Modification of polysulfone with phospholipid polymer for improvement of the blood compatibility. Part 2. Protein adsorption and platelet adhesion.

Protein adsorption and platelet adhesion from human plasma on polysulfone (PSf) membranes modified with 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer were studied. The modification was carried out by blending of the MPC polymer in the PSf. The amount of protein adsorbed on the PSf/MPC polymer blend membrane was significantly decreased with an increase in the composition of the blended MPC polymer. The distribution of the specific proteins adsorbed on the membrane surface was also determined by a gold-colloid immunoassay. Albumin, gamma-globulin and fibrinogen were observed on every membrane surface after contact with plasma. However, in the case of the blended membrane, the density of the adsorbed proteins decreased compared with that of original PSf membrane. That is, the MPC polymer blended in the membrane could function as a protein-adsorption-resistant additive. The number of platelets adhered on the PSf membrane was reduced, and change in the morphology of adherent platelets was also suppressed by the modification with the MPC polymer. Therefore, the PSf/MPC polymer blend membrane had improved blood compatibility compared with the PSf membrane.     

Improvement of blood compatibility on cellulose dialysis membrane. 2. Blood compatibility of phospholipid polymer grafted cellulose membrane.

The blood compatibility of a cellulose haemodialysis membrane whose surface was grafted with a methacrylate having a phospholipid polar group, 2-methacryloyloxyethyl phosphorylcholine, was evaluated with attention to platelet adhesion to the membrane surface and complement activation induced by the membrane. When the original cellulose membrane came in contact with platelet-rich plasma for 30 min, numerous platelets adhered to the surface and aggregated. On the other hand, the membrane grafted with 2-methacryloyloxyethyl phosphorylcholine effectively suppressed platelet adhesion and activation. This effect became more pronounced with increasing surface distribution. Especially, the 2-methacryloyloxyethyl phosphorylcholine grafted membranes, whose distribution exceeded 0.27, completely inhibited platelet adhesion, even when the contact time was 180 min. Moreover, the complement activation was also reduced with increased 2-methacryloyloxyethyl phosphorylcholine distribution on the surface of the membrane.     

Physical properties and blood compatibility of surface-modified segmented polyurethane by semi-interpenetrating polymer networks with a phospholipid polymer

Segmented polyurethanes, (SPU)s, are widely used in the biomedical fields because of their excellent mechanical property. However, when blood is in contact with the SPU, non-specific biofouling on the SPU occurs which reduces its mechanical property. To obtain novel blood compatible elastomers, the surface of the SPU was modified with 2-methacryloyloxyethyl phosphorylcholine (MPC) by forming a semi-interpenetrating polymer network (semi-IPN). The SPU film modified by MPC polymer with the semi-IPN (MS-IPN film) was prepared by visible light irradiation of the SPU film in which the monomers were diffused. X-ray photoelectron spectroscopy confirmed that the MPC units were exposed on the MS-IPN film surface. The mechanical properties of the MS-IPN film characterized by tensile testing were similar to those of the SPU film. Platelet adhesion on MS-IPN films was also investigated before and after stress loading to determine the effects of the surface modification on the blood compatibility. Many platelets did adhere on the SPU film before and after stress loading. On the other hand, the MS-IPN film prevented platelet adhesion even after repeated stress loading.     

Surface modification of polymeric biomaterials: utilization of cyclodextrins for blood compatibility improvement

A novel modified polymeric biomaterial surface using cyclodextrins (CDs) for improved blood compatibility was studied. Plasticized poly(vinyl chloride) (PVC-P) was selected for modification and polyethylene was used as a reference material. The modification was achieved by polymer blending. Fibrinogen and albumin adsorption were utilized as indices for the assessment of the blood compatibility. Surface characterization confirmed that CDs were able to accumulate at the PVC surface and alter the surface properties. The combination of other hydrophilic polymers such as poly(ethylene oxide) (PEO) and PEO/poly(propylene oxide) (PPO) copolymers, such as Pluronic F68 (F68), with CDs were also investigated. These modified materials have a remarkable protein-resistant surface. The combination of B-cyclodextrin (B-CD)/PEO and B-CD/F68 in certain feeding ratio are synergistic in producing enhanced blood compatibility.     

Chemically modified polysulfone hollow fibers with vinylpyrrolidone having improved blood compatibility

Hydrophilic polysulfone membranes (PVP-PSf) were prepared from polysulfone membranes covalently conjugated with polyvinylpyrrolidone (PVP) on the surface. The immobilized amount of vinylpyrrolidone on PVP-PSf membranes was controlled by the amount of vinylpyrrolidone monomer in the reaction solution and the reaction time. The PVP-PSf membranes were found to be the most hydrophilic membranes among the polysulfone and surface-modified polysulfone membranes prepared in this study. This is explained by the long hydrophilic side chain of polyvinylpyrrolidone on the PVP-PSf membranes which contributes to the hydrophilic wiper on the hydrophobic PSf membranes. It was found that PVP-PSf membranes gave lower protein adsorption from a plasma solution than polysulfone and other surface-modified membranes (p < 0.01). This is attributed to the hydrophilic surface of the PVP-PSf membranes, because the hydrophilic surface is known to reduce the protein adsorption on the membranes. The PVP-PSf membranes showed a much suppressed number of adhering platelets on the surface than polysulfone and other surface-modified membranes (p < 0.01). It is suggested that the hydrophilic surface of the PVP-PSf membranes without ionic groups causes the suppression of platelet adhesion on the PVP-PSf membranes and that the long hydrophilic side chain of polyvinylpyrrolidone on PVP-PSf membranes contributes to the hydrophilic and hemocompatible wipers on the surface of the hydrophobic PSf membranes.     

Behavior of blood cells in contact with water-soluble phospholipid polymer.

Omega-Methacryloyloxyalkyl phosphorylcholine (MAPC) polymer, which has various methylene chain lengths between the phosphorylcholine group and the backbone, was synthesized with attention to formation of the biomembrane. The effect of water-soluble poly(MAPC) on the function and activation of blood cells was evaluated to determine the interaction between blood cells and the MAPC polymer. The poly(MAPC) and the MAPC copolymer with a small amount of fluorescent units were synthesized by a conventional radical polymerization technique. Using a fluorescence spectrometer, it was determined that the MAPC polymer was adsorbed on the plasma membrane of platelets when the platelets were suspended in an aqueous solution of the MAPC copolymer. The hemolytic activity of poly(MAPC) was less than that of other water-soluble polymers, such as poly(ethylene glycol) and poly(1-vinyl-2-pyrrolidone) (PVPy). The change in the plasma membrane fluidity of platelets on contact with poly(MAPC) was determined with 1,6-diphenyl-1,3,5,-hexatriene. The plasma membrane fluidity of platelets decreased with an increase in the methylene chain length of the MAPC unit. The aggregation activity of platelets after contact with poly(MAPC) was also evaluated, but no significant difference between that of polymer-contacted platelets and native platelets was observed. Finally, the activity of platelets on contact with poly(MAPC) was determined by measuring the cytoplasmic calcium ion concentration ([Ca2+]i) in platelets. The increase in [Ca2+]i in the platelets after contact with poly(MAPC) was similar to that of native platelets. We conclude that the poly(MAPC) reduced platelet activation even though the poly(MAPC) adsorbed on the membrane surface of the platelets. In particular, poly(10-methacryloyloxydecyl phosphorylcholine) significantly reduced platelet activation compared with PVPy.     

Surface modification of tricalcium phosphate for improvement of the interfacial compatibility with biodegradable polymers

The surface of tricalcium phosphate (TCP) filler particles was activated by treatment with dilute aqueous phosphoric acid. ATR-IR spectra indicated the formation of calcium hydrogen phosphate dihydrate at the surface. Oligo(lactone)s were formed by the subsequent reaction of the activated TCP with L-lactide and epsilon -caprolactone, respectively, at 150 degrees C without any additional catalysts. After extraction of the oligo(lactide), the residue of modified TCP-included calcium lactate whereas the water of crystallization of the dihydrate disappeared as shown by ATR-IR spectroscopy.Owing to the insolubility of TCP in common solvents, the analogous reaction between water-soluble disodium hydrogen phosphate dihydrate and L-lactide was used to study the kind of chemical bonds by high-resolution NMR spectroscopy. The 1H and 13C NMR spectra of the reaction product also pointed out the presence of calcium lactate. Additionally, signals were found indicating a covalent attachment of lactic acid units onto the phosphorus.For the preparation of composites, poly(L,DL-lactide) was mixed with TCP and modified TCP, respectively, in a ratio of 75/25 (w/w) and directly injection moulded into tensile test specimens at a barrel temperature of 180 degrees C. Although mechanical properties were not improved, scanning electron microscopy (SEM) indicated a better interfacial phase interaction in the composite with the modified TCP. Chemical bonds between filler and polymer matrix are assumed to be formed by transesterification reactions.     

Effect of methylene chain length in phospholipid moiety on blood compatibility of phospholipid polymers

To investigate the effects of the methylene chain length between the phospholipid polar group and the backbone on blood compatibility of a phospholipid polymer, copolymers of ω-methacryloyloxyalkyl phosphorylcholine (MAPC) with n-butyl methacrylate (BMA) were synthesized. The methylene chains were ethylene (n = 2), tetramethylene (n = 4), and hexamethylene (n = 6). Every MAPC copolymer with an MAPC mole fraction in the range of 0.1-0.3 was soluble in ethanol but only swelled in water, and the equilibrium water fraction of the water-swollen MAPC copolymer membrane decreased with the length of the methylene chain. When a rabbit platelet-rich plasma was applied on the MAPC copolymer surface with an 0.1 MAPC mol fraction for 180 min, the number of adhered platelets depended on the length of the methylene chain in the MAPC moiety of the copolymer. The amount of phospholipid adsorbed on the MAPC copolymer from human plasma was larger than that on hydrophobic poly(BMA) and increased with the length of the methylene chain in the MAPC moiety. That is, the reduction of platelet adhesion corresponded to the increase in the amount of phospholipid adsorbed on the MAPC copolymer.     

血液相容性抗凝血生物医用高分子材料的制备及其机制

背景:由于生物医用材料要接触人体内环境,甚至必须植入生物体内,因此要求具有无毒性、优良的生物相容性、高化学稳定性、合适的物理机械性能以及易加工成型性。 目的：从生物惰性材料、生物活性表面和白蛋白的结构及其在抗凝血上的应用几个方面分析血液相容性抗凝血生物医用高分子材料的制备及其机制。 方法：由第一作者检索1969/2010 PubMed数据及万方数据库有关血液相容性抗凝血生物医用高分子材料的制备及其机制等方面的文献。 结果与结论：目前抗凝血材料的制备基本上只是采用单独的生物惰性表面或生物活性表面,虽然都获得了较好效果,但不能长期保持其生物相容性尤其是血液相容性,如果能将惰性表面与活性表面结合起来,使材料同时具备两者的长处,并能充分利用人体血液中的天然组分白蛋白或许会是抗凝血材料的一个发展趋势。今后希望通过采用高生物惰性的PEU和具有生物活性的白蛋白识别因子cibacron blue复合,合成具有优良性质的活性改性物,并以此对聚氨酯进行改性。     

Surface properties and blood compatibility of polyurethaneureas

A series of polyurethaneureas of varying soft segment type and hard/soft segment ratio were synthesized, and their bulk and surface properties evaluated. A canine ex vivo arteriovenous series shunt was used to monitor initial thrombus deposition. Significant levels of surface hard segment components are apparent in these materials. Polymers with poly(tetramethylene oxide) and poly(propylene oxide) soft segments showed blood compatibility variations with changes in hard/soft segment ratios: the more well-phase-separated materials showing lower platelet and fibrinogen deposition levels. Those trends apparent in polymers synthesized with poly(dimethylsiloxane) or poly(ethylene oxide) soft segments, but poly(dimethylsiloxane)-based materials showed higher levels of thrombus deposition than the poly(ethylene oxide)-based polymers.     

Preparation and performance of protein-adsorption-resistant asymmetric porous membrane composed of polysulfone/phospholipid polymer blend

To obtain protein-adsorption-resistant membrane for hemodialysis, we prepared a polymer blend composed of polysulfone and 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer (PSf/MPC polymer). The content of the MPC polymer in the PSf was 7 and 15 wt%. The asymmetric porous membrane was obtained by the dry/wet membrane processing method. The surface characterization of the PSf/MPC polymer membrane by X-ray photoelectron spectroscopy revealed that the MPC polymer located at the surface. The mechanical strength of the PSf/MPC polymer membrane did not change compared with that of the PSf membrane. On the other hand, the permeability of solute below a molecular weight (Mw) of 2.0 x 10(4) through the PSf membrane increased with the addition of the MPC polymer, which is considered to be an effect of the hydrophilic character of the MPC polymer. The amount of protein adsorbed on the PSf membrane from plasma was reduced by the addition of the MPC polymer. The permeability of low-molecular-weight protein (Mw = 1.2 x 10(4)) did not change even after the PSf/MPC polymer membrane was contacted with plasma protein solution for 4 h, whereas it decreased dramatically in the case of the PSf membrane. Platelet adhesion was also effectively suppressed on the PSf/MPC polymer membrane. Based on these results, the MPC polymer could serve as a doubly functional polymeric additive, that is, to generate a protein-adsorption-resistant characteristic and to render the membrane hydrophilic.     

Surface characteristics and blood compatibility of polyurethanes grafted by perfluoroalkyl chains.

Polyurethane (PU) surface was chemically modified by grafting of perfluorodecanoic acid (PFDA) to produce a highly hydrophobic surface to compare the blood compatability with hydrophilic poly(ethylene oxide) (PEO) grafted PUs. The advancing contact angle of modified PU-PFDA was increased up to 115 deg, while that of untreated PU was 86 deg. The PFDA grafted PU exhibited less adhesion and shape change of platelets than untreated PU, and the activated partial thromboplastin time (APTT) of PU-PFDA was considerably extended. The ex vivo occlusion time of untreated PU was only 50 min, but that of PFDA grafted PU was extended to 130 min, indicating that this hydrophobic surface is significantly blood compatible. It is interesting to find that the enhanced blood compatibility of very hydrophobic PU-PFDA was equivalent to hydrophilic PU-PEO.     

Surface modification of polycaprolactone membrane via layer-by-layer deposition for promoting blood compatibility

The polycaprolactone (PCL) membranes were successfully modified by deposition of chitosan/heparin multilayer via a simple electrostatic self-assembly method. To immobilize chitosan, a novel ternary polysaccharide derivate, chitosan-g-PCL-b-poly-(ethylene glycol) (PEG) was used coating on PCL film first, which resulted in the presence of positive charges onto PCL surface as the basis for following electrostatic self-assembly. The process of modification was monitored by X-ray photoelectron spectroscopy, static contact angle measurement, and atomic force microscopy. The chitosan-g-PCL-b-PEG/heparin complex immobilized on PCL surface presented it with increasing hydrophilicity and microphase separation structure. Then in vitro hemocompability experiments indicated that this multilayer deposition on PCL resisted the platelets adhesion and prolonged the plasma recalcification time effectively, relative to the untreated PCL. Such chitosan-g-PCL-b-PEG/heparin-modified PCL may have good potential for use in vascular tissue engineering.     

Surface modification of PBT nonwoven fabrics used for blood filtration and their blood compatibility study

Abstract It is necessary to remove residual leukocytes to prevent the blood transfusion-related adverse reactions. This paper describes a facile approach for the surface modification of commercial PBT nonwoven fabrics (PBTNF), used for blood filtration, followed by immobilizing polyvinylpyrrolidone (PVP). The whole blood filtration results revealed that the five types of PBTNF-PVPs' leucocytes retention rates and erythrocyte recovery rates increased to 96% and 92% compared with the untreated PBTNF. The blood compatibilities results indicated that PVP modified PBTNFs have good blood compatibility, suggesting that PVP-modified PBTNF is a very promising blood filter for selective removal of leukocytes.     

Surface characterization and platelet compatibility evaluation of surface-sulfonated chitosan membrane

The effect of various sulfonated derivatives of chitosan on platelet activation and blood coagulation was examined. The surface properties of artificial biomaterials have been thought as the key factors which mediate the interactions between the biological environment and biomaterial itself. In this study, the sulfonation was directly performed on the chitosan membrane surface. The chitosan membrane was surface-sulfonated by reactions with sulfur-pyridine trioxide complex (SO₃/pyridine) in H₂O solution and N,N-sulfur-dimethylformamide trioxide complex (SO₃/DMF) in DMF.Blood compatibility was evaluated by an in vitro platelet adhesion assay. The surface reaction of SO₃/pyridine in aqueous acid medium yields N,O-sulfated chitosan with cationic NH⁺ ₃ groups. After neutralization, this surface has been shown to induce a low degree of platelet adhesion and activation. When the surface-sulfonation is performed in an aqueous alkaline medium, although the degree of sulfonation is lower than the samples above, the N-sulfated chitosan significantly reduced the adhesion and activation of platelets. For the acidic SO₃/DMF reaction system, N,O-sulfated chitosan was obtained with a high extent of sulfonation and cationic NH3+groups. On this surface fully spread platelets and some platelet aggregates were found instead. This may be attributed to the ionic interactions between the platelets membrane surface and the cationic groups on the modified chitosan membrane.     

Surface characterization and platelet compatibility evaluation of surface-sulfonated chitosan membrane

The effect of various sulfonated derivatives of chitosan on platelet activation and blood coagulation was examined. The surface properties of artificial biomaterials have been thought as the key factors which mediate the interactions between the biological environment and biomaterial itself. In this study, the sulfonation was directly performed on the chitosan membrane surface. The chitosan membrane was surface-sulfonated by reactions with sulfur-pyridine trioxide complex (SO3/pyridine) in H2O solution and N,N-sulfur-dimethylformamide trioxide complex (SO3/DMF) in DMF. Blood compatibility was evaluated by an in vitro platelet adhesion assay. The surface reaction of SO3/pyridine in aqueous acid medium yields N,O-sulfated chitosan with cationic NH3+ groups. After neutralization, this surface has been shown to induce a low degree of platelet adhesion and activation. When the surface-sulfonation is performed in an aqueous alkaline medium, although the degree of sulfonation is lower than the samples above, the N-sulfated chitosan significantly reduced the adhesion and activation of platelets. For the acidic SO3/DMF reaction system, N,O-sulfated chitosan was obtained with a high extent of sulfonation and cationic NH3+ groups. On this surface fully spread platelets and some platelet aggregates were found instead. This may be attributed to the ionic interactions between the platelets membrane surface and the cationic groups on the modified chitosan membrane.     

Antifouling blood purification membrane composed of cellulose acetate and phospholipid polymer

The ideal surface of an artificial blood purification membrane needs hemocompatibility and durability of high performance; it should not adsorb any proteins or cells but should still have high permeability in the desired range of solute size. To improve the anti-fouling property of cellulose acetate (CA) membranes, a CA membrane blended with poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate (BMA)) (PMB30) was designed as a blood purification membrane. The polymer solutions for preparing the membrane were prepared using a solvent mixture composed of N, N-dimethylformamide, acetone, 2-propanol or water. The CA and CA/PMB30 blend membranes with an asymmetric and porous structure were prepared by a phase inversion process.The characteristics of the CA/PMB30 blend membrane, such as structural properties, mechanical properties, and solute permeability were examined with attention to changes in the preparation conditions of the membrane. The CA/PMB30 blend membrane had good water and solute permeability and a sharp molecular weight cut-off property. Moreover, the amount of proteins adsorbed on the CA/PMB30 blend membrane surface was less than that of the original CA membrane and a conventional polysulfone membrane. Adhesion and activation of platelets on the CA/PMB30 blend membrane were reduced compared with that on a CA membrane. In addition, the CA/PMB30 blend membrane showed good permselectivity and an antifouling property during a long time ultrafiltration experiment with protein solutions.