Tannic Acid Coatings Research Articles

Synthesis of Polymer Brushes on Tannic Acid-Coated Copper Particles and Surface Co-Assembly.

The synthesis of polymer brushes on inorganic particles is an effective approach to surface modification. The polymer brushes on the surface endow the substrates with new surface properties. However, the lack of functional groups and the difficulty of surface modification have made it difficult to develop an effective method for the synthesis of polymer brushes on metal surfaces. Herein, a simple and versatile strategy for synthesizing polymer brushes on copper particles is reported. Tannic acid (TA) molecules are adsorbed onto the surfaces of copper particles, forming TA coatings. Quaternized poly(2-(dimethylamino)ethyl methacrylate)-block-polystyrene (qPDMAEMA-b-PS) block copolymer (BCP) chains are grafted on the TA coatings through hydrogen bonding and electrostatic interaction, and PS brushes are grafted on the copper particles. The effects of TA concentration on the adsorption of TA and PS brush synthesis are discussed. The PS brushes are able to form surface nanostructures on the copper particles through co-assembly with PDMAEMA-b-PS BCP chains. The effect of BCP concentration on the surface nanostructures is investigated. It is reasonable to expect that polymer brushes and surface nanostructures can be synthesized on different metal surfaces by using the TA-coating approach reported in this paper.

Effect of Low-Temperature Oxygen Plasma Treatment of Titanium Alloy Surface on Tannic Acid Coating Deposition.

In this study, the effect of low-temperature oxygen plasma treatment with various powers of a titanium alloy surface on the structural and morphological properties of a substrate and the deposition of a tannic acid coating was investigated. The surface characteristics of the titanium alloy were evaluated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements. Following this, the tannic acid coatings were deposited on the titanium alloy substrates and the structural and morphological properties of the tannic acid coatings deposited were subject to characterization by XPS, SEM, and spectroscopic ellipsometry (SE) measurements. The results show that the low-temperature oxygen plasma treatment of titanium alloys leads to the formation of titanium dioxides that contain -OH groups on the surface being accompanied by a reduction in carbon, which imparts hydrophilicity to the titanium substrate, and the effect increases with the applied plasma power. The performed titanium alloy substrate modification translates into the quality of the deposited tannic acid coating standing out by higher uniformity of the coating, lower number of defects indicating delamination or incomplete bonding of the coating with the substrate, lower number of cracks, thinner cracks, and higher thickness of the tannic acid coatings compared to the non-treated titanium alloy substrate. A similar effect is observed as the applied plasma power increases.

Characterization of Tannic Acid-Coated AZ31 Mg Alloy for Biomedical Application and Comparison with AZ91.

Magnesium alloys are promising materials for bioresorbable implants that will improve patient life and reduce healthcare costs. However, their clinical use is prevented by the rapid degradation and corrosion of magnesium, which leads to a fast loss of mechanical strength and the formation of by-products that can trigger tissue inflammation. Here, a tannic acid coating is proposed to control the degradation of AZ31 and AZ91 alloys, starting from a previous study by the authors on AZ91. The coatings on the two materials were characterized both by the chemical (EDS, FTIR, XPS) and the morphological (SEM, confocal profilometry) point of view. Static degradation tests in PBS and electrochemical measurements in different solutions showed that the protective performances of the tannic acid coatings are strongly affected by the presence of cracks. The presence of fractures in the protective layer generates galvanic couples between the coating scales and the metal, worsening the corrosion resistance. Although degradation control was not achieved, useful insights on the degradation mechanisms of coated Mg surfaces were obtained, as well as key points for future studies: it resulted that the absence of cracks in protective coatings is of uttermost importance for novel biodegradable implants with proper degradation kinetics.

Combining QCM-D with live-cell imaging reveals the impact of serum proteins on the dynamics of fibroblast adhesion on tannic acid-functionalised surfaces.

Nanocoatings based on plant polyphenols have been recently suggested as a potent strategy for modification of implant surfaces for enhancing host cell attachment and reducing bacterial colonisation. In this study we aimed to investigate how serum proteins impact the early adhesion dynamics of human gingival fibroblasts onto titanium surfaces coated with tannic acid (TA). Silicate-TA nanocoatings were formed on titanium and pre-conditioned in medium supplemented with 0, 0.1, 1 or 10% FBS for 1 hour. Dynamics of fibroblasts adhesion was studied using quartz crystal microbalance with dissipation (QCM-D). Time-lapse imaging was employed to assess cell area and motility, while immunofluorescence microscopy was used to examine cell morphology and focal adhesion formation. Our results showed that in serum-free medium, fibroblasts demonstrated enhanced and faster adhesion to TA coatings compared to uncoated titanium. Increasing the serum concentration reduced cell adhesion to nanocoatings, resulting in nearly complete inhibition at 10% FBS. This inhibition was not observed for uncoated titanium at 10% FBS, although cell adhesion was delayed and progressed slower compared to serum-free conditions. In addition, 1% FBS dramatically reduced cell adhesion on uncoated titanium. We revealed a positive relationship between changes in dissipation and changes in cell spreading area, and a negative relationship between dissipation and cell motility. In conclusion, our study demonstrated that serum decreases fibroblasts interaction with surfaces coated with TA in a concentration dependent manner. This suggests that controlling serum concentration can be used to regulate or potentially prevent fibroblasts adhesion onto TA-coated titanium surfaces.

Influence of polydopamine and tannic acid coatings on thermal properties of polylactide

In this paper, the research findings about the impact of polydopamine and tannic acid coatings on specific thermal properties of polylactide are discussed. The influence of deposited coatings on the resistance to oxidation, heat resistance, and the temperatures of phase transitions was determined. Therefore, the oxidation induction temperature, thermogravimetry, and differential scanning calorimetry studies were carried out. To gain a deeper understanding of the findings, mass measurements for the samples before and after the deposition process were conducted, as well as scanning electron microscopy studies. Studies have shown that the application of coatings can improve the resistance of polylactide against oxidative and thermal degradation. However, these coatings have minimal impact on the intensity and temperature of phase transformations. The polylactide showed increased thermal resistance when coated with polydopamine, whereas tannic acid coating was found to be more effective in increasing oxidation resistance. The differences observed were likely caused by variations in the structure of the coatings applied, impacting the level of oxygen diffusion and heat transfer within the material.

Novel attempts for the assembly of tannic-based coatings in ethanol media

Tannic acid (TA) based coatings possessed attracted significant increasing attention in super extensive applications. An anhydrous and predictable TA-based coating synthesis process is desirable. The objective of this study was to develop a new method to fabricate TA-based coating in absolute alcohol. TA polymerization (pTA) caotings with modification efficiency up to 22.69% were synthesized by mixing TA and sodium ethoxide in absolute alcohol under various reaction times. Moreover, the anhydrous method also applicable to synthesis process of metal-TA (M−TA) coatings generated by chelation between TA and metal ions during self-assembly process. A series of M−TA using Ce and Cu as model were synthesized under different metal ions feeding ratios. The as-prepared TA coatings exhibited good waterproof and cation dye adsorption capabilities.

The Modification of Titanium Surface by Decomposition of Tannic Acid Coating

Titanium is one of the most widely used metals in implantology owing to its reduced modulus, improved corrosion resistance and good biocompatibility. In spite of its excellent biocompatibility, it does not exhibit inherent antibacterial and antioxidant activity. Tannic acid is a naturally occurring polyphenol compound which exhibits excellent antibacterial, antioxidant and antimutagenic activity. The development of tannic acid-based coatings on the titanium surface holds great potential to reduce the risks associated with implant applications, thereby increasing the longevity of implants. In the present study, tannic acid was deposited on the titanium surface and the surface displayed a slightly improved hydrophilic character with an increase in surface energy. The release kinetics of tannic acid from titanium surface was analyzed and it showed an initial burst effect followed by a gradual decrease over time. Hemolysis tests revealed the erythrocyte compatibility of the developed surfaces. The improved hydrophilicity observed the release kinetics of tannic acid and reduced hemolysis rates revealed the potential of this facile technique for implant surface engineering applications.

Synthesis of Polymer Brushes and Removable Surface Nanostructures on Tannic Acid Coatings

Polymer brushes refer to polymer chains that are end-grafted to surfaces or interfaces at high grafting density. Polymer brushes are able to make surface self-assembly or surface coassembly with free block copolymer (BCP) chains, and surface nanostructures with different morphologies are formed on the surfaces. The formation of the surface nanostructures endows materials with new surface properties. To develop a simple and versatile approach to the synthesis of polymer brushes and surface nanostructures, the synthesis of polymer brushes and surface nanostructures on tannic acid (TA) coatings was investigated in this research. TA molecules were coated on the surfaces of amino-modified silica particles (SiO2-NH2) through noncovalent bonds. Quaternized poly(2-(dimethylamino)ethyl methacrylate)-block-polystyrene (qPDMAEMA-b-PS) chains were anchored onto the TA coatings through electrostatic interaction between qPDMAEMA blocks and TA coatings, and PS brushes are formed on the particle surfaces. Thermo gravimetric analysis demonstrates the grafting of the BCP chains on the TA coatings, and the calculation results indicate that the PS chains on the silica particles are in the polymer brush regime. PS brushes on TA coatings are able to make surface coassembly with free BCP chains, and surface nanostructures with different sizes and morphologies are produced on TA coatings. The grafting density of PS blocks and BCP concentration both exert significant influences on the formation of the surface nanostructures. The surface nanostructures can be removed from the particle surfaces in the aqueous solution of sodium chloride. This research provides a simple and versatile method for the fabrication of polymer brushes and removable surface nanostructures on any solid substrates, which have specific interactions with TA molecules.

Tannic Acid Coatings to Control the Degradation of AZ91 Mg Alloy Porous Structures

Porous structures of magnesium alloys are promising bioimplants due to their biocompatibility and biodegradability. However, their degradation is too rapid compared to tissue regeneration and does not allow a progressive metal substitution with the new biological tissue. Moreover, rapid degradation is connected to an accelerated ion release, hydrogen development, and pH increase, which are often causes of tissue inflammation. In the present research, a natural organic coating based on tannic acid was obtained on Mg AZ91 porous structures without toxic reagents. Mg AZ91 porous structures have been prepared by the innovative combination of 3D printing and investment casting, allowing fully customized objects to be produced. Bare and coated samples were characterized using scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS), fluorescence microscopy, Fourier transformed infrared spectroscopy (FTIR), tape adhesion test, Folin–Ciocalteu, and degradation tests. Different parameters (solvent, dipping time) were compared to optimize the coating process. The optimized coating was uniform on the outer and inner surfaces of the porous structures and significantly reduced the material degradation rate and pH increase in physiological conditions (phosphate-buffered saline—PBS).

Fabrication of polymer functionalized Mn2+-tannic acid coatings on magnetism-responsive nano-microspheres for Immobilized Penicillin G acylase

Firstly, Fe3O4 nanoparticles (Fe3O4 NPs) were synthesized by the inverse microemulsion method, and then, Mn2+ was doped in the process of coating tannin(TA) on the surface of Fe3O4 NPs to obtain Mn2+-Fe3O4@PTA NPs. The composite carrier containing Mn2+ could activate the catalytic activity of immobilized Penicillin G acylase (PGA). After the GMA was introduced into the carrier surface by ring-opening reaction, the above preparation carrier was modified by introducing RAFT reagent to obtain Mn2+-Fe3O4@PTA-GMA-g-RAFT NPs. Lastly, glycidyl methacrylate (GMA) and methyl methacrylate (MMA) were employed as the target monomer and the monomer for regulating the spacing between the targets, respectively. Herein, PGA was covalently immobilized on the surface of the magnetic microspheres by reaction of the amino groups of the PGA molecules with the epoxy groups of the magnetic polymer microspheres. Selections of immobilization conditions, including enzyme concentration, pH, temperature, and time of immobilization, were explored. The condition under which enzyme loading capacity (ELC), enzyme activity (EA), and enzyme activity recovery (EAR) of immobilized PGA were maximized as follows: enzyme concentration 2.5 vol%, pH = 8.0, time 20 h, and temperature 37 °C. Under the optimal immobilization conditions, ELC, EA, and EAR of immobilized PGA were 120 mg/g, 31,361 U/g, and 93.7%, respectively. Immobilized PGA remained 90.1% of initial activity and the carrier recovery was 97.8% after 14 successive cycles. These results indicated that the biocatalytic systems with potential use in biomedical application by the influence of polyhydroxy groups, target spacing, and Mn2+.

Characterization of the foreign body response of titanium implants modified with polyphenolic coatings.

The foreign body response is dictating the outcome of wound healing around any implanted materials. Patients who suffer from chronic inflammatory diseases and impaired wound healing often face a higher risk for implant failure. Therefore, functional surfaces need to be developed to improve tissue integration. For this purpose, we evaluated the impact of surface coatings made of antioxidant polyphenolic molecules tannic acid (TA) and pyrogallol (PG) on the host response in human blood. Our results showed that although the polyphenolic surface modifications impact the initial blood protein adsorption compared to Ti, the complement and coagulation systems are triggered. Despite complement activation, monocytes and granulocytes remained inactivated, which was manifested in a low pro‐inflammatory cytokine expression. Under oxidative stress, both coatings were able to reduce intracellular reactive oxygen species in human gingival fibroblasts (hGFs). However, no anti‐inflammatory effects of polyphenolic coatings could be verified in hGFs stimulated with lipopolysaccharide and IL‐1β. Although polyphenols reportedly inhibit the NF‐κB signaling pathway, phosphorylation of NF‐κB p65 was observed. In conclusion, our results indicated that TA and PG coatings improved the hemocompatibility of titanium surfaces and have the potential to reduce oxidative stress during wound healing.

Surface modification of maize stem with polydopamine and tannic acid coatings

The paper presents the results of research on the modification of maize stem. The modification consisted in depositing polydopamine or tannic acid coatings on the surface of the stems. The coatings were deposited from solutions without and with an oxidant (potassium permanganate) with different deposition times. The deposition effects were assessed by measuring the mass of the samples, optical microscopy and scanning electron microscopy. The thermal stability of the modified maize stem was also determined and differential scanning calorimetry tests were carried out. Studies have shown that as a result of the deposition, a coating of polydopamine or tannic acid was formed on the surface of the maize stem, and the quantity of coating increased with increasing deposition time. The oxidant used was only effective for the polydopamine coating, greatly increasing the deposition rate. The thermal stability of the coatings deposited on the maize stem is sufficient for the modified filler to be used in the processing of biodegradable polymers. The modified maize stem is planned to be used as filler for biodegradable polymers hopefully increasing adhesion strength between matrix and filler and improving the mechanical properties of the resulting composites.

Synthesis of Silica Nanoparticles with Physical Encapsulation of Near-Infrared Fluorescent Dyes and Their Tannic Acid Coating.

This study reports a novel method for the synthesis of silica nanoparticles (NPs) encapsulating near-infrared (NIR) fluorescent dyes through physical adsorption. Although a NIR cationic fluorescent dye, oxazine 725 (OXA), has no chemical bonding moiety toward silica NPs such as the triethoxysilyl group, the dyes were successfully incorporated into silica NPs without denaturation under the mild reaction conditions. Next, tannic acid (TA) molecules were coated in the presence of Fe3+ on the particle surface for the functionalization of silica NPs encapsulating OXA (OXA@SiO2 NPs). The TA coating on the surface of OXA@SiO2 NPs was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy. The TA coating significantly contributed to the resistance improvement against photobleaching and leakage of the dyes in the NPs. Furthermore, the obtained TA-coated silica NPs encapsulating OXAs (OXA@SiO2@TA NPs) were used for the fluorescence imaging of African green monkey kidney (COS-7) cells, and it was shown that the fluorescence originated from OXA@SiO2@TA NPs was clearly observed in the COS-7 cells.

Photocatalytic anti-biofouling coatings with dynamic surfaces of hybrid metal-organic framework nanofibrous mats for uranium (VI) separation from seawater

• Anchoring ZIF-8 by polyphenol-metal coordination, covalent and noncovalent bonds. • Self-renewing ZIF-8/TA coatings with zinc-ions-releasing and ROS-producing abilities. • Synergetic uranium adsorption by pyrogallol, amidoxime, and imidazole groups. For the commercial development of nuclear technology, the isolation of uranyl ions from sea water becomes a strategic key work. However, a major challenge remains in uranium extraction to resist marine biofouling, through suppressing microorganisms' growth and adhesion on the surface of the adsorbent. In this study, by introducing a hydrolyzable tannic acid (TA) cross-linked coating with dynamic surface, we synthesized a self-polishing hybrid zeolitic imidazolate framework-8 (ZIF-8)/amidoximed polyacrylonitrile (AOP) nanofibrous mat (AOP@ZIF-8/TA) that has durable and outstanding anti-fouling performance. Subsequently, a variety of batch adsorption tests have been undertaken to determine the efficiency of the adsorbent. As a result, the maximum uranium-adsorbing capability of 1387.37 mg/g could be acquired at pH 5.0, and the sorption of uranium was not influenced by other co-existing ions. AOP@ZIF-8/TA mat also showed a long service life with favourable sorption capability after at least 5 adsorption-desorption cycles. Most importantly, the prepared hydrolyzable ZIF-8/TA coatings with zinc-ions-releasing and ROS-producing abilities form a dynamic self-renewing surface and contribute to high resistance to biofouling. After a 25‐day uptake measurement in natural sea water, the uranium sorption equilibrium was reached with the maximal adsorption capability of 11.17 mg·g −1 . Therefore, the self-peeling surface coating has the promise to be used in the production of U(VI)-binding antibiofouling adsorbents in the raw seawater.

Heterostructured graphene oxide membranes with tunable water-capture coatings for highly selective water permeation

Heterostructured graphene oxide membranes with water-capture tannic acid coatings were constructed for highly selective water permeation.

Tannic Acid Radicals in the Presence of Alkali Metal Salts and Their Impact on the Formation of Silicate-Phenolic Networks.

Polyphenolic molecules have become attractive building blocks for bioinspired materials due to their adhesive characteristics, capacity to complex ions, redox chemistry, and biocompatibility. For the formation of tannic acid (TA) surface modifications based on silicate-phenolic networks, a high ionic strength is required. In this study, we investigated the effects of NaCl, KCl, and LiCl on the formation of TA coatings and compared it to the coating formation of pyrogallol (PG) using a quartz-crystal microbalance. We found that the substitution of NaCl with KCl inhibited the TA coating formation through the high affinity of K+ to phenolic groups resulting in complexation of TA. Assessment of the radical formation of TA by electron paramagnetic resonance spectroscopy showed that LiCl resulted in hydrolysis of TA forming gallic acid radicals. Further, we found evidence for interactions of LiCl with the Siaq crosslinker. In contrast, the coating formation of PG was only little affected by the substitution of NaCl with LiCl or KCl. Our results demonstrate the interaction potential between alkali metal salts and phenolic compounds and highlight their importance in the continuous deposition of silicate-phenolic networks. These findings can be taken as guidance for future biomedical applications of silicate-phenolic networks involving monovalent ions.

Coordination driven self-assembly for enhancing the biological stability of nobiletin

In our previous study, zein nanoparticles (NPs) coupled with tannic acid (TA) and metal ions coatings have been successfully introduced in delivery systems as effective carriers for anticancer drug delivery. Herein, nobiletin (NOB), a kind of low soluble and crystallizable nutraceutical, was encapsulated into these NPs engineered from zein, TA and different metal ions (named ZT-metal NPs) to achieve high loading capacity (LC) and long-term stability. From the result, the maximum load capacity of ZT-metal NPs was achieved at a NOB concentration of 800 μg/mL, much higher than that in zein NPs. Better stabilities of particles after storage were obtained in the nanoparticle formulations with TA and metal ions coatings. The physicochemical characteristics of the formulated NPs were observed by X-ray diffraction (XRD), together with X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). In vitro release studies illustrated that the ZT-metal NPs obtained the effect of slow release compared with free NOB. Furthermore, NOB-loaded NPs had excellent anticancer bioactivity in H1299 cells at higher NOB concentration. Confocal laser scanning microscopy (CLSM) demonstrated that the NPs could transport encapsulated molecular into cancer cells effectively. Hence, NOB encapsulated coordination driven self-assembly owned enormous potential as effective hydrophobic nutraceutical delivery vehicles.

Silicate-Phenolic Networks: Coordination-Mediated Deposition of Bioinspired Tannic Acid Coatings.

Surface modification with polyphenolic molecules has been pursued in biomedical materials owing to their antioxidant, anti‐inflammatory, and antimicrobial characteristics. Recently, the use of silicic acid (Siaq) as a mediator for efficient surface deposition of tannic acid (TA) was reported, but the postulated Si‐TA polymeric networks were not characterized. Herein, we present unambiguous evidence for silicate‐TA networks that involve Si−O−C motifs by using solid‐state NMR spectroscopy, further supported by XPS and ToF‐SIMS. By using QCM‐D we demonstrate the advantages of Siaq, compared to using transition‐metal ions, to improve the coating efficiency under mildly acidic conditions. The presented homogenous coating buildup and validated applicability in inorganic buffers broadens the use of TA for surface modifications in technological and biomedical applications.

Photochemically Enhanced Selective Adsorption of Gold Ions on Tannin-Coated Porous Polymer Microspheres.

Metal recovery from electronic waste and industrial wastewater has attracted increasing attention to recycle precious metals and inhibit the emission of hazardous heavy metals. However, the selective recovery of precious metals with a large quantity is still very challenging because wastewater contains a variety of different cations while precious metal ions are relatively scarce. Here, we introduce a simple method to selectively increase the adsorption of gold ions using tannin-coated porous polymer microspheres through photochemical reduction. Mesoporous poly(ethylene glycol dimethacrylate- co-acrylonitrile) microspheres with an average pore diameter of 13.8 nm were synthesized and used as an adsorbent matrix. Tannic acid (TA) was deposited onto the internal pores of the polymer matrix by simple immersion in an aqueous milieu. TA coatings increased the maximum number of adsorbed gold ions by 1.3 times because of the well-known metal ion chelation of TA. Under light illumination, the maximum number of adsorbed gold ions dramatically increased by 6.1 times. We examined two distinct mechanisms presumably involved in the enhanced adsorption: the photooxidation of TA and plasmon-induced hot electrons. Moreover, TA-coated microspheres exhibited remarkable selectivity for gold ions among competing metal ions commonly found in waste resources. This work suggests that the photochemically activated TA can serve as an excellent adsorbent for the selective and efficient recovery of gold ions from wastewater.

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.