Number Of Adherent Platelets Research Articles

Robust underwater superoleophobic coatings based on zwitterionic P(CBMAE‐co‐TMSPMA)/SiO2 with anti‐adhesive behavior

AbstractThis study focuses on the surface modification of substrates using a poly(N,N‐dimethyl‐N‐(ethoxycarbonylmethyl)‐N‐[2′‐(methacryloyloxy) ethyl]‐ammonium chloride‐co‐3‐(trimethoxysilyl)propylmethacrylate) P(CBMAE‐co‐TMSPMA) and ethyl orthosilicate (TEOS). By covalently bonding the Si‐OH pendant of the copolymer with hydroxyl residues on the material's surface, a stable polymer coating is formed. The properties of P(CBMAE‐co‐TMSPMA) coatings were evaluated using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and contact angle (CA) meter. The addition of TEOS allows for the regulation of surface roughness. With the increase of TEOS content, the contact angle of underwater oil first increased and then decreased. The water contact angles were 8°, the underwater superoleophobic contact angle reached 168°, and the number of adherent platelets and Escherichia coli were significantly reduced to 7.5% and 5% on the surface of the coating, respectively. After undergoing simultaneous hydrolysis, the superoleophobic contact angle of P(CBMAE‐co‐TMSPMA)/SiO2 coating further increased to 174°. These interesting and robust properties make them promising candidates for biomedical applications.Highlights The underwater superoleophobic coating (contact angles of 174°). The P(CBMAE‐co‐TMSPMA)/SiO2 coating with excellent resistance to oil adhesion. Solve the hydroxyl residue problem. The coating resistance to E. coli and platelet adhesion.

Synthesis and Antiplatelet Adhesion Behavior of a Poly(L-lactide-co-glycolide)-Poly(1,5-dioxepan-2-one) Multiblock Copolymer.

Platelet adhesion and denaturation on artificial medical implants induce thrombus formation. In this study, bioabsorbable copolymers composed of poly(l-lactide-co-glycolide) (PLGA) and poly(1,5-dioxepan-2-one) (PDXO) were synthesized and evaluated for their antiplatelet adhesive properties. The PLGA–PXO multiblock copolymer (PLGA–PDXO MBC) and its random copolymer (PLGA–PDXO RC) showed effective antiplatelet adhesive properties, and the number of adhered platelets was similar to those adhered on poly(2-methoxyethylacrylate), a known antiplatelet adhesive polymer, although a large number of denatured platelets were observed on a PLGA–poly(ε-caprolactone) multiblock copolymer (PLGA–PCL MBC). Using monoclonal antifibrinogen IgG antibodies, we also found that both αC and γ-chains, the binding sites of fibrinogen for platelets, were less exposed on the PLGA–PDXO MBC surface compared to PLGA–PCL MBC. Furthermore, free-standing films of PLGA–PDXO MBC were prepared by casting the polymer solution on glass plates and showed good tensile properties and slow hydrolytic degradation in phosphate-buffered saline (pH = 7.4). We expect that the unique properties of PLGA–PDXO MBC, i.e., antiplatelet adhesive behavior, good tensile strength, and hydrolytic degradation, will pave the way for the development of new bioabsorbable implanting materials suitable for application at blood-contacting sites.

Antithrombogenic poly(2-methoxyethyl acrylate) elastomer via triblock copolymerization with poly(methyl methacrylate)

For the development of blood-contacting biomedical devices, preventing platelet adhesion and avoiding subsequent thrombosis through antithrombogenic surface are vitally important. Poly (2-methoxyethyl acrylate) (PMEA) is a synthetic viscous polymer with an excellent antithrombogenic property, which has already been used as an antithrombogenic coating for biomedical purposes. The PMEA coating, however, can be easily broken due to its liquid-like feature, since the glass transition temperature (Tg) of PMEA is at −25οC. Solidifying PMEA has, therefore, been desperately desired for the improvement of the stability of PMEA coating. Also, once solidified, PMEA could be utilized not only for coating but also for structural materials for medical devices, expanding the application range of PMEA. In this study, PMEA was first solidified by triblock copolymerization with poly (methyl methacrylate) (PMMA) to obtain thermoplastic elastomers with excellent antithrombogenicity. We synthesized PMMA-PMEA-PMMA triblock copolymers with different volume fractions of PMMA (fMMA) by atom transfer radical polymerization (ATRP). The synthesis and the chemical structures of the new triblock copolymers were characterized and confirmed by proton nuclear magnetic resonance (1H NMR) analyses and gel permeation chromatography (GPC). The synthesized elastomeric triblocks were then compression-molded at 180οC to obtain solid transparent films. The tensile property was measured and the drastic change from the soft-elastomer phase to the hard-plastic phase was clearly observed by varying fMMA. It was found that the new triblocks possessed significantly higher tensile strengths than the other solidified PMEA by the previous studies. The platelet adhesion test revealed that the number of adherent platelets on the triblocks with fMMA of 0.12 and 0.40 was almost the same as that on pure PMEA, indicating that the synthesized triblocks possessed excellent antithrombogenicity similar to liquid PMEA. Further investigation on hydrated water and microphase-separated structures eventually revealed that the new triblock copolymers with a sufficient amount of intermediate water or with microphase separation on the surface resulted in excellent antithrombogenicity.

Effect of interfacial structure based on grafting density of poly(2-methoxyethyl acrylate) on blood compatibility

An excellent blood-compatible polymer, poly(2-methoxyethyl acrylate) (PMEA), exhibits nanometer-scale phase-separated structures at the interface with water or phosphate-buffered saline (PBS), and fibrinogen adsorption is suppressed, especially on the water-rich region. To understand the correlation between the interfacial structure based on the grafting density of PMEA and blood compatibility, grafted PMEA (gPMEA) surfaces with controlled density were prepared by immobilizing thiol-terminated PMEA on a gold substrate. The amount of adsorbed fibrinogen and the number of adhered platelets on gPMEAs decreased first with the increasing grafting density (σ), but increased after showed minimum at σ of approximately 0.11 chains/nm2. The interfacial structures of the gPMEA/PBS interface changed with grafting density, and the maximum area of water-rich region was obtained at σ = 0.11. The water contact angle at σ = 0.11 is smaller than that at the other grafting density. These results revealed that hydration to the polymer is very effective to suppress the platelet adhesion and water-rich region shows excellent blood compatibility on gPMEA surfaces. This work clearly indicated that the density of PMEA affects the interfacial structure and plays an important role in the blood compatibility of the material.

Tough and Three-Dimensional-Printable Poly(2-methoxyethyl acrylate)-Silica Composite Elastomer with Antiplatelet Adhesion Property.

Poly(2-methoxyethyl acrylate) (PMEA) has attracted attention as a biocompatible polymer that is used as an antithrombotic coating agent for medical devices, such as during artificial heart and lung fabrication. However, PMEA is a viscous liquid polymer with low Tg, and its physical strength is poor even if a cross-linker is used, so it is difficult to make tough and freestanding objects from it. Here, we design and fabricate a biocompatible elastomer made of tough, self-supporting PMEA-silica composites. The toughness of the composite elastomer increases as a function of silica particle filling, and its stress at break is improved from 0.3 to 6.7 MPa. The fracture energy of the composite elastomer with 39.5 vol % silica particles is up to 15 times higher than that of the cross-linked PMEA with no silica particles and the material demonstrates stress-strain behavior that is similar to that of biological soft tissue, which exhibits nonlinear elasticity. In addition, the composite elastomer shows the potential to be an antithrombotic property, while the results of the platelet adhesion test of the composite elastomer show that the number of adhered platelets is not significantly affected by the silica addition. As the composite elastomer can be rapidly three-dimensional-printed into complex geometries with high-resolution features, it is expected to contribute to the development of medical devices from readily available materials.

Antithrombogenic properties ofTulbaghia violacea–loaded polycaprolactone nanofibers

A broad range of polymers have been utilized for the development of blood-contacting implantable medical devices; however, their rate of failure has raised the need for developing more hemocompatible biomaterial surfaces. In this study, a novel scaffold based on polycaprolactone incorporated with 10% and 15% (w/w) Tulbaghia violacea plant extracts were fabricated using electrospinning technique. The fabricated scaffolds were then treated with T. violacea aqueous plant extracts (100 and 1000 µg/mL) to investigate their use as interfaces for blood-contacting implants. The 10% Tvio scaffold produced the lowest mean fibre diameter (193 ± 30 nm), whereas the 15% Tvio scaffold produces the highest mean fibre diameter (538 ± 236 nm) when compared with the control polycaprolactone (275 ± 61 nm) scaffold. The number of adhered platelets was directly linked to fibre diameter and concentration of plant extract in such a way that the lowest fibre diameter scaffold (10% Tvio) inhibited platelet adhesion, whereas more platelets adhered to the scaffold with the highest fibre diameter (15% Tvio scaffolds). There was also an increase in platelet adhesion as the concentration of T. violacea was increased from 100 to 1000 µg/mL for all designed scaffolds. The improved blood compatibility demonstrated by the 10% Tvio scaffold suggests that the plant possesses antithrombogenic properties, particularly at lower concentrations.

Hemocompatibility of biodegradable Zn-0.8 wt% (Cu, Mn, Li) alloys.

Zinc alloys have been explored as potential materials for biodegradable vascular stents due to their tolerable corrosion rates and tunable mechanical properties. However, the performances of Zn alloys were not supported with enough toxicity or biological compatibility evaluation, particularly hemocompatibility for vascular scaffolding application. In this work, the hemocompatibility of three zinc alloys (Zn-0.8Cu, Zn-0.8Mn and Zn-0.8Li) was evaluated with 316 L stainless steel and pure zinc as controls. The hemolysis ratios of 316 L stainless steel, pure Zn, Zn-0.8Cu, Zn-0.8Mn and Zn-0.8Li were 0.38 ± 0.08%, 1.04 ± 0.21%, 0.47 ± 0.21%, 0.57 ± 0.14% and 0.52 ± 0.22%, respectively, for direct contact method. Platelets aggregation on the 316 L stainless steel was observed, while the adhered platelets on the Zn alloys exhibited round shape with few pseudopodia spreading. The number of adhered platelets on the three zinc alloys (Zn-0.8Cu, Zn-0.8Mn and Zn-0.8Li) had no statistically difference compared with 316 L stainless steel, while significant fewer than the pure Zn group. None remarkable platelet activation, hematocyte aggregation, coagulation or complement activation was observed in any Zn alloy group. Furthermore, the Zn alloys prolonged prothrombin time and partial thromboplastin time, demonstrating a potential function of anticoagulation. The results demonstrated that Zn alloys presented in this work are indeed meeting the hemocompatible requirements of implant and showing the promise for perspective application as biodegradable stent.

Kinetic study of NTPDase immobilization and its effect of haemocompatibility on polyethylene terephthalate

Poor haemocompatibility of material surfaces is a serious limitation that can lead to failure of blood-contacting devices and implants. In this work, we have improved the haemocompatibility of polyethylene terephthalate (PET) surfaces by immobilizing apyrase/ecto-nucleoside triphosphate diphosphohydrolase (NTPDase) on to the carboxylated PET. NTPDase immobilized PET surfaces scavenge the ADP released by activated platelets, which prevents further platelet activation and aggregation. The surface properties of the modified PET were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDAX), and contact angle measurement. The enzyme attachment and stability on the modified PET surfaces were evaluated. The kinetics of free enzyme and immobilized enzyme were studied and fitted using the Michaelis-Menten kinetic model. Both free and immobilized NTPDase followed Michaelis-Menten kinetics with similar Michaelis-Menten constants (Km). This suggests that the activity of NTPDase was unchanged upon immobilization. Protein adsorption and %hemolysis was significantly reduced for carboxylated PET and NTPDase immobilized PET surfaces compared to unmodified PET. Lactate dehydrogenase assay showed that the number of adhered platelets reduced by more than an order of magnitude for the NTPDase immobilized PET surface compared to unmodified PET. These results clearly indicate that NTPDase immobilization significantly enhances the haemocompatibility of PET surfaces.

Differential Modulation of Platelet Adhesion and Spreading by Adhesive Ligand Density.

Platelets play a major role in hemostasis and thrombosis, by binding to the underlying extracellular matrix around injured blood vessels, via integrin receptors. In this study, we investigated the effects of adhesive ligand spacing on the stability of platelets’ adhesion and the mode of their spreading on extracellular surfaces. Toward this end, we have examined the differential adhesion and spreading of human platelets onto nanogold-patterned surfaces, functionalized with the αIIbβ3 integrin ligand, SN528. Combining light- and scanning electron-microscopy, we found that interaction of platelets with surfaces coated with SN528 at spacing of 30–60 nm induces the extension of filopodia through which the platelets stably attach to the nanopatterned surface and spread on it. Increasing the nanopattern-gold spacing to 80–100 nm resulted in a dramatic reduction (>95%) in the number of adhering platelets. Surprisingly, a further increase in ligand spacing to 120 nm resulted in platelet binding to the surface at substantially larger numbers, yet these platelets remained discoid and were essentially devoid of filopodia and lamellipodia. These results indicate that the stimulation of filopodia extension by adhering platelets, and the consequent spreading on these surfaces depend on different ligand densities. Thus, the extension of filopodia occurs on surfaces with a ligand spacing of 100 nm or less, while the sustainability and growth of these initial adhesions and induction of extensive platelet adhesion and spreading requires lower ligand-to-ligand spacing (≤60 nm). The mechanisms underlying this differential ligand-density sensing by platelets, as well as the unexpected retention of discoid platelets on surfaces with even larger spacing (120 nm) are discussed.

Titanium Nitride Film on Titanium Film by Magnetron Sputtering Method

Titanium nitride (TiN) film on titanium film (Ti) was formed by magnetron sputtering method. Pure titanium substrates with TiN/Ti multi-layered films deposited using DC sputter-deposition machine in Ar gas atmosphere, in order to improve not only the blood compatibility of pure titanium but also the adhesion between the deposited TiN coating and the pure titanium substrate. The effects of the thickness of a pure titanium interlayer on adhesion of the TiN coating to the pure titanium substrate were investigated. And the effects of the TiN coating obtained in this study on blood compatibility were also investigated. The obtained multi-layered films looked yellow gold and appeared to be uniform and adhesive without any peel-offs. Based on the results of the platelet test, the ratio of the number of adhered platelets for the TiN/Ti film to that for the pure titanium substrate was estimated to be 0.54. Thus it was found that the platelet adhesion of the obtained TiN/Ti film was much smaller than the pure titanium, concluding that the TiN coating improved the blood compatibility.

BIOCOMPATIBILITY EVALUATION OF DRUG RELEASING ABSORBABLE VASCULAR STENTS

This study examined the biocompatibility of blood vessels and a biodegradable drug-loaded vascular stent. The Traditional Chinese Medicine System Laboratory of Chung Yuan Christian University prepared the vascular stent, and our study verified the sustained release of drugs from the stent when it was within blood vessels. A platelet adhesion experiment revealed that stents with less surface roughness resulted in a reduction in the number of adhered platelets and decreased fibrinogen accumulation. The results of a hemolysis experiment verified that the hemolysis index was between 1% and 1.4%, within the range of no hemolysis and would not cause hypoxia. Subsequently, a drug release rate experiment indicated that the amount of released everolimus increased with time. The greatest amount of drug that was released occurred at 8[Formula: see text]h, with a release rate of 36.95%. A swelling rate experiment revealed that the degree of swelling of the hyaluronic acid (HA) that contained everolimus was 10 times less than that of the original HA; therefore, the use of a material with a low swelling rate in vascular stents did not immediately cause an obstruction in blood vessels. A lactate dehydrogenase (LDH) toxicity experiment revealed that the percentage of LDH released was 13–18%. This indicated that the cell viability was not affected and that there was no cytotoxicity; thus, the stent was suitable for use in blood vessels. This study proved that the prepared biodegradable drug-loaded vascular stent had favorable blood compatibility, no cytotoxicity, and a suitable drug release rate. Moreover, the drug release material was made from a material with a low degree of swelling. As a result of our findings, this new type of stent is suitable for application in blood vessels.

Biocompatibility of Polysulfone Hemodialysis Membranes and Its Mechanisms: Involvement of Fibrinogen and Its Integrin Receptors in Activation of Platelets and Neutrophils.

Activation of blood cells during hemodialysis is considered to be a significant determinant of biocompatibility of the hemodialysis membrane because it may affect patient health adversely through microvascular inflammation and oxidative stress. This study found very different cell activation among various polysulfone (PSf) hemodialysis membranes. For example, CX‐U, a conventional PSf membrane, induced marked adhesion of platelets to its surface and increased surface expression of activated CD11b and production of reactive oxygen species (ROS) by neutrophils; while NV‐U, a hydrophilic polymer‐immobilized PSf membrane, caused little platelet adhesion and slight CD11b expression and ROS production by neutrophils. Analysis of the molecular mechanisms of the above phenomena on CX‐U and NV‐U indicated that anti‐integrin GPIIb/IIIa antibody blocked platelet adhesion, and that the combination of anti‐CD11b (integrin α subunit of Mac‐1) and anti‐integrin αvβ3 antibodies blocked ROS production by neutrophils. Plasma‐derived fibrinogen, a major ligand of GPIIb/IIIa, Mac‐1, and αvβ3 on membranes, was thus analyzed and found to be more adsorbed to CX‐U than to NV‐U. Moreover, comparison between five PSf membranes showed that the number of adherent platelets and neutrophil ROS production increased with increasing fibrinogen adsorption. These results suggested that fibrinogen, adsorbed on membranes, induced GPIIb/IIIa‐mediated platelet activation and Mac‐1/αvβ3‐mediated neutrophil activation, depending on the amount of adsorption. In conclusion, the use of biocompatible membranes like NV‐U, which show lower adsorption of fibrinogen, is expected to reduce hemodialysis‐induced inflammation and oxidative stress by minimizing cell activation.

Comparative efficacy of hemorrhage control of a novel mesoporous bioactive glass versus two commercial hemostats

Mesoporous bioactive glass containing 1% Ga2O3 (1%Ga-MBG) is attractive for hemorrhage control because of its surface chemistry which can promote blood-clotting. The present study compares this proprietary inorganic coagulation accelerator with two commercial hemostats, CeloxTM (CX) and QuikClot Advanced Clotting Sponge PlusTM (ACS+). The results indicate that the number of adherent platelets were higher on the 1%Ga-MBG and CX surfaces than ACS+ whereas a greater contact activation was seen on 1%Ga-MBG and ACS+ surfaces than CX. 1%Ga-MBG not only resulted in larger platelet aggregates and more extensive platelet pseudopodia compared to CX and ACS+ but also significantly accelerated the intrinsic pathways of the clotting cascade. In vitro thrombin generation assays also showed that CX and ACS+ induced low levels of thrombin formation while 1%Ga-MBG had significantly higher values. 1%Ga-MBG formed a larger red blood cell aggregate than both CX and ACS+. Direct exposure of 1%Ga-MBG to fibroblast cells increased cell viability after 3 days relative to CX and ACS+, inferring excellent cytocompatibility. The results of this study promote 1%Ga-MBG as a promising hemostat compared to the commercially available products as it possesses essential factors required for coagulation activation.

In vitro measurement of platelet adhesion to intact endothelial cells under low shear conditions.

Prediction of thrombus formation at intact arterial walls under low shear flow conditions is clinically important particularly for better prognoses of embolisation in cerebral aneurysms. Although a new mathematical model for this purpose is necessary, little quantitative information has been known about platelet adhesion to intact endothelial cells. The objective of this study is to measure the number of platelets adhering to intact endothelial cells with a focus upon the influence of the shear rate. Endothelial cells disseminated in μ-slides were exposed to swine whole blood at different shear rates. Adenosine diphosphate (ADP) was used as an agonist. Adherent platelets were counted by means of scanning electron microscopy. At an ADP concentration of 1µM, 20.8 ± 3.1 platelets per 900µm2 were observed after 30-minute perfusion at a shear rate of 0.8s-1 whereas only 3.0 ± 1.4 per 900µm2 at 16.8s-1. The number of adherent platelets is determined by a balance between the shear and the degree of stimulation by the agonist. At an ADP concentration of 1µM, a limit to the shear rate at which platelets can adhere to intact endothelial cells is considered to be slightly higher than 16.8s-1.

In vitro basic fibroblast growth factor (bFGF) delivery using an antithrombogenic 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer coated with a micropatterned diamond-like carbon (DLC) film.

In this study, a newly designed drug-release platform composed of an antithrombogenic 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer was introduced, which was impregnated with basic fibroblast growth factor (bFGF) (bFGF/MPC polymer) to enhance the endothelial cell activation. The platform was also coated with an ultrathin micropatterned diamond-like carbon (DLC) film (DLC/bFGF/MPC polymer) to precisely control the drug release rate and the cell compatibility. The resulting DLC/bFGF/MPC polymer could effectively prolong the bFGF release rate by depositing the micropatterned DLC. The number of adherent platelets on the DLC/bFGF/MPC polymer was significantly lower (about 1/14) than that on a currently used stent made of stainless steel (SUS316L), indicating the enhanced antithrombogenicity in the DLC/bFGF/MPC polymer. The proliferation of endothelial cells on the DLC/bFGF/MPC polymer and the DLC/MPC polymer (without bFGF) were also examined. It was found that the optical density of HUVEC on the DLC/bFGF/MPC polymer determined by WST-8 assay was higher by 25%than that on the DLC/MPC polymer (without bFGF) measured after 72 h of incubation. Our results suggest that the released bFGF that contributes to the expression of other growth factors results in the early proliferation of the HUVEC on the DLC/bFGF/MPC polymer. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3384-3391, 2017.

Time course analysis of antithrombogenic properties of fluorinated diamond-like carbon coating determined via accelerated aging tests: Quality control for medical device commercialization

We have previously reported that fluorine-incorporated amorphous carbon (a-C:H:F) coating dramatically reduced the number and activation of adherent platelets in contact with human blood. In order to convert a-C:H:F coating into a commercial reality, it is necessary to estimate its life span and the sustainability of antithrombogenic properties using accelerated aging tests under various temperature conditions. The purpose of this study was to investigate the effect of different temperature conditions using accelerated aging tests on the antithrombogenic properties of a-C:H:F.The a-C:H:F film was deposited on silicon substrates from a mixture of acetylene and octafluoropropane using the inductively coupled plasma enhanced chemical vapor deposition method. The a-C:H:F coated substrates were then stored at room temperature, 55°C, 70°C and 90°C, respectively. The surface chemical compositions of a-C:H:F film were examined using X-ray photoelectron spectroscopy (XPS). The antithrombogenic properties were evaluated through incubation with platelet-rich plasma isolated from human whole blood, and the properties of adhesion between film and metallic stents were evaluated by examining before-and-after balloon expansion. The XPS analysis showed that the relative amount of fluorine atoms slightly decreased and the amount of oxygen increased over time on the surface of a-C:H:F samples. Furthermore, the change in chemical composition was the most prominent in the samples stored at 90°C. However, no significant difference in the number of adherent platelets were observed among a-C:H:F coated sample surfaces after accelerated aging tests, suggesting that changes in chemical composition due to elapsed time and temperature changes do not significantly affect the antithrombogenic properties. Furthermore, the stability of the adhesive properties on a-C:H:F coated stents was revealed, because there were no cracks or instances of delamination on any a-C:H:F coated stent surfaces after expansion.This work demonstrated that excellent antithrombogenic properties of a-C:H:F were maintained over time at each temperature, and thus a-C:H:F film could be utilized as a coating material for medical device commercialization. Prime novelty statementWe report that the antithrombogenic and adhesive properties of fluorine-incorporated amorphous carbon (a-C:H:F) are stable even after accelerated aging tests, and thus a-C:H:F film could be utilized as a coating material for medical device commercialization.

A novel blood incubation system for the in‐vitro assessment of interactions between platelets and biomaterial surfaces under dynamic flow conditions: The Hemocoater

Hemocompatibility evaluation of biomaterials necessitates the use of blood incubation systems which simulate physiological flow conditions. However, most of the current systems have various limitations, especially restricted material variability, poor access to the test surface or damage of blood cells due to the use of a pump. In this paper, we combined the advantages of existent setups and developed a new planar shaped incubation test bench to lift those restrictions and mimic the pulsatile in-vivo situation. The adjustable flow conditions at the tested material surface were defined and corresponded to those in blood vessels. Platelet/material-interaction, as major aspect of hemocompatibility, was investigated for four common polymeric materials (polyoxymethylene, polypropylene, polyethylene and silicone elastomer) with platelet deprivation and platelet adhesion tests. Highly significant differences in the adhesion of platelets onto the tested material surfaces were measured. The number of adhered platelets on the most hydrophobic sample (silicone elastomer) was four-times higher than on the most hydrophilic sample (polyoxymethylene). These findings were confirmed with a scanning microscopic analysis and demonstrated the suitability of the testing device for the evaluation of platelet/material interactions. Moreover, hemolysis measurements demonstrated that the system did not provoke blood damage. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2430-2440, 2016.

Hemocompatible poly(trimethylene carbonate) derivatives for potential application to biodegradable artificial blood vessels

Event Abstract Back to Event Hemocompatible poly(trimethylene carbonate) derivatives for potential application to biodegradable artificial blood vessels Kazuki Fukushima1*, Shunya Takaoka1*, Shunsuke Shishido1*, Yuto Inoue1*, Takayuki Ota1* and Masaru Tanaka1, 2* 1 Yamagata University, Department of Polymer Science and Engineering, Japan 2 Kyushu University, Institute for Materials Chemistry and Engineering, Japan Introduction: Poly(trimethylene carbonate) (PTMC) attratcs increasing attention as a degradable polymeric platform for biomedical applications, due to the softness and its unique degradation behavior unlike biodegradable polyesters.[1] In addition, PTMC analogs with a functional side chain (PMTC) now afford many functionalized implantable biomaterials.[2] Recent progress in organocatalysis allows controlled polymerization of MTCs, monomers of PMTC, enabling formation of complex architecture and multi-functionalization.[3] One of the critical features as biomaterials used in the body involves hemocompatibility. So far, few biodegradable polymers have presented sufficient blood compatibility. Then, we focused on a blood compatible polymer, poly(2-methoxyethyl acrylate) (PMEA). According to Tanaka et al., the ether side chain plays a significant role in hydration and formation of ‘intermediate water’ that is recognized to contribute to suppression of protein and platelet adsorption.[4] Thus, we have produced poly(2-methoxyethyl 2-methyltrimethylene carbonate carboxylate) (PMEMTC), demonstrating decent hemocompatibility and enzymatic degradability. However, as for the vascular regeneration application, adhesion of endothelial cells (ECs) is also important. Poly(tetrahydrofurfuryl acrylate) (PTHFA) is another blood compatible polymer and effective in ECs attachment and proliferation. Thus, we designed new analogs of PMEMTC with cyclic ether moiety at the side chain to install both hemocompatibility and EC adhesion property. Furthermore, we also developed a new facile synthetic route to MTC-type monomers through an ammonium salt intermediate TEA-MTC (Figure 1). Results and Discussion: PTHFMTC and PTHPEMTC were successfully prepared as a consequence of the relatively controlled ROP, allowing for Mn and molar mass distribution, 11,000 (1.12) and 9,400 (1.14), respectively. All carbonate polymers used in this study were hydrophobic. Interestingly, contact angles were 61° for PTHFMTC and 58° for PTHPEMTC, which are comparable to that of PMEMTC, despite more hydrocarbons installed. Figure 2 represents the comparison of adherent human platelets on the polymer surfaces after treatment at 37°C for 1 h. A few platelets adhered on PTHFMTC and PMEMTC. The numbers of adherent platelets are slightly higher than that on PMEA, but significantly lower than that on PTMC. Then, we investigated water structure of hydrated water bound by polymer structure. On the cooling DSC chart of the hydrated polymers, crystallization exotherms were observed around -40°C for both PMEMTC and PTHFMTC (Figure 3). These crystalized water peaks should not be asigned as free or bulk water, exhibiting the exotherm above -20°C, according to our recent report.[5] Thus, we currently believe that this type of water also is attributed to suppression of platelet adhesion. Further studies are ongoing. The results of EC adhesion test will also be discussed. Preliminarily, human umbilical vein endothelial cells (HUVECs) were found to reasonably adhere on PMEMTC at 1 and 3 days after incubation. Conclusion: These (potentially) biodegradable polycarbonates with ether side chain can be applicable for both a coating of blood contacting devices and a candidate scaffold for vascular regeneration.

Physical Characterization and Platelet Interactions under Shear Flows of a Novel Thermoset Polyisobutylene-based Co-polymer.

Over the years, several polymers have been developed for use in prosthetic heart valves as alternatives to xenografts. However, most of these materials are beset with a variety of issues, including low material strength, biodegradation, high dynamic creep, calcification, and poor hemocompatibility. We studied the mechanical, surface, and flow-mediated thrombogenic response of poly(styrene-coblock-4-vinylbenzocyclobutene)-polyisobutylene-poly(styrene-coblock-4-vinylbenzocylcobutene) (xSIBS), a thermoset version of the thermoplastic elastomeric polyolefin poly(styrene-block-isobutylene-block-styrene) (SIBS), which has been shown to be resistant to in vivo hydrolysis, oxidation, and enzymolysis. Uniaxial tensile testing yielded an ultimate tensile strength of 35 MPa, 24.5 times greater than that of SIBS. Surface analysis yielded a mean contact angle of 82.05° and surface roughness of 144 nm, which was greater than for poly(ε-caprolactone) (PCL) and poly(methyl methacrylate) (PMMA). However, the change in platelet activation state, a predictor of thrombogenicity, was not significantly different from PCL and PMMA after fluid exposure to 1 dyn/cm(2) and 20 dyn/cm(2). In addition, the number of adherent platelets after 10 dyn/cm(2) flow exposure was on the same order of magnitude as PCL and PMMA. The mechanical strength and low thrombogenicity of xSIBS therefore suggest it as a viable polymeric substrate for fabrication of prosthetic heart valves and other cardiovascular devices.

The nitric oxide donor pentaerythritol tetranitrate reduces platelet activation in congestive heart failure.

BackgroundPlatelet activation associated with endothelial dysfunction and impaired endogenous platelet inhibition is part of the cardiovascular phenotype of congestive heart failure (CHF) and contributes to the increased risk for thromboembolic complications. Pentaerythritol tetranitrate (PETN) has been shown to release nitric oxide without development of nitrate tolerance. We investigated the effect of chronic PETN treatment on platelet activation and aggregation in an experimental CHF model.Methods and ResultsChronic ischemic heart failure was induced in male Wistar rats by coronary artery ligation. Starting 7 days thereafter, rats were randomised to placebo or PETN (80 mg/kg twice daily). After 9 weeks, activation of circulating platelets was determined measuring platelet bound fibrinogen, which requires activated glycoprotein IIb/IIIa on the platelet surface. Binding was quantified by flow-cytometry using a FITC-labelled anti-fibrinogen antibody. Platelet-bound fibrinogen was significantly increased in CHF-Placebo (mean fluorescence intensity: Sham 88±4, CHF-Placebo 104±6, p<0.05) and reduced following treatment with PETN (89±7, p<0.05 vs. CHF-Placebo). Maximal and final ADP-induced aggregation was significantly enhanced in CHF-Placebo vs. Sham-operated animals and normalized / decreased following chronic PETN treatment. Moreover, platelet adhesion was significantly reduced (number of adherent platelets: control: 85.6±5.5, PETN: 40±3.3; p<0.001) and VASP phosphorylation significantly enhanced following in vitro PETN treatment.ConclusionChronic NO supplementation using PETN reduces platelet activation in CHF rats. Thus, PETN may constitute a useful approach to prevent thromboembolic complications in CHF.