Nitrogen Self-Doping Carbon Derived from Functionalized Poly(Vinylidene Fluoride) (PVDF) for Supercapacitor and Adsorption Application.

A new synthetic strategy has been developed for the facile fabrication of a N-doped porous carbon (NC-800) material via a facile carbonization of functionalized poly(vinylidene fluoride) (PVDF). The prepared NC-800 exhibits good specific capacitance of 205 F/g at 1 A/g and cycle stability (95.2% retention after 5000 cycles at 1 A/g). The adsorption capacity of NC-800 on methylene blue and methyl orange was 780 mg/g and 800 mg/g, respectively. The facile and economical method and good performance (supercapacitor and adsorption) suggest that the NC-800 is a promising material for energy storage and adsorption.

Waste PET as a Reactant for Lanthanide MOF Synthesis and Application in Sensing of Picric Acid.

In this study, a lanthanide metal organic framework based on the ligand of terephthalic acid derived from waste polyethylene terephthalate (PET) bottles was designed and synthesized. The structure and morphology of the Tb-BDC was investigated by X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The Tb-BDC displays a high selectivity and sensitivity towards picric acid (TNP). The luminescence intensities exhibit a linear relation, with a concentration of TNP over the range of 1 × 10-5-1 × 10-4 M, with a limit of detection of 1 × 10-5 M. The sensing mechanism is also discussed. This is the first time that waste PET materials have been used as the starting precursor of terephthalic acid (BDC) for the fabrication of lanthanide MOF (metal organic framework), which is applied in sensing TNP.

Room-Temperature Fabrication of a Nickel-Functionalized Copper Metal⁻Organic Framework (Ni@Cu-MOF) as a New Pseudocapacitive Material for Asymmetric Supercapacitors.

A nickel-functionalized copper metal-organic framework (Ni@Cu-MOF) was prepared by a facile volatilization method and a post-modification synthesis method at room temperature. The obtained Ni@Cu-MOF electrode delivered a high capacitance of 526 F/g at 1 A/g and had a long-term cycling stability (80% retention after 1200 cycles at 1 A/g) in a 6 M KOH aqueous solution. Furthermore, an asymmetric supercapacitor device was assembled from this Ni@Cu-MOF and activated carbon electrodes. The fabricated supercapacitor delivered a high capacitance of 48.7 F/g at 1 A/g and a high energy density of 17.3 Wh/kg at a power density of 798.5 kW/kg. This study indicates that the Ni@Cu-MOF has great potential for supercapacitor applications.

Codeposition of Polydopamine and Zwitterionic Polymer on Membrane Surface with Enhanced Stability and Antibiofouling Property.

Although abundant works have been developed in mussel-inspired antifouling coatings, most of them suffer from poor chemical stability, especially in a strongly alkaline environment. Herein, we report a robust one-step mussel-inspired method to construct a highly chemical stable and excellent antibiofouling membrane surface coating with a highly efficient codeposition of polydopamine (PDA) with zwitterionic polymer. In the study, PDA and polyethylenimine-quaternized derivative (PEI-S) are codeposited on the surface of poly(ether sulfone) (PES) ultrafiltration membrane in water at room temperature. In contrast to individual PDA coating, the obtained PDA/PEI-S coating exhibits excellent chemical stability even in a strongly alkaline environment owing to the cross-linking and unexpected cation-π interaction between the PEI-S and PDA. Thanks to the introduction of PEI-S, systematic protein adsorption tests and bacteria adhesion experiments demonstrated that the surfaces could prevent bovine serum fibrinogen and lysozyme adsorption and could reduce Gram-positive bacteria S. aureus and Gram-negative bacteria E. coli adhesion. Benefiting from the versatile functionality of PDA, the proposed strategy is not limited to PES membrane surface but also others such as poly(ethylene terephthalate) sheets and commercial polypropylene microfiltration membranes. Overall, this work enriches the exploration of a remarkable coating with enhanced stability and excellent antifouling property via a facile, robust, and material-independent approach to modifying the membrane surface.

Melt Crystallization Behavior and Crystalline Morphology of Polylactide/Poly(ε-caprolactone) Blends Compatibilized by Lactide-Caprolactone Copolymer.

Lactide-Caprolactone copolymer (LACL) was added to a Polylactide/Poly(ε-caprolactone) (PLA/PCL) blend as a compatibilizer through solution mixing and the casting method. The melt crystallization behavior and crystalline morphology of PLA, PLA/PCL, and PLA/PCL/LACL were investigated using differential scanning calorimeter (DSC) and polarized optical microscopy (POM), respectively. The temperature of the shortest crystallization time for the samples was observed at 105 °C. The overall isothermal melt crystallization kinetics of the three samples were further studied using the Avrami theory. Neat PLA showed a higher half-time of crystallization than that of the PLA/PCL and PLA/PCL/LACL blends, whereas the half-time of crystallization of PLA/PCL and PLA/PCL/LACL showed no significant difference. The addition of PCL decreased the spherulite size of crystallized PLA, and the nuclei density in the PLA/PCL/LACL blend was much higher than that of the PLA and PLA/PCL samples, indicating that LACL had a compatibilization effect on the immiscible PLA/PCL blend, thereby promoting the nucleation of PLA. The spherulites in the PLA/PCL and PLA/PCL/LACL blend exhibited a smeared and rough morphology, which can be attributed to the fact that PCL molecules migrated to the PLA spherulitic surface during the crystallization of PLA.

Graphene oxide linked sulfonate-based polyanionic nanogels as biocompatible, robust and versatile modifiers of ultrafiltration membranes.

Aiming to enhance the current biological performances of ultrafiltration membranes, in this study, a new kind of graphene oxide linked sulfonate-based polyanionic nanogel (GO-SPN) was fabricated by free radical cross-linked copolymerization. Then, GO-SPN embedded polyethersulfone (PES/GO-SPN) ultrafiltration (UF) membranes were achieved through one-pot PES dissolution and interpenetration, followed by a liquid-liquid phase inversion method. The GO-SPN modified UF membranes exhibited increased porous cross-section structures with a pH-dependent water flux. Notably, the modified UF membranes showed excellent in vitro hemocompatibility and cytocompatibility performances, such as good anti-coagulant activity, red blood cell compatibility (with very low hemolysis ratios below 0.2%), anti-platelet adhesion and activation, low inflammation potential, and high endothelial cell compatibility. Moreover, to confirm the actual application potential of the GO-SPN embedded membranes in diverse fields, we also examined the performances of PES/GO-SPN composite hollow fiber UF membranes. It was validated that the mechanical properties of the hollow fiber UF membranes (tensile strength higher than 1.2 MPa) could satisfy the demands of industrial or clinical applications. Furthermore, the modified membranes exhibited versatile ability, i.e. they could load Ag-nanoparticles which bestowed them with excellent bactericidal capability (about 97%) against both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Due to the integration of hemo- and cyto-compatibility, good mechanical strength as well as bactericidal capability, the GO-SPN embedded membranes offer a new protocol to greatly extend the application potential of UF membranes in fields ranging from clinical hemodialysis to water purification.

A facile approach toward multifunctional polyethersulfone membranes via in situ cross-linked copolymerization.

In this study, multifunctional polyethersulfone (PES) membranes are prepared via in situ cross-linked copolymerization coupled with a liquid-liquid phase separation technique. Acrylic acid (AA) and N-vinylpyrrolidone (VP) are copolymerized in PES solution, and the solution is then directly used to prepare PES membranes. The infrared and X-ray photoelectron spectroscopy testing, scanning electron microscopy, and water contact angle measurements confirm the successful modification of pristine PES membrane. Protein adsorption, platelet adhesion, plasma recalcification time, and activated partial thromboplastin time assays convince that the modified PES membranes have a better biocompatibility than pristine PES membrane. In addition, the modified membranes showed good protein antifouling property and significant adsorption property of cationic dye. The loading of Ag nanoparticles into the modified membranes endows the composite membranes with antibacterial activity.

Layer by layer assembly of sulfonic poly(ether sulfone) as heparin-mimicking coatings: scalable fabrication of super-hemocompatible and antibacterial membranes.

In this study, to approach the scalable fabrication of super-hemocompatible and antibacterial membranes, surface engineered 3D heparin-mimicking coatings were designed by layer by layer (LBL) assembly of water-soluble heparin-mimicking polymer (WHP) and quaternized chitosan (QC). The low cost and scalable WHP was synthesized by a combination of polycondensation and post-carboxylation method, and the antibacterial QC was prepared by a two-step quaternization reaction. Then, the as-prepared negatively charged WHP and positively charged QC were used to conduct the LBL assembly on the widely used poly(ether sulfone) (PES) membrane surface to prepare heparin-mimicking modified membrane. The results indicated that the assembled heparin-mimicking coating nanofilms exhibited 3D porous morphology. The systematic blood compatibility and antithrombotic evaluation revealed that the functionalized membrane owned prolonged clotting times and greatly suppressed platelet adhesion and activation; further contacting activation detection (TAT and PF-4) and complement activation (C3a and C5a) experiments indicated that the heparin-mimicking membranes had lower blood activation compared to the pristine membrane. The cell observations demonstrated that the surface assembled heparin-mimicking nanofilms showed superior performances in endothelial cells adhesion and growth than the pure PES membrane. The results of the antibacterial study indicated that the QC contained coating exhibited significant inhibition ability for both Escherichia coli and Staphlococcus aureus. In general, the LBL assembled heparin-mimicking coatings conferred the functionalized PES membranes with integrated blood compatibility, cytocompatibility and antibacterial property for multi-applications, which may forward the fabrication and application of heparin-mimicking biomedical devices.

Bionic design for surface optimization combining hydrophilic and negative charged biological macromolecules.

While polyethersulfone (PES) membrane represents a promising option for blood purification, the blood compatibility must be dramatically enhanced to meet today's ever-increasing demands for many emerging application. In this study, we report a bionic design for optimization and development of a modified PES membrane combining hydrophilic and negative charged biological macromolecules on its surface. The hydrophilic and ionic charged biological macromolecules sulfonated poly(styrene)-b-poly(methyl methacrylate)-b-poly-(styrene) (PSSMSS) and poly(vinyl pyrrolidone)-b-poly(methyl methacrylate)-b-poly-(vinyl pyrrolidone) were synthesized via reversible addition-fragmentation chain transfer polymerization and used together to modify PES membranes by blending method. A hydrophilic membrane surface with negative charged surface coating was obtained, imitating the hydrophilic and negatively charged structure feature of heparin. The modified PES membranes showed suppressed platelet adhesion, and a prolonged blood clotting time, and thereby improved blood compatibility. In addition, the blood clotting time of the modified membranes increased with the blended PSSMSS amounts increment, indicating that both the hydrophilic and negative charged groups play important roles in improving the blood compatibility of PES membranes.

A simple method to prepare modified polyethersulfone membrane with improved hydrophilic surface by one-pot: The effect of hydrophobic segment length and molecular weight of copolymers.

A simple method to prepare modified polyethersulfone (PES) membrane by one-pot is provided, and the method includes three steps: polymerization of vinyl pyrrolidone (VP), copolymerization of methyl methacrylate (MMA) and blending with PES. The effect of the PMMA segment length and molecular weight of the copolymer (PVP-b-PMMA-b-PVP, as an additive) on the structures and properties of the modified membranes was investigated. Activated partial thromboplastin time (APTT) tests indicated that with the increase of the poly(methyl methacrylate) (PMMA) segment length in the chains of the copolymers and with the increase of the molecular weight of the copolymers, the APTTs of the modified membranes increased to some extent, since less of the additives were lost during liquid-liquid phase separation process. Therefore, the copolymer was designed and prepared with appropriate ratio of poly(vinyl pyrrolidone) (PVP) to MMA and with appropriate molecular weight for better membrane performance. When the copolymer was blended in the membrane, the water permeance, protein anti-fouling property and sieving coefficients for PEG-12000 increased obviously. The simple, credible and feasible method had the potential to be used for the modification of membranes with improved blood compatibility, ultrafiltration and antifouling properties of biomaterials and for practical production.

Blood activation and compatibility on single-molecular-layer biointerfaces.

Research on the interactions between living systems and materials is fuelled by diverse biomedical needs, for example, drug encapsulation and stimulated release, stem cell proliferation and differentiation, cell and tissue cultures, as well as artificial organs. Specific single-molecular-layer biointerface design is one of the most important processes to reveal the interactions or biological responses between synthetic biomaterials and living systems. However, until now, there is limited literature on comprehensively revealing biomaterials induced blood component activation and hemocompatibility based on the single-molecular-layer interface approach. In this study, the effects of different groups on blood compatibility are presented using single-molecular-layer silicon (Si) interfaces. Typical hydrophilic groups (hydroxyl, carboxyl, sulfonic, and amino groups) and hydrophobic groups (alkyl, benzene, and fluorinated chains) are introduced onto single-molecular-layer Si interfaces and confirmed by atomic force microscopy, X-ray photoelectron spectroscopy, and water contact angle. The blood activation and compatibility for the prepared biointerfaces are systematically investigated by protein adsorption, clotting time, Factor XII detection, platelet adhesion, contacting activation, and complement activation experiments. The results indicate that the blood activation and hemocompatibility for the biointerfaces are complex and highly related to the chemical groups and hydrophilicity of the surfaces. Our results further indicate the vital importance of carefully designed biointerfaces for specific biomedical applications. The carboxyl group, sulfonic group, and hydroxyl group may be more suitable for the interface designs of antifouling materials. The results also reveal that the sulfonic group and fluorinated surface possess great potential for applications of blood contacting devices due to their low contacting blood activation.

Biologically inspired membrane design with a heparin-like interface: prolonged blood coagulation, inhibited complement activation, and bio-artificial liver related cell proliferation.

In the present work, inspired by the chemical structure of heparin molecules, we designed a polyethersulfone (PES) membrane with a heparin-like surface for the first time by physically blending sulfonated polyethersulfone (SPES), carboxylic polyethersulfone (CPES), and PES at rational ratios. Evaporation and phase-inversion membranes of PES/CPES/SPES were prepared by evaporating the solvent in a vacuum oven, and by a liquid-liquid phase separation technique, respectively. Scanning electron microscopy (SEM) images revealed that the structures of the PES/CPES/SPES membranes were dependent on the proportions of the additives and no obvious phase separation was detected. The blood compatibility of the modified membrane surfaces was characterized in terms of bovine serum fibrinogen (BFG) adsorption, platelet adhesion, thrombin-antithrombin (TAT) generation, percentage of platelets positive for CD62p expression, clotting times (activated partial thromboplastin time (APTT) and prothrombin time (PT)), and complement activation on C3a and C5a levels. The results indicated that the blood compatibility of PES matrix was improved due to the biologically inspired membrane design with a heparin-like interface by introducing functional sulfonic acid and carboxylic acid groups. Furthermore, cell morphology observation and cell culture assays demonstrated that the modified membranes showed better performance in bio-artificial liver related cell proliferation than the pristine PES membrane. In general, the intriguing PES/CPES/SPES membranes, especially the phase-inversion one, showed improved blood and cell compatibility, which might have great potential application in the blood purification field.

Toward a highly hemocompatible membrane for blood purification via a physical blend of miscible comb-like amphiphilic copolymers.

Comb-like amphiphilic copolymers (CLACs) consisting of functional chains of poly(vinyl pyrrolidone) and polyethersulfone-based hydrophobic chains were firstly synthesized by reversible addition-fragmentation chain transfer polymerization. The CLAC can be used as an additive to blend with polyethersulfone (PES) at any ratio due to the excellent miscibility, and then a surface segregation layer with permanent hydrophilicity could be obtained. The surfaces of the CLAC modified PES membranes were characterized using X-ray photoelectron spectroscopic analysis, Fourier transform infrared and water contact angle measurements. The surfaces are self-assembled with numerous functional branch-like -PVP chains, which can improve the hemocompatibility. The root-like -PES chains (the hydrophobic part) are embedded in the membranes firmly, which greatly reduces the elution during the membrane preparation procedure and repeated usage, and makes the membranes have a permanent stability. The PES-based hydrophobic chains have the same structure as the membrane bulk material, which makes the miscibility of the additive and the membrane material good to ensure the intrinsic properties of the membrane. The modified membranes showed suppressed platelet adhesion and prolonged blood coagulation time (activated partial thromboplastin time, APTT); thus, the blood compatibility of the membranes was highly improved. The strategy may be extended to synthesize other PES-based functional copolymers and to prepare a modified PES dialysis membrane for blood purification.

Blood compatibility of polyethersulfone membrane by blending a sulfated derivative of chitosan.

In this study, a novel sulfated derivative of chitosan, which could be dissolved in many common organic solvents, is conveniently synthesized for the modification of polyethersulfone (PES) membrane. Elemental analysis, FTIR, (1)H NMR and X-ray diffraction diagrams (XRD) are used to demonstrate the introduction of functional groups. Owing to the solubility in organic solvents, the sulfated derivative of chitosan could be directly blended with PES in organic solvent to prepare membrane by means of a liquid-liquid phase separation technique. The modified membrane showed lower protein (bovine serum albumin (BSA) and bovine serum fibrinogen (BFG)) adsorption and suppressed platelet adhesion. Moreover, the activated partial thromboplastin time (APTT) for the modified membrane was enhanced as high as 60% compared to pure PES membrane. The lower protein adsorption, suppressed platelet adhesion and increased APTT confirmed that the blood compatibility of the modified PES membrane by the sulfated derivative of chitosan was significantly improved.

Synthesized negatively charged macromolecules (NCMs) for the surface modification of anticoagulant membrane biomaterials.

A series of negatively charged macromolecules (NCMs) including poly (sulfonated styrene-co-methyl methacrylate) (P(SS-co-MMA)), poly (acrylic acid-co-methyl methacrylate) (P(AA-co-MMA)) and poly (sulfonated styrene-co-acrylic acid-co-methyl methacrylate) (P(SS-co-AA-co-MMA)) are synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization using carboxyl-terminated trithiocarbonate as a RAFT agent. Activated partial thromboplastin time (APTT) tests indicate that the NCMs can retard blood clotting due to the negatively charged groups. The synthesized NCMs can be blended with polyethersulfone (PES) in dimethylacetamide (DMAC) to prepare membranes by means of a liquid-liquid phase separation technique. The prepared membranes were regular and smooth, except P(AA-co-MMA) modified membranes which were crude and rough due to the poor miscibility of AA segment and PES. The NCM modified PES membranes exhibited good anticoagulant ability due to the existence of the large density of the negative charges on the membrane surface, which induced a strong electrostatic repulsion with the negatively charged blood constituents. Therefore, the P(SS-co-AA-co-MMA) was designed and prepared with appropriate proportions of SS, AA and MMA for better membrane performance. The results indicated that the P(SS-co-AA-co-MMA) had potential to improve the anticoagulant property of biomaterials and to be applied in blood purification.

Biopolymer functionalized reduced graphene oxide with enhanced biocompatibility via mussel inspired coatings/anchors.

A green and facile method for preparing biopolymer functionalized reduced graphene oxide (RGO) by using mussel inspired dopamine (DA) as the reducing reagent and the functionalized molecule is proposed. In the study, GO is reduced by DA and DA is adhered to RGO by one-step pH-induced polymerization of DA (polydopamine, PDA), and then heparin or protein is grafted onto the PDA adhered RGO (pRGO) through catechol chemistry. The obtained pRGO, heparin grafted pRGO (Hep-g-pRGO), and BSA grafted pRGO (BSA-g-pRGO) exhibit fine 2D morphology and excellent stability in water and PBS solution. Furthermore, the biocompatibility of the biopolymer functionalized RGO are investigated using human blood cells and human umbilical vein endothelial cells (HUVECs). The biopolymer functionalized RGO exhibits an ultralow hemolysis ratio (lower than 1.8%), and the cellular toxicity assay suggests that the biopolymer functionalized RGO has good cytocompatibility for HUVEC cells, even at a high concentration of 100 µg mL-1. Moreover, the high anticoagulant ability of Hep-g-pRGO indicates that the grafted biopolymer could maintain its biological activity after immobilization onto the surface of pRGO. Therefore, the proposed safe and green biomimetic method confers the biopolymer functionalized RGO with great potential for various biological and biomedical applications.

General and biomimetic approach to biopolymer-functionalized graphene oxide nanosheet through adhesive dopamine.

Graphene oxide (GO), reduced graphene oxide (rGO), and their derivatives are investigated for various biomedical applications explosively. However, the defective biocompatibility was also recognized, which restricted their potential applications as biomaterials. In this study, a facile biomimetic approach for preparation of biopolymer adhered GO (rGO) with controllable 2D morphology and excellent biocompatibility was proposed. Mussel-inspired adhesive molecule dopamine (DA) was grafted onto heparin backbone to obtain DA grafted heparin (DA-g-Hep) by carbodiimide chemistry method; then, DA-g-Hep was used to prepare heparin-adhered GO (Hep-a-GO) and heparin-adhered rGO (Hep-a-rGO). The obtained heparin-adhered GO (rGO) showed controllable 2D morphology, ultrastable property in aqueous solution, and high drug and dye loading capacity. Furthermore, the biocompatibility of the heparin-adhered GO (rGO) was investigated using human blood cells and human umbilical vein endothelial cells, which indicated that the as-prepared heparin-adhered GO (rGO) exhibited ultralow hemolysis ratio (lower than 1.2%) and high cell viability. Moreover, the highly anticoagulant bioactivity indicated that the adhered heparin could maintain its biological activity after immobilization onto the surface of GO (rGO). The excellent biocompatibility and high bioactivity of the heparin-adhered GO (rGO) might confer its great potentials for various biomedical applications.

Photoresponsive surface molecularly imprinted poly(ether sulfone) microfibers.

In the present study, photoresponsive surface molecularly imprinted poly(ether sulfone) microfibers are prepared via nitration reaction, the wet-spinning technique, surface nitro reduction reaction, and surface diazotation reaction for the selectively photoregulated uptake and release of 4-hydrobenzoic acid. The prepared molecularly imprinted microfibers show selective binding to 4-HA under irradiation at 450 nm and release under irradiation at 365 nm. The simple, convenient, effective, and productive method for the preparation of azo-containing photoresponsive material is also applied to the modification of polysulfone and poly(ether ether ketone). All three benzene-ring-containing polymers show significant photoresponsibility after the azo modification.

Improved blood compatibility of polyethersulfone membrane with a hydrophilic and anionic surface.

In this study, a novel triblock copolymer of poly (styrene-co-acrylic acid)-b-poly (vinyl pyrrolidone)-b-poly(styrene-co-acrylic acid) (P(St-co-AA)-b-PVP-b-P(St-co-AA)) is synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization, and used for the modification of blood contacting surface of polyethersulfone (PES) membrane to improve blood compatibility. The synthesized block copolymer can be directly blended with PES to prepare PES membranes by a liquid-liquid phase separation technique. The compositions and structure of the PES membranes are characterized by thermogravimetric analysis (TGA), ATR-FTIR, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM); the surface charge density of the modified PES membrane was measured by Zeta-potential; the blood compatibility of the PES membranes was assessed by detecting bovine serum albumin (BSA) and bovine serum fibrinogen (BFG) adsorption, platelet adhesion, activated partial thromboplastin time (APTT), platelet activation, and thrombin-antithrombin III (TAT) generation. The results indicated that the blood compatibility of the modified PES membrane was improved due to the membrane surface modification by blending the amphiphilic block copolymer and the surface segregation of the block copolymer.

Heparin-like macromolecules for the modification of anticoagulant biomaterials.

A heparin-like structured macromolecule (HLSM) is synthesized by RAFT polymerization using carboxyl-terminated trithiocarbonate as the RAFT agent. The HLSM can be directly blended with PES in DMAC to prepare flat-sheet membrane by means of a liquid-liquid phase separation technique. The synthesized polymeric material retard blood clotting and the modified membrane exhibits good anticoagulant ability due to the existence of the important functional groups SO(3) H, COOH and OH. The anionic groups on the membrane surface may bind coagulation factors and thus improve anticoagulant ability. The results indicate that the HLSM has potential to improve the anticoagulant properties of biomaterials and to be applied in blood purification including hemodialysis and bioartificial liver supports.