Tannic Acid-Based Coatings Containing Zwitterionic Copolymers for Improved Antifouling and Antibacterial Properties

The prevention of biofilm formation on medical devices has become highly challenging in recent years due to its resistance to bactericidal agents and antibiotics, ultimately resulting in chronic infections to medical devices. Therefore, developing inexpensive, biocompatible, and covalently bonded coatings to combat biofilm formation is in high demand. Herein, we report a coating fabricated from tannic acid (TA) as an adhesive and a reducing agent to graft the zwitterionic polymer covalently in a one-step method. Subsequently, silver nanoparticles (AgNPs) are generated in situ to develop a coating with antifouling and antibacterial properties. To enhance the antifouling property and biocompatibility of the coating, the bioinspired zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC) was copolymerized with 2-aminoethyl methacrylamide hydrochloride (AEMA) using conventional free-radical polymerization. AEMA moieties containing amino groups were used to facilitate the conjugation of the copolymer with quinone groups on TA through the Michael addition reaction. Three copolymers with different ratios of monomers were synthesized to understand their impacts on fouling resistance: PMPC100, p(MPC80-st-AEMA20), and p(MPC90-st-AEMA10). To impart antibacterial properties to the surface, AgNPs were formed in situ, utilizing the unreacted quinone groups on TA, which can reduce the silver ions. The successful coating of TA and copolymer onto the surfaces was confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and its excellent wettability was verified by the water contact angle (CA). Furthermore, the functionalized coatings showed antibacterial properties against E. coli and S. aureus and remarkably decreased the adhesion of the BSA protein. The surfaces can also prevent the adhesion of bacteria cells, as confirmed by the inhibition zone test. In addition, they showed negligible cytotoxicity to normal human lung fibroblast cells (MRC-5). The as-prepared coatings are potentially valuable for biomedical applications.

Molybdenum Phosphide Quantum Dots Encapsulated by P/N-Doped Carbon for Hydrogen Evolution Reaction in Acid and Alkaline Electrolytes

A facile and eco-friendly strategy is presented for synthesizing novel nanocomposites, with MoP quantum dots (QDs) as cores and graphitic carbon as shells, these nanoparticles are dispersed in a nitrogen and phosphorus-doped porous carbon and carbon nanotubes (CNTs) substrates (MoP@NPC/CNT). The synthesis involves self-assembling reactions to form single-source precursors (SSPs), followed by pyrolysis at 900 °C in an inert atmosphere to obtain MoP@NPC/CNT-900. The presence of carbon layers on the MoP QDs effectively prevents particle aggregation, enhancing the utilization of active MoP species. The optimized sample, MoP@NPC/CNT-900, exhibits remarkable electrocatalytic activity and durability for the hydrogen evolution reaction (HER). It demonstrates a low overpotential of 155 mV at 10 mA cm-2 , a small Tafel slope of 76 mV dec-1 , and sustained performance over 20 hours in 0.5 M H2 SO4 . Furthermore, the catalyst shows excellent activity in 1 M KOH, with a relatively low overpotential of 131 mV and long-term durability under constant current input. The exceptional HER activity can be attributed to several factors: the superior performance of MoP QDs, the large surface area and good conductivity of the carbon substrates, and the synergistic effect between MoP and carbon species.

Phenolic-Compound-Based Functional Coatings: Versatile Surface Chemistry and Biomedical Applications

Phenolic-compound-based functional coatings that allow for flexible modulation of chemical and surface properties have found widespread uses in a diverse range of biomedical applications from antibiofouling and antioxidation to bioimaging, therapeutics, and controlled drug delivery. It is imperative to understand the formation mechanism of phenolic coatings to fully meet the needs of their emerging applications in controlling the surface properties of biomaterials and medical devices. In this Perspective, we highlight the versatile chemical and self-assembly approaches to generate phenolic coatings with tailored surface properties and reactivities and also discuss how the surface properties and chemical reactivities impart functional materials for translational research.

Metal-Phenolic Networks Assembled on TiO2 Nanospikes for Antimicrobial Peptide Deposition and Osteoconductivity Enhancement in Orthopedic Applications

The lack of antimicrobial and osteoconductive activities of titanium (Ti) for orthopedic implants has led to problems such as infection and structural looseness, which bring physical and psychological sufferings to patients as well as economic burden on the healthcare system. To endow Ti implants with anti-infective function and bioactivity, in this study, we successfully constructed TiO2 nanospike (TNS) structure on the surface of Ti followed by assembling metal-polyphenol networks (MPNs) and depositing antimicrobial peptides (AMPs). The TNSs' structure can disrupt the bacteria by physical puncture, and it was also proved to have excellent photothermal conversion performance upon near-infrared light irradiation. Furthermore, with the assistance of contact-active chemo bactericidal efficacy of AMPs, TNS-MPN-AMP nanocoating achieved physical/photothermal/chemo triple-synergistic therapy against pathogenic bacteria. The anti-infective efficiency of this multimodal treatment was obviously improved, with an antibacterial ratio of >99.99% in vitro and 95.03% in vivo. Moreover, the spike-like nanostructure of TNSs and the bioactive groups from MPNs and AMPs not only demonstrated desirable biocompatibility but also promoted the surface hydroxyapatite formation in simulated body fluid for further osseointegration enhancement. Altogether, this multifaceted TNS-MPN-AMP nanocoating endowed Ti implants with enhanced antibacterial activity, excellent cytocompatibility, and desirable osteoconductive ability.

Biomimetic anti-inflammatory and osteogenic nanoparticles self-assembled with mineral ions and tannic acid for tissue engineering

Bone healing involves complex processes including inflammation, induction, and remodeling. In this context, anti-inflammatory and osteoconductive multi-functional nanoparticles have attracted considerable attention for application in improved bone tissue regeneration. In particular, nanoparticles that promote suppression of inflammatory response after injury and direction of desirable tissue regeneration events are of immense interest to researchers. We herein report a one-step method to prepare multi-functional nanoparticles using tannic acid (TA) and simulated body fluid (SBF) containing multiple mineral ions. Mineral-tannic acid nanoparticles (mTNs) were rapidly fabricated in 10 min, and their size (around 250-350 nm) and chemical composition were controlled through the TA concentration. In vitro analysis using human adipose derived stem cells (hADSCs) showed that mTNs effectively scavenged reactive oxygen species (ROS) and enhanced osteogenesis of hADSCs by inducing secretion of alkaline phosphatase. mTNs also increased osteogenic marker gene expression even in the presence of ROS, which can generally arrest osteogenesis (OPN: 1.74, RUNX2: 1.90, OCN: 1.47-fold changes relative to cells not treated with mTNs). In vivo analysis using a mouse peritonitis model revealed that mTNs showed anti-inflammatory effects by decreasing levels of pro-inflammatory cytokines in blood (IL-6: 73 ± 4, TNF-α: 42 ± 2%) and peritoneal fluid (IL-6: 78 ± 2, TNF-α: 21 ± 6%). We believe that this one-step method for fabrication of multi-functional nanoparticles has considerable potential in tissue engineering approaches that require control of complex microenvironments, as required for tissue regeneration.

Tannic acid modified PdAu alloy nanowires as efficient oxygen reduction electrocatalysts

Design of the structure, composition and interface of the catalysts is very important to improve oxygen reduction reaction (ORR) catalytic activity under alkaline environment. Herein, we propose a direct method to rapid synthesis of tannic acid (TA) modified PdAu alloy nanowires (PdAu@TA NWs). Compared with pure PdAu NWs and commercial Pt/C, the PdAu@TA NWs exhibit superior ORR electrocatalytic activity (mass activity: 0.73 A mg^-1_metaland specific activity: 3.50 mA cm^-2), stability, and methanol tolerance in an alkaline medium because PdAu@TA NWs possess sufficient active sites and synergistic effect that can effectively promote the oxygen reduction, inhibit the oxidation of the catalyst and improve the methanol tolerance of the catalyst. This synthetic method is a promising strategy to prepare metallic catalyst with surface functionalization.

Versatile polyphenolic platforms in regulating cell biology

Polyphenolic materials are a class of fascinating and versatile bioinspired materials for biointerfacial engineering. In particular, due to the presence of active chemical groups, a series of unique physicochemical properties become accessible and tunable of the as-prepared polyphenolic platforms, which could delicately regulate the cell activities via cell-material contact-dependent interactions. More interestingly, polyphenols could also affect the cell behaviors via cell-material contact-independent manner, which arise due to their intrinsically functional characteristics (e.g., antioxidant and photothermal behaviors). As such, a comprehensive understanding on the relationship between material properties and desired biomedical applications, as well as the underlying mechanism at the cellular and molecular level would provide material design principles and accelerate the lab-to-clinic translation of polyphenolic platforms. In this review, we firstly give a brief overview of cell hallmarks governed by surrounding cues, followed by the introduction of polyphenolic material engineering strategies. Subsequently, a detailed discussion on cell-polyphenols contact-dependent interfacial interaction and contact-independent interaction was also carefully provided. Lastly, their biomedical applications were elaborated. We believe that this review could provide guidances for the rational material design of multifunctional polyphenols and extend their application window.

Recent progress in Tannic Acid-driven antimicrobial/antifouling surface coating strategies

Medical devices and surgical implants are a necessary part of tissue engineering and regenerative medicines. However, the biofouling and microbial colonization on the implant surface continues to be a major...

Nisin-based antibacterial and antiadhesive layer-by-layer coatings

Some removable medical devices such as catheters and cardiovascular biomaterials require antiadhesive properties towards both prokaryotic and eukaryotic cells in order to prevent the tissues from infections upon implantation and, from alteration upon removal. In order to inhibit cell adhesion, we developed ultrathin hydrated Layer-by-Layer (LbL) coatings composed of biocompatible polyelectrolytes, namely chondroitin sulfate A (CSA) and poly-l-lysine (PLL). The coatings were crosslinked with genipin (GnP), a natural and biocompatible crosslinking agent, to increase their resistance against environmental changes. In order to confer antibacterial activity to the coatings, we proceeded to the electrostatically-driven immobilization of nisin Z, an antimicrobial peptide (AMP) active against gram-positive bacteria. The nisin-enriched coatings had a significantly increased anti-proliferative impact on fibroblasts, as well as a strong contact-killing activity against Staphylococcus aureus in the short and long term.

Synthesis and characterization of tannic acid pillared bentonite composite for the efficient adsorption of aflatoxins

Tannic acid (TA) is a hydrolysable polyphenol with established antioxidant and antibacterial activity along with its tendency to bind both organic and inorganic ions/molecules. In the present study, the sequestration performance of TA pillared bentonite for various aflatoxins (AFs) including AFB1, AFB2, AFG1 and AFG2 from aqueous solutions and simulated poultry gastrointestinal model solution was studied via adsorption. The adsorbents were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), N₂ adsorption-desorption study and X-ray photoelectron spectroscopy (XPS). The reaction conditions including pH, agitation time, initial toxin concentration and temperature were systematically optimized. The Langmuir adsorption capacity of the adsorbent reached to 86, 71, 74 and 149 mg/g for AFB1, AFB2, AFG1 and AFG2 respectively. Adsorption kinetics and thermodynamic studies showed rapid AFs uptake and the exothermicity of the adsorption reaction respectively. Simultaneous removal of AFs by BTA3 revealed their independent and uninterrupted adsorption and the adsorption mechanism of AFs over BTA3 was elaborated with the help of XPS results. The outstanding AFs sequestering capability of BTA3 in aqueous solution and simulated poultry gastrointestinal model can be envisioned of great promise for the remediation of AFs and other hazardous pollutants from food and poultry industrial products.

Antibacterial Layer-by-Layer Coatings for Medical Implants

The widespread occurrence of nosocomial infections and the emergence of new bacterial strands calls for the development of antibacterial coatings with localized antibacterial action that are capable of facing the challenges posed by increasing bacterial resistance to antibiotics. The Layer-by-Layer (LbL) technique, based on the alternating assembly of oppositely charged polyelectrolytes, can be applied for the non-covalent modification of multiple substrates, including medical implants. Polyelectrolyte multilayers fabricated by the LbL technique have been extensively researched for the development of antibacterial coatings as they can be loaded with antibiotics, antibacterial peptides, nanoparticles with bactericide action, in addition to being capable of restricting adhesion of bacteria to surfaces. In this review, the different approaches that apply LbL for antibacterial coatings, emphasizing those that can be applied for implant modification are presented.

Effect of the Buffer on the Buildup and Stability of Tannic Acid/Collagen Multilayer Films Applied as Antibacterial Coatings

The deposition of polyelectrolyte multilayers, obtained by the layer-by-layer (LbL) method, is a well-established technology to design biocompatible and antibacterial coatings aimed at preventing implant-associated infections. Several types of LbL films have been reported to exhibit antiadhesive and/or antibacterial (contact-killing or release-killing) properties governed not only by the incorporated compounds but also by their buildup conditions or their postbuildup treatments. Tannic acid (TA), a natural polyphenol, is known to inhibit the growth of several bacterial strains. In this work, we developed TA/collagen (TA/COL) LbL films built in acetate or citrate buffers at pH 4. Surprisingly, the used buffer impacts not only the physicochemical but also the antibacterial properties of the films. When incubated in physiological conditions, both types of TA/COL films released almost the same amount of TA depending on the last layer and showed an antibacterial effect against Staphylococcus aureus only for citrate-built films. Because of their granular topography, TA/COL citrate films exhibited an efficient release-killing effect with no cytotoxicity toward human gingival fibroblasts. Emphasis is put on a comprehensive evaluation of the physicochemical parameters driving the buildup and the antibacterial property of citrate films. Specifically, complexation strengths between TA and COL are different in the presence of the two buffers affecting the LbL deposition. This work constitutes an important step toward the use of polyphenols as an antibacterial agent when incorporated in LbL films.

Protein-resistant surface based on zwitterion-functionalized nanoparticles for marine antifouling applications

A functional nanocomposite (PSBMA@VTMO@silica/TA-PEG) coating was successfully developed through a facile deposition method, and was able to effectively block the adhesion of proteins and subsequent biofouling deposition.

Flower-like gold nanoparticles for enhanced photothermal anticancer therapy by the delivery of pooled siRNA to inhibit heat shock stress response

Surface modified gold nanoflowers were employed as synergistic therapeutics for photothermal ablation and gene silencing.

Highly Active Protein Surfaces Enabled by Plant-Based Polyphenol Coatings

Proteins represent complex biomolecules capable of wide-ranging but also highly specific functionalities. Their immobilization on material supports can enable broad applications from sensing and industrial biocatalysis to biomedical interfaces and materials. We demonstrate the advantages of using aqueous-processed cross-linked polyphenol coatings for immobilizing proteins, including IgG, avidin, and various single and multidomain enzymes on diverse materials, to enable active biofunctional structures (e.g., ca. 2.2, 1.7, 1.1, and 4.8 mg·m^-2 active phosphatase on nanoporous cellulose and alumina, steel mesh, and polyester fabric, respectively). Enzyme assays, X-ray photoelectron spectroscopy, silver staining, supplemented with contact angle, solid-state ¹³C NMR, HPLC, and ESI-MS measurements were used to characterize the polyphenols, coatings, and protein layers. We show that the functionalization process may be advantageously optimized directly for protein activity rather than the traditional focus on the thickness of the coating layer. Higher activities (by more than an order of magnitude in some cases) and wider process pH and material compatibility are demonstrated with polyphenol coatings than other approaches such as polydopamine. Coatings formed from different plant polyphenol extracts, even at lowered purity (and cost), were also found to be highly functional. Chemically, our results indicate that polyphenol coatings differ from polydopamine mainly because of the elimination of amine groups, and that polyphenol layers with intermediate levels of reactivity may better lead to high immobilized protein activity. Overall, an improved understanding of simple-to-use polyphenol coatings has been obtained, which enabled a significant development in active protein surfaces that may be applied across diverse materials and nanostructured supports.

Tannic Acid-Lung Fluid Assemblies Promote Interaction and Delivery of Drugs to Lung Cancer Cells

Lung cancer (LC) is one of the leading causes of death in both men and women in the United States. Tannic acid (TA), a water-soluble polyphenol, exhibits a wide range of biological activities. TA has received much attention as a promising compound in the biomaterial and drug delivery fields. Lung fluid (LF) is a major barrier for distribution of drugs to the lungs. Therefore, the purpose of this study was to examine TA interaction with LF for effective delivery of anti-cancer drug molecules via pulmonary delivery. The extent of adsorption of LF proteins by TA was revealed by fluorescence quenching in fluorescence spectroscopy. The presence of LF in TA-LF complexes was noticed by the presence of protein peaks at 1653 cm-1. Both protein dot and SDS-PAGE analysis confirmed LF protein complexation at all TA concentrations employed. A stable particle TA-LF complex formation was observed through transmission electron microscopy (TEM) analysis. The complexation pattern measured by dynamic light scattering (DLS) indicated that it varies depending on the pH of the solutions. The degree of LF presence in TA-LF complexes signifies its interactive behavior in LC cell lines. Such superior interaction offered an enhanced anti-cancer activity of drugs encapsulated in TA-LF complex nanoformulations. Our results indicate that TA binds to LF and forms self-assemblies, which profoundly enhance interaction with LC cells. This study demonstrated that TA is a novel carrier for pharmaceutical drugs such as gemcitabine, carboplatin, and irinotecan.

Investigation of the antibiofilm capacity of peptide-modified stainless steel

Biofilm formation on surfaces is an important research topic in ship tribology and medical implants. In this study, dopamine and two types of synthetic peptides were designed and attached to 304 stainless steel surfaces, aiming to inhibit the formation of biofilms. A combinatory surface modification procedure was applied in which dopamine was used as a coupling agent, allowing a strong binding ability with the two peptides. X-ray photoelectron spectroscopy (XPS), elemental analysis, contact angle measurement and surface roughness test were used to evaluate the efficiency of the peptide modification. An antibiofilm assay against Staphylococcus aureus was conducted to validate the antibiofilm capacity of the peptide-modified stainless steel samples. XPS analysis confirmed that the optimal dopamine concentration was 40 µg ml^-1 in the coupling reaction. Element analysis showed that dopamine and the peptides had bound to the steel surfaces. The robustness assay of the modified surface demonstrated that most peptide molecules had bound on the surface of the stainless steel firmly. The contact angle of the modified surfaces was significantly changed. Modified steel samples exhibited improved antibiofilm properties in comparison to untreated and dopamine-only counterpart, with the peptide 1 modification displaying the best antibiofilm effect. The modified surfaces showed antibacterial capacity. The antibiofilm capacity of the modified surfaces was also surface topography sensitive. The steel sample surfaces polished with 600# sandpaper exhibited stronger antibiofilm capacity than those polished with other types of sandpapers after peptide modification. These findings present valuable information for future antifouling material research.

Acidity-triggered charge-reversible multilayers for construction of adaptive surfaces with switchable bactericidal and bacteria-repelling functions

Microenvironment acidity of infected sites was utilized to control the surface charge, and therefore, manipulate bacterial behavior.

Polyelectrolyte Multilayer Nanocoating Dramatically Reduces Bacterial Adhesion to Polyester Fabric

Bacterial adhesion to textiles is thought to contribute to odor and infection. Alternately exposing polyester fabric to aqueous solutions of poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) is shown here to create a nanocoating that dramatically reduces bacterial adhesion. Ten PDDA/PAA bilayers (BL) are 180 nm thick and only increase the weight of the polyester by 2.5%. The increased surface roughness and high degree of PAA ionization leads to a surface with a negative charge that causes a reduction in adhesion of Staphylococcus aureus by 50% when compared to uncoated fabric, after rinsing with sterilized water, because of electrostatic repulsion. S. aureus bacterial adhesion was quantified using bioluminescent radiance measured before and after rinsing, revealing 99% of applied bacteria were removed with a ten bilayer PDDA/PAA nanocoating. The ease of processing, and benign nature of the polymers used, should make this technology useful for rendering textiles antifouling on an industrial scale.

Antimicrobial spray nanocoating of supramolecular Fe(III)-tannic acid metal-organic coordination complex: applications to shoe insoles and fruits

Numerous coating strategies are available to control the surface properties and confer new properties to substrates for applications in energy, environment, biosystems, etc., but most have the intrinsic limitations in the practical setting: (1) highly specific interactions between coating materials and target surfaces are required for stable and durable coating; (2) the coating of bulk substrates, such as fruits, is time-consuming or is not achievable in the conventional solution-based coating. In this respect, material-independent and rapid coating strategies are highly demanded. We demonstrate spray-assisted nanocoating of supramolecular metal-organic complexes of tannic acid and ferric ions. The spray coating developed is material-independent and extremely rapid (<5 sec), allowing for coating of commodity goods, such as shoe insoles and fruits, in the controlled fashion. For example, the spray-coated mandarin oranges and strawberries show significantly prolonged post-harvest shelf-life, suggesting practical potential in edible coating of perishable produce.

Arginine-Based Polymer Brush Coatings with Hydrolysis-Triggered Switchable Functionalities from Antimicrobial (Cationic) to Antifouling (Zwitterionic)

Arginine polymer based coatings with switchable properties were developed on glass slides (GS) to demonstrate the smart transition from antimicrobial (cationic) to fouling-resistant (zwitterionic) surfaces. l-Arginine methyl ester-methacryloylamide (Arg-Est) and l-arginine-methacryloylamide (Arg-Me) polymer brushes were grafted from the GS surface via surface-initiated reversible addition-fragmentation chain-transfer (SI-RAFT) polymerization. In comparison to the pristine GS and Arg-Me graft polymerized GS (GS-Arg-Me) surfaces, the Arg-Est polymer brushes-functionalized GS surfaces exhibit a superior antimicrobial activity. Upon hydrolysis treatment, the strong bactericidal efficacy switches to good resistance to adsorption of bovine serum albumin (BSA), the adhesion of Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli, as well as the attachment of Amphora coffeaeformis. In addition, the switchable coatings are proven to be biocompatible. The stability and durability of the switchable coatings are also ascertained after exposure to filtered seawater for 30 days. Therefore, deposition of the proposed "smart coatings" offers another environmentally friendly alternative for combating biofouling.

Delivery systems for antimicrobial peptides

Due to rapidly increasing resistance development against conventional antibiotics, finding novel approaches for the treatment of infections has emerged as a key health issue. Antimicrobial peptides (AMPs) have attracted interest in this context, and there is by now a considerable literature on the identification such peptides, as well as on their optimization to reach potent antimicrobial and anti-inflammatory effects at simultaneously low toxicity against human cells. In comparison, delivery systems for antimicrobial peptides have attracted considerably less interest. However, such delivery systems are likely to play a key role in the development of potent and safe AMP-based therapeutics, e.g., through reducing chemical or biological degradation of AMPs either in the formulation or after administration, by reducing adverse side-effects, by controlling AMP release rate, by promoting biofilm penetration, or through achieving co-localization with intracellular pathogens. Here, an overview is provided of the current understanding of delivery systems for antimicrobial peptides, with special focus on AMP-carrier interactions, as well as consequences of these interactions for antimicrobial and related biological effects of AMP-containing formulations.

Methacrylate-ended polypeptides and polypeptoids for antimicrobial and antifouling coatings

Methacrylate-terminated polypept(o)ides were directly synthesized via NCA-ROP, and then surface-grafted to form a polymer brush coating with infection-resistant efficacy.

Improved antifouling and antimicrobial efficiency of ultrafiltration membranes with functional carbon nanotubes

In this study, functional polymer brush grafted carbon nanotubes (p-CNTs) were developed as multifunctional modifiers for PES membrane modification.