PDA Coatings Research Articles

Polydopamine-assisted smart bacteria-responsive hydrogel: Switchable antimicrobial and antifouling capabilities for accelerated wound healing

IntroductionWound infections and formation of biofilms caused by multidrug-resistant bacteria have constituted a series of wound deteriorated and life-threatening problems. The in situ resisting bacterial adhesion, killing multidrug-resistance bacteria, and releasing dead bacteria is strongly required to supply a gap of existing sterilization strategies. ObjectivesThis study aims to present a facile approach to construct a bacteria-responsive hydrogel with switchable antimicrobial-antifouling properties through a “resisting-killing-releasing” method. MethodsThe smart bacteria-responsive hydrogel was constructed by two-step immersion strategy: a simple immersion-coating process to construct Polydopamine (pDA) coatings on the surface of a gelatin-chitosan composite hydrogel and followed by grafting of bactericidal quaternary ammonium chitosan (QCS) as well as pH-responsive PMAA to this pDA coating. The in vitro antimicrobial activity, biocompatibility and the in vivo wound healing effects in a mouse MRSA-infected full-thickness defect model of the hydrogel were further evaluated. ResultsAssisted by polydopamine coating, the pH-responsive PMAA and bactericidal QCS are successfully grafted onto a gelatin-chitosan composite hydrogel surface and hydrogels maintain the adequate mechanical properties. At physiological conditions, the PMAA hydration layer endows the hydrogel with resistance to initial bacterial attachment. Once bacteria colonize and acidize local environment, the swelling PMAA chains tend to collapse then expose the bactericidal QCS, realizing the on-demand kill bacteria. Moreover, the dead bacteria can be released and the hydrogel will resume the resistance due to hydrophilicity of PMAA at increased pH, endowing the surface renewable ability. In vitro and in vivo studies demonstrate the favorable biocompatibility and wound healing capacity of hydrogels that can inhibit infection and further facilitate granulation tissue, angiogenesis, and collagen synthesis. ConclusionThis strategy provides a novel methodology for the development and design of smart wound dressing to combat multidrug-resistant bacteria infections.

In situ grown, super-hydrophilic and multifunctional hydroxyapatite composite membrane for oil–water separation

In this paper, a method of growing SiO2 on hydroxyapatite in situ and depositing it into polydopamine-modified MCEM membrane was reported to prepare super-hydrophilic underwater super-oleophobic coatings. The results showed that the hydrophilic properties of SiO2, the hydroxy-rich structure of hydroxyapatite and the synergistic action of polydopamine made the membrane have excellent hydrophilicity. The modified HAP@SiO2/PDA coating membrane not only had excellent mechanical properties, but also had good oil and water selectivity. At the same time, the membrane separation flux of light oil can reach 3000 L/(m2·h), and the oil discharge rate of heavy oil can reach 98.95%. More importantly, the membrane can remove 90.90% of the actual oilfield wastewater. As a result, HAP@SiO2/PDA coatings can effectively treat a wide range of oily wastewater and demonstrate attractive separation capabilities.

Surface mineralization with controlled polymerization of dopamine

AbstractPolydopamine (PDA) has been utilized as a scaffolding for various biomedical applications since its discovery. This versatility arises from the unique property of PDA to coat virtually any surface and its high biocompatibility. In this study, PDA has been used to synthesize calcium phosphate in simulated body fluid on surfaces that normally could not form these mineral layers. PDA has the potential to reduce calcium phosphate. Due to its natural hydrophilicity and the high density of charged surface groups. Adjusting the reaction conditions has been shown to alter the properties of the PDA coatings and in turn the applications. In this study, we will observe how controlling the reaction conditions to adjust properties of PDA can alter the mineral layer formed on the polymer surface. By maximizing the surface area of the polymer, the number of polar groups on the surface available to bind the mineralization. We will illustrate both the degree of mineralization on the surface as well as the chemical content of the minerals. We will illustrate that the ability of PDA to form calcium phosphate can be enhanced to allow for better biocompatibility for biomedical implants.

Non-antibiotic antimicrobial polydopamine surface coating to prevent stable biofilm formation on satellite telemetry tags used in cetacean conservation applications

Satellite telemetry tags, used to monitor the migratory behavior of cetaceans, have the potential to be a vehicle for infection due to their invasive nature. Antibiotic coatings have been previously employed to reduce the chances of infection via the formation of a stable biofilm on the surface of the tags. However, increased use of antibiotics has the potential to lead to the development of antibiotic-resistant pathogens. To prevent the formation of antibiotic-resistant pathogens, a polydopamine surface coating that, when exposed to oxygen, releases low doses (~40-100µM) of hydrogen peroxide over a prolonged period (>24 hours) can be used to replace current antibiotic coatings used in the field. These pDA coatings can reduce bacterial adhesion from model bacteria from the two most common genotypes found on the skin of cetaceans (Psychrobacter and Tenacibaculum). The adhesion of Psychrobacter bacteria was reduced by 80% (p<0.01) while Tenacibaculum was reduced by 70% (p<0.001). When the bacteria were dosed with a non-lethal quantity of hydrogen peroxide (200µM) prior to being exposed to pDA surface coatings, there was no decrease in the efficacy of the coatings. This indicates a resistance to hydrogen peroxide will not be formed quickly. Overall, the polydopamine surface coatings were able to reduce the adhesion of model bacteria strains on the surface of medical grade stainless steel, which could increase the functional tag service life while reducing the chances of infection.

How thick, uniform and smooth are the polydopamine coating layers obtained under different oxidation conditions? An in-depth AFM study

To clarify inconsistencies that still exist in the literature data, a systematic AFM study of polydopamine coating layers is performed for three different oxidants: air-O2, NaIO4, and KMnO4. The focus was on assessing reproducibility and uniformity in the measured morphological parameters by analyzing a statistically relevant set of AFM data. Mechanical stability was investigated by comparing only washed with washed, followed by 30 min sonicated samples. The PDA coating always contains two components: a quasi-flat film, with intrinsic roughness in the order of 1 nm, and many “sedimented” PDA aggregates lying on the top of this film. The larger aggregates were found loosely bound to the film, they could be easily detached by sonication, leaving surfaces with more uniform coverage and reduced roughness, up to one order of magnitude less in some cases. The largest thickness was found under NaIO4 oxidation, followed by KMnO4 and O2, which contradicts recent reports of thicknesses approaching 1 µm for KMnO4 oxidation, the value determined here being almost 30 times less. The causes for this large difference and other inconsistencies were identified and discussed. Overall, the present study demonstrates the importance of establishing a standardized protocol for morphological characterization of PDA coatings.

Polyethyleneimine-assisted co-deposition of polydopamine coating with enhanced stability and efficient secondary modification.

The stability and grafting efficiency are important for polydopamine (pDA) coatings used as platforms for secondary grafting. In this work, polyethyleneimine (PEI) was co-deposited with dopamine on various materials (PP, PTFE and PVC), then immersed in a 1.0 M HCl solution or 1.0 M NaOH solution to investigate the detachment of the coatings using UV-vis spectroscopy, SEM, FTIR spectroscopy and XPS, and the effect of PEI molecular weight on the secondary grafting of heparin on the pDA/PEI coating was investigated through clotting time tests. The results showed that the detachment rates of the pDA/PEI coating (14.6%, 23.7%) co-deposited on PTFE in 1.0 M HCl or 1.0 M NaOH solutions were both lower than that of the pDA coating (35.0%, 74.6%), indicating that pDA/PEI coatings could better remain on substrates in a 1.0 M NaOH solution. Besides, pDA/PEI coatings on a PP membrane with both a higher deposition density and stability could be obtained when the mass ratio of DA/PEI was 2 : 1-1 : 1 and PEI molecular weight was 600 Da. After grafting heparin, it was found that the pDA/PEI coating with lower molecular weight (600 Da and 1800 Da) PEI could achieve a higher grafting density of heparin with a longer clotting time. Thus, the results provided better understanding about the stability of pDA/PEI coatings and efficiency of heparin grafting.

Polydopamine-Assisted Surface Modification of Ti-6Al-4V Alloy with Anti-Biofilm Activity for Dental Implantology Applications

Coating the surfaces of implantable materials with various active principles to ensure inhibition of microbial adhesion, is a solution to reduce infections associated with dental implant. The aim of the study was to optimize the polydopamine films coating on the Ti-6Al-6V alloy surface in order to obtain a maximum of antimicrobial/antibiofilm efficacy and reduced cytotoxicity. Surface characterization was performed by evaluating the morphology (SEM, AFM) and structures (Solid-state 13C NMR and EPR). Antimicrobial activity was assessed by logarithmic reduction of CFU/mL, and the antibiofilm activity by reducing the adhesion of Escherichia coli, Staphylococcus aureus, and Candida albicans strains. The release of NO was observed especially for C. albicans strain, which confirms the results obtained for microbial adhesion. Among the PDA coatings, for 0.45:0.88 (KMnO4:dopamine) molar ratio the optimal compromise was obtained in terms of antimicrobial activity and cytotoxicity, while the 0.1:1.5 ratio (KMnO4:dopamine) led to higher NO release and implicitly the reduction of the adhesion capacities only for C. albicans, being slightly cytotoxic but with moderate release of LDH. The proposed materials can be used to reduce the adhesion of yeast to the implantable material and thus inhibit the formation of microbial biofilms.

Rapid Biocidal Activity of N-Halamine-Functionalized Polydopamine and Polyethylene Imine Coatings.

Microorganisms easily adhere to the surface of substrates and further form biofilms, which present problems in various fields. Therefore, the development of surfaces with antimicrobial adhesion or viability is a promising approach. In this study, we were committed to develop a rapid sterilizing coating. First, polyester fibers were immersed into a mixing solution of dopamine (PDA) and polyethyleneimine (PEI) for forming the co-deposition of PDA and PEI coatings. After this, the co-deposition of PDA and PEI coatings was immersed in a solution of household bleach for chlorination. We found that the nitrogens of PDA and PEI could be chlorinated repeatedly and that the oxidative chlorine content increased with the increasing PEI concentration upon co-deposition. Next, the efficacy of the co-deposition of chlorinated PDA and PEI coatings in eliminating Staphylococcus aureus and Escherichia coli was investigated. We found that the antibacterial ability of the coatings increased with increasing PEI content. In addition, the chlorinated co-deposition coatings had significantly improved antibacterial properties compared to the unchlorinated ones. The chlorinated co-deposition coatings inactivated >99.99% of S. aureus and >99.9% of E. coli after contact of less than 10 min. Therefore, chlorination of a PDA/PEI co-deposition surface is a feasible method for use in antibacterial coatings.

Durable, magnetic-responsive melamine sponge composite for high efficiency, in situ oil–water separation

The development of durable and high-performance absorbents for in situ oil–water separation is of critical importance for addressing severe water pollution in daily life as well as for solving accidental large-scale oil spillages. Herein, we demonstrate a simple and scalable approach to fabricate magnetic-responsive superhydrophobic melamine sponges by in situ deposition of PDA coatings and Fe3O4 nanoparticles, followed by surface silanization with low surface energy 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PTOS) layer. The prepared melamine sponge composite (PTOS-Fe3O4@PDA/MF) not only exhibits a very high water contact angle of 165 ± 1.5° and an excellent ability to uptake a variety of oils and organic solvents (e.g. up to 141.1 g/g for chloroform), but also shows robust durability and superior recyclability. The PTOS-Fe3O4@PDA/MF sponge can also efficiently separate oils (or organic solvents) and water, as demonstrated by different model systems including immiscible oil–water solution mixture and miscible water–oil (W/O) emulsion (stabilized by surfactants). Furthermore, the PTOS-Fe3O4@PDA/MF sponge is able to in situ recover organics from water using a peristaltic pump, which gives it significant advantages over other traditional batch processes for oil–water separation. We believe that the PTOS-Fe3O4@PDA/MF sponge provides a very promising material solution to address oil–water separation, especially for the large-scale problems that have been long-time challenges with conventional sorption methods.

Sustainable Advanced Fenton-like Catalysts Based on Mussel-Inspired Magnetic Cellulose Nanocomposites to Effectively Remove Organic Dyes and Antibiotics.

The development of biocompatible advanced Fenton-like catalysts with high catalytic activity, good stability, and recyclability using sustainable biosourced materials is of considerable interest yet remains a challenge. Herein, we develop a novel mussel-inspired magnetic cellulose nanocomposite (MCNF/PDA) with carboxylated cellulose nanofibers (CNF) and explore as advanced Fenton-like catalysts to effectively degrade organic dyes and antibiotics. The MCNF/PDA nanocomposites were prepared by anchoring Fe3O4 nanoparticles to CNFs via chemical deposition followed with PDA coatings. The composites exhibit an excellent degradation activity toward methylene blue (MB) in a wide pH range of 2-10 in the presence of H2O2 and have a maximum degradation capacity of 2265 mg/g. Moreover, the MCNF/PDA nanocatalysts are highly stable and can be easily regenerated. After four cycles, it can still achieve the removal rate as high as 95%. In addition, the MCNF/PDA nanocatalysts also demonstrate an excellent degradation performance to the antibiotic tetracycline. This work provides new insights into fabricating biocompatible cellulosic-based advanced Fenton catalysts with sustainable biomass-derived materials to efficiently remove organic pollutants from wastewater.

Mechanical Enhancement of Bioinspired Polydopamine Nanocoatings.

Inspired by the catechol and amine-rich adhesive proteins of mussels, polydopamine (pDA) has become one of the most widely employed methods for functionalizing material surfaces, powered in part by the versatility and simplicity of pDA film deposition that takes place spontaneously on objects immersed in an alkaline aqueous solution of dopamine monomer. Despite the widespread adoption of pDA as a multifunctional coating for surface modification, it exhibits poor mechanical performance. Attempts to modify the physical properties of pDA by incorporation of oxidizing agents, cross-linkers, or carbonization of the films at ultrahigh temperatures have been reported; however, improving mechanical properties with mild post-treatments without sacrificing the functionality and versatility of pDA remains a challenge. Here, we demonstrate thermal annealing at a moderate temperature (130 °C) as a facile route to enhance mechanical robustness of pDA coatings. Chemical spectroscopy, X-ray scattering, molecular force spectroscopy, and bulk mechanical analyses indicate that monomeric and oligomeric species undergo further polymerization during thermal annealing, leading to fundamental changes in molecular and bulk mechanical behavior of pDA. Considerable improvements in scratch resistance were noted in terms of both penetration depth (32% decrease) and residual depth (74% decrease) for the annealed pDA coating, indicating the enhanced ability of the annealed coating to resist mechanical deformations. Thermal annealing resulted in significant enhancement in the intermolecular and cohesive interactions between the chains in the pDA structure, attributed to cross-linking and increased entanglements, preventing desorption and detachment of the chains from the coating. Importantly, improvements in pDA mechanical performance through thermal annealing did not compromise the ability of pDA to support secondary coating reactions as evidenced by electroless deposition of a metal film adlayer on annealed pDA.

Development and Characterization of an Antimicrobial Polydopamine Coating for Conservation of Humpback Whales.

Migration patterns of humpback whales have been monitored using 316L stainless steel (SS) satellite telemetry tags. The potential for tissue infection and necrosis is increased if the bacteria, naturally a part of the diverse microbiome on the skin of humpback whales, can adhere to and colonize the surface of the tags. Polydopamine (pDA) has the potential to prevent the adhesion of one of the most prevalent bacterial strains on the surface of the skin of cetaceans (Psychrobacter) through the release of hydrogen peroxide. The release of hydrogen peroxide from the pDA coatings (40–100 μM) has the ability to induce a bacteriostatic response in E. coli, a commonly used bacteria strain in antimicrobial studies and potentially P. cryohalolentis, a common humpback associated bacteria. The H2O2 dose required to induce bacteriostatic conditions in E. coli is approximately 60 μM and in P. cryohalolentis is 100 μM. Bacterial adhesion on the surface of pDA coated SS coupons was measured first using E. coli. The coating successfully prevented adhesion of E. coli on the surface of SS coupons under certain conditions (60% reduction, p < 0.05) but the same was not seen with P. cryohalolentis. When coating conditions were altered (an increase in pH and temperature) the adhesion of P. cryohalolentis was reduced (80% reduction, p < 0.001). Overall, the pDA coatings have the capacity to generate varying amounts of hydrogen peroxide by altering the coating conditions and have the ability to reduce bacterial adhesion on the surface of satellite telemetry tags, and therefore the potential to increase tag functional service lifetime.

Enhanced Electrochemical Performance of Silicon-Based Anode Material Via a Synergistic Effect Between Sodium Alginate and Dopamine Hydrochloride

Silicon (Si) material, which has the advantages of good safety and high capacity, is expected to replace the commercial graphite as the next generation anode material for lithium ion batteries (LIBs) application. Herein, we developed a strategy to largely enhance the cycling stability and rate performance of the Si-based material. In that, sodium alginate (SA) was employed as a coating material. As a result, both of the cycling stability and rate performance of the material were effectively enhanced. For instance, the SA-coated Si(O) showed capacity enhancement of 28.2%, 26.6%, 49.1% and 115% as compared to the bare one at the current densities of 100 mA g−1, 250 mA g−1, 500 mA g−1 and 1000 mA g−1, respectively. Moreover, a synergistic effect between SA and dopamine hydrochloride (PDA) was discovered, which effectively impeded the drastically capacity degradation in the beginning several cycles at various current densities, leading to excellent rate performance of the Si(O)/SA–PDA material. The calculated specific capacity of this material reached as high as 3440 mAh g−1 at 50 mA g−1 by excluding the energy storage contribution from the graphite in the electrode. Importantly, both SA and PDA coatings were completed by a simply ball-milling method. Altogether, this work bears significant meaning to the actual application of Si-based material in LIBs field.

Regenerable urchin-like Fe3O4@PDA-Ag hollow microspheres as catalyst and adsorbent for enhanced removal of organic dyes

In this work, novel urchin-like Fe3O4@polydopamine (PDA)-Ag hollow microspheres have been prepared via a facile synthesis method by in situ reduction and growth of Ag nanoparticles on mussel-inspired PDA layers coated on Fe3O4 hollow cores. The catalytic reduction efficiency and adsorption performance of the as-prepared urchin-like Fe3O4@polydopamine (PDA)-Ag hollow microspheres for model organic dyes (i.e., methylene blue and rhodamine B) under varying pH condition have been systematically investigated, which are demonstrated to be significantly enhanced as compared to that of spherical (relatively smooth) solid Fe3O4@PDA-Ag microspheres. The as-prepared urchin-like Fe3O4@PDA-Ag hollow microspheres show high reusability, easy separability, and fast regeneration ability, with no obvious drop in the catalytic and adsorption efficiency after cyclic reuse. The versatile PDA coatings on the urchin-like microspheres allow further surface functionalization for development of multifunctional catalyst and adsorbent materials. This work provides a very useful and facile methodology for synthesizing and tuning the urchin-like morphology of Fe3O4@PDA-Ag microspheres, with great potential applications in catalysis and wastewater treatment.

Microwave-Accelerated Rapid, Chemical Oxidant-Free, Material-Independent Surface Chemistry of Poly(dopamine).

A simple strategy for the rapid preparation of multifunctional polydopamine (pDA) coatings is demonstrated. Microwave irradiation of the coating solution enables the formation of a ≈18 nm thick, genuine pDA coating in 15 min, which is ≈18 times faster than conventional coating. The acceleration effect results from the radical generation and temperature increase, which facilitate thermally accelerated radical polymerization of dopamine.

Functionalization of Polydopamine via the Aza-Michael Reaction for Antimicrobial Interfaces.

Polydopamine (pDA) coatings afford tremendous versatility due to their capabilities to provide substrate-independent functionalization with a wide range of amine- and thiol-containing molecules. In this work, we developed a new and facile conjugation approach to the formation of β-amino carbonyl linkages between pDA and acrylate/acrylamide molecules via the aza-Michael reaction. Sulfobetaine acrylamide (SBAA), sulfobetaine methacrylate (SBMA), and poly(ethylene glycol) methacrylate (PEGMA) were employed to graft onto pDA films, giving rise to formation of antifouling coatings. Because of the universal adhesive property of pDA, the coating strategy was applied to different substrates, including TiO2, gold, SiO2, Nitinol alloy, polystyrene, and poly(dimethylsiloxane). The variation of surface chemistry and surface wettability upon pDA modification and subsequent conjugation was monitored with X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Antifouling properties of coatings were challenged by three common Gram-negative and Gram-positive bacteria. Cytocompatibility of the coatings with NIH-3T3 fibroblasts was accessed using MTT assay. The results showed that pDA coatings grafted with SBAA exhibited superhydrophilicity and excellent fouling resistance likely due to the high chemical reactivity of acrylamide, leading to high grafting density. In addition, dual functional coatings containing passive and active antibacterial components were constructed through the in situ deposition of antimicrobial agent, silver nanoparticles, in pDA, followed by the grafting of SBAA for bacterial repellence. The composite coatings allowed reducing adsorption of E.coli by >95%, while killing attached bacteria by up to 98% upon the releasing of Ag(+) ions as measured by inductively coupled plasma mass spectrometry. Consequently, this work paves a new avenue to the grafting strategy to engineer pDA and to the functional bioinspired antifouling interfaces in a substrate-independent fashion.

Tunable fabrication of hierarchical hybrids via the incorporation of poly(dopamine) functional interlayer

Two kinds of ternary hybrids were prepared by anchoring different shapes and loadings of Au nanoparticles (NPs) on poly(dopamine) (PDA) functionalized polystyrene (PS) microspheres with two different strategies, i.e., in situ reduction and self-assembly approach. PDA coatings were firstly introduced to functionalize the hydrophobic PS surface with sufficient amino and hydroxyl groups, which enhanced the interaction between Au NPs and the polymer spheres. Thus, Au NPs could be easily immobilized onto the surface of the PDA/PS microspheres, and the hierarchical composite microspheres exhibited a well-defined core/shell structure without sacrificing the spherical PS morphology. PS/PDA/Au-R and PS/PDA/Au-A microspheres fabricated by in situ reduction and self-assembly approach showed different distinct Au nano-shell morphology with the corresponding optical, catalytic and electrochemical properties. Field emission scanning electron microscopy and transmission electronic microscopy verified these hierarchical structures with the ultrathin PDA film incorporating between the inner PS core and the outer Au NPs shell. X-ray diffraction and X-ray photoelectron spectroscopy confirmed the presence of PDA and Au layer on the surface of the composite particles. These green and facile methods with mild experimental conditions can extend to fabricate other polymer or inorganic substrates coated by various noble metals.

Construction of poly-dopamine coating with copper ion for controllable and sustained release of nitric oxide on the surface of cardiovascular implants

Event Abstract Back to Event Construction of poly-dopamine coating with copper ion for controllable and sustained release of nitric oxide on the surface of cardiovascular implants Qiufen Tu1, 2, Long Li1, Pengkai Qi1, Yalong Li1, Zhilu Yang1, 2 and Nan Huang1, 2 1 Southwest Jiaotong University, Department of Materials Science and Engineering, China 2 Education Ministry of China, Key Laboratory of Advanced Technology of Materials, China Introduction: Nitric oxide (NO) became a desirable molecule in the surface modification of cardiovascular implants because of its multi-physiological functions, such as anti-thrombosis and anti-hyperplasia of smooth muscle cell (SMC)[1], and the release rate and persistence of NO guarantee the long-term success rate of cardiovascular implants. So in this paper, we developed a controllable and sustained NO releasing surface for cardiovascular implants based on poly-dopamine coating loaded with different concentrations of copper ion (PDA@Cu), which have been reported able to catalyze the generation of NO from NO donor in vivo (e.g. S-nitrosothiols, RSNO) in the existence of glutathione (GSH)[2]. Methods and materials: The 316L SS samples were immersed in dopamine solution (1 mg/mL in 10 mM Tris buffer, pH 8.5) mixed with CuCl2 solution of different concentration (0, 0.1, 0.2, 0.3 mg/mL respectively) at 25° C for 12h. All the samples were ultrasonically washed in distilled water. The content of Cu in the PDA@Cu coatings was detected via XPS. Their NO catalyzing abilities were detected using Griess reagent. Platelet adhesion experiment was carried out to value their hemo-compatibility. Results and Discussion: During the polymerization of dopamine, the addition of CuCl2 solution resulted in the loading of Cu ion in the PDA coatings, just as what was shown in Figure 1 A. Moreover, the Cu atomic ratios in the PDA@Cu coatings increased with the increase concentration of additive CuCl2 solution (Figure 1 C). From the high-resolution XPS spectra of Cu element (Figure 1 B), we found that when the concentration of additive CuCl2 solution increased to 0.3 mg/mL, copper ion in the PDA@Cu coatings was dominated by two valence copper, differed from the concentration of 0.1 and 0.2 mg/mL which was dominated by univalent copper. The NO catalyzing abilities of PDA@Cu coatings were shown in Figure 2. The higher Cu content, the higher NO catalyzing rate (Figure 2 A). Continued treatment of the PDA@Cu coatings with NO donor resulted in the significant decreased of NO catalyzing rate which may due to the loss of copper ion. Furthermore, the NO catalyzing abilities of PDA@Cu coatings lasted for more than 7 days (Figure 2 D). Platelet adhesion experiment was carried out to evaluate the hemocompatibility of PDA@Cu coatings, and the results were shown in Figure 3. The existence of Cu ion in PDA coating had no effect on platelet adhesion, but the catalyzed release of NO by Cu ion from NO donor resulted in significant decrease of platelet adhesion. All these results suggest that the PDA@Cu coatings have huge potential for development of cardiovascular implants. Conclusion: During the polymerization of dopamine, the addition of CuCl2 solution resulted in the loading of Cu ion, and the content of Cu ion in PDA coatings was controllable. Cu ion in the PDA coatings had the ability to catalyze NO release from NO donor, which depended on the content of Cu ion. The catalyzing ability can last for more than 7 days. Figure 1. Full spectrum (A), high-resolution XPS spectra of Cu element (B) and the atomic compositions and ratios of the PDA@Cu coating samples. Figure 2. The NO catalyzing ability of the PDA@Cu coating samples after continued treatment with NO donor RSNO for 0h (A), 1h (B), 3d (C) and 7d (D) via Griess reagent. Figure 3. Platelets adhesion on 316L SS and PDA@Cu coating samples with (+Donor) and without NO donor. This work was supported by the National Natural Science Foundation of China (Project 81271701, 31570957, 81501596 and Key Program 81330031) and the Ministry of Science and Technology of China (Key Basic Research Project No. 2011CB606204).

Au nanoparticle-coated, PLGA-based hybrid capsules for combined ultrasound imaging and HIFU therapy.

Herein, we present a simple method to prepare Au nanoparticle-coated, polydopamine-modified poly(lactic-co-glycolic acid) (AuNPs@PDA/PLGA) hybrid capsules for combined ultrasound imaging and high-intensity focused ultrasound (HIFU) therapy. In this approach, PLGA nanocapsules are prepared firstly via a facile and efficient water/oil/water (W/O/W) emulsion strategy, and are then modified with PDA through the self-polymerization of dopamine in a weakly alkaline aqueous environment. Subsequently, chloroauric acid (HAuCl4) solution is added, and AuCl4 - ions are absorbed on the surfaces of the PDA/PLGA nanocapsules by the active catechol and amine groups of PDA coatings. Finally, these absorbed AuCl4 - ions are reduced in situ to AuNPs to form AuNPs@PDA/PLGA hybrid capsules. The in vitro ultrasound imaging experiments show that AuNPs@PDA/PLGA hybrid capsules are suitable for ultrasound contrast imaging. Moreover, the potential of the nanocapsules to enhance HIFU therapy is also demonstrated. These results show that ultrasound-guided HIFU therapy ex vivo with AuNPs@PDA/PLGA hybrid capsules is highly efficient on degassed bovine livers due to the high thermal energy accumulation of AuNPs. Thus, the successful integration of the AuNPs and PLGA nanocapsules provides an alternative strategy for highly efficient ultrasound-guided HIFU therapy.

Mussel-inspired cell-adhesion peptide modification for enhanced endothelialization of decellularized blood vessels.

Enhanced endothelialization of tissue-engineered blood vessels is essential for vascular regeneration and function of engineered vessels. In this study, mussel-inspired surface chemistry of polydopamine (pDA) coatings are applied to functionalize decellularized vein matrix (DVM) with extracellular matrix-derived cell adhesion peptides (RGD and YIGSR). DVMs engineered with pDA-peptides enhance focal adhesion, metabolic activity, and endothelial differentiation of human endothelial progenitor cells (EPCs) derived from cord blood and embryonic stem cells compared with EPCs on non-coated or pDA-coated DVMs. These results indicate that pDA-peptide functionalization may contribute to enhanced, rapid endothelialization of DVM surfaces by promoting adhesion, proliferation, and differentiation of circulating EPCs. Ultimately, this approach may be useful for improving in vivo patency and function of decellularized matrix-based blood vessels.