Inhibited Platelet Adhesion Research Articles

Immobilizing argatroban and mPEG-NH2 on a polyethersulfone membrane surface to prepare an effective nonthrombogenic biointerface

Systemic anticoagulation is not suitable for hemodialysis (HD) patients with a high risk of bleeding in the clinic. An HD membrane that provides a localized anticoagulation membrane surface may be a promising strategy to solve this intractable problem for HD patients. Herein, we modified a nonthrombogenic polyethersulfone (PES) dialyzer membrane by grafting argatroban (AG) and methoxy polyethylene glycol amine (mPEG-NH2) via a polydopamine (PDA) strategy. The PES substrates were immersed in an alkaline dopamine solution for 24 h, and then, AG and mPEG-NH2 were sequentially grafted covalently onto the resultant membrane. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) were utilized to confirm the successful introduction of PDA and the immobilization of AG and mPEG-NH2. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to observe the surface structure and morphology after the surface modification. The excellent antithrombotic abilities of the modified membrane were demonstrated by the suppression of platelet adhesion and activation, prolongation of clotting times, and inhibition of thrombin generation and complement activation. This work describes an efficient and convenient method to immobilize AG and mPEG-NH2 to create a nonthrombogenic biointerface for blood-contacting devices such as HD membranes.

The pCONUS HPC: 30-Day and 180-Day In Vivo Biocompatibility Results

BackgroundEndovascular stents are commonly used during neurointerventional procedures; however, the concomitant use of dual anti-platelet treatment (DAPT) can limit their use. There is a need to develop stent coatings that mitigate requirement for DAPT.MethodsThe hydrophilic polymer coating is a novel glycan-based multilayer polymer that inhibits platelet adhesion. After Institutional Animal Care and Use Committee approval, 18 New Zealand white rabbits (mean weight 4.02 ± 0.51 kg) were commenced on DAPT (ASA 10 mg/kg/day and clopidogrel 10 mg/kg/day). A bare nitinol pCONUS and coated pCONUS HPC were implanted into the common carotid arteries of each rabbit. Histological examinations were performed at 30 days (n = 9) and 180 days (n = 8) to assess the acute and chronic inflammatory reactions to the pCONUS HPC. Wilcoxon/Kruskal–Wallis and ANOVA were used with p value < 0.05 considered as significant.ResultsThere is no statistically significant difference in inflammation within the intima/media or adventitia at 30 days (p = 0.3901 and p = 1, respectively) or at 180 days (p = 0.144 and p = 1, respectively) between pCONUS and pCONUS HPC cohorts. There is no significant difference in the presence of granulomas or giant cells between the cohorts at either 30 days (p = 1 and p = 0.8363) or 180 days (p = 1.00 and p = 0.149). At 30 days and 180 days, there was near-complete endothelialisation of the stent struts and no significant difference between the pCONUS or pCONUS HPC (p = 0.7832 and p = 0.334, respectively).ConclusionpCONUS HPC stents do not elicit an acute or chronic inflammatory response in vivo with no significant difference in the tissue response to bare nitinol pCONUS stents or pCONUS HPC stents.

A peptide antagonist of F11R/JAM-A reduces plaque formation and prolongs survival in an animal model of atherosclerosis

Background and aimsThe F11 Receptor (F11R), AKA Junctional Adhesion Molecule-A (JAM-A) (F11R/JAM-A), is an adhesion protein constitutively expressed on the membrane surface of circulating platelets and the luminal surface of inflamed endothelial cells (EC).Platelet adhesion to an inflamed endothelium is one of the early steps of atherosclerotic plaque formation. Our previous studies, conducted with cultured EC in vitro, have demonstrated the expression of F11R/JAM-A on the luminal surface of inflamed EC, platelet adhesion to inflamed EC through F11R/JAM-A interactions, and inhibition of this interaction by the presence of F11R/JAM-A antagonistic peptide (F11Rpeptide 4D). In the present study, we examined in vivo the overall health-benefits and cardiovascular effects of long-term treatment of animals prone to atherosclerosis, ApoE−/− mice, with F11R-peptide 4D. MethodsTwenty ApoE−/− mice were assigned to daily treatment with peptide 4D and compared to their counterparts control untreated mice. Mice were observed for wellness and survival. Plaque size in the aorta and heart was measured using histological analysis. Effects of peptide 4D (or scramble control) on platelet adhesion to inflamed endothelium were measured using intravital microscopy. ResultsSignificant reductions in atherosclerotic plaques number and size, an overall robust health with longer survival were found in the peptide 4D treated group of ApoE−/− mice. Intravital microscopic studies conducted in exposed vessels of ApoE−/− mice demonstrated significant inhibition by peptide 4D of platelet adhesion to the cytokine-inflamed endothelium. ConclusionsOur results demonstrate that peptide 4D significantly reduces atherosclerotic plaque formation in ApoE−/− mice and inhibits platelet adhesion to the inflamed arterial endothelium.

Heparinized Polyurethane Surface Via a One-Step Photografting Method.

Traditional methods using coupling chemistry for surface grafting of heparin onto polyurethane (PU) are disadvantageous due to their generally low efficiency. In order to overcome this problem, a quick one-step photografting method is proposed here. Three heparin derivatives incorporating 0.21, 0.58, and 0.88 wt% pendant aryl azide groups were immobilized onto PU surfaces, leading to similar grafting densities of 1.07, 1.17, and 1.13 μg/cm2, respectively, yet with increasing densities of anchoring points. The most negatively charged surface and the maximum binding ability towards antithrombin III were found for the heparinized PU with the lowest amount of aryl azide/anchor sites. Furthermore, decreasing the density of anchoring points was found to inhibit platelet adhesion to a larger extent and to prolong plasma recalcification time, prothrombin time, thrombin time, and activated partial thromboplastin time to a larger extent. This was also found to enhance the bioactivity of immobilized heparin from 22.9% for raw heparin to 36.9%. This could be explained by the enhanced molecular mobility of immobilized heparin when it is more loosely anchored to the PU surface, as well as a higher surface charge.

Copper-Based SURMOFs for Nitric Oxide Generation: Hemocompatibility, Vascular Cell Growth, and Tissue Response.

A coating that can generate nitric oxide (NO) for surface modification of cardiovascular stents with adaptable NO release is an efficient approach to prevent thrombosis and neointimal hyperplasia. Herein, we prepared a copper-based surface-attached metal-organic framework (Cu-SURMOFs) of copper(II) benzene-1,3,5-tricarboxylate (CuBTC) using a layer-by-layer assembly method (LBL) for NO generation on the surface of alkali-activated titanium. It was easy to control surface chemistry and NO release by changing the number of LBL deposition cycles. The obtained CuBTC coating was characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy analysis and was able to decompose endogenous S-nitrosoglutathoine (GSNO) to catalytically produce NO. The resulting NO flux increased with increased deposition cycles. The coating prepared with 10 cycles of deposition showed ideal NO release and promoted proliferation of endothelial cells, suppressed growth of smooth muscle cells and macrophages, and inhibited platelet adhesion and activation. Further evaluation of thrombogenicity in an arteriovenous shunt model showed that the CuBTC coating had great ability to prevent thrombosis, and in vivo implantation of CuBTC-coated titanium wire demonstrated a significant inhibition of intimal hyperplasia. The results showed that use of copper-based SURMOFs could be a promising strategy for the surface modification of cardiovascular stents.

Synthesis and characterisation of composite sulphonated polyurethane/polyethersulphone membrane for blood purification application

Polyurethane (PU) with three different functional groups: carboxyl, hydroxyl and sulphonyl group on its molecular structure were synthesised in this work. The synthesised material suppresses blood clotting and exhibits anticoagulant characteristics due to the presence of the important anionic groups. The synthesised PU was blended with polyethersulphone (PES) and fabricated into flat-sheet membrane to study the physico-chemical and biocompatibility properties of the PES membrane for blood purification application. PES-PU flat-sheet membranes were fabricated via the dry-wet phase separation technique. Different loading of PU (0, 1, 2, 3, 4, and 5%) blended with PES was studied and compared. Based on the in-vitro biocompatibility analysis of the membrane, it can be suggested that the membrane incorporated with PU has better anticoagulant properties compared to the pristine PES membrane. PU incorporation prolonged the clotting time, decreased the formation of thrombin, decreased soluble complement component 3a (C3a) generation and suppressed platelet adhesion and aggregation. The anionic groups on the membrane surface might bind to coagulation factors (antithrombin) and the calcium ions, Ca2+ and thus improve anticoagulant ability. Based on both physico-chemical and in-vitro studied, 4% loading of PU is the optimum loading for incorporation with PES membrane. These results suggested that the blended PES-PU membranes with good haemocompatibility allowed practical application in the field of blood purification.

Micelle-embedded coating with ebselen for nitric oxide generation.

Nitric oxide generation is considered to be a key factor to mimic endothelial function in terms of anti-coagulation and anti-hyperplasia. Herein, ebselen which could play the similar role as glutathion peroxidase-like was loaded into micelles and was further assembled into a layer-by-layer coating. The ability of nitric oxide generation and corresponding biological effect were investigated. Endothelial-mimetic surface has now attracted huge attention in blood-contacting materials, due to its inherent ability of secreting nitric oxide. Among those categories, nitric oxide generation surface is considered to be safe and tunable in the modification of vascular biomedical devices. How to adsorb or immobilize glutathion peroxidase-like catalyst and maintain sustained/safe nitric oxide generation is full of interest. This study aimed at developing a functional coating constructed via layer-by-layer assembly to introduce the catalyst into the coating by pre-loading ebselen in micelles. We firstly introduced phenylboronic acid moiety into the micelle molecule backbone and grafted catechol moiety to chitosan backbone. Then, chitosan, micelles (containing ebselen) and heparin were adopted as polyelectrolytes and then alternatively assembled onto the substrate via layer-by-layer protocol. The catechol was conjugated to the amine groups of chitosan by Schiff base reaction to synthesize chitosan-catechol. The hydrophobic cholesterol was conjugated to the one end of the hydrophilic hyaluronic acid, and the hydroxymethylphenylboronic acid was conjugated to the other end via the esterification of carboxyl (–COOH) and hydroxyl (–OH). The modified hyaluronic acid could spontaneously form micelles in aqueous solution. Ebselen was the loaded into the as-prepared micelles. Chitosan-catechol, heparin, and micelles were alternatively assembled onto the substrate layer by layer to form a micelle-embedded coating. The micelle-embedded coating with ebselen was successfully obtained and the nitric oxide generation ability was in a safe level which was close to healthy endothelial cells. The coating could effectively inhibit platelet adhesion and smooth muscle cell proliferation. The use of ebselen preloaded into micelles could provide a sustained release of catalyst for in situ nitric oxide generation. Besides, this method could also be used to load diverse drugs and regulate desired properties. The study was approved by the Institutional Review Board of the West China Hospital in Sichuan University on March 3, 2018, with approval No. K2018044.

Study of hemocompatibility and endothelial cell interaction of tecoflex-based electrospun vascular grafts

Ensuring long-term functioning and efficient endothelialization of small diameter vascular grafts (VG) is an urgent task of tissue engineering. A solution may be to use electrospun VGs prepared from blends polyurethane with gelatin and/or bivalirudin. Here, properties of 3D matrices were explored by SEM, contact angle measurements and IR spectroscopy, and their interaction with blood and endothelial cells was studied. Introduction of gelatin into matrices enhanced adhesion and proliferation of endotheliocytes and enabled adhesion of platelets, whereas bivalirudin inhibited platelet adhesion while having no negative effect on the adhesion and proliferation of endothelial cells.

Coaxially-structured fibres with tailored material properties for vascular graft implant

Readily-available small-diameter arterial grafts require a great combination of materials properties, including high strength, compliance, suturability, blood sealing and anti-thrombogenicity, as well as anti-kinking property for those used in challenging anatomical situations. We have constructed grafts composed of coaxially-structured polycaprolactone (PCL)/gelatin nanofibres, and tailored the material structures to achieve high strength, compliance and kink resistance, as well as excellent water sealing and anti-thrombogenicity. Coaxially-structured fibres in the grafts provided mechanical stability through the core, while flexibility and cell adhesion through the sheath. Results showed that graft compliance increased while strength decreased with the concentration ratio between core and sheath polymers. Compared to pure PCL fibrous surfaces, coaxial PCL/gelatin fibrous surfaces potently inhibited platelet adhesion and activation, providing excellent anti-thrombogenicity. To render sufficient burst strength and suturability, an additional layer of pure PCL was necessary to cap the layer of coaxial PCL/gelatin fibres. The two-layered grafts with the wall thickness comparable to native arteries demonstrated artery-like compliance and kink resistance, properties important to arteries under complex mechanical loading. The in vivo evaluation was performed using the interposition carotid artery graft model in rabbits for three months. Interestingly, results from ultrasonic imaging and histological analysis demonstrated that the two-layered grafts with a thinner outer PCL layer, which possessed higher compliance and kink resistance, showed increased blood flow, minimal lumen reduction and fibrosis. All vascular grafts exhibited patency and induced limited cell infiltration. Together, we presented a facile and useful approach to fabricate vascular grafts with superior graft performances, biomechanical properties, and blood compatibility. Grafts with artery-like compliance and flexibility have demonstrated improved implantation outcomes.

Transfusion of Platelets Loaded With Recombinant ADAMTS13 (A Disintegrin and Metalloprotease With Thrombospondin Type 1 Repeats-13) Is Efficacious for Inhibiting Arterial Thrombosis Associated With Thrombotic Thrombocytopenic Purpura.

Objective- ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats-13) cleaves VWF (von Willebrand factor). This process is essential for hemostasis. Severe deficiency of plasma ADAMTS13 activity, most commonly resulting from autoantibodies against ADAMTS13, causes thrombotic thrombocytopenic purpura. Therapeutic plasma exchange is the standard of care to date, which removes autoantibodies and replenishes ADAMTS13. However, such a therapy is often ineffective to raise plasma ADAMTS13 activity, and in-hospital mortality rate remains as high as 20%. Approach and Results- To overcome the inhibition by autoantibodies, we developed a novel approach by delivering rADAMTS13 (recombinant ADAMTS13 ) using platelets as vehicles. We show that both human and murine platelets can uptake rADAMTS13 ex vivo. The endocytosed rADAMTS13 within platelets remains intact, active, and is stored in α-granules. Under arterial shear (100 dyne/cm2), the rADAMTS13 in platelets is released and effectively inhibits platelet adhesion and aggregation on a collagen-coated surface in a concentration-dependent manner. Transfusion of rADAMTS13-loaded platelets into Adamts13-/- mice dramatically reduces the rate of thrombus formation in the mesenteric arterioles after FeCl3 injury. An ex vivo transfusion of rADAMTS13-loaded platelets to a reconstituted whole blood containing plasma from a patient with immune-mediated thrombotic thrombocytopenic purpura and the cellular components (eg, erythrocytes and leukocytes) from a healthy individual, as well as a fresh whole blood obtained from a patient with congenital or immune-mediated thrombotic thrombocytopenic purpura also dramatically reduces the rate of thrombus formation under arterial flow. Conclusions- Our results demonstrate that transfusion of rADAMTS13-loaded platelets may be a novel and potentially effective therapeutic approach for arterial thrombosis, associated with congenital and immune-mediated thrombotic thrombocytopenic purpura.

A new approach for membrane modification based on electrochemically mediated living polymerization and self-assembly of N-tert-butyl amide- and β-cyclodextrin-involved macromolecules for blood purification

We report a convenient, highly efficient, and universal approach for blood-compatible modification of polymer membrane based on the SI-eATRP, RAFT, and self-assembly of N-tert-butyl amide and β-cyclodextrin existed in macromolecules chains. The functional membrane surfaces with any polymer chains of hydrophilic, ionic polymer, and polysaccharide segments, for example, the copolymers of N-vinyl pyrrolidone, sodium p-styrenesulfonate hydrate, and glucose allyl amide, are easily designed and fabricated; and the thickness of polymer brushes are efficiently controlled by polymerization conditions like monomer concentration and initiator amount. As a key bio-plastic, the modified polyethersulfone membrane shows suppressed platelet adhesion, significant decreases in thrombin-antithrombin generation, and the complement activations on C3a and C5a levels compared with pristine polyethersulfone membrane; while the platelet activation (PF4) decreased. Due to the similar groups as heparin-like structure, the modified membrane effectively prolonged the activated partial thromboplastin time, thrombin time, and prothrombin time. The water contact angle of the modified membrane decreases from 89.2 to 22.3°, and the cytocompatibility of the modified membranes largely enhanced. It could be concluded that the new approach could be widely used for polymer membrane modification, and the mimic heparin-like surface seems to be a promising structure to improve the biocompatibility for blood purification application.

Nanofibrous composite hemodiafiltration membrane: A facile approach towards tuning the barrier layer for enhanced performance

In order to develop advanced hemodiafiltration membrane with favorable biocompatibility and efficient dialysis performance, novel thin film nanofibrous composite (TFNC) ultrafiltration (UF) membranes consisting of sulfonated poly(vinyl alcohol) (s-PVA) blended PVA hydrogel barrier layer and electrospun polyacrlonitrile (PAN) nanofibrous supporting layer were designed and fabricated by combining electrospinning and conventional surface coating techniques. The mesh sizes of hydrogel network of s-PVA/PVA barrier layer could be tuned by varying the blending content of s-PVA. The optimized s-PVA/PVA TFNC UF membrane (S-P-TFNC-1-3) possessed high pure water flux up to 380 L m−2 h−1 bar−1 with high bovine serum albumin (BSA) rejection (>90%). Besides, the introduction of s-PVA into the hydrogel barrier layer endowed the TFNC membranes with enhanced hydrophilicity, antifouling property and biocompatibility (decreased protein adsorption, prolonged clotting time, suppressed platelet adhesion, lower hemolysis ratio and more benefits for cell proliferation) due to the presence of sulfonic groups. The dialysis simulation experiment results of S-P-TFNC-1-3 showed that 84.2% of urea and 60.9% of lysozyme were cleaned and over 95% of BSA was retained after 4 h dialysis process. Especially, the removal of middle-molecule uremic toxin was more efficient than conventional hemodialysis membranes reported so far, and high retention of big proteins was achieved simultaneously. This work exposes a window of opportunity for modified PVA TFNC membranes in blood purification applications.

Poly-ε-caprolactone/polysulfhydrylated polyester blend: A platform for topical and degradable nitric oxide-releasing materials

Polymeric biomaterials for implantable medical devices are subject to demands that go beyond passive biocompatibility. Inhibition of thrombus formation, reduced inflammatory response and the eventual complete bioabsorption of the implant are central challenges for emerging polymeric biomaterials. Nitric oxide (NO) released at the biomaterial/tissue interface may inhibit platelet adhesion and improve tissue integration in blood-contacting/implanted devices. In addition, local NO release may increase vasodilation, thereby improving ischemic conditions in topical applications. In this study, we present a novel degradable NO-releasing polymeric platform based on blended poly-ε-caprolactone (PCL)/polysulfhydrylated polyester (PSPE). PCL formed miscible blends with PSPE up to 45 wt% of PSPE. S-nitrosation of the PCL/PSPE blends converted the surface PSPE component into a NO-releasing polynitrosated polyester (PNPE). Real-time chemiluminescence NO detection showed that blends with different PCL:PSPE ratios allow surface S-nitrosothiol concentrations in the range of 0.5–1.5 μmol/cm2. Topical application of blended PCL/PNPE films on the healthy skin led to a 6–10-fold increase in the skin blood flow due to local NO delivery, as shown by in vivo laser-Doppler flowmetry. Blended PCL/PSPE films displayed higher hydrophilicity and a 2–11-fold increase in the hydrolytic mass loss, compared to pure PCL films. Therefore, PCL/PSPE blend is a potential biomaterial platform for local NO delivery and more quickly degradable biomedical devices.

The clinical evaluation of novel polymethyl methacrylate membrane with a modified membrane surface: a multicenter pilot study

BackgroundPolymethyl methacrylate (PMMA) membranes have the unique property of adsorption, which can remove medium- and large-weight molecular substances that cannot be removed by normal hemodialysis and hemodiafiltration. Filtryzer® NF (NF) is a newly developed PMMA membrane that suppresses platelet adhesion on the membrane surface and retains an adsorption property. NF is expected to improve inflammatory conditions and clinical symptoms in hemodialysis patients compared with conventional PMMA membranes.MethodsThirty-seven maintenance hemodialysis patients treated with polysulfone (PS) membranes and who had detectable chronic inflammation were enrolled into the study. The patients were randomly allocated into the NF and PS groups and observed for 1 year. C-reactive protein (CRP) values were measured as the primary endpoint. Nutrition, blood cell count, and dialysis itchiness were evaluated as secondary endpoints.ResultsSignificant differences in CRP values were not found between the NF and PS groups. In the PS group, the creatinine generation rate (%CGR) and platelet count, which were included in nutrition and blood cell count, respectively, significantly decreased after 6 and 9 months compared with the start of study, but these parameters did not significantly change in the NF group within 1 year. Dialysis itchiness in the NF group was significantly improved compared with the PS group after 9 months.ConclusionsOur results showed that a new PMMA membrane, NF, has a potential to maintain nutritional conditions and the platelet counts and improve dialysis itchiness.Trial registrationThis study is retrospectively registered with the Clinical Trials Registry of the University Hospital Medical Information Network on February 17, 2015 (registration ID, UMIN000016567).

Hydrophilic Stent Coating Inhibits Platelet Adhesion on Stent Surfaces: Initial Results In Vitro

BackgroundEndovascular stents and flow diverter stents (FDS) have revolutionized the treatment of intradural aneurysms; however, the need for dual anti-platelet treatment (DAPT) limits their use and can cause additional issues. Therefore, there is a need to develop stent coatings that negate the need for DAPT.MethodsTwo different hydrophilic polymer coatings (HPC-I and HPC-II) were used to coat small nickel titanium plates to initially test the hydrophilic properties of these coatings when applied to nickel titanium. The plates were subsequently incubated with non-medicated whole blood from healthy volunteers for 10 min and stained with a CD61 immunofluorescent antibody that allows detection of adherent platelets. The coatings were applied to FDS wires and were again incubated with non-medicated whole blood from the same volunteers. Scanning electron microscopy was used to detect adherent platelets on the wire surface.ResultsThe HPC-II coating (1.12 ± 0.4%) showed a significantly lower CD61 +ve cell count (p ≤ 0.001) compared to both uncoated NiTi plates (48.61 ± 7.3%) and those with the HPC-I coating (mean 40.19 ± 8.9%). Minimal adherent platelets were seen on the FDS nickel titanium wires coated with the HPC-II compared to uncoated FDS under electron microscopy.ConclusionThere is a significant decrease in the number of adherent CD61 +ve platelets on nickel titanium surfaces coated with the HPC-II coating compared to uncoated surfaces. The coating can be successfully applied to the wires of flow diverters. The results of this study are promising with regard to the development of new anti-thrombogenic endovascular devices.

Construction of a bilayered vascular graft with smooth internal surface for improved hemocompatibility and endothelial cell monolayer formation

Formation of a continuous endothelial cell (EC) monolayer inside the luminal surface with enhanced hemocompatibility, is a promising solution for improving performance and overall patency of small-diameter vascular grafts. There has been much debate regarding the ideal substrate surface topography to achieve this. Here, we investigated different polycaprolactone (PCL)-derived substrate surfaces fabricated from nanofibers, microfibers, or with smooth surfaces, and evaluated their effect on hemocompatibility and EC behavior. Our results demonstrated that, compared with the other two substrates, smooth surfaces inhibited platelet adhesion and activation, suppressed fibrinogen adsorption, and enhanced EC monolayer formation. In addition, smooth surfaces increased EC nitric oxide (NO) production and acetylated low-density lipoprotein (Ac-LDL) uptake. Thus, we designed and fabricated a bi-layered vascular graft composed of a smooth ultrathin internal layer and a microfibrous external layer, which were capable of preventing spiral-flow and decreasing wall-shear stress. Arterio-venous shunt models revealed that bi-layered grafts avoided bleeding and inhibited both protein absorption and platelet adhesion. Overall, these findings indicated that the prepared bi-layered grafts could perform better for in vivo implantation. Furthermore, this approach doesn't require chemical or biological modifications, and therefore can be easily applied to the fabrication of other implantable tubular grafts using various materials.

LMU Munich: platelet inhibition novel aspects on platelet inhibition and function.

A core research area in the Department of Cardiology at Ludwig-Maximilians-University (LMU) Munich focuses on antiplatelet therapy, its translational aspects, and its underlying mechanism with respect to platelet physiology. We are conducting a broad range of investigator-initiated clinical trials (phase II-IV) and preclinical studies on the topic of antithrombotic therapy for percutaneous coronary intervention patients, platelet activation, and reactivity as well as on novel inhibitors of platelet adhesion. Just recently, we completed the large multi-centre investigator-initiated TROPICAL-ACS trial on guided early de-escalation of antiplatelet treatment in acute coronary syndrome (ACS) patients (Sibbing et al. in Lancet 390:1747-1757, 2017; Sibbing et al. in Thromb Haemost 117:1240-1248), done at 33 sites in Europe. Furthermore, besides other ongoing clinical studies, we initiated and are currently recruiting patients for the multi-centre randomized APixaban versus PhenpRocoumon in Patients With ACS and AF: APPROACH-ACS-AF study as well as for the multi-centre phase II randomized, double-blind, placebo-controlled study of revacept in Patients With Stable Coronary Artery Disease (Revacept/CAD/02) trial.

Surface Nanostructuring of Parylene-C Coatings for Blood Contacting Implants.

This paper investigates the effects on the blood compatibility of surface nanostructuring of Parylene-C coating. The proposed technique, based on the consecutive use of O2 and SF6 plasma, alters the surface roughness and enhances the intrinsic hydrophobicity of Parylene-C. The degree of hydrophobicity of the prepared surface can be precisely controlled by opportunely adjusting the plasma exposure times. Static contact angle measurements, performed on treated Parylene-C, showed a maximum contact angle of 158°. The nanostructured Parylene-C retained its hydrophobicity up to 45 days, when stored in a dry environment. Storing the samples in a body-mimicking solution caused the contact angle to progressively decrease. However, at the end of the measurement, the plasma treated surfaces still exhibited a higher hydrophobicity than the untreated counterparts. The proposed treatment improved the performance of the polymer as a water diffusion barrier in a body simulating environment. Modifying the nanotopography of the polymer influences the adsorption of different blood plasma proteins. The adsorption of albumin—a platelet adhesion inhibitor—and of fibrinogen—a platelet adhesion promoter—was studied by fluorescence microscopy. The adsorption capacity increased monotonically with increasing hydrophobicity for both studied proteins. The effect on albumin adsorption was considerably higher than on fibrinogen. Study of the proteins simultaneous adsorption showed that the albumin to fibrinogen adsorbed ratio increases with substrate hydrophobicity, suggesting lower thrombogenicity of the nanostructured surfaces. Animal experiments proved that the treated surfaces did not trigger any blood clot or thrombus formation when directly exposed to the arterial blood flow. The findings above, together with the exceptional mechanical and insulation properties of Parylene-C, support its use for packaging implants chronically exposed to the blood flow.

Dynamical Analysis of the Inhibitory Effect of Aspirin and Clopidogrel on Platelet Adhesion and Aggregation for Healthy People under Physiological Flow Condition by Microfluidic Chip Technology

Objective To explore the inhibitory effect of aspirin and clopidogrel on platelet adhesion and aggregation behaviors under the physiological flow condition using microfluidic chip technology for health volunteers. Methods Peripheral venous blood samples collected from twelve randomly recruited health volunteers were treated with 20 μmol/L acetylsalicylic acid,50 μmol/L 2-methlthioadenosine-5'-monophosphate triethylammonium salt,and their combination,respectively,with untreated blood samples being control group. The blood samples were flowed through a microchannel modified with type I collagen protein at a physiological relevant shear rate of 1000 s-1 for 300 s,while the fluorescent images of platelet aggregations were dynamic captured using a microscope. Based on the images,the platelet coverage rates were calculated and used as quantitative parameters for evaluating platelet adhesion and aggregation behaviors. Results Under a flow condition of 1000 s-1 shear rate,an expected in vivo-like platelet adhesion and aggregation behaviors were observed at the surfaces of collagen proteins for control blood samples. Aspirin alone or clopidogrel alone suppressed platelet adhesion and aggregation at the later period of flow(200-300 s),while the combination of aspirin and clopidogrel reduced the adhesion numbers of platelets at the earlier stage of flow(≤150 s) and compromised the stability of platelet aggregation at the later period of flow(200-300 s). The combination showed synergistic effect in inhibiting platelet aggregation. Furthermore,such inhibitory effect was heterogeneous among 12 volunteers. Conclusion This simple microfluidic technology can offer a new technical platform for analyzing the inhibitory effect of antiplatelet drugs.

Bone marrow-derived mononuclear cell seeded bioresorbable vascular graft improves acute graft patency by inhibiting thrombus formation via platelet adhesion

BackgroundAcute thrombosis is a crucial cause of bioresorbable vascular graft (BVG) failure. Bone marrow-derived mononuclear cell (BM-MNC)-seeded BVGs demonstrated high graft patency, however, the effect of seeded BM-MNCs against thrombosis remains to be elucidated. Thus, we evaluated an antithrombotic effect of BM-MNC-seeding and utilized platelet-depletion mouse models to evaluate the contribution of platelets to acute thrombosis of BVGs. Methods and resultsBVGs were composed of poly(glycolic acid) mesh sealed with poly(l-lactideco-ε-caprolactone). BM-MNC-seeded BVGs and unseeded BVGs were implanted to wild type C57BL/6 mice (n = 10/group) as inferior vena cava interposition conduits. To evaluate platelet effect on acute thrombosis, c-Mpl−/− mice and Pf4-Cre+; iDTR mice with decreased platelet number were also implanted with unseeded BVGs (n = 10/group). BVG patency was evaluated at 2, 4, and 8 weeks by ultrasound. BM-MNC-seeded BVGs demonstrated a significantly higher patency rate than unseeded BVGs during the acute phase (2-week, 90% vs 30%, p = .020), and patency rates of these grafts were sustained until week 8. Similar to BM-MNC-seeded BVGs, C-Mpl−/− and Pf4-Cre+; iDTR mice also showed favorable graft patency (2-week, 90% and 80%, respectively) during the acute phase. However, the patency rate of Pf4-Cre+; iDTR mice decreased gradually after DTR treatment as platelet number recovered to baseline. An in vitro study revealed BM-MNC-seeding significantly inhibited platelet adhesion to BVGs compared to unseeded BVGs, (1.75 ± 0.45 vs 8.69 ± 0.68 × 103 platelets/mm2, p < .001). ConclusionsBM-MNC-seeding and the reduction in platelet number prevented BVG thrombosis and improved BVG patency, and those results might be caused by inhibiting platelet adhesion to the BVG.