Blood-contacting Materials Research Articles

Improving blood-compatibility via surface heparin-immobilization based on a liquid crystalline matrix

Blood compatibility is of considerable importance in developing medical materials and devices that are in contact with blood. In this work, we successfully developed a novel liquid crystalline heparin-immobilized material (Hep-OPPC) by two-step modification for further improvement of hydrophilicity and hemocompatibility of the liquid crystalline hydroxypropyl cellulose ester (OPCL). The results showed that Hep-immobilization on the OPCL led to dramatic changes in the surface morphology and crystallinity, whereas, the Hep-OPPCs also maintained the liquid crystalline feature at room temperature after heparinization. Furthermore, the hemocompatibility of the Hep-OPPCs was markedly enhanced at low levels of hemolysis assay (HR) with unimpaired erythrocytomorphology, significantly lower concentrations of C3a in blood plasma and remarkable increases in plasma re-calcification time (PRT). This suggests that the heparinized surface could restrict the transformation of fibrinogen with less activation of the intrinsic coagulation system. Moreover, the activated partial thromboplastin time (APTT) and prothrombin time (PT) values of the Hep-OPPCs with low heparin density could also be prolonged in this study suggesting that the liquid crystal feature of the matrix might be blocking the clotting factors. We concluded that the heparin-immobilized liquid crystalline material has the potential to be used in blood-contact materials.

Biomimetic modification of silicone tubes using sodium nitrite-collagen immobilization accelerates endothelialization.

Biomimetic coatings to increase endothelialization of blood-contacting materials in biomedical devices are promising to improve the biocompatibility of these devices. Although a stable extracellular matrix protein coating on a biomaterial's surface is a prerequisite for endothelial cell attachment, it also stimulates platelet adhesion. Therefore, antithrombotic additives, such as nitric oxide donors, to a stable protein coating might lead to successful endothelialization of a material's surface. We aimed to test whether immobilized bioactive nitrite and acidified nitrite-generating sodium nitrite-collagen conjugate on silicone tubes enhances endothelialization by increasing the number of endothelial cells as well as growth hormone production and by decreasing platelet adhesion. Stable collagen immobilization on acrylic acid-grafted silicone tubes decreased the water contact angle from 102° to 56°. Initial 25 µM sodium nitrite in conjugate resulted in maximal growth hormone production (2.5-fold increase) and endothelial cell number (1.8-fold increase) after 2 days. A 95% confluent endothelial cell monolayer on sodium nitrite-collagen conjugate coating was obtained after 6 days. Maximum (2.7-fold) inhibition of platelet adhesion was reached with initial 500 µM sodium nitrite in conjugate. Our data showing that sodium nitrite-collagen conjugate coating with 25-50 µM sodium nitrite on silicone tubes increases the number of endothelial cells attached and inhibits platelet adhesion suggest that this coating is highly promising for use in blood-contacting parts of biomedical devices. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1311-1321, 2016.

Correlations of Materials Surface Properties with Biological Responses

More than 50 years have passed since it was first recognized that the surface properties, and predominantly the surface energies of materials controlled their interactions with all biological phases via their spontaneous acquisition of proteinaceous “conditioning films” of differing degrees of denaturation but usually of the same substances within any given system. This led to the understanding that useful engineering control of such interactions could thus be manifested through adjustments to those surface properties, giving significant control and utility to the biomaterials developer without requiring detailed discovery of the biological specifications of the components involved. Thus, effective selection of adhesive versus abhesive (non-stick, non-retention) outcomes for such useful appliances as dental implants versus substitute blood vessels, or water-resistant bonded structures versus clean, nontoxic ship bottoms is now facilitated with little biological background required. A historical overview is presented, followed by a brief survey of the forces involved and most useful analyses applied. Utility for blood-contacting materials is described in contrast to utility for bone- and tissue-contacting materials, demonstrating practical uses in controlling cell-surface interactions and preventing biofouling. New research directions being explored are noted, urging applications of this prior knowledge to replace the use of toxicants.

Blood compatibility comparison for polysulfone membranes modified by grafting block and random zwitterionic copolymers via surface-initiated ATRP

For blood-contacting materials, good blood compatibility, especially good anticoagulant property is of great importance. Zwitterionic polymers have been proved to be resistant to nonspecific protein adsorption and platelet adhesion; however, their anticoagulant property is always inadequate. In this study, two kinds of zwitterionic copolymers (sulfobetaine methacrylate and sodium p-styrene sulfonate random copolymer and block copolymer) with sulfonic groups were covalently grafted from polysulfone (PSf) membranes via surface-initiated atom transfer radical polymerization (SI-ATRP) to improve blood compatibility. Field emission scanning electron microscopy (FE-SEM), attenuated total reflectance–Fourier transform infrared spectra (ATR–FTIR), X-ray photoelectron spectroscopy (XPS), and static water contact angle (WCA) were applied to characterize the morphologies, chemical compositions and hydrophilicity of the modified membranes. All the zwitterionic copolymer modified membranes showed improved blood compatibility, especially the anticoagulant property was obviously enhanced compared to the pristine PSf and simple zwitterionic polymer modified membranes. We also found that the random copolymer modified membranes showed better resistance to platelet adhesion than the block copolymer modified membranes. The zwitterionic copolymer modified membranes with integrated antifouling property and blood compatibility provided wide choice for specific applications such as hemodialysis, hemofiltration, and plasma separation.

Real time visualization and characterization of platelet deposition under flow onto clinically relevant opaque surfaces

Although the thrombogenic nature of the surfaces of cardiovascular devices is an important aspect of blood biocompatibility, few studies have examined platelet deposition onto opaque materials used for these devices in real time. This is particularly true for the metallic surfaces used in current ventricular assist devices (VADs). Using hemoglobin depleted red blood cells (RBC ghosts) and long working distance optics to visualize platelet deposition, we sought to perform such an evaluation. Fluorescently labeled platelets mixed with human RBC ghosts were perfused across six opaque materials (a titanium alloy (Ti6Al4V), silicon carbide (SiC), alumina (Al2O3, 2-methacryloyloxyethyl phosphorylcholine polymer coated Ti6Al4V (MPC-Ti6Al4V), yttria partially stabilized zirconia (YZTP), and zirconia toughened alumina (ZTA)) for 5 min at wall shear rates of 400 and 1000 s(-1). Ti6Al4V had significantly increased platelet deposition relative to MPC-Ti6Al4V, Al2 O3 , YZTP, and ZTA at both wall shear rates (p < 0.01). For all test surfaces, increasing the wall shear rate produced a trend of decreased platelet adhesion. The described system can be a utilized as a tool for comparative analysis of candidate blood-contacting materials with acute blood contact.

Simultaneous comparison of thrombogenic reactions to different combinations of anticoagulants, activated clotting times, and materials

Thrombogenic reactions under multiple interactions of pharmacological agents, doses, and materials have not been well understood yet. The aim of this study was to investigate the ability to simultaneously compare thrombogenic reactions to different combinations of anticoagulants, doses, and blood-contacting materials, in a single human blood using an in vitro test method. Four venous blood samples were drawn from each of six healthy volunteers into syringes that contained two different amounts of heparin and argatroban to set the activated clotting time (ACT) to approximately 200 or 500 s, respectively. The four blood samples from each volunteer were immediately poured into two clinical-grade extracorporeal circulation tubes: a polyvinyl chloride (PVC) tube and a poly(2-methoxyethyl acrylate)-coated (PMEA) PVC tube. These tubes with an inner diameter of 12.7 mm were rotated at 183 rpm in a 37°C chamber for 10 min. The results indicated that the in vitro thrombogenicity test method was capable of assessing differences in platelet factor 4 and β-thromboglobulin increases among different combinations of the two materials, two anticoagulants, and two ACTs. Higher amounts of total plasma proteins were absorbed on PVC tubes than on PMEA-coated tubes when using the same anticoagulant and dose. These data elucidate that the in vitro thrombogenicity test method is useful for the simultaneous quantitative evaluation of the influences of various combinations of materials, pharmacological agents, and doses on thrombogenicity in a single human blood.

Modified blood-contacting polymers

New blood-contacting materials have been synthesized via graft copolymerization of a mixture of a hydrophilic monomer and the macromonomers hirudin and ovomucoid onto a synthetic polymer, either polyethylene, poly(ethylene terephthalate), or polydimethylsiloxane. It has been shown that the surface modification of the polymer via grafting of the hydrophilic monomer alone reduces the degree of denaturation of adsorbed proteins and that the introduction of hirudin and ovomucoid into the hydrophilic layer leads to a decrease in the amount of platelets adhering to the polymer surface and an increase in the clotting time on the polymer surface.

Functionalization of Polycarbonate Surfaces by Grafting PEG and Zwitterionic Polymers with a Multicomb Structure

The hemocompatibility of polycarbonateurethane (PCU) surfaces is improved by decoration with poly(poly(ethylene glycol) methacrylate) (poly(PEGMA)) and zwitterionic poly(3-((2-(methacryloyloxy)ethyl)dimethylammonio)propane-1-sulfonate) (poly(DMAPS)) blocks providing a novel multicomb structure obtained by application of surface-initiated atom transfer radical polymerization (s-ATRP) conditions. The PCU-poly(PEGMA-g-DMAPS) surface shows high hydrophilicity with a low contact angle of 20.6 ± 1.8°, while PCU-poly(PEGMA-b-DMAPS) surface exhibitsed a contact angle of 30.5 ± 2.6°. Furthermore, PCU-poly(PEGMA-g-DMAPS) surface shows very low platelet adsorption indicating that multicomb structure modified PCUs are preferred candidate materials for blood-contacting materials.

Microstructure and Platelet Adhesion Behavior of Titanium Oxide Films Synthesized by Reactive High-Power Pulse Magnetron Sputtering

Titanium oxide films are promising as a blood-contacting biomedical material. In this paper, titanium oxide films are deposited on a Si (1 0 0) substrate by high-power pulsed magnetron sputtering (HPPMS) at different oxygen flow rates. The microstructure and surface morphology are investigated for a variety of oxygen flow rates mixed with argon gas. The blood compatibility of the films is evaluated using a platelet adhesion experiment, and the quantity and morphology of the adhered platelets are investigated through optical microscopy. The oxygen flow rate is varied from 2 to 10 sccm with a fixed argon flow rate of 60 sccm. The composition of the deposited films was TiO and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm Ti}_{2}{\rm O}$</tex></formula> mixtures at an oxygen flow rate of 2 sccm. An anatase and rutile mixed phase is found at an oxygen flow rate of 4 sccm. The titanium oxide film is in the rutile phase with an increasing oxygen flow rate up to 6 sccm or higher. This suggests that the rutile-structured titanium oxide films could be synthesized by HPPMS without heating the substrate. The titanium oxide films with a rutile structure had a very smooth surface with a minimum surface roughness of 0.3 nm. The result of a platelet adhesion experiment indicates that the rutile phase titanium oxide film showed better blood compatibility. From this point of view, the films synthesized by HPPMS are promising to be as biomaterials showing excellent corrosion resistance and a smoothed surface.

Biocompatibility of novel carboxylated graphene oxide–glutamic acid complexes

The biocompatibility improvement of graphene oxide is crucial for biomedical applications. Herein, we propose to prepare carboxylated graphene oxide (GeneO–COOH) with glutamic acid (Glu) at different pH values. The complexes (GemeO–COOH/Glu) are characterized by FT-IR, XRD, TG, and Zeta potential. The results show that the complexes have close relation with pH value due to the acid-responsive Glu. It is demonstrated that GeneO–COOH complexes with Glu via amidation reaction in the basic domain. The blood compatibility of GeneO–COOH/Glu complexes is evaluated by hemolysis and recalcification test. The results show that the plasma recalcification time is prolonged greatly in the whole blood, and the hemolysis rates are less than 5 %. In a word, GeneO–COOH/Glu complexes are blood compatible at low concentration, which is potential for producing blood-contacting materials.

Plasma Proteins Adsorption Mechanism on Polyethylene-Grafted Poly(ethylene glycol) Surface by Quartz Crystal Microbalance with Dissipation

Protein adsorption has a vital role in biomaterial surface science because it is directly related to the hemocompatibility of blood-contacting materials. In this study, monomethoxy poly(ethylene glycol) (mPEG) with two different molecular weights was grafted on polyethylene as a model to elucidate the adsorption mechanisms of plasma protein through quartz crystal microbalance with dissipation (QCM-D). Combined with data from platelet adhesion, whole blood clotting time, and hemolysis rate, the blood compatibility of PE-g-mPEG film was found to have significantly improved. Two adsorption schemes were developed for real-time monitoring of protein adsorption. Results showed that the preadsorbed bovine serum albumin (BSA) on the surfaces of PE-g-mPEG films could effectively inhibit subsequent adsorption of fibrinogen (Fib). Nonspecific protein adsorption of BSA was determined by surface coverage, not by the chain length of PEG. Dense PEG brush could release more trapped water molecules to resist BSA adsorption. Moreover, the preadsorbed Fib could be gradually displaced by high-concentration BSA. However, the adsorption and displacement of Fib was determined by surface hydrophilicity.

Improvement in endothelial cell adhesion and retention under physiological shear stress using a laminin–apatite composite layer on titanium

Apatite (Ap), laminin-apatite composite (L5Ap, L10Ap, L20Ap and L40Ap) and albumin-apatite (AlbAp) composite layers were prepared on titanium (Ti) using a supersaturated calcium phosphate solution supplemented with laminin (0, 5, 10, 20 and 40 μg ml(-1)) or albumin (800 μg ml(-1)). With an increase in the concentrations of laminin in the supersaturated calcium phosphate solutions, the amounts of laminin immobilized on the Ti increased. The number of human umbilical vein endothelial cells (HUVECs) adhered to the laminin-apatite composite layers were remarkably higher than those to the untreated Ti, Ap layer and AlbAp composite layer. The number of cells adhered to the L40Ap was 4.3 times the untreated Ti. Moreover, cells adhered to the laminin-apatite composite layers showed significantly higher cell retention under the physiological shear stress for 1 h and 2 h than those to the untreated Ti, Ap layer and AlbAp composite layer. The number of cells remaining on the L40Ap under the physiological shear stress for 2 h was 9.5 times that of the untreated Ti. The laminin-apatite composite layer is a promising interfacial layer for endothelialization of blood-contacting materials.

Regulation of fibrinolytic protein adsorption on polyurethane surfaces by modification with lysine-containing copolymers

A new strategy to regulate the attachment of plasminogen and its activator, t-PA, to a polyurethane surface is reported. The method is based on the one-step graft copolymerization of a lysine-containing methacrylic monomer and hydroxyethyl methacrylate (HEMA). The copolymer-modified PU surfaces showed high capacity for plasminogen and t-PA binding. The release of pre-adsorbed t-PA from the lysine-containing PU surfaces in contact with plasma was also investigated. It was shown that the interactions of plasminogen and t-PA on this type of surface can be controlled simply by changing the monomer feed ratio, and thus the relative quantities of HEMA and lysine in the grafts. This approach may be useful for the development of fibrinolytic, blood-contacting materials and, more generally, for controlling protein-surface interactions for biocompatibility.

Self-assembling surfaces of blood-contacting materials

The optimal scaffold should have the self-organising property of activating the appropriate tissues surrounding the re-population. The anti-bacterial property of the coating was obtained through surface pre-treatment with coatings a few nanometres in thickness deposited using vapour-based methods. The coating's anti-thrombogenic properties were obtained by the selective mobilisation of cellular functions, which was controlled by the structure of porous coatings deposited on bulk substrates and by the small biological agent-L-arginyl-glycyl-L-aspartic acid (tripeptide Arg-Gly-Asp-RGD) protein domains. Two tests simulating arterial flow conditions were performed: Impact-R, for examining platelet function under near physiological conditions, and radial flow chamber, a cell detachment test that gives an overview of cell behaviour and shear stresses that could appear between the cell and the biomaterial. Cell structures were analysed using laser scanning confocal microscopy and flow cytometry. The performed in vitro dynamic test for the haemo-compatibility revealed the most promising surface functionalization was based on porous extracellular-like structure covered with endothelium cells simultaneously. The antibacterial function was achieved by the appropriate phase composition of the coating used for the pre-treatment stage. The coating for the pre-treatment was selected on the basis of the blood-material and bacteria-material interaction.

Titania Nanotube Arrays as Interfaces for Blood-Contacting Implantable Devices: A Study Evaluating the Nanotopography-Associated Activation and Expression of Blood Plasma Components

The constant exposure of implantable biomaterials such as titanium and titanium alloys to blood-introducesserious and ongoing concerns regarding poor blood-material interactions. To date, all blood-contacting materials have been shown to initiate immunological events in the form of inflammation, thrombosis, fibrosis and infection; potentially leading to complete implant failure. Material surfaces that provide biomimetic cues such as nanoscale architectures have been shown to elicit improved cellular interaction; and thus, may provide possible solutions for enhancing blood-compatibility. However, limited information exists about the thrombogenicityof nanoscalesurface architectures. In this study, we have evaluated the efficacy of titania nanotube arrays as interfaces for blood contacting devices by investigating the thrombogenic effects using whole blood plasma. Thus, platelet/leukocyte adhesion, activation and interaction, morphology, complement activation, contact activation, platelet release reaction, fibrinogen expression and material cytotoxicity were evaluated to determine the in vitro thrombogenicity. The results presented here indicate a decrease in thrombogenic effects of titania nanotube arrays as compared to biomedical grade titanium after 2 hours of contact with whole blood plasma. This work shows the improved blood-compatibility of titania nanotube arrays, identifying this specific nanoarchitecture as a potentially optimal interface for promoting the long-term success of blood contacting biomaterials.

Mussel‐Inspired Coating of Polydopamine Directs Endothelial and Smooth Muscle Cell Fate for Re‐endothelialization of Vascular Devices

Polydopamine (PDAM), a mussel adhesive protein inspired coating that can be easily deposited onto a wide range of metallic, inorganic, and organic materials, gains interest also in the field of biomaterials. In this work, PDAM is applied as coating on 316L stainless steel (SS) stents and the response of cells of the blood vessel wall, human umbilical vein endothelial cell (HUVEC), and human umbilical artery smooth muscle cell (HUASMC) as predictors for re-endothelialization is tested. It is found that the PDAM-modified surface significantly enhances HUVEC adhesion, proliferation, and migration, release of nitric oxide (NO), and secretion of prostaglandin I(2) (PGI(2) ). Additionally, the PDAM-modified surface shows a remarkable ability to decrease the adhesion and proliferation of HUASMCs. As a blood-contacting material, the PDAM tends to improve the hemocompatibility compared with the substrate 316L SS. It is noteworthy that the PDAM coating shows good resistance to the deformation behavior of compression and expansion of a stent. These data suggest the potential of PDAM as a blood-contacting material for the application in vascular stents or grafts.

Synthesis and anticoagulation activities of polymer/functional graphene oxide nanocomposites via Reverse Atom Transfer Radical Polymerization (RATRP)

The anticoagulation properties of biomaterials are crucial for biomedical applications, especially for blood-contacting materials. In this work, a range of functional graphene oxide based on the biomimetic monomer 2-(methacryloyloxy) ethyl phosphorylcholine (GO-g-pMPC) were synthesized by RATRP in alcoholic media using peroxide groups as initiator, and then filled into the polyurethane matrix to obtain the polyurethane (PU)/functional graphene oxide nanocomposite films (PU/GO-g-pMPC). The tensile strength and elongation and morphology of the PU/GO-g-pMPC were characterized by mechanical properties test, Transmission electron microscope (TEM), respectively. The results showed that a small amount of graphene oxide can improve the mechanical properties of PU. The blood compatibility of the PU substrates was evaluated by protein adsorption tests and platelet adhesion tests in vitro. It was found that all the PU/GO-g-pMPC showed improved resistance to nonspecific protein adsorption and platelet adhesion.

Biomimetic surface modification of polycarbonateurethane film via phosphorylcholine-graft for resisting platelet adhesion

Phosphorylcholine groups were covalently introduced onto a polycarbonateurethane (PCU) surface in order to create a biomimetic structure on the polymer surfaces. After introducing primary amine groups onto the polymer surface by 1,6-hexanediamine, phosphorylcholine groups were covalently linked onto the surface by the reductive amination between the amino group and the aldehyde group of phosphorylcholine glyceraldehyde (PCGA). The results of water contact angle test, X-ray photoelectron spectroscopy (XPS), and X-ray fluorescence spectrometer (XRF) analysis of the modified films indicated that PCGA had already been covalently linked to the PCU surface. The topographies and surface roughnesses were both imaged and measured by atomic force microscopy (AFM). Scanning electron microscopy (SEM) observation of the PCU films after treatment with platelet-rich plasma demonstrated that platelets had rarely adhered to the surface of the PCGA-grafted PCU films but had mainly adhered to the surface of the blank PCU films. The platelet adhesion result indicated that the PC modified PCU films could resist platelet adhesion after grafting with PCGA, and that these PCGA-grafted PCU materials, potentially, might be applied as blood-contacting materials. Open image in new window

Haemocompatibility of titanium and its alloys

This review outlines the current understanding of the interactions of titanium and its alloys with blood components, and the ways in which surface modification techniques can be used to alter the surface physicochemical and topographical features that determine blood-material interactions. Surface modification of the spontaneously formed titanium oxide surface layer is a highly attractive means of improving haemocompatibility without forgoing the advantageous mechanical and physical properties of titanium and its alloys. A number of surface modification techniques and treatment processes are discussed in the context of enhancing the haemocompatibility of titanium and its alloys, with a view to optimising the clinical efficacy of blood-contacting devices and materials.

Biomimetic Hemo-compatible Surfaces of Polyurethane by Grafting Copolymer Brushes of Poly(ethylene glycol) and Poly(phosphorylcholine methacrylate)

ABSTRACTPolyurethanes (PU) have been widely used as biomaterial in recent years, while thrombus may still occur when contacting with blood especially for extended period of time. Poly(ethylene glycol) (PEG) and phosphorylcholine (PC)-based polymers are commonly employed for surface modification to create protein repellent surfaces. PC-based polymers have been investigated as biomimetic materials because PC is the major component in the outer layer of cell membranes. In this study, the biomimetic copolymer brush of PEG-b-poly(2-methacryloyloxyethyl phosphorylcholine) on PU surfaces was synthesized via atom transfer radical polymerization (ATRP) with a surface initiator. The flexible PEG chain was 200 g·mol-1, while the poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) chain length was controlled by the ratio of monomer to sacrificial initiator in solution. The topology of the modified surfaces was characterized by the phase image of atomic force microscopy (AFM) to study the synergy effect between PEG chains and poly(MPC) chains. The unmodified and modified surfaces were characterized by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), water contact angle and platelet adhesion. The results demonstrated that efficient grafting of PEG-b-poly(MPC) brushes on the surfaces was achieved. The PU surfaces modified with PEG and phosphorylcholine zwitterionic brushes showed effective resistance to platelet adhesion and high hemocompatibility in vitro. These PEG and PC-grafted PU materials might be potentially applied in blood-contacting materials or devices due to their good mechanical and hemocompatible properties.