A facile approach towards amino-coated ferroferric oxide nanoparticles for environmental pollutant removal.

A facile and environmental-friendly approach was developed to prepare magnetic nano-adsorbent for environmental pollutant removal. Based on the mussel-inspired polymerization, amino-coated Fe3O4 nanoparticles were fabricated by simply immersing Fe3O4 nanoparticles into an aqueous solution of catechol and hexanediamine with stirring at room temperature. The magnetic nano-adsorbent was characterized via Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), thermo gravimetric analysis (TGA), and Brunauer-Emmett-Teller's test (BET). The effects of initial mole ratio of catechol/hexanediamine and coating time on the adsorption capacity were investigated, using Congo red as a model organic dye. Under the optimal preparation condition, the absorption capacity of the amino-coated Fe3O4 nanoparticles reached 97.3 mg/g for Congo red, and the adsorption reached about 80% of the equilibrium adsorption amount within 200 min. Adsorption kinetics and isotherm studies indicated that the absorption process fitted the pseudo-second-order kinetic and Langmuir isotherm models well. Besides, desired functional groups could be introduced onto the surface of Fe3O4 nanoparticles, to tailor the adsorption capacity for Congo red, amaranths red, methylene blue and methylene violet. It is believed that the amino-coated magnetic nano-adsorbent prepared by the proposed method in this study has a good prospect for wastewater treatment.

Engineering of hemocompatible and antifouling polyethersulfone membranes by blending with heparin-mimicking microgels.

To improve the hemocompatibility and antifouling property of polyethersulfone (PES) membranes, heparin-mimicking microgels of poly(acrylic acid-co-N-vinyl-2-pyrrolidone) (P(AA-VP)) and poly(2-acrylamido-2-methylpropanesulfonic acid-co-acrylamide) (P(AMPS-AM)) were synthesized by conventional free radical copolymerization, and then incorporated into a PES matrix by blending. The results of Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and scanning electron microscopy (SEM) confirmed that heparin-mimicking microgels were successfully synthesized. The presence of the microgels in the membrane matrix was also confirmed by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), and SEM. Compared with pristine PES membranes, the improvement of the antifouling property of the heparin-mimicking microgel modified membranes was demonstrated by the increased flux recovery ratio and improved anti-bacterial adhesion, while the enhancement of hemocompatibility for the modified membranes was proved by the decreased plasma protein adsorption, suppressed platelet adhesion, prolonged clotting times, as well as depressed blood-related complement activation. Additionally, after introducing the heparin-mimicking microgels, the membranes showed enhanced cell adhesion and proliferation properties. These results indicated that the heparin-mimicking microgel modified membranes had great potential to be used as blood contacting materials.

Host-Guest Self-Assembly Toward Reversible Thermoresponsive Switching for Bacteria Killing and Detachment.

A facile method to construct reversible thermoresponsive switching for bacteria killing and detachment was currently developed by host-guest self-assembly of ß-cyclodextrin (ß-CD) and adamantane (Ad). Ad-terminated poly(N-isopropylacrylamide) (Ad-PNIPAM) and Ad-terminated poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride (Ad-PMT) were synthesized via atom transfer radical polymerization, and then assembled onto the surface of ß-CD grafted silicon wafer (SW-CD) by simply immersing SW-CD into a mixed solution of Ad-PNIPAM and Ad-PMT, thus forming a thermoresponsive surface (SW-PNIPAM/PMT). Atomic force microscopy (AFM), X-ray photoelectron spectrometry (XPS), and water contact angle (WCA) analysis were used to characterize the surface of SW-PNIPAM/PMT. The thermoresponsive bacteria killing and detachment switch of the SW-PNIPAM/PMT was investigated against Staphyloccocus aureus. The microbiological experiments confirmed the efficient bacteria killing and detachment switch across the lower critical solution temperature (LCST) of PNIPAM. Above the LCST, the Ad-PNIPAM chains on the SW-PNIPAM/PMT surface were collapsed to expose Ad-PMT chains, and then the exposed Ad-PMT would kill the attached bacteria. While below the LCST, the previously collapsed Ad-PNIPAM chains became more hydrophilic and swelled to cover the Ad-PMT chains, leading to the detachment of bacterial debris. Besides, the proposed method to fabricate stimuli-responsive surfaces with reversible switches for bacteria killing and detachment is facile and efficient, which creates a new route to extend the application of such smart surfaces in the fields requiring long-term antimicrobial treatment.

Graphene oxide and sulfonated polyanion co-doped hydrogel films for dual-layered membranes with superior hemocompatibility and antibacterial activity.

In this study, a new kind of hemocompatible and antibacterial dual-layered polymeric membrane was fabricated by coating a top layer of graphene oxide and a sulfonated polyanion co-doped hydrogel thin film (GO-SPHF) on a bottom membrane substrate. After a two-step spin-coating of casting solutions on glass plates, dual-layered membranes were obtained by a liquid-liquid phase inversion method. The GO-SPHF composite polyethersulfone (PES) membranes (PES/GO-SPHF) showed top layers with obviously large porous structures. The chemical composition tests indicated that there were abundant hydrophilic groups enriched on the membrane surface. The examination of membrane mechanical properties indicated that the composite membranes exhibited only slightly decreased performance compared to pristine PES membranes. Moreover, to validate the potential applications of this novel dual-layered membrane in diverse fields, we tested the hemocompatibility and antibacterial activity of the membranes, respectively. Notably, the PES/GO-SPHF membranes showed highly improved in vitro hemocompatibility, such as good anti-coagulant activity, suppressed platelet adhesion and activation, low inflammation potential, and good red blood cell compatibility. Furthermore, the dual-layered membranes exhibited robust antibacterial ability after in situ loading of Ag-nanoparticles with excellent bactericidal capability to both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Due to the integration of the porous membrane structure, good mechanical strength, excellent hemocompatibility, as well as robust bactericidal capability, the GO and sulfonated polyanion co-doped dual-layered membranes may open up a new protocol to greatly demonstrate the potential application of polymeric membranes for clinical hemodialysis and many other biomedical therapies.

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.