Immobilization of heparin on PVDF membranes with microporous structures

Biomedical applications of carbohydrate-based polyurethane: From biosynthesis to degradation

The foremost common natural polymers are carbohydrate-based polymers or polysaccharides, having a long chain of monosaccharide or disaccharide units linked together via a glycosidic linkage to form a complex structure. There are several uses of carbohydrate-based polymers in biomedical sector due to its attractive features including less toxicity, biocompatibility, biodegradability, high reactivity, availability, and relatively inexpensive. The aim of our study was to explore the synthetic approaches for the preparation of numerous carbohydrate-based polyurethanes (PUs) and their wide range of pharmaceutical and biomedical applications. The data summarized in this study shows that the addition of carbohydrates in the structural skeleton of PUs not only improve their suitability but also effect the applicability for employing them in biological applications. Carbohydrate-based units are incorporated into the PUs, which is the most convenient method for the synthesis of novel biocompatible and biodegradable carbohydrate-based PUs to use in various biomedical applications.

Development of Hydrogen-Permselective Porous Membranes Using Radiation-Induced Graft Polymerization

Hydrogen-permselective membranes were developed using a radiation-induced grafting method. Styrene (St) and acrylic acid (AAc) monomers were introduced into porous polyvinylidene fluoride (PVDF) membranes to obtain St- and AAc-grafted PVDF membranes with grafting degrees of 82% and 92%, respectively. The porosities of the grafted membranes were controlled in the range 30–40% by hot-press compression at 159 °C and 4 MPa. The hydrogen permeability was found to be of the order of 10−7 mol/m2∙s∙Pa, which was higher than the permeability for water vapor and nitrogen (oxygen model). The St- and AAc-grafted membranes exhibited 9.0 and 34 times higher permeability for H2 than for H2O and N2, respectively.

Preparation of MFI zeolite membranes on coarse macropore stainless steel hollow fibers for the recovery of bioalcohols

Hydrophobic MFI zeolite membranes are considered suitable for the recovery of bioalcohols (bioethanol and biobutanol) from fermentation broths.

SURFACE CHARACTERIZATION AND HEMOCOMPATIBILITY OF HEPARINIZED 316L STAINLESS STEEL

Poor compatibility between blood and metallic coronary artery stents is one reason for arterial restenosis. Immobilization of heparin on stent's surface is feasible for improving compatibility. We examined possible surface-coupling agents for anticoagulant agent immobilization. Hexamethylene diisocyanate (HMDI) was examined as surface-coupling agent to activate 316L stainless steel (e.g. stent material). Afterwards, we grafted PEG on the HMDI activated surface to provide heparin with higher conformational freedom and a more hydrophilic environment. The effectiveness of HMDI activated and PEG grafted surface was confirmed by FTIR, XPS, and water contact angle test. Heparin was then immobilized onto the activated 316L stainless steel. The heparin surface density was 9.5 μg/cm2. Sessile drop water contact angles showed that the heparingrafted surface is even more hydrophilic than the PEG grafted one. The function of grafted heparin was evaluated by antithrombrin III (ATIII) adsorption testing and SEM. The surface with heparin grafting shows better ATIII binding ability and hemocompatibility than the native one.

Osteogenic activities of MC3T3-E1 cells on heparin-immobilized poly(caprolactone) membranes

The aim of this study was to investigate the effects of heparin on the activity of osteoblast-like cells seeded on poly(caprolactone) (PCL) membranes. The membranes were prepared by solvent-casting technique in ~150 µm thickness. Then they were treated with 1,6-hexanediamine solution and functionalized with covalently bound heparin. The morphology, proliferation, and differentiation of MC3T3-E1 preosteoblasts on these membranes were investigated in vitro. The heparin functionalized PCL membranes, compared to non-functionalized membranes, significantly stimulated osteoblast proliferation. The Scanning electron microscope images confirmed the stimulative effect of covalently bound heparin on the osteoblast-like cell proliferation. The alkaline phosphatase and osteocalcin levels for cells proliferated on heparin containing PCL membranes were higher than that of nonfunctionalized membranes.

Electrochemical impedance spectroscopy as a highly sensitive tool for a dynamic interaction study between heparin and antithrombin: a novel antithrombin sensor

Specific recognition between two biological partners is widely exploited in biosensors nowadays. To explore this avenue, a novel biosensor for antithrombin (AT) detection was constructed. Heparin was used as the affinity ligand. A well-known acrylic monomer (butyl methacrylate) was polymerized and grafted onto the heparin polysaccharide by the use of ceric ammonium nitrate as a redox initiator in aqueous nitric acid medium. Polymers were deposited as a thin layer onto surface of stainless steel electrode (SS316L). The obtained polymers were studied by Fourier transform infrared spectroscopy (FTIR) and analyzed by differential scanning calorimetry (DSC). Moreover, the films were characterized by electrochemical impedance spectroscopy (EIS), contact-angle measurements and AFM. EIS was used to study the biosensor affinity to AT and the relationship between functionalization growth of modified electrode and the response of the sensor. The proposed approach appears to be simple, sensitive and correlated with methods that analyse the detection of antithrombin.

Hemocompatibility of poly(vinylidene fluoride) membrane grafted with network-like and brush-like antifouling layer controlled via plasma-induced surface PEGylation

In this work, the hemocompatibility of PEGylated poly(vinylidene fluoride) (PVDF) microporous membranes with varying grafting coverage and structures via plasma-induced surface PEGylation was studied. Network-like and brush-like PEGylated layers on PVDF membrane surfaces were achieved by low-pressure and atmospheric plasma treatment. The chemical composition, physical morphology, grafting structure, surface hydrophilicity, and hydration capability of prepared membranes were determined to illustrate the correlations between grafting qualities and hemocompatibility of PEGylated PVDF membranes in contact with human blood. Plasma protein adsorption onto different PEGylated PVDF membranes from single-protein solutions and the complex medium of 100% human plasma were measured by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. Hemocompatibility of the PEGylated membranes was evaluated by the antifouling property of platelet adhesion observed by scanning electron microscopy (SEM) and the anticoagulant activity of the blood coagulant determined by testing plasma-clotting time. The control of grafting structures of PEGylated layers highly regulates the PVDF membrane to resist the adsorption of plasma proteins, the adhesion of platelets, and the coagulation of human plasma. It was found that PVDF membranes grafted with brush-like PEGylated layers presented higher hydration capability with binding water molecules than with network-like PEGylated layers to improve the hemocompatible character of plasma protein and blood platelet resistance in human blood. This work suggests that the hemocompatible nature of grafted PEGylated polymers by controlling grafting structures gives them great potential in the molecular design of antithrombogenic membranes for use in human blood.