollution and the derivative drug-resistant bacteria issues.

In Situ Preparation of MnO2 on the Catechol/Silane-Coated Polypropylene Nonwoven Fabrics for Effective Removal of Cationic Dyes.

Previous studies have confirmed that MnOx removes heavy metal ions and organic pollutants from water with dual effects of adsorption and oxidation coupling, significantly improving the ability to remove impurities. Nanometal oxides have a highly reactive surface but tend to agglomerate during preparation and are challenging to recycle after use. A common method is to combine nano-MnO2 with Fe3O4 to prepare magnetic materials for easy recycling. Our previous research has confirmed that catechol (CA) and (3-aminopropyl) triethoxysilane (KH550) can be co-deposited on the surface of polypropylene nonwovens to form a stable CK coating under alkaline conditions. In addition, the coating has many active groups, including hydroxyl groups, amino groups, etc. This study further investigates the secondary reactivity of CK coatings. The coordination of catechol groups and metal ions was used to anchor manganese ions to the coating. Meanwhile, the hydroxyl and amino groups were used to reduce manganese ions to Mn4+ in situ to prepare PP-(CK-MnO2). We found that the sample had an excellent decolorization effect on cationic dyes but was limited to anionic dyes. The decolorization mechanism of cationic dyes was further discussed. The results showed that the decolorization of cationic dyes had a dual effect of adsorption and oxidative degradation. Under acidic conditions, its oxidation properties were enhanced. It can be used as a highly effective decolorizing agent for cationic dyes, and the decolorization behavior is consistent with the first-order kinetics. As the pH increases, its oxidation properties gradually decrease. Although the electrostatic adsorption effect was enhanced, the overall decolorization performance was significantly reduced. Recycling experiments have proved that it can maintain >90% removal rate after five cycles. This study also demonstrated that the CK coating has dopamine-like properties, which can coordinate with metal ions to prepare metal-organic hybrid materials.