Chuanxiong Nie

Mussel-inspired self-coating at macro-interface with improved biocompatibility and bioactivity via dopamine grafted heparin-like polymers and heparin

In this study, multifunctional mussel-inspired self-coated membranes with remarkable blood and cell compatibilities are prepared by a facile and green approach. A highly sulfonated linear heparin-like polymer (HepLP, poly(sodium 4-vinylbenzenesulfonate)-co-poly(sodium methacrylate)) and heparin are chosen for the mussel-inspired heparin-mimicking coating, respectively. Firstly, DA is grafted onto the backbone of HepLP or heparin to obtain DA grafted HepLP (DA-g-HepLP) or DA grafted heparin (DA-g-Hep) by means of the carbodiimide chemistry method. Then, the DA-g-HepLP and DA-g-Hep are used to prepare surface coated heparin-mimicking substrates; the polyethersulfone (PES) dialysis membrane is chosen as the model substrate. The coated surface composition, surface morphology, water contact angle, surface zeta-potential, blood compatibility and cell compatibility are systematically investigated. The results of surface spectra, scanning electron microscopy (SEM) and atomic force microscopy (AFM) indicated that the DA-g-HepLP and DA-g-Hep were successfully coated onto the membranes. The coated membranes showed increased hydrophilicity and electronegativity, decreased plasma protein adsorption, and suppressed platelet adhesion compared to the pristine membrane. The cell morphology observation and cytotoxicity assays demonstrated that the surface coated heparin-mimicking membranes showed superior performance in endothelial cell proliferation and morphology differentiation. In addition, the excellent anticoagulant bioactivities indicated that the adhered DA-g-HepLP (or DA-g-Hep) could function or maintain its biological activity after the immobilization. In general, the mussel-inspired protocol of surface self-coating conferred the modified membranes with integrated blood compatibility, cell proliferation and biological activity for multi-biomedical applications, like hemodialysis, blood purification, organ implantation, and cell and tissue cultures.

Heparin-Mimicking Multilayer Coating on Polymeric Membrane via LbL Assembly of Cyclodextrin-Based Supramolecules

In this study, multifunctional and heparin-mimicking star-shaped supramolecules-deposited 3D porous multilayer films with improved biocompatibility were fabricated via a layer-by-layer (LbL) self-assembly method on polymeric membrane substrates. Star-shaped heparin-mimicking polyanions (including poly(styrenesulfonate-co-sodium acrylate; Star-PSS-AANa) and poly(styrenesulfonate-co-poly(ethylene glycol)methyl ether methacrylate; Star-PSS-EGMA)) and polycations (poly(methyl chloride-quaternized 2-(dimethylamino)ethyl methacrylate; Star-PMeDMA) were first synthesized by atom transfer radical polymerization (ATRP) from β-cyclodextrin (β-CD) based cores. Then assembly of 3D porous multilayers onto polymeric membrane surfaces was carried out by alternating deposition of the polyanions and polycations via electrostatic interaction. The surface morphology and composition, water contact angle, blood activation, and thrombotic potential as well as cell viability for the coated heparin-mimicking films were systematically investigated. The results of surface ATR-FTIR spectra and XPS spectra verified successful deposition of the star-shaped supramolecules onto the biomedical membrane surfaces; scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations revealed that the modified substrate had 3D porous surface morphology, which might have a great biological influence on the biointerface. Furthermore, systematic in vitro investigation of protein adsorption, platelet adhesion, human platelet factor 4 (PF4, indicates platelet activation), activate partial thromboplastin time (APTT), thrombin time (TT), coagulation activation (thrombin-antithrombin III complex (TAT, indicates blood coagulant)), and blood-related complement activation (C3a and C5a, indicates inflammation potential) confirmed that the heparin-mimicking multilayer coated membranes exhibited ultralow blood component activations and excellent hemocompatibility. Meanwhile, after surface coating, endothelial cell viability was also promoted, which indicated that the heparin-mimicking multilayer coating might extend the application fields of polymeric membranes in biomedical fields.

Graphene oxide based heparin-mimicking and hemocompatible polymeric hydrogels for versatile biomedical applications

Studies on the design of heparin and heparin-mimicking polymer based hydrogels are of tremendous interest and are fuelled by diverse emerging biomedical applications, such as antithrombogenic materials, growth factor carriers, and scaffolds for tissue engineering and regeneration medicine. In this study, inspired by the recent developments of heparin-based hydrogels, graphene oxide (GO) based heparin-mimicking hydrogels with hemocompatibility and versatile properties were prepared via free radical copolymerization, and poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 2-hydroxyethyl methacrylate (HEMA) hydrogels were used as the control samples. The GO based heparin-mimicking polymeric hydrogels exhibited interconnected structures with thin pore walls and high porosity. Because of the increased ionization and electrostatic repulsion of sodium styrene sulfonate (SSNa) segments, the swelling ratios of the SSNa added hydrogels were dramatically increased; after incorporating flexible GO nanosheets, as the 3D skeleton of the hydrogels, the swelling ability was further increased. In addition, the GO based heparin-mimicking hydrogels showed superior red blood cell compatibility, anti-platelet adhesion ability and anticoagulant ability. Furthermore, drug release data indicated that the GO based heparin-mimicking hydrogels had high drug loading ability and prolonged drug releasing ability; the antibacterial tests showed coincident results with large inhibition zones and long effective periods. Due to the integration of blood compatibility, drug loading and releasing abilities, as well as an excellent ability for the removal of toxic molecules, the GO based heparin-mimicking hydrogels can be used for versatile biomedical applications.

Substrate-Independent Robust and Heparin-Mimetic Hydrogel Thin Film Coating via Combined LbL Self-Assembly and Mussel-Inspired Post-Cross-linking.

In this work, we designed a robust and heparin-mimetic hydrogel thin film coating via combined layer-by-layer (LbL) self-assembly and mussel-inspired post-cross-linking. Dopamine-grafted heparin-like/-mimetic polymers (DA-g-HepLP) with abundant carboxylic and sulfonic groups were synthesized by the conjugation of adhesive molecule, DA, which exhibited substrate-independent adhesive affinity to various solid surfaces because of the formation of irreversible covalent bonds. The hydrogel thin film coated substrates were prepared by a three-step reaction: First, the substrates were coated with DA-g-HepLP to generate negatively charged surfaces. Then, multilayers were obtained via LbL coating of chitosan and the DA-g-HepLP. Finally, the noncovalent multilayers were oxidatively cross-linked by NaIO4. Surface ATR-FTIR and XPS spectra confirmed the successful fabrication of the hydrogel thin film coatings onto membrane substrates; SEM images revealed that the substrate-independent coatings owned 3D porous morphology. The soaking tests in highly alkaline, acid, and concentrated salt solutions indicated that the cross-linked hydrogel thin film coatings owned high chemical resistance. In comparison, the soaking tests in physiological solution indicated that the cross-linked hydrogel coatings owned excellent long-term stability. The live/dead cell staining and morphology observations of the adhered cells revealed that the heparin-mimetic hydrogel thin film coated substrates had low cell toxicity and high promotion ability for cell proliferation. Furthermore, systematic in vitro investigations of protein adsorption, platelet adhesion, blood clotting, and blood-related complement activation confirmed that the hydrogel film coated substrates showed excellent hemocompatibility. Both the results of inhibition zone and bactericidal activity indicated that the gentamycin sulfate loaded hydrogel thin films had significant inhibition capability toward both Escherichia coli and Staphylococcus aureus bacteria. Combined the above advantages, it is believed that the designed heparin-mimetic hydrogel thin films may show high potential for applications in various biological and clinical fields, such as long-term hemocompatible and drug-loading materials for implants.

Catechol Chemistry Inspired Approach to Construct Self-Cross-Linked Polymer Nanolayers as Versatile Biointerfaces

In this study, we proposed a catechol chemistry inspired approach to construct surface self-cross-linked polymer nanolayers for the design of versatile biointerfaces. Several representative biofunctional polymers, P(SS-co-AA), P(SBMA-co-AA), P(EGMA-co-AA), P(VP-co-AA), and P(MTAC-co-AA), were first synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization, and then the catecholic molecules (dopamine, DA) were conjugated to the acrylic acid (AA) units by the facile carbodiimide chemistry. Then, the catechol (Cat) group conjugated biofunctional polymers, named PSS-Cat, PSBMA-Cat, PEGMA-Cat, PVP-Cat, and PMTAC-Cat, were applied for the construction of self-cross-linked nanolayers on polymeric substrates via the pH induced catechol cross-linking and immobilization. The XPS spectra, surface morphology, and wettability gave robust evidence that the catechol conjugated polymers were successfully coated, and the coated substrates possessed increased surface roughness and hydrophilicity. Furthermore, the systematic in vitro investigation of protein adsorption, platelet adhesion, activated partial thromboplastin time (APTT), thrombin time (TT), cell viability, and antibacterial ability confirmed that the coated nanolayers conferred the substrates with versatile biological performances. The PSS-Cat coated substrate had low blood component activation and excellent anticoagulant activity; while the PEGMA-Cat and PSBMA-Cat showed ideal resistance to protein fouling and inhibition of platelet activation. The PSS-Cat and PVP-Cat coated substrates exhibited promoted endothelial cell proliferation and viability. The PMTAC-Cat coated substrate showed an outstanding activity on bacterial inhibition. In conclusion, the catechol chemistry inspired approach allows the self-cross-linked nanolayers to be easily immobilized on polymeric substrates with the stable conformation and multiple biofunctionalities. It is expected that this low-cost and facile bioinspired coating system will present great potential in creating novel and versatile biointerfaces.

Nanofibrous Heparin and Heparin-Mimicking Multilayers as Highly Effective Endothelialization and Antithrombogenic Coatings

Combining the advantages of the fibrous nanostructure of carbon nanotubes (CNTs) and the bioactivities of heparin/heparin-mimicking polyanions, functional nanofibrous heparin or heparin-mimicking multilayers were constructed on PVDF membrane with highly promoted endothelialization and antithrombogenic activities. Oxidized CNT (oCNT) was first functionalized with water-soluble chitosan (polycation), then enwrapped with heparin or a typical sulfonated heparin-mimicking polymers (poly(sodium 4-styrenesulfonate-co-sodium methacrylate)) to construct the multilayers. Then, the surface-deposited multilayers were constructed via electrostatic layer-by-layer assembly of the functionalized oCNTs. The scanning electron microscope and atom force microscope images confirmed that the coated multilayers exhibited nanofibrous and porous structure. The live/dead cell staining and cell viability assay results indicated that the coated nanofibrous multilayers had excellent compatibility with endothelial cells. The cell morphology observation further confirmed the promotion ability of surface endothelialization due to the coated heparin/heparin-mimicking multilayers. Further systematical evaluation on blood compatibility revealed that the surface heparin/heparin-mimicking multilayer-coated membranes also had significantly improved blood compatibility including restrained platelet adhesion and activation, prolonged blood clotting times, and inhibited activation of coagulation and complement factors. In summary, the proposed nanofibrous multilayers integrated endothelialization and antithrombogenic properties; meanwhile, the heparin-mimicking coating validated comparable performances as heparin coating. Herein, it is expected that the surface coating of nanofibrous multilayers, especially the facilely constructed heparin-mimicking coating, may have great application potential in biomedical fields.

One-pot cross-linked copolymerization for the construction of robust antifouling and antibacterial composite membranes

This study reports a highly efficient, convenient and universal protocol for the fabrication of robust antifouling and antibacterial polymeric membranes via one-pot cross-linked copolymerization of methyl acryloyloxygen ethyl trimethyl ammonium chloride (DMC) and poly(ethylene glycol) methyl ether methacrylate (PEGMA). The infrared testing and X-ray photoelectron spectroscopy gave obvious evidence that abundant DMC and PEGMA chains had enriched on the membrane surface. The surface and cross-sectional SEM images indicated that the addition of DMC and PEGMA had a little effect on the membrane roughness and inner structure. Meanwhile, the systematic investigations into the water contact angle, protein adsorption, ultrafiltration and bacterial inhibition indicated that the composite membranes showed improved hydrophilicity, decreased protein adsorption, increased water flux and antifouling property, as well as greatly enhanced antibacterial ability. Furthermore, it was found that the cross-linked copolymerization could further endow the composite membrane with multi-chemical properties, for instance the charged interface. As a model system, Ag nanoparticle-PDMC multilayers were coated onto the positively charged PES-DMC6 membranes via layer by layer assembly, and the successful surface coating confirmed their versatile ability and also provided a more effective and durable antibacterial coating to the composite membranes. All these results suggest that the robust antifouling and antibacterial composite membranes can be prepared via the proposed one-pot cross-linked copolymerization, and it is believed that this approach has great potential to be applied in various biomedical or industrial fields where antifouling and antibacterial properties are highly demanded.

Anticoagulant sodium alginate sulfates and their mussel-inspired heparin-mimetic coatings

In this work, we synthesized novel sodium alginate sulfates (SASs) with different sulfation degrees, which had similar chemical structure and bioactivity as those of heparin. Blood clotting time tests indicated that the heparin-mimetic SASs exhibited excellent and sulfation-degree-dependent anticoagulant activity. Beyond applications as anticoagulant reagents, the heparin-mimetics also showed potential applications for surface modification of blood-contacting devices. To achieve the goal of surface modification, we synthesized the mussel inspired adhesive macromolecules, dopamine grafted SASs (DA-g-SASs), which were capable of coating the surface of polymeric substrates in a basic buffer solution in a substrate-independent manner. The DA-g-SASs exhibited substrate-independent adhesive affinity to a variety of solid surfaces due to the formation of irreversible covalent bonds. By using polyethersulfone (PES) as a model blood contacting substrate, the surface properties of DA-g-SASs coated substrates were fully explored. ATR-FTIR and XPS spectra demonstrated the successful formation of the heparin-mimetic coatings. Endothelial cell staining and morphological observations revealed that the heparin-mimetic coatings could significantly promote cell adhesion and proliferation. In addition, systematic in vitro studies of blood clotting, protein adsorption, platelet adhesion, and blood-related complement activation demonstrated that the heparin-mimetic macromolecule coated substrates dramatically inhibited the thrombotic potential and inflammation induced by the material interface. Combining the above advantages, it is believed that the proposed integration of heparin-mimetic SASs and mussel inspired coating may open new operational principles for surface anticoagulant modification of various biological and clinical devices for blood purification, tissue implants, and other micro-nanoscale materials.

Hemocompatible polyethersulfone/polyurethane composite membrane for high‐performance antifouling and antithrombotic dialyzer

Researches on blood purification membranes are fuelled by diverse clinical needs, such as hemodialysis, hemodiafiltration, hemofiltration, plasmapheresis, and plasma collection. To approach high-performance dialyzer, the integrated antifouling and antithrombotic properties are highly necessary for the design/modification of advanced artificial membranes. In this study, we propose and demonstrate that the physical blend of triblock polyurethane (PU) and polyethersulfone (PES) may advance the performance of hemodialysis membranes with greatly enhanced blood compatibility. It was found that the triblock PU could be blended with PES at high ratio owing to their excellent miscibility. The surfaces of the PES/PU composite membranes were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, water contact angle measurement, and surface ζ-potentials. The results indicated that the membrane surfaces were assembled with hydrophilic segregation layer owing to the migration of amphiphilic PU segments during membrane preparation, which might confer the composite membranes with superior hemocompatibility. The cross-section scanning electron microscopy images of the composite membranes exhibited structure transformation from finger-like structure to sponge-like structure, which indicated that the composite membrane had tunable porosity and permeability. The further ultrafiltration experiments indicated that the composite membranes showed increased permeability and excellent antifouling ability. The blood compatibility observation indicated that PES/PU composite membranes owned decreased protein adsorption, suppressed platelet adhesion, and prolonged plasma recalcification time. These results indicated that the PES/PU composite membranes exhibited enhanced antifouling and antithrombotic properties than the pristine PES membrane. The strategy may forward the fabrication of blood compatible composite membranes for clinical blood dialysis by using the various functional miscible polymers.

Versatile and Rapid Postfunctionalization from Cyclodextrin Modified Host Polymeric Membrane Substrate

Surface modification has long been of great interest to impart desired functionalities to the bioimplants. However, due to the limitations of recent technologies in surface modification, it is highly desirable to explore novel protocols, which can advantageously and efficiently endow the inert material surfaces with versatile biofunctionalities. Herein, to achieve versatile and rapid postfunctionalization of polymeric membrane, we demonstrate a new strategy for the fabrication of β-cyclodextrin (β-CD) modified host membrane substrate that can recognize a series of well-designed guest macromolecules. The surface assembly procedure was driven by the host-guest interaction between adamantane (Ad) and β-CD. β-CD immobilized host membrane was fabricated via two steps: (1) epoxy groups enriched poly(ether sulfone) (PES) membrane was first prepared via in situ cross-linking polymerization and subsequently phase separation; (2) mono-6-deoxy-6-ethylenediamine-β-CD (EDA-β-CD) was then anchored onto the surface of the epoxy functionalized PES membrane to obtain PES-CD. Subsequently, three types of Ad-terminated polymers, including Ad-poly(styrenesulfonate-co-sodium acrylate) (Ad-PSA), Ad-methoxypoly(ethylene glycol) (Ad-PEG), and Ad-poly(methyl chloride-quaternized 2-(dimethylamino)ethyl methacrylate (Ad-PMT), were separately assembled onto the β-CD immobilized surfaces to endow the membranes with anticoagulant, antifouling, and antibacterial capability, respectively. Activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT) measurements were carried out to explore the anticoagulant activity. The antifouling capability was evaluated via protein adsorption and platelet adhesion measurements. Moreover, Staphyllococcous aureus (S. aureus) was selected as model bacteria to evaluate the antibacterial ability of the functionalized membranes. The results indicated that well-regulated blood compatibility, antifouling capability, and bactericidal activity could be achieved by the proposed rapid postfunctionalization on polymeric membranes. This approach of versatile and rapid postfunctionalization is promising for the preparation of multifunctional polymeric membrane materials to meet with various demands for the further applications.