Biofouling-resistance expanded poly(tetrafluoroethylene) membrane with a hydrogel-like layer of surface-immobilized poly(ethylene glycol) methacrylate for human plasma protein repulsions

In general, it is a challenge to control the highly polar material grafting from the chemically inert Teflon-based membrane surface. This work describes the surface modification and characterization of expanded poly(tetrafluoroethylene) (ePTFE) membranes grafted with poly(ethylene glycol) methacrylate (PEGMA) macromonomer via surface-activated plasma treatment and thermally induced graft copolymerization. The chemical composition and microstructure of the surface-modified ePTFE membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), contact angle, and bio-atomic force microscopy (bio-AFM) measurements. Biofouling property of the modified membranes was evaluated by the measurements of the plasma protein (γ-globulin, fibrinogen, or albumin) adsorption determined using an enzyme-linked immunosorbent assay (ELISA). In general, the hydrophilicity of the surface of ePTFE membranes increases with increasing the grafting degree of the copolymerized PEGMA. The highly hydrated PEGMA chain on the resulting ePTFE membranes was found to form a surface hydrogel-like layer with regulated coverage in aqueous state, which can be controlled by the content of PEGMA macromonomer in the reaction solution. The relative protein adsorption was effectively reduced with increasing capacity of the hydration for the PEGMA chain grafted on the ePTFE membrane surface. From both results of protein adsorption and platelet adhesion test in vitro, it is concluded that the PEGMA-grafted hydrophilic ePTFE membranes could provide good biofouling resistance to substantially reduce plasma protein and blood platelet fouling on the membrane surface in human body temperature.     

Improvement of hemocompatibility of polycaprolactone film surfaces with zwitterionic polymer brushes

Polycaprolactone (PCL) has been widely adopted as a scaffold biomaterial, but further improvement of the hemocompatibility of a PCL film surface is still needed for wide biomedical applications. In this work, the PCL film surface was functionalized with zwitterionic poly(3-dimethyl(methacryloyloxyethyl) ammonium propane sulfonate) (P(DMAPS)) brushes via surface-initiated atom transfer radical polymerization (ATRP) for enhancing hemocompatibility. Kinetics study revealed an approximately linear increase in graft yield of the functional P(DMAPS) brushes with polymerization time. The blood compatibilities of the modified PCL film surfaces were studied by platelet adhesion tests of platelet-rich plasma and human whole blood, hemolysis assay, and plasma recalcification time (PRT) assay. The improvement of hemocompatibility is dependent on the coverage of the grafted P(DMAPS) brushes on the PCL film. Lower or no platelet and blood cell adhesion was observed on the P(DMAPS)-grafted film surfaces. The P(DMAPS) grafting can further decrease hemolysis and enhance the PRT of the PCL surface. With the versatility of surface-initiated ATRP and the excellent hemocompatibility of zwitterionic polymer brushes, PCL films with desirable blood properties can be readily tailored to cater to various biomedical applications.     

Biofunctionalization of titanium with PEG and anti-CD34 for hemocompatibility and stimulated endothelialization

Thrombosis and restenosis are the main causes of failure of cardiovascular and other blood-contacting biomedical devices. It is recognized that rapid endothelialization is a promising method for preventing these complications. Convincing evidence in vivo has further emerged that the vascular homing of endothelial progenitor cells (EPCs) contributes to rapid endothelial regeneration. This study deals with improving the hemocompatibility and enhancing EPC colonization of titanium by covalently bonding PEG(600) or PEG(4000), then end-grafting of an anti-CD34 antibody. For this, a chemically hydroxylated titanium surface was aminosilanized, which was further used for covalent grafting of polyethylene glycol and the antibody. The grafting efficiency was verified in each step. In vitro platelet adhesion analysis confirmed superior hemocompatibility of the modified surface over the control. Affinity of EPC to the surface and inhibition of smooth muscle cell adhesion, two prerequisites for endothelialization, are demonstrated in in vitro cell culture. While the coating selectively stimulates EPC adhesion, its antifouling properties prevent formation of an extracellular matrix and proliferation of the cells. Additional affinity for matrix proteins in the coating is considered for further studies. Potent inhibitory effect on macrophage activation and the relative stability of the coating render this technique applicable.     

Blood compatibility of polyurethane surface grafted copolymerization with sulfobetaine monomer

Surface modification is an effective way to improve the hemocompatibility and remain bulk properties of biomaterials. Recently, polymer tailed with zwitterions was found having good blood compatibility. In this study, the grafting copolymerization of sulfobetaine onto polyurethane surface was obtained through two steps. In the first step, polyurethane film coupled with vinyl groups was obtained through the reaction between the carboxyl group of acrylic acid (AA) and the NH-urethane group of polyurethane by dicyclohexylcarbodiimide (DCC). In the second step, sulfobetaine was grafted copolymerization on the surface using AIBN as an initiator. The reaction process was monitored with ATR-IR spectra and X-ray photoelectron spectroscopy (XPS) spectra. The wettability of films was investigated by water contact angle measurement. The blood compatibility of the grafted films was evaluated by platelet adhesion in platelet rich plasma (PRP) and protein absorption in bovine fibrinogen (BFG). Low platelet adhesion was observed on the grafted films incubated in PRP for 1 and 3 h, respectively. The protein absorption was reduced on the grafted films after incubated in bovine fibrinogen for 2 h. All of these results revealed that the improved blood compatibility was obtained by grafting copolymerization with zwitterionic monomer of sulfobetaine onto polyurethane film. In addition, introducing vinyl groups onto surface through DCC and AA is a novel method to functionalize polyurethane for further modification.     

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.     

Surface modification of polycarbonate urethane by grafting polyethylene glycol and bivalirudin drug for improving hemocompatibility

As the clinical demand for blood-contacting materials increases, higher requirements are placed on their physicochemical properties, durability and hemocompatibility in vivo. In this work, a multiple functionalized material was developed through a facile modification process. Herein, polycarbonate urethane (PCU) surface was co-modified with polyethylene glycol (PEG) and bivalirudin (BVLD). PCU provides excellent physical and mechanical properties, PEG and BVLD, especially BVLD, enable the surface with outstanding anticoagulant capacity. Specifically, PCU surface was first treated with hexamethylene diisocyanate to introduce active isocyanate groups onto the surface, followed by hydroxy-PEG grafting to improve the hydrophilicity. Finally, BVLD was immobilized on the surface via Michael addition reaction to improve antithrombotic properties. Attenuated total reflection Fourier transforms infrared spectroscopy and UV spectrophotometers were used to confirm the modified surfaces. The hydrophilicity was characterized by static water contact angle measurement, the morphology of the modified surfaces was observed by scanning electron microscopy. Blood compatibility of the modified surfaces was characterized by the hemolysis rate, platelet adhesion assay and cell culture test. The results showed that the BVLD immobilized surface has excellent anticoagulant properties, good fibrin-bound thrombin inhibition, and good resistance against non-specific adhesion of proteins. Hence, the co-modification with PEG and BVLD was proved an encouraging strategy for improving hemocompatibility.     

Polyurethane vascular catheter surface grafted with zwitterionic sulfobetaine monomer activated by ozone

Polyurethane (PU) is a conventional biomedical material with favorable biocompatibility and excellent mechanical properties and widely used in making vascular catheter, but its antithrombogenic property is not good enough to make it as a more demanding applicable biomaterial. Surface modification is an effective way to improve the hemocompatibility for biomaterials. The purpose of present study was to use ozonization method to modify the surface of PU vascular catheter slice to improve its antithrombogenicity by grafting N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl) ammonium (DMMSA), a zwitterionic sulfobetaine monomer. PU vascular catheter (PUVC) grafted with DMMSA (PUVC-g-PDMMSA) was characterized by ATR-FTIR and XPS. ATR-FTIR and XPS investigation confirmed the graft polymerization. The blood compatibility of the grafted films was evaluated by platelet rich plasma (PRP) platelet adhesion study and scanning electron microscopy (SEM) was used to observe the morphology of platelet using PU vascular catheter (PUVC) as the reference. No platelet adhesion was observed for the grafted PUVC slice incubated with PRP at 37 degrees C for 120 min. It is significant that this new zwitterionic sulfobetaine grafted PUVC have improved antithrobogenicity. It is effective that the inner surface of vascular catheter with inner diameter in only 3mm can be grafted with PDMMSA by using ozonization method.     

Cell outer membrane mimetic modification of a cross-linked chitosan surface to improve its hemocompatibility

A novel strategy has been developed to improve the hemocompatibility of chitosan surface by cell outer membrane mimetic structure able to reduce protein adsorption and cell adhesion. Phosphorylcholine dichloride was synthesized and grafted onto a glutaraldehyde-cross-linked chitosan (CS-GA) film surface to prepare phosphorylcholine-coated CS-GA film (CS-GA-PC) through a heterogeneous reaction process. The spectroscopic and contact angle characterization show that a cell outer membrane mimetic structure was formed on the cross-linked chitosan surface, and the significantly improved hemocompatibility of the modified surface was shown by a suppression of 94% on platelet adhesion, a suppression of 60–70% for bovine plasma fibrinogen and bovine serum albumin adsorptions. These results demonstrated that this cell outer membrane mimetic surface modification with phosphorylcholine dichloride is a promising strategy to improve the hemocompatibility of chitosan.     

Various approaches to modify biomaterial surfaces for improving hemocompatibility

In this paper, the mechanism of thrombus formation on the surface of polymeric materials and the various approaches of modifying biomaterial surfaces to improve their hemocompatibility are reviewed. Moreover, the blood compatibility of the cellulose membrane grafted with O-butyrylchitosan (OBCS) by using a radiation grafting technique was studied. Surface analysis of grafted cellulose membrane was verified by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and electron spectroscopy for chemical analysis (ESCA), which confirmed that OBCS was successfully grafted onto the cellulose membrane surfaces. Blood compatibility of the grafted cellulose membranes was evaluated by platelet rich plasma (PRP) contacting experiments and protein adsorption experiments using blank cellulose membranes as the control. The blood compatibility of OBCS grafted cellulose membranes is better than that of blank cellulose membranes. These results suggest that the photocrosslinkable chitosan developed here has the potential of serving in blood-contacting applications in medical use.     

Synthesis and characterization of poly(2‐methacryloyloxyethyl phosphorylcholine) onto graphene oxide

The polyzwitterionic brushes comprised of poly(2‐methacryloyloxyethyl phosphorylcholine) (pMPC) segments, which are used for surface modification of polymers and biocompatible coatings, were investigated. In this work, reverse surface‐initiated atom transfer radical polymerization (RATRP) of zwitterionic 2‐methacryloyloxyethyl phosphorylcholine (MPC) is employed to tailor the functionality of graphene oxide (GeneO) in a well‐controlled manner and produce a series of well‐defined hemocompatible hybrids (termed as GeneO‐g‐pMPC). The complexes were characterized by FT‐IR, XRD, and Raman. Results show that MPC has been coordinated on the graphene oxide sheet. Thermal stability of the nanocomposites in comparison with the neat copolymer is revealed by thermogravimetric analysis and differential thermal analysis. Scanning electron microscopy and transmission electron microscope images of the nanoconposite displays pMPC chains were capable of existing on GeneO sheet by RATRP. The biocompatibility properties were measured by plasma recalcification profile tests, hemolysis test, and MTT assays, respectively. The results confirm that the pMPC grafting can substantially enhance the hemocompatibility of the GeneO particles, and the GeneO‐g‐pMPC hybrids can be used as biomaterials without causing any hemolysis. With the versatility of RATRP and the excellent hemocompatibility of zwitterionic polymer chains, the GeneO‐g‐pMPC nanoparticles with desirable blood properties can be readily tailored to cater to various biomedical applications. Copyright © 2013 John Wiley & Sons, Ltd.     

In-vitro hemocompatibility evaluation of a thermoplastic polyurethane membrane with surface-immobilized water-soluble chitosan and heparin

The surface of a thermoplastic polyurethane (TPU) membrane was treated with low temperature plasma (LTP) and was then grafted with poly(acrylic acid) (PAA), followed by the grafting of water-soluble chitosan (WSC) and heparin (HEP). The surface was characterized with static contact-angle and X-ray photoelectron spectroscopy (XPS). The results showed that the surface densities of peroxides and PAA reached a maximum when treated with LTP for 90 s. A higher pH of the reacting solution led to higher graft densities of WSC and HEP. After WSC and HEP grafting, the hydrophilicity of the TPU membrane was increased. The adsorption of proteins on HEP-grafted TPU membranes was effectively curtailed. In addition, HEP grafting also reduced platelet adhesion, elevated thrombin inactivation, and prolonged the blood coagulation time. According to the L929 fibroblast cell growth inhibition index, the HEP-grafted TPU membranes exhibited non-cytotoxicity. Overall results demonstrated that the HEP immobilization could not only improve the hydrophilicity but also the hemocompatibility of the TPU membrane, while maintaining the ascendant biocompatibility.     

生物医用磷脂化聚氨酯的设计、制备与性能

聚氨酯因其具有优异的力学性能和良好的生物相容性广泛地应用于医疗领域.但医用聚氨酯常常会引起蛋白吸附、血小板激活、凝血、血栓和补体激活等不良生物学反应,使其应用受到限制.仿生物膜的磷脂表面被认为是和人体最亲和的表面,聚氨酯磷脂化是提高医用聚氨酯材料生物相容性的非常有效的手段之一.近年来国内外课题组在生物医用磷脂化聚氨酯的设计、制备与生物相容性等方面开展了大量的工作,取得了重要的研究进展.本文综述了磷脂改进医用聚氨酯的最新研究成果,指出含氟磷脂化聚氨酯和可降解的磷脂聚氨酯因其优异的性能,代表了该领域的发展方向并具有重要的应用前景.     

Biofunctionalized Electrospun PCL‐PIBMD/SF Vascular Grafts with PEG and Cell‐Adhesive Peptides for Endothelialization

Artificial small‐caliber vascular grafts are still limited in clinical application because of thrombosis, restenosis, and occlusion. Herein, a small‐caliber vascular graft (diameter 2 mm) is fabricated from poly(ε‐caprolactone)‐b‐poly(isobutyl‐morpholine‐2,5‐dione) (PCL‐PIBMD) and silk fibroin (SF) by electrospinning technology and then biofunctionalized with low‐fouling poly(ethylene glycol) (PEG) and two cell‐adhesive peptide sequences (CREDVW and CAGW) with the purpose of enhancing antithrombogenic activity and endothelialization. The successful grafting of PEG and peptide sequences is confirmed by X‐ray photoelectron spectroscopy. The suitable surface wettability of the modified vascular graft is testified by water contact angle analysis. The surface hemocompatibility is verified by platelet adhesion assays and protein adsorption assays, and the results demonstrate that both platelet adhesion and protein adsorption on the biofunctionalized surface are significantly reduced. In vitro studies demonstrate that the biofunctionalized surface with suitable hydrophilicity and cell‐adhesive peptides can selectively promote the adhesion, spreading, and proliferation of human umbilical vein endothelial cells. More importantly, compared with control groups, this biofunctionalized small‐caliber vascular graft shows high long‐term patency and endothelialization after 10 weeks of implantation. The biofunctionalization with PEG and two cell‐adhesive peptide sequences is an effective method to improve the endothelialization and long‐term performance of synthetic vascular grafts.     

层层组装构建抗凝血和内皮细胞化协同功能界面

本文采用天然细胞外基质组分、强抗凝血活性的肝素和促细胞黏附生长的胶原蛋白, 在不锈钢支架表面构建肝素/胶原多层膜, 探索利用层层组装多层膜所显示出的协同效应, 实现抗凝血和促进内皮细胞生长的协同功能, 为改善心血管支架抗凝血和抗再狭窄修饰寻求新方法.     

Development of lauroyl sulfated chitosan for enhancing hemocompatibility of chitosan

Chitosan (CS) has received much attention as a functional biopolymer especially in pharmaceutical applications, but has serious limitations owing to its poor hemo-compatibility property. Present paper focuses on the chemical modification of CS in order to enhance hemocompatibility. Amphiphilic derivative (lauroyl sulfated chitosan, LSCS) was prepared by the inclusion of sulfo group (hydrophilic) and lauroyl group (hydrophobic) to CS backbone and particles were prepared by an ionic-gellation approach. Modification was confirmed by FTIR, NMR and zeta potential measurements and the microparticles were evaluated for its particle size, swelling properties and thermal behaviour. Blood compatibility studies like hemolysis, RBC, WBC, platelet aggregation studies, blood clotting time, protein adsorption and C3 protein depletion assay were carried out for these polymers using standard techniques and cytotoxicity studies were performed to understand its applicability. Negatively charged (-6.06 mV) LSCS submicroparticles (886 nm) were prepared in this study. Blood compatibility studies demonstrated that the amphiphilic modification improved the hemocompatibility of CS. RBC aggregation and hemolysis induced by CS were significantly reduced by this modification. Further amphiphilic modification was effective in reducing the protein adsorption on CS. LSCS derivatives were found to be non-toxic in L929 cell lines. From these studies, it appears that LSCS is a hemocompatible version of CS.     

Effect of conjugated linoleic acid immobilization on the hemocompatibility of cellulose acetate membrane

Conjugated linoleic acid (CLA) was covalently immobilized onto cellulose acetate (CA) membranes. The effects of CLA immobilization on the blood coagulation, platelet aggregation, and oxidative stress were evaluated using human blood. The resulting CLA grafting CA membranes were characterized with X-ray photoelectronic spectroscopy (XPS). The complete blood count (CBC) and coagulation time (CT) was evaluated in vitro for the hemocompatibility. Human serum albumin (HSA) and human plasma fibrinogen (HPF) was evaluated for the protein affinity. The production of reactive oxygen species (ROS) was measured by chemiluminescence (CL) method to evaluate the oxidative stress. The results showed that the CLA-immobilizing CA membrane could keep the CBC values more stable than unmodified CA membrane. The CLA-immobilized CA membranes also showed longer CT and less adsorption of plasma proteins. CLA-immobilized CA membrane could keep the CL counts of hydrogen peroxide and superoxide values more stable than unmodified CA membrane. These results suggest that a CLA-immobilized CA membrane could offer protection for patients against oxidative stress and would be helpful for reducing the dosage of anticoagulant during hemodialysis.     

In vitro study of a HPγ-cyclodextrin grafted PET vascular prosthesis for application as anti-infectious drug delivery system

Hydroxypropyl-γ-cyclodextrin (HPγ-CD) was grafted onto woven polyester (PET) vascular prosthesis by using citric acid (CTR) as crosslinking agent. A polyCTR-HPγ CD polymer was physically fixed onto the PET fibers. An optimal compromise between fixation temperature and fixation time was found and a grafting rate of 6.7% was obtained. The study of the inclusion of ciprofloxacin (CFX) and HPγ-CD was evidenced by using spectrophotometry. Sorption tests also showed that modified prosthesis could adsorb 5 times more CFX than the control. Biological tests revealed proliferation rates of human pulmonary micro-vascular endothelial cells (HPMEC) of 73 and 48% on virgin and modified prostheses respectively. We demonstrated that this was rather due to the increase of surface roughness of the fibers after their modification than to a toxic effect the polyCTR-HPγCD polymer coating. Prostheses samples modified with HPγCD and impregnated with CFX stayed up to 24 h in blood plasma. At various moments some aliquots were withdrawn from the medium and a positive antibacterial activity against Staphylococcus epidermidis was observed within the 24 h period for the grafted sample, whilst that of the virgin one had disappeared within 4 h. So, cyclodextrin coating of vascular prostheses may be suitable for the controlled release of CFX, and thus should help to the prevention of post surgery complications.     

Design, synthesis and evaluation of graftable thrombin inhibitors for the preparation of blood-compatible polymer materials

Piperazinyl-amide derivatives of N-alpha-(3-trifluoromethyl-benzenesulfonyl)-L-arginine (1) were synthesized as graftable thrombin inhibitors. The possible disturbance of biological activity due to a variable spacer-arm fixed on the N-4 piperazinyl position was evaluated in vitro, against human alpha-thrombin, and in blood coagulation assay. Molecular modelling (in silico analysis) and X-ray diffraction studies of thrombin-inhibitor complexes were also performed. The fixation of bioactive molecules on poly(butylene terephthalate) (PBT) and poly(ethylene terephthalate) (PET) membranes was performed by wet chemistry treatment and evaluated by XPS analysis. Surface grafting of inhibitor 1d improved the membrane hemocompatibility by reducing blood clot formation on the modified surface.     

Blood compatibility of surface modified Si incorporated carbon nanotubes film

There is an increasing interest in developing novel film to improve the biocompatibility of cardiovascular implants. In this study, carbon nanotubes (CNT) film was synthesized by on the Si wafers using thermal chemical vapor deposition. The structure, surface properties as well as surface biomedical compatibility were evaluated using different characterization techniques. The contact angles of water on Si, stainless steel and CNT film were 33.7°, 72.4° and 105.1°, respectively. In vitro platelet adhesion experimental results demonstrated that the CNT film significantly reduced thrombogenicity by minimizing the platelet adhesion, activation and aggregation, compared to Si wafer and 316L stainless steel. The hydrophobic properties were determined to be factor contributing to the improved haemocompatibility.     

Influence of Plasma Treatments on the Hemocompatibility of PET and PET + TiO<Subscript>2</Subscript> Films

A dielectric barrier discharge (DBD) in helium was used to ameliorate the interface between the blood and the surface of polymeric implants: polyethylene terephthalate (PET) and PET with titanium oxide (PET + TiO₂). A higher crystallinity degree was found for the DBD treated samples. The wettability of polymers was improved after the treatment. The chemical composition, analyzed by infrared spectroscopy was preserved during the DBD treatment. The surface modifications have been correlated with polymers hemocompatibility. Concerning the polymer surface–blood interaction, the treatment induced a decrease of the interfacial tension between the blood components and the treated surfaces. The in vitro tests of hemocompatibility showed no perturbation in the blood composition when the polymer samples are present in the blood volume. An interesting result is related to the whole blood clotting time that shows a dramatic increase on the treated surfaces. Moreover, the coagulation kinetics on the treated surfaces is modified.