Enhancing protein dynamics analysis with hydrophilic polyethylene glycol cross-linkers.

Cross-linkers play a critical role in capturing protein dynamics in chemical cross-linking mass spectrometry techniques. Various types of cross-linkers with different backbone features are widely used in the study of proteins. However, it is still not clear how the cross-linkers' backbone affect their own structure and their interactions with proteins. In this study, we systematically characterized and compared methylene backbone and polyethylene glycol (PEG) backbone cross-linkers in terms of capturing protein structure and dynamics. The results indicate the cross-linker with PEG backbone have a better ability to capture the inter-domain dynamics of calmodulin, adenylate kinase, maltodextrin binding protein and dual-specificity protein phosphatase. We further conducted quantum chemical calculations and all-atom molecular dynamics simulations to analyze thermodynamic and kinetic properties of PEG backbone and methylene backbone cross-linkers. Solution nuclear magnetic resonance was employed to validate the interaction interface between proteins and cross-linkers. Our findings suggest that the polarity distribution of PEG backbone enhances the accessibility of the cross-linker to the protein surface, facilitating the capture of sites located in dynamic regions. By comprehensively benchmarking with disuccinimidyl suberate (DSS)/bis-sulfosuccinimidyl-suberate(BS3), bis-succinimidyl-(PEG)2 revealed superior advantages in protein dynamic conformation analysis in vitro and in vivo, enabling the capture of a greater number of cross-linking sites and better modeling of protein dynamics. Furthermore, our study provides valuable guidance for the development and application of PEG backbone cross-linkers.

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.

Functional polyethersulfone particles for the removal of bilirubin.

In this study, polyethersulfone/poly (glycidyl methacrylate) particles are prepared via in situ cross-linked polymerization coupled with a phase inversion technique. The surfaces of these particles are then further modified by grafting amino groups using tetraethylenepentamine, dethylenetriamine, ethylenediamine, or 1,6-hexanediamine for the removal of bilirubin. The particles are characterized by Flourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Batch adsorption experiments are performed to verify the adsorption capability, and the effect of bilirubin initial concentration, bovine serum albumin concentration, and solution ionic strength on the adsorption is also investigated. In addition, both adsorption kinetic and isotherm models are applied to analyze the adsorption process of bilirubin, and a particle column is used to further study the bilirubin removal ability.To prove that the method was a universal portal to prepare functional particles, polysulfone, polystyrene, and poly(vinylidene fluoride) based functional particles were also prepared and used for the removal of bilirubin. This study and the results indicated that the particles had a great potential to be used in hemoperfusion treatment for hyperbilirubinemia.

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 alkynyl-poly(sulfobetaine methacrylate) (alkynyl-PSBMA) and azide-poly(sulfobetaine methacrylate) (azide-PSBMA). The copolymers are directly used to modify azido-functionalized polysulfone (PSf-N3) membrane via click chemistry-enabled layer-by-layer (LBL) assembly. Alkynyl-citric acid is then clicked onto the membrane when the outermost layer was azide-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 alkynyl-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.

Incidence and prognosis of olfactory and gustatory dysfunctions related to SARS-CoV-2 Omicron strain infection in China: A national multicenter survey of 35,566 individuals.

Objective: This cross-sectional study aimed to determine the epidemiology of olfactory and gustatory dysfunctions related to COVID-19 in China. Methods: This study was conducted by 45 tertiary Grade-A hospitals in China. Online and offline questionnaire data were obtained from patients infected with COVID-19 between December 28, 2022, and February 21, 2023. The collected information included basic demographics, medical history, smoking and drinking history, vaccination history, changes in olfactory and gustatory functions before and after infection, and other postinfection symptoms, as well as the duration and improvement status of olfactory and gustatory disorders. Results: Complete questionnaires were obtained from 35,566 subjects. The overall incidence of olfactory and taste dysfunction was 67.75%. Being female or being a cigarette smoker increased the likelihood of developing olfactory and taste dysfunction. Having received four doses of the vaccine or having good oral health or being a alcohol drinker decreased the risk of such dysfunction. Before infection, the average olfactory and taste VAS scores were 8.41 and 8.51, respectively; after infection, they decreased to 3.69 and 4.29 and recovered to 5.83 and 6.55 by the time of the survey. The median duration of dysosmia and dysgeusia was 15 and 12 days, respectively, with 0.5% of patients having symptoms lasting for more than 28 days. The overall self-reported improvement rate was 59.16%. Recovery was higher in males, never smokers, those who received two or three vaccine doses, and those that had never experienced dental health issues, or chronic accompanying symptoms. Conclusions: The incidence of dysosmia and dysgeusia following infection with the SARS-CoV-2 virus is high in China. Incidence and prognosis are influenced by several factors, including sex, SARS-CoV-2 vaccination, history of head-facial trauma, nasal and oral health status, smoking and drinking history, and the persistence of accompanying symptoms.

Simultaneous determination of furfural, acetic acid, and 5-hydroxymethylfurfural in corncob hydrolysates using liquid chromatography with ultraviolet detection.

A single-laboratory validation study was conducted using HPLC for detecting and quantifying acetic acid, furfural, and 5-hydroxymethylfurfural (HMF) in corncob hydrolysates. A pretreatment procedure using dilute sulfuric acid was optimized for corncob hydrolysis. The final hydrolysates were analyzed by HPLC using a C18 RP column with aqueous 0.01% (v/v) H2SO4-CH3OH (95 + 5) as the mobile phase at a flow rate of 1 mL/min. The wavelengths for detecting the three compounds were changed to their optimal UV detection wavelengths at the time of elution. The wavelength detection adjustments were as follow: 205 nm (0 to 4 min); 284 nm (4 to 7 min); and 276 nm (7 to 10 min). Separation was achieved with a chromatographic run time of 10 min. The calibration curves for the three compounds had correlation coefficients (r2) > or = 99.8%. The analytical range, as defined by the calibration curves, was 0.5-10 mg/L for acetic acid, 0.4-22 mg/L for furfural, and 0.1-18 mg/L for HMF. The LODs for acetic acid, furfural, and HMF were estimated to be 0.05, 0.03, and 0.02 mg/L, respectively; the LOQs were 0.196, 0.135, and 0.074 mg/L, respectively. The RSD values for the intraday precision study ranged from 0.31 to 2.22%, and from 0.57 to 2.43% for the interday study. The mean recovery rates in all compounds were between 100.08 and 101.49%.

Enhancing the antibacterial activity of biomimetic HA coatings by incorporation of norvancomycin.

BACKGROUND: Bacterial infections associated with the use of biomaterials remain a great challenge for orthopedic surgery. The main purpose of the work discussed in this paper was to improve the antibacterial activity of a biomimetic calcium phosphate (CP) coating widely used in orthopedic biomaterials by incorporation of norvancomycin in the biomimetic process. METHODS: CP coating and CP coating containing norvancomycin were produced on a titanium alloy (Ti6Al4V) surface by a biomimetic process. The morphology, surface crystal structure, and concentrations of elements in the coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX), respectively. The amount of norvancomycin and its release were investigated by UV-visible spectroscopy. MTT was used to investigate cell behavior. The morphology of adhered bacteria was observed by SEM. Antibacterial activity was expressed as inhibition zone by using Staphylococcus aureus (ATCC 25923) as model bacteria. RESULTS: Results from SEM, EDX, and XRD revealed formation of a hydroxyapatite (HA) coating. The amount of antibiotic in the CP coating increased with increasing concentration of norvancomycin in the coating solution, followed by a plateau when the concentration of norvancomycin in the coating solution reached 600 mg/l. Approximately 2.16 µg norvancomycin per mg coating was co-precipitated with the CP layer onto titanium alloy discs when 600 mg/l norvancomycin coating solution was applied. The norvancomycin had a fast release profile followed by slow release. The MTT test of osteoblast cell cultures suggested that coatings containing norvancomycin did not cause any cytotoxicity compared with the CP coating and control titanium plate. The antibacterial activity test showed that the norvancomycin released from the coatings inhibited the growth of Staphylococcus aureus; more bacteria were found on the CP coating than on the norvancomycin-loaded coating. CONCLUSIONS: A norvancomycin-loaded HA-like coating was successfully obtained on titanium surfaces. The norvancomycin incorporated had no negative effects on osteoblast cell behavior. The released norvancomycin results in excellent antibacterial activity of Ca-P coatings. Therefore, incorporation of norvancomycin can enhance antibacterial activity and the norvancomycin-loaded CP coating can be used to inhibit post-surgical infections in orthopaedics.

A novel Hv1 inhibitor reveals a new mechanism of inhibition of a voltage-sensing domain.

Voltage-gated sodium, potassium, and calcium channels consist of four voltage-sensing domains (VSDs) that surround a central pore domain and transition from a down state to an up state in response to membrane depolarization. While many types of drugs bind pore domains, the number of organic molecules known to bind VSDs is limited. The Hv1 voltage-gated proton channel is made of two VSDs and does not contain a pore domain, providing a simplified model for studying how small ligands interact with VSDs. Here, we describe a ligand, named HIF, that interacts with the Hv1 VSD in the up and down states. We find that HIF rapidly inhibits proton conduction in the up state by blocking the open channel, as previously described for 2-guanidinobenzimidazole and its derivatives. HIF, however, interacts with a site slowly accessible in the down state. Functional studies and MD simulations suggest that this interaction traps the compound in a narrow pocket lined with charged residues within the VSD intracellular vestibule, which results in slow recovery from inhibition. Our findings point to a "wrench in gears" mechanism whereby side chains within the binding pocket trap the compound as the teeth of interlocking gears. We propose that the use of screening strategies designed to target binding sites with slow accessibility, similar to the one identified here, could lead to the discovery of new ligands capable of interacting with VSDs of other voltage-gated ion channels in the down state.

Vertical distribution of microplastics in bay sediment reflecting effects of sedimentation dynamics and anthropogenic activities.

Microplastics are ubiquitous in our environment, yet we have little knowledge on their accumulation profile and changing trend. In this study, we selected the semi-enclosed Jiaozhou Bay as the research area to study the vertical distribution characteristics of microplastic in the sediment and analyzed factors that might affect this distribution pattern. We found six different polymer types and the microplastic abundance ranged between 2.5 items/kg d.w.-27.5 items/kg d.w.. Microplastic abundance was very low in deep sediment and generally showed a decreasing trend from the surface down with some shifts at different depth at certain sites. Based on our data, the total microplastics in the sediment were estimated to reach 3.71 tons in Jiaozhou Bay. This study shows that the vertical microplastic abundance profile in the sediment can not only show the microplastics pollution level but also reflect environmental factors and anthropogenic impacts.

Molecular basis of the lipid-induced MucA-MucB dissociation in Pseudomonas aeruginosa.

MucA and MucB are critical negative modulators of sigma factor AlgU and regulate the mucoid conversion of Pseudomonas aeruginosa. Previous studies have revealed that lipid signals antagonize MucA-MucB binding. Here we report the crystal structure of MucB in complex with the periplasmic domain of MucA and polyethylene glycol (PEG), which unveiled an intermediate state preceding the MucA-MucB dissociation. Based on the biochemical experiments, the aliphatic side chain with a polar group was found to be of primary importance for inducing MucA cleavage. These results provide evidence that the hydrophobic cavity of MucB is a primary site for sensing lipid molecules and illustrates the detailed control of conformational switching within MucA-MucB in response to lipophilic effectors.

Multifunctionalized polyethersulfone membranes with networked submicrogels to improve antifouling property, antibacterial adhesion and blood compatibility.

Intensive efforts have been employed in modifying biomedical membranes. Among them, blending is recognized as a simple method. However, the conventional blending materials commonly lead to an insufficient modification, which is mainly caused by the poor miscibility between the blending materials and the matrixes, the elution of the hydrophilic materials from the matrixes during the use and storage, and the insufficient surface enrichment of the blending materials. Aiming to solve the abovementioned disadvantages, we developed novel polyethersulfone/poly(acrylic acid-co-N-vinyl-2-pyrrolidone) networked submicrogels (PES/P(AA-VP) NSs), which were blended with PES to enhance the antifouling properties, antibacterial adhesion and haemocompatible properties of PES membranes. As results, the PES/P(AA-VP) NSs showed good miscibility with the PES matrix, and hydrophilic submicrogels would enrich onto the membrane surface during the phase inversion process due to the surface segregation. The entanglement between the PES matrix and the networked submicrogels would effectively limit the elution of the submicrogels. In conclusion, the modified PES membranes prepared by blending with the PES/P(AA-VP) NSs might draw great attention for the application in haemodialysis fields.

[In vivo effect of nanophase Ti6Al4V on osseointegration: experiment with rabbits].

OBJECTIVE: To evaluate the effect of nanophase Ti6Al4V substrates on the osseointegration in vivo. METHOD: Novel nanophase Ti6Al4V substrates were prepared according to the severe plastic deformation principle. Eighteen New Zealand white rabbits were randomly divided into 3 equal groups with their trochanters of femur exposed and implanted with titanium substrate with common surface (Ti group), nanophase Ti6Al4V substrate (nano-Ti group), and hydroxyapatite-coated substrate (HA group) respectively. Four, 8, and 12 weeks later X-ray films were taken on 6 rabbits from each group, tetracycline and calcein were injected intramuscularly, and one day later the rabbits were sacrificed. The histological changes of the tissue surrounding the implant including the bone kinesics parameter were evaluated; the bone-implant interfaces were examined with scanning electron microscope (SEM) and transmission electron microscope (TEM) respectively. RESULT: Radiographic examinations showed that the bone recovery around the implant in the nano-Ti group was earlier compared to that in the Ti group. Histological examination suggested that the interface osseointegration rates 4, 8, and 12 weeks later of the nano-Ti groups were all significantly higher than those of the Ti group ( all P < 0.01). Strong tetracycline labeling and calcein labeling were observed around the implants in the nano-Ti group, indicating the active form action of new bone. The rates of bone mineralization and deposition 4, 8, and 12 weeks later of the nano-Ti group were higher than those of the Ti group. SEM and TEM examinations showed greater degradation of the surface and much more grains in cells in the HA group as compared to those in the nano-Ti group. The bone mineralization and osseointegration rates 4 weeks later of the HA group were significantly higher than those of the nano-Ti group (both P < 0.05), however, there were no significant differences in the bone mineralization and osseointegration rates 8 weeks later between these 2 groups. The bone mineralization and osseointegration rates 12 weeks later of the nano-Ti group were even higher than those of the HA group. CONCLUSION: The novel nanophase Ti6Al4V substrates improves the bone-implant osseointegration without significant grains of degradation in vivo, suggesting that the novel substrates and nano technology should be further considered for the orthopedic implant applications.

Balloon kyphoplasty versus percutaneous vertebroplasty for osteoporotic vertebral compression fracture: a meta-analysis and systematic review.

BACKGROUND: This meta-analysis was aimed to explore the overall safety and efficacy of balloon kyphoplasty versus percutaneous vertebroplasty for osteoporotic vertebral compression fracture (OVCF) based on qualified studies. METHODS: By searching multiple databases and sources, including PubMed, Cochrane, and Embase by the index words updated to January 2018, qualified studies were identified and relevant literature sources were also searched. The qualified studies included randomized controlled trials, prospective or retrospective comparative studies, and cohort studies. The meta-analysis was performed including mean difference (MD) or relative risk (RR) and 95% confidence interval (95% CI) to analyze the main outcomes. RESULTS: A total of 16 studies were included in the meta-analysis to explore the safety and efficacy of kyphoplasty versus vertebroplasty for the treatment of OVCF. The results indicated that kyphoplasty significantly decreased the kyphotic wedge angle (SMD, 0.98; 95% CI 0.40-1.57), increased the postoperative vertebral body height (SMD, - 1.27; 95% CI - 1.86 to - 0.67), and decreased the risk of cement leakage (RR, 0.62; 95% CI 0.47-0.80) in comparison with vertebroplasty. However, there was no statistical difference in visual analog scale (VAS) scores (WMD, 0.04; 95% CI - 0.28-0.36) and Oswestry Disability Index (ODI) scores (WMD, - 1.30; 95% CI - 3.34-0.74) between the two groups. CONCLUSIONS: Kyphoplasty contributes especially to decreasing the mean difference of kyphotic wedge angle and risk of cement leakage and increasing the vertebral body height when compared with vertebroplasty. But radiographic differences did not significantly influence the clinical results (no significant difference was observed in VAS scores and ODI scores between the two groups); thus, kyphoplasty and vertebroplasty are equally effective in the clinical outcomes of OVCF. In addition, more high-quality multi-center RCTs with a larger sample size and longer follow-up are warranted to confirm the current findings.

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.

Effect of strontium ions on the growth of ROS17/2.8 cells on porous calcium polyphosphate scaffolds.

Preparation, characterization and cellular biocompatibility study of a series of calcium polyphosphate containing 0-100 mol% of Ca2+ replaced by Sr2+ were reported. The osteoblastic ROS17/2.8 cell line was used and seeded on the strontium-doped calcium polyphosphate (SCPP) scaffolds to estimate its optimal dose and to study its potential to support the growth of osteoblastic cells for bone tissue engineering. The effects of SCPP on cells' proliferation and differentiation were evaluated by MTT and ALP activity assay. The results showed that porous SCPP did not exert cytotoxic effect on the cells. In addition, the proliferation and differentiation of the growth of ROS17/2.8 cells on the SCPP containing a low dose of strontium showed a higher level compared to the control, and the SCPP containing 1% strontium was optimal according to the results of MTT and ALP activity assay. The cells on the porous SCPP formed a continuous layer on the outer and inner surface observed by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The bunchy collagens were excreted from the cells and the calcium granules wrapped by collagens were sedimentated on the surface of cells. The results suggested that the biodegradable SCPP could stimulate the proliferation and differentiation of ROS17/2.8 cells in vitro after addition of proper dose of strontium. The porous SCPP may be a promising material for the bone tissue engineering.

[Isolation of Quorum Quenching Bacteria and Their Function for Controlling Membrane Biofouling].

Interspecies quorum quenching by bacterial cells has been reported as a novel approach for mitigating the biofouling via restraining quorum sensing(QS). Five indigenous quorum quenching bacterial strains were isolated from activated sludge taken from wastewater treatment plant. Strain HG10 showed high degrading activity against C6-HSL(N-hexanoyl-L-Homoserine lactone). The result of 16S rDNA sequencing showed that the isolated strain HG10 belonged to the genus Bacillus cereus. Strain HG10 was immobilized in sodium alginate(SA), and the biofouling inhibition of SA-HG10 in membrane filtration treatment system was investigated. The results showed that the membrane flux in experimental group B(provided with SA-HG10)was 181.29 L·(m2·h)-1, and the membrane flux in control group A (without the beads) was 110.64 L·(m2·h)-1, The membrane flux in group B was 63.86% higher than group A. The content of extracellular polymeric substances (EPS) in the biofilm on the membrane filter was also measured. The results showed that the contents of polysaccharides and proteins in the experimental group B decreased by 29% and 48% respectively than those of group A. A large decrease in the content of hydrophobic proteins was the main reason for the decrease of membrane fouling. The content of EPS in the membrane surface decreased by 43%, indicating that SA-HG10 could inhibit biofilm formation on the membrane filter and effectively improve the filtering performance.

A robust way to prepare blood-compatible and anti-fouling polyethersulfone membrane.

Functional copolymers were successfully grafted onto polyethersulfone (PES) membrane surfaces by free radical mechanism using ammonium persulfate (APS) as an initiator. The anti-coagulant and anti-fouling properties of the membranes were well controlled by changing the functional copolymer compositions. Attenuated total reflection-Fourier transforminfrared (ATR-FTIR), X-ray photoelectron spectrometer spectrum (XPS), water contact angles (WCAs), and scanning electron microscopy (SEM) images were used to characterize the membranes. The results of protein adsorption, clotting times, platelet adhesion and bacteria attachment indicated that the membranes had good blood-compatibility and/or anti-fouling ability. Meanwhile, the modification didn't cause an adverse effect on the membrane permeability. This new method provides a general, robust and flexible way to adjust membrane surface performance and potentially has wide applications.

A facile approach toward multi-functional polyurethane/polyethersulfone composite membranes for versatile applications.

The complex synthesis through multistep reactions and tedious purifications based on different monomers or macromolecules limits the practical applications of functional polymers. Herein, a facile approach toward a series of functional polyurethanes (PUs) is designed for versatile biological applications within fewer step reactions under mild conditions. The tertiary amino groups in the PU are converted into zwitterions or quaternary ammonium salt via simple one-step synthesis, and then used to prepare PU/polyethersulfone composite membranes. The composite membrane with tertiary amine groups exhibits significant adsorption capability to anionic dye Congo red (CR) and toxin bilirubin. The membrane bearing zwitterionic PU displays excellent blood compatibility; while which with quaternary ammonium salts has antibacterial property. Furthermore, carboxybetaine-functional composite membrane is exploited to bear Ag nanoparticles to endow with dual functions of antibacterial and antifouling properties. This work demonstrates the potential of PUs as readily available, multi-functional, and easy-to-use materials for biological applications.

Zwitterionic polymer functionalization of polysulfone membrane with improved antifouling property and blood compatibility by combination of ATRP and click chemistry.

The chemical compositions are very important for designing blood-contacting membranes with good antifouling property and blood compatibility. In this study, we propose a method combining ATRP and click chemistry to introduce zwitterionic polymer of poly(sulfobetaine methacrylate) (PSBMA), negatively charged polymers of poly(sodium methacrylate) (PNaMAA) and/or poly(sodium p-styrene sulfonate) (PNaSS), to improve the antifouling property and blood compatibility of polysulfone (PSf) membranes. Attenuated total reflectance-Fourier transform infrared spectra, X-ray photoelectron spectroscopy and water contact angle results confirmed the successful grafting of the functional polymers. The antifouling property and blood compatibility of the modified membranes were systematically investigated. The zwitterionic polymer (PSBMA) grafted membranes showed good resistance to protein adsorption and bacterial adhesion; the negatively charged polymer (PNaSS or PNaMAA) grafted membranes showed improved blood compatibility, especially the anticoagulant property. Moreover, the PSBMA/PNaMAA modified membrane showed both antifouling property and anticoagulant property, and exhibited a synergistic effect in inhibiting blood coagulation. The functionalization of membrane surfaces by a combination of ATRP and click chemistry is demonstrated as an effective route to improve the antifouling property and blood compatibility of membranes in blood-contact.

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.