Antithrombogenic Drug Research Articles

Surface modification of polyurethane with eptifibatide-loaded degradable nanoparticles reducing risk of blood coagulation

The main purpose of the work was to develop a drug releasing coatings on the surface of medical devices exposed to blood flow, what should enable effective inhibition of blood coagulation process. As a part of the work, the process of encapsulating the anticoagulant drug eptifibatide (EPT) in poly(DL-lactic-co-glycolic acid) (PLGA) nanoparticles was developed. EPT encapsulation efficiency was 29.1 ± 2.1%, while the EPT loading percentage in the nanoparticles was 4.2 ± 0.3%. The PLGA nanoparticles were suspended in a polyanion solution (hyaluronic acid (HA)) and deposited on the surface-treated thermoplastic polyurethane (TPU) by a layer-by-layer method. As a polycation poly-L-lysine (PLL) was used. The influence of released EPT on the activation of the coagulation system was analyzed using dynamic blood tester. Performed experiments show an effective delivery of the drug to the bloodstream and low risk of platelets (membrane receptor) activation. The dynamic blood test process, including its physical phenomenon, was described using numerical methods, i.e. a finite volume cone-and-plate test model as well as non-Newtonian blood models. The values of shear stress and blood flow velocity under the fast-rotating cone were computed applying boundary conditions of cylinder wall imitating blood-nanomaterial interaction. Implementing boundary conditions as initial shear stress values of bottom cylinder wall resulted in the increase of shear stress in blood under rotating cone. The developed system combining drug eluting polymeric nanoparticles with the polyelectrolyte “layer-by-layer” coating can be easily introduced to medical implants of various shape, with the advantages of resorbable drug carriers allowing for local and controllable delivery of anti-thrombogenic drugs.

A Technology for Anti-Thrombogenic Drug Coating of Small-Diameter Biodegradable Vascular Prostheses.

The aim of the study was to develop a technology for anti-thrombogenic drug coating of biodegradable porous scaffolds and to evaluate the physicomechanical and hemocompatible properties of functionally active vascular prostheses with and without a drug coating.Materials and Methods.Vascular prostheses from polyhydroxybutyrate/valerate and polycaprolactone with the incorporated vascular endothelial growth factor, the main fibroblast growth factor, and the chemoattractant SDF-1α were made by emulsion electrospinning. Additional surface modification of the prostheses was carried out by forming a hydrogel coating of polyvinylpyrrolidone capable of binding drugs as a result of complexation. Unfractionated heparin and iloprost were used as anti-thrombogenic drugs.Results.We show that after the modification of vascular prostheses with heparin and iloprost, a 5.8-fold increase in the Young’s modulus value was noted, which indicated a greater stiffness of these grafts compared to the unmodified controls. Platelet aggregation on the surface of heparin + iloprost coated vascular prostheses was 3.3 times less than that with the unmodified controls, and 1.8 times less compared to intact platelet-rich plasma. The surface of vascular prostheses with heparin and iloprost was resistant to adhesion of platelets and blood proteins.Conclusion.Drug (unfractionated heparin and iloprost) coating of the surface of biodegradable prostheses significantly improved the anti-thrombogenic properties of these grafts but contributed to the increased stiffness of the prostheses.

Expanded Poly(tetrafluoroethylene) Blood Vessel Grafts with Embedded Reactive Oxygen Species (ROS)-Responsive Antithrombogenic Drug for Elimination of Thrombosis.

Treatment of cardiovascular diseases suffers from the lack of transplantable small-diameter blood vessel (SDBV) grafts that can prohibit/eliminate thrombosis. Although expanded poly(tetrafluoroethylene) (ePTFE) has the potential to be used for SDBV grafts, recurrence of thrombus remains the biggest challenge. In this study, a reactive oxygen species (ROS)-responsive antithrombogenic drug synthesis and a bulk coating process were employed to fabricate functional ePTFE grafts capable of prohibiting/eliminating blood clots. The synthesized drug that would release antiplatelet ethyl salicylate (ESA), in responding to ROS, was dissolved in a polycaprolactone (PCL) solution, followed by a bulk coating of the as-fabricated ePTFE grafts with the PCL/drug solution. Nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM) were employed to investigate and confirm the synthesis and presence of the ROS-responsive drug in the ePTFE grafts. The ESA release functions were demonstrated via the drug-release profile and dynamic anticoagulation tests. The biocompatibility of the ROS-responsive ePTFE grafts was demonstrated via lactate dehydrogenase (LDH) cytotoxicity assays, live and dead cell assays, cell morphology, and cell-graft interactions. The ROS-responsive, antithrombogenic ePTFE grafts provide a feasible way for maintaining long-term patency, potentially solving a critical challenge in SDBV applications.

Preparation of biofiltration membranes by coating electrospun polyacrylonitrile fiber membranes with layer-by-layer supermolecular polyelectrolyte films

Electrospun polyacrylonitrile fiber membranes (EPFMs) were coated with multilayer films, assembled using the layer-by-layer (LbL) technique through the alternate deposition of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA), to develop an antithrombogenic drug release membrane for hemodialysis. Methylene blue (MB) and heparin (HEP) were attached to the PAH and PAA multilayers, respectively, as model drug and antithrombogenic agent to investigate the dual functionality of the membranes. The positively (PAH, MB) and negatively (PAA, HEP) charged groups generated a supermolecular polyelectrolyte multilayer film (SPF) capable of loading high amounts of MB and HEP on the EPFMs at appropriate composition. The pH was fixed at 5.5 during assembly to stabilize the SPF. Heavy assembly of the PAH/PAA multilayer occurred at 10 wt% of both MB and HEP with 25 cycles of LbL deposition, and it exhibited long-term release of MB and low release of HEP at pH 7.4 in a circulatory system. The SPF-coated EPFMs also achieved low platelet attachment after 4 h of platelet rich plasma circulation and showed prolonged clotting times including thromboplastin, thrombin, and prothrombin times. Collectively, these observations suggest that SPF-coated EPFMs have great potential for use as hemodialysis membranes with positively charged drug loading.

Cellular and Molecular Mechanisms of Antithrombogenic Plants: A Narrative Review.

Heart attack, stroke, and deep vein thrombosis are among the conditions that alter blood coagulation and are modulated by antithrombogenic drugs. Natural products are an important source of antithrombogenic agents and have been considered remarkable alternatives with greater efficacy and usually with fewer side effects. However, the efficacy and toxicity of many of these plants that are used in traditional medicine must be scientifically tested. Despite a large number of published articles that report that plants or plant-derived components may act as antithrombogenic agents, few studies have investigated the mechanism of action of medicinal plants. This review presents the current knowledge about the major cellular and molecular mechanisms of antithrombogenic plants and their main components. Many well-established mechanisms (e.g., platelet aggregation, coagulation factors, and thrombolysis) are related to the antithrombogenic activity of many natural products. However, the central pathways that are responsible for their activity remain unclear. Further studies are needed to clarify the central role of each of these pathways in the pleiotropic response to these agents.

Preparation and characterization of Lecithin–heparin intercalated in montmorillonite nanocomposite

Abstract In this work, a study of Lecithin–heparin intercalated in montmorillonite was performed in order to synthesize an antithrombogenic hybrid. The hybrid of montmorillonite (Mt)/Lecithin–heparin (LEC-HEP) was synthesized by the intercalation method under mechanical stirring. The composite was characterized by X-ray diffraction (XRD) analysis, X-ray fluorescence (XRF) and C, H, and N elemental analyses, zeta potentials, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) techniques. The d001-value was increased by LEC-HEP intercalation. Fourier transform infrared spectroscopy also confirmed the intercalation of Lecithin–heparin into Mt interlayer space. In vitro release study of the antithrombogenic drug–Mt intercalates in phosphate buffer saline (pH 7.4) media at 37 °C was investigated. The heparin showed an initial burst effect for 24 h and then continuously released for 30 d. In-vitro blood compatibility of the Mt/LEC-HEP was carried out via hemolysis assay. The Mt/LEC-HEP exhibited hemolysis below 5% which is permissible for biomaterials. These modified materials have the potential for being used as blood contact materials.

Enhancing anti-thrombogenicity of biodegradable polyurethanes through drug molecule incorporation.

Sufficient and sustained anti-thrombogenicity is essential for blood-contacting materials, because blood coagulation and thrombosis caused by platelet adhesion and activation on material surfaces may lead to functional failure and even fatal outcomes. Covalently conjugating antithrombogenic moieties into polymer, instead of surface modifying or blending, can maintain the anti-thrombogenicity of polymer at a high level over a time range. In this study, series of randomly crosslinked, elastic, biodegradable polyurethanes (PU-DPA) were synthesized through a one-pot and one-step method from polycaprolactone (PCL) diol, hexamethylene diisocyanate (HDI) and anti-thrombogenic drug, dipyridamole (DPA). The mechanical properties, hydrophilicity, in vitro degradation, and anti-thrombogenicity of the resultant PU-DPA polymers can be tuned by altering the incorporated DPA amount. The surface and bulk hydrophilicity of the polyurethanes decreased with increasing hydrophobic DPA amount. All PU-DPA polymers exhibited strong mechanical properties and good elasticity. The degradation rates of the PU-DPAs decreased with increasing DPA content in both PBS and lipase/PBS solutions. Covalently incorporating DPA into the polyurethane significantly reduced the platelet adhesion and activation compared to the polyurethane without DPA, and also can achieve sustained anti-thrombogenicity. The PU-DPA films also supported the growth of human umbilical vein endothelial cells. The attractive mechanical properties, blood compatibility, and cell compatibility of this anti-thrombogenic biodegradable polyurethane indicate that it has a great potential to be utilized for blood-contacting devices, and cardiovascular tissue repair and regeneration.

Emergent Pancreatobiliary Endoscopic Treatment for who Taking Antithrombogenic Drugs

Emergent Pancreatobiliary Endoscopic Treatment for who Taking Antithrombogenic Drugs

脳出血における血腫増大および予後に関連する因子について

We examined factors related to hematoma growth in 932 consecutive patients with intracerebral bleeding. Eighty-seven (9.3%) of patients had hematoma growth. The ratio of estimated hematoma volume in the second CT versus that in the first CT in patients with hematoma growth was 2.57±2.52 (mean±SD) times (range: 1.12–17.90 times). The modified Rankin Scale (mRS) at discharge in all patients was 0 (22 patients), 1 (33), 2 (90), 3 (182), 4 (149), 5 (371), and 6 (85). Bivariate and multivariate analyses both showed that the incidence of hematoma growth was significantly higher in patients with internal administration of an antiplatelet drug, those with high prothrombin time-international normalized ratio (PT-INR), and those with concomitant development of liver disorders including hepatic dysfunction. The odds ratio for hematoma growth was 2.78 in patients with internal administration of an antiplatelet drug, 1.69 in those with high PT-INR, and 2.89 in those with concomitant development of liver disorders including hepatic dysfunction, showing that these factors would be closely related to hematoma growth. In addition, the mRS at discharge was significantly poor in aged patients, patients with a low Glasgow Coma Scale (GCS), those with high systolic arterial pressure, and those with concomitant development of renal disorders including renal dysfunction. Especially relevant was the odds ratio of poor mRS at discharge, which was 0.71 in GCS, and 3.52 in those with concomitant development of renal disorders including renal dysfunction. This suggests that these factors are highly related to low mRS at discharge. When considering the potential development of intracerebral bleeding in the future, it will be desirable to administer an antithrombogenic drug only to patients for which it is essential. Concomitant administration of antiplatelet drugs and anticoagulants should be avoided as much as possible. When patients with concomitant development of hepatic dysfunction and renal dysfunction develop intracerebral bleeding, administration of an antithrombogenic drug should be minimized due to high risks of hematoma growth and poor prognosis.

Development of a probucol‐releasing antithrombogenic drug eluting stent

The success of drug eluting stents (DESs) has been challenged by the manifestation of late stent thrombosis after DES implantation. The incomplete regeneration of the endothelial layer poststenting triggers adverse signaling processes precipitating in thrombosis. Various approaches have been attempted to prevent thrombosis, including the delivery of biological agents, such as estradiol, that promote endothelialization, and the use of natural polymers as coating materials. The underlying challenge has been the inability to release the biological agent in synchronization with the temporal sequence of vascular wound healing in vivo. The natural healing process of the endothelium after an injury starts after a week and may take up to a month in humans. This article presents a novel DES formulation using a hemocompatible polyurethane (PU) matrix to sustain the release of probucol (PB), an endothelial agonist, by exploiting the greater difference in the solubility parameters of PB and PU. This results in the formation of crystalline PB aggregates retarding drug release from PU. The physicochemical properties of PB in PU were confirmed using differential scanning calorimetry and X-ray diffraction. Drug-polymer compatibility was examined using infrared spectral analysis. Also, in vitro studies using primary human aortic endothelial cells resulted in the selection of 5% w/w PB as the optimal dose, to be further tested in vitro and in vivo. This work develops and tests a promising new DES formulation to enable faster endothelial cell proliferation poststenting, potentially minimizing the incidence and severity of thrombotic events after DES implantation.

New poly(3-hydroxybutyrate)-based systems for controlled release of dipyridamole and indomethacin

New poly-(3-hydroxybutyrate)-based systems for controlled release of anti-inflammatory and antithrombogenic drugs have been studied. The release occurs via two mechanisms (diffusion and degradation) operating simultaneously. Dipyridamole and indomethacin diffusion processes determine the rate of the release at the early stages of the contact of the system with the environment (the first 6-8 days). The coefficient of the release diffusion of a drug depends on its nature, the thickness of the poly-(3-hydroxybutyrate) films containing the drug, the concentrations of dipyridamole and indomethacin, and the molecular weight of the poly-(3-hydroxybutyrate). The results obtained are critical for developing systems of release of diverse drugs, thus, enabling the attainment of the requisite physiological effects on tissues and organs of humans.

RGD-modified liposomes targeted to activated platelets as a potential vascular drug delivery system

Local drug delivery has become an important treatment modality for the prevention of thrombotic events following coronary angioplasty. In this study, we investigate the ability of liposomes bearing surface conjugated linear Arg-Gly-Asp (RGD) peptide (GSSSGRGDSPA) moieties to target and bind activated platelets, and the effect of such RGD-modified liposomes on platelet activation and aggregation. The binding of RGD-liposomes to human platelets was assessed by fluorescence microscopy, phase contrast microscopy and flow cytometry. The effect of RGD-modified liposomes on platelet activation and aggregation was investigated in vitro, with and without platelet agonists. RGD-liposomes were found to bind activated platelets at levels significantly greater than the control RGE-liposomes. The RGD-liposomes did not exhibit any statistically significant effect on platelet activation or aggregation. The results demonstrate the ability of the RGD-modified liposomes to target and bind activated platelets without causing significant platelet aggregation and suggests a feasible way for the development of a platelet-targeted anti-thrombogenic drug delivery system. Furthermore, the approach can be extended to the development of liposomes for other vascular targets, for application in drug delivery or gene therapy.

New resorbable polymeric systems with antithrombogenic activity.

The synthesis and application as resorbable coatings of vascular grafts of a new polyacrylic derivative of Triflusal (2-acetyloxy-4-trifluoromethyl)benzoic acid, a commercial drug with antithrombogenic properties, are described. The high-molecular-weight polyacrylic system is rather stable in physiological conditions and provides a chemical support for the slow release of the pharmacologically active compound, Triflusal, or its main metabolite (2-hydroxy-4-trifluoromethyl)benzoic acid (HTB). Experiments of deposition and retention of platelets in static basal conditions using plasma-rich medium from blood of sheep, seem to indicate that the polymeric coating of the polyacrylic derivative of Triflusal improves the antiaggregating character for platelets of the surface of small-diameter vascular grafts without the application of other antithrombogenic drugs.

Differential Effect of SIN-1 on Thromboxane and Prostacyclin Formation in Platelets and Endothelial Cells

The effect of SIN-1, the active metabolite of molsidomine that inhibits platelet aggregation, was tested upon the oxidation of arachidonic acid in platelets and endothelial cells. The metabolism of arachidonic acid from both exogenous and endogenous sources was investigated by determining the formation of thromboxane and prostacyclin. These prostanoids were measured in platelets and endothelial cells alone or during their interaction, in the absence or presence of SIN-1. The presence of endothelial cells decreased the generation of thromboxane by the platelets, especially from endogenous arachidonate, whereas the platelets tended to increase that of prostacyclin under basal conditions. SIN-1 significantly reduced the production by the platelets of metabolites from endogenous arachidonic acid but did not affect those from exogenous sources. The reduction in metabolism of endogenous arachidonate was more pronounced in the presence of endothelial cells. In contrast, SIN-1 did not alter the production of cyclo-oxygenase metabolites of arachidonic acid in endothelial cells. Thus, the liberation of arachidonic acid, leading to prostanoid synthesis, may be regulated differentially in platelets and endothelial cells: molsidomine might be a potential antithrombogenic drug because it alters specifically the phospholipase activity in the platelets.

Enzymatic basis for platelet: collagen adhesion as the primary step in haemostasis.

The formation of an enzyme-acceptor complex as the effective intermediate in platelet: collagen adhesion provides a simple model for studying the primary step in haemostasis and may provide a rational basis for the design of anti-thrombogenic drugs.

Role of surface charge of the blood vessel wall, blood cells, and prosthetic materials in intravascular thrombosis.

Intravascular thrombosis is an interfacial reaction. One can therefore expect it to depend on the surface charge characteristics of the blood vessel wall, blood cells, and prosthetic materials. Electrokinetic methods (electroosmosis, streaming potentials, electrophoresis) have been used to determine these characteristics. The results of the experiments to date may be summarized as follows: (1) under normal conditions, the blood vessel wall and blood cells are negatively charged; (2) injury to the blood vessel wall reduces the magnitude of the negative charge density and very often even causes a reversal in the sign of the surface charge—injury is generally accompanied by thrombus formation; (3) a decrease in pH reduces the negative charge density of the blood vessel wall and of blood cells. The isoelectric point occurs at a pH of about 4.7; (4) antithrombogenic drugs increase the magnitude of the negative charge density, whereas thrombogenic drugs have the opposite effect and in many cases even reverse its sign; and (5) positively charged prosthetic materials are thrombogenic whereas negatively charged surfaces tend to be nonthrombogenic—the higher and the more uniform the negative charge density, the better is the chance of the materials being nonthrombogenic.

Effects of Chemical Compounds upon Current Induced Thrombosis in Rat Mesenteric Vessels

SummaryFrom previous work in our laboratories, there is a large amount of evidence for an electrochemical mechanism of thrombosis. The blood vessel wall and blood cells are negatively charged under normal conditions. Antithrombogenic drugs increase their negative charge densities while thrombogenic drugs have the opposite effect. Injury makes the blood vessel wall less negatively charged or even positively charged. There is a relation between vascular injury currents and thrombosis. In the present study, the effect of certain chemical agents upon in situ thrombosis in rat mesoappendix vessels, produced by an applied electric current of the sign and magnitude of physiological injury currents, is examined. Compounds such as polyquarternary, with basic groups enhance thrombosis while compounds such as heparin with acidic groups inhibit thrombosis.