Covalent Deposition of Zwitterionic Polymer and Citric Acid by Click Chemistry-Enabled Layer-by-Layer Assembly for Improving the Blood Compatibility of Polysulfone Membrane

Development of blood compatible membranes is critical for biomedical applications. Zwitterionic polymers have been proved to be resistant to nonspecific protein adsorption and platelet adhesion. In this work, two kinds of zwitterionic copolymers bearing alkynyl and azide groups are synthesized by atom transfer radical polymerization (ATRP) and subsequent reactions, namely <i>alkynyl</i>-poly­(sulfobetaine methacrylate) (<i>alkynyl</i>-PSBMA) and <i>azide</i>-poly­(sulfobetaine methacrylate) (<i>azide</i>-PSBMA). The copolymers are directly used to modify <i>azido</i>-functionalized polysulfone (PSf-N₃) membrane via click chemistry-enabled layer-by-layer (LBL) assembly. <i>Alkynyl</i>-citric acid is then clicked onto the membrane when the outermost layer was <i>azide</i>-PSBMA. The chemical compositions, surface morphologies, and hydrophilicity of the zwitterionic polymer and citric acid multilayer modified membranes are characterized. The composite multilayer is resistant to protein adsorption and platelet adhesion and also prolongs clotting times, indicating that the blood compatibility is improved. Moreover, after clicking the small molecule anticoagulant <i>alkynyl</i>-citric acid onto the outermost of the zwitterionic multilayer, the membrane shows further improved anticoagulant property. The deposition of zwitterionic polymer and citric acid via click chemistry-enabled LBL assembly can improve the blood compatibility of the PSf membrane

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 β-cyclodextrin (β-CD) and adamantane (Ad). Ad-terminated poly­(<i>N</i>-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 β-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 <i>Staphyloccocus aureus</i>. 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

Design of Carrageenan-Based Heparin-Mimetic Gel Beads as Self-Anticoagulant Hemoperfusion Adsorbents

The currently used hemoperfusion adsorbents such as activated carbon and ion-exchange resin show dissatisfactory hemocompatibility, and a large dose of injected heparin leads to the increasing cost and the risk of systematic bleeding. Natural polysaccharide adsorbents commonly have good biocompatibility, but their application is restricted by the poor mechanical strength and low content of functional groups. Herein, we developed an efficient, self-anticoagulant and blood compatible hemoperfusion adsorbent by imitating the structure and functional groups of heparin. Carrageenan and poly­(acrylic acid) (PAA) cross-linked networks were built up by the combination of phase inversion of carrageenan and post-cross-linking of AA, and the formed dual-network structure endowed the beads with improved mechanical properties and controlled swelling ratios. The beads exhibited low protein adsorption amounts, low hemolysis ratios, low cytotoxicity, and suppressed complement activation and contact activation levels. Especially, the activated partial thromboplastin time, prothrombin time, and thrombin time of the gel beads were prolonged over 13, 18, and 4 times than those of the control. The self-anticoagulant and biocompatible beads showed good adsorption capacities toward exogenous toxins (560.34 mg/g for heavy metal ions) and endogenous toxins (14.83 mg/g for creatinine, 228.16 mg/g for bilirubin, and 18.15 mg/g for low density lipoprotein (LDL)), thus, highlighting their potential usage for safe and efficient blood purification

In Situ Cross-Linked Polymerization toward Poly(ether sulfone)/Poly(sodium acrylate) Hybrid Particles for the Removal of Environmental Toxins

In this study, poly­(ether sulfone) (PES)/poly­(sodium acrylate) (PSA) hybrid particles for the removal of environmental toxins were prepared via in situ cross-linked polymerization coupled with a liquid–liquid phase separation technique. The particles were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Batch experiments were performed to verify the adsorption capability of the particles, and the initial concentrations and pH values of the solutions significantly affected the adsorption process. In addition, both adsorption kinetic and adsorption isotherm models were used to analyze the adsorption process of Cu²⁺. The modified PES particles showed high adsorption capability for Cu²⁺ and methylene blue (MB), and a particle column was used to further study the removal ability of environmental toxins. The results indicated that the hybrid particles had great potential to remove heavy metal ions and cationic dyes for wastewater treatment on an industrial scale