Anticoagulant and antiplatelet agents: their clinical and device application(s) together with usages to engineer surfaces

Three-Component Reaction between 3-Acetylcoumarins, Amines, and Elemental Sulfur: A Designed Approach to 3-Amino-4H-thieno[3,2-c]coumarins

In this work, a series of novel 3-amino-4H-thieno[3,2-c]coumarins were designed and synthesized by a one-pot, catalyst-free, and three-component reaction of 3-acetylcoumarins with amines and elemental sulfur. Readily available starting materials, simple heating conditions, facile installation of a sulfur atom into the molecule using S8 as a sulfur source, acceptable functional group tolerance, and synthetically useful yields are some highlighted benefits of this process.

Thermoplastic polyurethane/POSS nanohybrids: Synthesis, morphology, and biological properties

Recent studies show good osteoinductive properties of polyurethanes modified with polyhedral oligomeric silsesquioxanes (POSS). In this work, three types of POSS; propanediolisobutyl-POSS (PHI-POSS), disilanolisobutyl-POSS (DSI-POSS), and octahydroxybutyl-POSS (OCTA-POSS) were chemically incorporated into linear polyurethane based on an aliphatic isocyanate, hexamethylene diisocyanate (HDI), to obtain new nanohybrid PU-POSS materials. The full conversion of POSS was confirmed by Fourier transform infrared spectroscopy (FTIR-ATR) spectra of the model reactions with pure HDI. The materials obtained were investigated by FTIR, SEM-EDS, and DSC. The DSC studies showed the thermoplasticity of the obtained materials and apparently good recovery. 30-day immersion in SBF (simulated body fluid) revealed an increase in the rate of deposition of hydroxyapatite (HAp) for the highest POSS loadings, resulting in thick layers of hydroxyapatite (~60-40 μm), and the Ca/P ratio 1.67 (even 1.785). The structure and properties of the inorganic layer depend on the type of POSS, the number of hard segments, and those containing POSS, which can be tailored by changing the HDI/poly(tetramethylene glycol) (PTMG) ratio. Furthermore, the obtained composites revealed good biocompatibility, as confirmed by cytotoxicity tests conducted on two cell lines; normal human dermal fibroblasts (NHDF) and primary human osteoblasts (HOB). Adherent cells seeded on the tested materials showed viability even after a 48-h incubation. After this time, the population of viable, and proliferating cells exceeded 90%. Bioimaging studies have shown the fibroblast and osteoblast cells were well attached to the surface of the tested materials.

Self-anticoagulant sponge for whole blood auto-transfusion and its mechanism of coagulation factor inactivation

Clinical use of intraoperative auto-transfusion requires the removal of platelets and plasma proteins due to pump-based suction and water-soluble anticoagulant administration, which causes dilutional coagulopathy. Herein, we develop a carboxylated and sulfonated heparin-mimetic polymer-modified sponge with spontaneous blood adsorption and instantaneous anticoagulation. We find that intrinsic coagulation factors, especially XI, are inactivated by adsorption to the sponge surface, while inactivation of thrombin in the sponge-treated plasma effectively inhibits the common coagulation pathway. We show whole blood auto-transfusion in trauma-induced hemorrhage, benefiting from the multiple inhibitory effects of the sponge on coagulation enzymes and calcium depletion. We demonstrate that the transfusion of collected blood favors faster recovery of hemostasis compared to traditional heparinized blood in a rabbit model. Our work not only develops a safe and convenient approach for whole blood auto-transfusion, but also provides the mechanism of action of self-anticoagulant heparin-mimetic polymer-modified surfaces.

Strategies for surface coatings of implantable cardiac medical devices

Cardiac medical devices (CMDs) are required when the patient's cardiac capacity or activity is compromised. To guarantee its correct functionality, the building materials in the development of CMDs must focus on several fundamental properties such as strength, stiffness, rigidity, corrosion resistance, etc. The challenge is more significant because CMDs are generally built with at least one metallic and one polymeric part. However, not only the properties of the materials need to be taken into consideration. The biocompatibility of the materials represents one of the major causes of the success of CMDs in the short and long term. Otherwise, the material will lead to several problems of hemocompatibility (e.g., protein adsorption, platelet aggregation, thrombus formation, bacterial infection, and finally, the rejection of the CMDs). To enhance the hemocompatibility of selected materials, surface modification represents a suitable solution. The surface modification involves the attachment of chemical compounds or bioactive compounds to the surface of the material. These coatings interact with the blood and avoid hemocompatibility and infection issues. This work reviews two main topics: 1) the materials employed in developing CMDs and their key characteristics, and 2) the surface modifications reported in the literature, clinical trials, and those that have reached the market. With the aim of providing to the research community, considerations regarding the choice of materials for CMDs, together with the advantages and disadvantages of the surface modifications and the limitations of the studies performed.

Synthesis, docking studies, biological activity of carbon monoxide release molecules based on coumarin derivatives

In the present work, we synthesized seven complexes. All complexes were identified by ESI-HRMS, ¹H-NMR, ¹⁹F-NMR and ¹³C-NMR spectroscopies. The synthesized complexes were tested for their anticancer activities in vitro against three different human cell lines, including breast MDAMB231, cervical Hela, liver HepG2. IC₅₀ values of complexes 1-7 were 34.98–667.35 µM. Complex 5 revealed higher sensitivity towards MDAMB231 cells with IC₅₀ values 34.98 μM in comparison to 5-FU as positive control. Moreover, complex 5 caused a decrease of mitochondrial membrane potential and effectively induced ROS production against MDAMB231 cells. Western blot analysis showed that complex 5 could up-regulate the expression of Bax protein and down-regulate the expression of Bcl-2, activate Caspase-3, slightly down-regulate the expression of HO-1. The docking studies showed that complex 5 could be interacted with Bcl-2 protein through hydrophobic interactions, hydrogen bonds and salt bridges to enhance the binding affinity. All the analyzed coumarins obeyed the Lipinski’s rule of five for orally administered drugs. Based on the aforementioned results, it suggests that the complex induced apoptosis cell via mitochondria pathways. Collectively, complex 5 could be considered as a promising hit for new anti-breast cancer agents. Carbonyl cobalt CORMs, as potential anticancer therapeutic agents, provided a new idea for the development of metal anticancer drugs.

Control of Blood Coagulation by Hemocompatible Material Surfaces-A Review

Hemocompatibility of biomaterials in contact with the blood of patients is a prerequisite for the short- and long-term applications of medical devices such as cardiovascular stents, artificial heart valves, ventricular assist devices, catheters, blood linings and extracorporeal devices such as artificial kidneys (hemodialysis), extracorporeal membrane oxygenation (ECMO) and cardiopulmonary bypass. Although lower blood compatibility of materials and devices can be handled with systemic anticoagulation, its side effects, such as an increased bleeding risk, make materials that have a better hemocompatibility highly desirable, particularly in long-term applications. This review provides a short overview on the basic mechanisms of blood coagulation including plasmatic coagulation and blood platelets, as well as the activation of the complement system. Furthermore, a survey on concepts for tailoring the blood response of biomaterials to improve the hemocompatibility of medical devices is given which covers different approaches that either inhibit interaction of material surfaces with blood components completely or control the response of the coagulation system, blood platelets and leukocytes.

The antithrombotic activity of natural and synthetic coumarins

Thrombosis, which seriously endangers human health and life, is the leading cause of morbidity and mortality globally. Antithrombotic drugs can interfere with the occurrence and development of thrombotic diseases and play an important role in the treatment of thrombotic diseases. However, unsatisfactory efficacy and serious adverse effects of existing antithrombotic drugs increase the research for new, efficient and safer drugs. Natural and synthetic coumarins have been shown to possess antithrombotic activity, namely, anticoagulation and antiplatelet aggregation. Especially, coumarin-based warfarin, phenprocoumon and cloricromen have long been used in clinical treatment of thrombosis. Coumarin with low toxicity is the privileged structure for developing novel antithrombotic drugs with multiple mechanisms of action. The present review aims to compile current research on the development of coumarins against thrombosis, emphasizing the relationship between their chemical structures and therapeutic effectiveness. It is intended to provide promising ideas for the discovery of novel coumarin derivatives with high antithrombotic activity.

Considerations in the Development of Small-Diameter Vascular Graft as an Alternative for Bypass and Reconstructive Surgeries: A Review

BACKGROUND

Current design strategies for small diameter vascular grafts (< 6 mm internal diameter; ID) are focused on mimicking native vascular tissue because the commercially available grafts still fail at small diameters, notably due to development of intimal hyperplasia and thrombosis. To overcome these challenges, various design approaches, material selection, and surface modification strategies have been employed to improve the patency of small-diameter grafts.

REVIEW

The purpose of this review is to outline various considerations in the development of small-diameter vascular grafts, including material choice, surface modifications to enhance biocompatibility/endothelialization, and mechanical properties of the graft, that are currently being implanted. Additionally, we have taken into account the general vascular physiology, tissue engineering approaches, and collective achievements of the authors in this area. We reviewed both commercially available synthetic grafts (e-PTFE and PET), elastic polymers such as polyurethane and biodegradable and bioresorbable materials. We included naturally occurring materials by focusing on their potential application in the development of future vascular alternatives.

CONCLUSION

Until now, there are few comprehensive reviews regarding considerations in the design of small-diameter vascular grafts in the literature. Here-in, we have discussed in-depth the various strategies employed to generate engineered vascular graft due to their high demand for vascular surgeries. While some TEVG design strategies have shown greater potential in contrast to autologous or synthetic ePTFE conduits, many are still hindered by high production cost which prevents their widespread adoption. Nonetheless, as tissue engineers continue to develop on their strategies and procedures for improved TEVGs, soon, a reliable engineered graft will be available in the market. Hence, we anticipate a viable TEVG with resorbable property, fabricated via electrospinning approach to hold a greater potential that can overcome the challenges observed in both autologous and allogenic grafts. This is because they can be mechanically tuned, incorporated/surface-functionalized with bioactive molecules and mass-manufactured in a reproducible manner. It is also found that most of the success in engineered vascular graft approaching commercialization is for large vessels rather than small-diameter grafts used as cardiovascular bypass grafts. Consequently, the field of vascular engineering is still available for future innovators that can take up the challenge to create a functional arterial substitute.

Antiplatelet Effect of a Pulaimab [Anti-GPIIb/IIIa F(ab)2 Injection] Evaluated by a Population Pharmacokinetic-pharmacodynamic Model

BACKGROUND

Cardiovascular disease has one of the highest mortality rates among all the diseases. Platelets play an important role in the pathogenesis of cardiovascular diseases. Platelet membrane glycoprotein GPIIb/IIIa antagonists are the most effective antiplatelet drugs, and pulaimab is one of these. The study aims to promote individual medication of pulaimab [anti-GPIIb/IIIa F(ab)2 injection] by discovering the pharmacological relationship among the dose, concentration, and effects. The goal of this study is to establish a population pharmacokineticpharmacodynamic model to evaluate the antiplatelet effect of intravenous pulaimab injection.

METHODS

Data were collected from 59 healthy subjects who participated in a Phase-I clinical trial. Plasma concentration was used as the pharmacokinetic index, and platelet aggregation inhibition rate was used as the pharmacodynamic index. The basic pharmacokinetics model was a two-compartment model, whereas the basic pharmacodynamics model was a sigmoid-EMAX model with a direct effect. The covariable model was established by a stepwise method. The final model was verified by a goodness-of-fit method, and predictive performance was assessed by a Bootstrap (BS) method.

RESULTS

In the final model, typical population values of the parameters were as follows: central distribution Volume (V1), 183 L; peripheral distribution Volume (V2), 349 L; Central Clearance (CL), 31 L/h; peripheral clearance(Q), 204 L/h; effect compartment concentration reaching half of the maximum effect (EC50), 0.252 mg/L; maximum effect value (EMAX), 54.0%; and shape factor (γ), 0.42. In the covariable model, thrombin time had significant effects on CL and EMAX. Verification by the goodness-of-fit and BS methods showed that the final model was stable and reliable.

CONCLUSION

A model was successfully established to evaluate the antiplatelet effect of intravenous pulaimab injection that could provide support for the clinical therapeutic regimen.

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 (K_m). 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.

New Hybrid Scaffolds based on Hydrazinyl Thiazole Substituted Coumarin; As Novel Leads of Dual Potential; In Vitro α-Amylase Inhibitory and Antioxidant (DPPH and ABTS Radical Scavenging) Activities

Background:

Despite many side effects associated, there are many drugs which are being clinically used for the treatment of type-II diabetes mellitus (DM). In this scenario, there is still need to develop new therapeutic agents with more efficacy and less side effects. By keeping in mind the diverse spectrum of biological potential associated with coumarin and thiazole, a hybrid class based on these two heterocycles was synthesized.

Method:

Hydrazinyl thiazole substituted coumarins 4-20 were synthesized via two step reaction. First step was the acid catalyzed reaction of 3-formyl/acetyl coumarin derivatives with thiosemicarbazide to form thiosemicarbazone intermediates 1-3, followed by the reaction with different phenacyl bromides to afford products 4-20. All the synthetic analogs 4-20 were characterized by different spectroscopic techniques such as EI-MS, HREI-MS, 1H-NMR and 13C-NMR. Stereochemical assignment of the iminic double bond was carried out by the NOESY experiments. Elemental analysis was found in agreement with the calculated values.

Results:

Compounds 4-20 were screened for α-amylase inhibitory activity and showed good activity in the range of IC50 = 1.829 ± 0.102-3.37 ± 0.17 µM as compared to standard acarbose (IC50 = 1.819 ± 0.19 µM). Compounds were also investigated for their DPPH and ABTS radical scavenging activities and displayed good radical scavenging potential. In addition to that molecular modelling study was conducted on all compounds to investigate the interaction details of compounds 4-20 (ligands) with active site (receptor) of enzyme.

Conclusion:

The newly identified hybrid class may serve as potential lead candidates for the management of diabetes mellitus.

Heterocoumarins Are Selective Carbonic Anhydrase IX and XII Inhibitors with Cytotoxic Effects against Cancer Cells Lines

We have synthesized a new series of coumarin-based compounds demonstrating high selectivity and potent effects with low nanomolar affinity against the tumor associated carbonic anhydrase (CA, EC 4.2.1.1) isoforms hCA IX and XII. A number of these compounds were evaluated ex vivo against human prostate (PC3) and breast (MDA-MB-231) cancer cell lines. Compounds 4b and 15 revealed effective cytotoxic effects after 48 h of incubation in both normoxic and hypoxic conditions with PC3 cancer cell line. However, compound 3 showed selective cytotoxic effects against MDA-MB-231 in hypoxic condition. These results may be of particular importance for the choice of future drug candidates targeting hypoxic tumors and metastases, considering the fact that a selective carbonic anhydrase CA IX inhibitor (SLC-0111) is presently in phase II clinical trials.

Biomedical Porous Shape Memory Alloys for Hard-Tissue Replacement Materials

Porous shape memory alloys (SMAs), including NiTi and Ni-free Ti-based alloys, are unusual materials for hard-tissue replacements because of their unique superelasticity (SE), good biocompatibility, and low elastic modulus. However, the Ni ion releasing for porous NiTi SMAs in physiological conditions and relatively low SE for porous Ni-free SMAs have delayed their clinic applications as implantable materials. The present article reviews recent research progresses on porous NiTi and Ni-free SMAs for hard-tissue replacements, focusing on two specific topics: (i) synthesis of porous SMAs with optimal porous structure, microstructure, mechanical, and biological properties; and, (ii) surface modifications that are designed to create bio-inert or bio-active surfaces with low Ni releasing and high biocompatibility for porous NiTi SMAs. With the advances of preparation technique, the porous SMAs can be tailored to satisfied porous structure with porosity ranging from 30% to 85% and different pore sizes. In addition, they can exhibit an elastic modulus of 0.4⁻15 GPa and SE of more than 2.5%, as well as good cell and tissue biocompatibility. As a result, porous SMAs had already been used in maxillofacial repairing, teeth root replacement, and cervical and lumbar vertebral implantation. Based on current research progresses, possible future directions are discussed for "property-pore structure" relationship and surface modification investigations, which could lead to optimized porous biomedical SMAs. We believe that porous SMAs with optimal porous structure and a bioactive surface layer are the most competitive candidate for short-term and long-term hard-tissue replacement materials.

Surface-modified polymers for cardiac tissue engineering

Cardiovascular disease (CVD), leading to myocardial infarction and heart failure, is one of the major causes of death worldwide. The physiological system cannot significantly regenerate the capabilities of a damaged heart. The current treatment involves pharmacological and surgical interventions; however, less invasive and more cost-effective approaches are sought. Such new approaches are developed to induce tissue regeneration following injury. Hence, regenerative medicine plays a key role in treating CVD. Recently, the extrinsic stimulation of cardiac regeneration has involved the use of potential polymers to stimulate stem cells toward the differentiation of cardiomyocytes as a new therapeutic intervention in cardiac tissue engineering (CTE). The therapeutic potentiality of natural or synthetic polymers and cell surface interactive factors/polymer surface modifications for cardiac repair has been demonstrated in vitro and in vivo. This review will discuss the recent advances in CTE using polymers and cell surface interactive factors that interact strongly with stem cells to trigger the molecular aspects of the differentiation or formulation of cardiomyocytes for the functional repair of heart injuries or cardiac defects.

ROS Modulator Molecules with Therapeutic Potential in Cancers Treatments

Reactive Oxygen Species (ROS) are chemically reactive chemical species containing oxygen. The redox status of a cell is function of the relative concentrations of oxidized and reduced forms of proteins, enzymes, ROS, molecules containing thiol and other factors. In the organism, the redox balance is based on the generation and elimination of ROS produced by endogenous and exogenous sources. All living organisms must maintain their redox equilibrium to survive and proliferate. Enzymatic and molecular pathways control ROS levels tightly but differentially depending on the type of cell. This review is an overview of various molecules that modulate ROS production/detoxification and have a synergistic action with the chemotherapies to kill cancer cells while preserving normal cells to avoid anticancer drugs side effects, allowing a better therapeutic index of the anticancer treatments.

Biofunctionalisation of magnesium alloys by successive immobilisation of poly(ethylene glycol), fibronectin and heparin

In the present study, with the aim of improving their corrosion resistance, anticoagulation and cytocompatibility with endothelial cells, a magnesium alloy (AZ31B) was modified by the alkali heat treatment followed by the immobilisation of the dopamine layer. Subsequently, molecules of poly(ethylene glycol) (PEG) and fibronectin or fibronectin–heparin complexes were successively immobilised on the dopamine-modified surface. After the surface modification, the hydrophilicity of magnesium alloy was obviously improved. The corrosion resistance of the magnesium alloy was improved through alkali heat treatment, and the immobilisation of dopamine and PEG can further reduce the corrosion rate. However, the corrosion resistance of the magnesium alloy was slightly reduced by the grafting of fibronectin or fibronectin–heparin complex. Furthermore, the modified samples showed improved hemocompatibility and good cytocompatibility with the endothelial cells on the fibronectin or fibronectin–heparin-modified surfaces. Therefore, the corrosion resistance, anticoagulation and cytocompatibility of the magnesium alloy can be enhanced by alkali heat treatment and subsequent immobilisation of biomolecules. The method of this study can be used for surface modification of magnesium alloys to impart these with better corrosion resistance, blood compatibility and cytocompatibility with endothelial cells simultaneously.

Improved Hemocompatibility of Multilumen Catheters via Nitric Oxide (NO) Release from S-Nitroso-N-acetylpenicillamine (SNAP) Composite Filled Lumen

Blood-contacting devices, such as intravascular catheters, suffer from challenges related to thrombus formation and infection. Nitric oxide (NO) is an endogenous antiplatelet and antimicrobial agent. Exogenous release of NO from various polymer matrices has been shown to reduce thrombosis and infection of/on implantable medical devices. However, the clinical applications of such materials have been hindered due to factors such as NO donor leaching and thermal instability. In this study, a novel approach is demonstrated in which one lumen of commercial dual lumen catheters is dedicated to the NO release chemistry, allowing the other lumen to be available for clinical vascular access. A composite consisting of poly(ethylene glycol) (PEG) and S-nitroso-N-acetylpenicillamine (SNAP) is used to fill the NO-releasing lumen of commercial 7 French silicone catheters. Physiological levels of NO are released from the SNAP-PEG catheters for up to 14 d, as measured by chemiluminescence NO analyzer (in PBS buffer at 37 °C). PEG facilitates the NO release from SNAP within the lumen by increasing the water absorption and slowly dissolving the solid SNAP-PEG composite. In a CDC biofilm bioreactor, the SNAP-PEG catheters are found to reduce >97% bacterial adhesion as compared to the PEG controls for single bacterial species including E. coli and S. aureus. SNAP-PEG and PEG control catheters were implanted in rabbit veins for 7 h (single lumen) and 11 d (dual lumen) to evaluate their hemocompatibility properties. Significant reductions in thrombus formation on the SNAP-PEG vs PEG controls were observed, with ca. 85% reduction for 7 h single lumen catheters and ca. 55% reduction for 11 d dual lumen catheters.

Recent advances in thromboresistant and antimicrobial polymers for biomedical applications: just say yes to nitric oxide (NO)

Biomedical devices are essential for patient diagnosis and treatment; however, when blood comes in contact with foreign surfaces or homeostasis is disrupted, complications including thrombus formation and bacterial infections can interrupt device functionality, causing false readings and/or shorten device lifetime. Here, we review some of the current approaches for developing antithrombotic and antibacterial materials for biomedical applications. Special emphasis is given to materials that release or generate low levels of nitric oxide (NO). Nitric oxide is an endogenous gas molecule that can inhibit platelet activation as well as bacterial proliferation and adhesion. Various NO delivery vehicles have been developed to improve NO's therapeutic potential. In this review, we provide a summary of the NO releasing and NO generating polymeric materials developed to date, with a focus on the chemistry of different NO donors, the polymer preparation processes, and in vitro and in vivo applications of the two most promising types of NO donors studied thus far, N-diazeniumdiolates (NONOates) and S-nitrosothiols (RSNOs).

Syntheses of new 3-thiazolyl coumarin derivatives, in vitro α-glucosidase inhibitory activity, and molecular modeling studies

3-Thiazolylcoumarin derivatives 1-14 were synthesized via one-pot two step reactions, and screened for in vitro α-glucosidase inhibitory activity. All compounds showed inhibitory activity in the range of IC50 = 0.12 ± 0.01-16.20 ± 0.23 μM as compared to standard acarbose (IC50 = 38.25 ± 0.12 μM), and also found to be nontoxic. Molecular docking study was carried out in order to establish the structure-activity relationship (SAR) which demonstrated that electron rich centers at one and electron withdrawing centers at the other end of the molecules showed strong inhibitory activity. All the synthesized compounds were characterized by spectroscopic techniques such as EI-MS, HREI-MS, (1)H NMR and (13)C NMR. CHN analysis was also performed.

Hemocompatibility of styrenic block copolymers for use in prosthetic heart valves

Certain styrenic thermoplastic block copolymer elastomers can be processed to exhibit anisotropic mechanical properties which may be desirable for imitating biological tissues. The ex-vivo hemocompatibility of four triblock (hard-soft-hard) copolymers with polystyrene hard blocks and polyethylene, polypropylene, polyisoprene, polybutadiene or polyisobutylene soft blocks are tested using the modified Chandler loop method using fresh human blood and direct contact cell proliferation of fibroblasts upon the materials. The hemocompatibility and durability performance of a heparin coating is also evaluated. Measures of platelet and coagulation cascade activation indicate that the test materials are superior to polyester but inferior to expanded polytetrafluoroethylene and bovine pericardium reference materials. Against inflammatory measures the test materials are superior to polyester and bovine pericardium. The addition of a heparin coating results in reduced protein adsorption and ex-vivo hemocompatibility performance superior to all reference materials, in all measures. The tested styrenic thermoplastic block copolymers demonstrate adequate performance for blood contacting applications.

Design and synthesis of coumarin–glyoxal hybrids for spermicidal and antimicrobial actions: a dual approach to contraception

Today there is an urgent need for safe and effective dual-purpose contraceptive agents, which can simultaneously prevent unintended pregnancies and sexually transmitted infections (STI).

BF3·Et2O Catalysed 4-Aryl-3-phenyl-benzopyrones, Pro-SERMs, and Their Characterization

We have synthesized the novel 4-(4-hydroxy-benzyl)-3-phenyl-chromen-2-one which is a precursor of SERMs with a smaller number of steps and good yield. Two methodologies for the synthesis have been worked out. Anhydrous BF3·Et2O catalyzed reaction was found to be selective for product formation while anhydrous AlCl3, FeCl3, and SnCl4 catalyzed ones were nonselective.

Layer-by-layer heparinization of decellularized liver matrices to reduce thrombogenicity of tissue engineered grafts

Background:

Tissue–engineered liver grafts may offer a viable alternative to orthotopic liver transplantation and help overcome the donor organ shortage. Decellularized liver matrices (DLM) have a preserved vasculature and sustain hepatocellular function in culture, but graft survival after transplantation remains limited due to thrombogenicity of the matrix.

Aim:

To evaluate the effect of heparin immobilization on DLM thrombogenicity.

Methods:

Heparin was immobilized on DLMs by means of layer-by-layer deposition. Grafts with 4 or 8 bilayers and 2 or 4 g/L of heparin were recellularized with primary rat hepatocytes and maintained in culture for 5 days. Hemocompatibility of the graft was assessed by ex vivo diluted whole-blood perfusion and heterotopic transplantation.

Results:

Heparin was deposited throughout the matrix and the heparin content in the graft was higher with increasing number of bilayers and concentration of heparin. Recellularization and in vitro albumin and urea production were unaffected by heparinization. Resistance to blood flow during ex vivo perfusion was lower with increased heparinization and, macroscopically, no clots were visible in grafts with 8 bilayers. Following transplantation, flow through the graft was limited in all groups. Histological evidence of thrombosis was lower in heparinized DLMs, but transplantation of DLM grafts was not improved.

Conclusions:

Layer-by-layer deposition of heparin on a DLM is an effective method of immobilizing heparin throughout the graft and does not impede recellularization or hepatocellular function in vitro. Thrombogenicity during ex vivo blood perfusion was reduced in heparinized grafts and optimal with 8 bilayers, but transplantation remained unsuccessful with this method.

Relevance for patients:

Tissue engineered liver grafts may offer a viable solution to dramatic shortages in donor organs

Poly(l-lysine)-graft-folic acid-coupled poly(2-methyl-2-oxazoline) (PLL-g-PMOXA-c-FA): a bioactive copolymer for specific targeting to folate receptor-positive cancer cells

In this study, we present the preparation, characterization and application of a novel bioactive copolymer poly(l-lysine)-graft-folic acid-coupled poly(2-methyl-2-oxazoline) (PLL-g-PMOXA-c-FA), which has a specific interaction with folate receptor (FR)-positive cancer cells. Glass surface immobilized with PLL-g-PMOXA-c-FA was demonstrated to be adhesive to FR-positive cancer cells (HeLa, JEG-3) while nonadhesive to FR-negative ones (MCF-7, HepG2) in 3 h. The specific interaction between conjugated FA on the substrate and FRs on the cells could hardly be inhibited unless a high concentration (5 mM) of free FA was used due to the multivalent nature of it. The FA functionality ratio of the copolymer on the substrate had a significant influence on the adhesion of HeLa cells, and our experiments revealed that the affinity of the substrate to the cells declined dramatically with the decrease of functionality ratio. This was believed to be caused by the polydispersity of PMOXA tethers, as supported by GPC and ToF-SIMS data. As a proof of concept in the application of our material, we demonstrated successful recovery of HeLa cells from mixture with MCF-7 (1:100) on the copolymer-coated glass, and our results showed that both high sensitivity (95.6 ± 13.3%) and specificity (24.3 ± 8.6%) were achieved.

Reduction in Thrombosis and Bacterial Adhesion with 7 Day Implantation of S-Nitroso-N-acetylpenicillamine (SNAP)-Doped Elast-eon E2As Catheters in Sheep

Thrombosis and infection are two common problems associated with blood-contacting medical devices such as catheters. Nitric oxide (NO) is known to be a potent antimicrobial agent as well as an inhibitor of platelet activation and adhesion. Healthy endothelial cells that line the inner walls of all blood vessels exhibit a NO flux of 0.5~4×10^-10 mol cm^-2 min^-1 that helps prevent thrombosis. Materials with a NO flux that is equivalent to this level are expected to exhibit similar anti-thrombotic properties. In this study, NO-releasing catheters were fabricated by incorporating S-nitroso-N-acetylpenicillamine (SNAP) in the Elast-eon E2As polymer. The SNAP/E2As catheters release physiological levels of NO for up to 20 d, as measured by chemiluminescence. Furthermore, SNAP is stable in the E2As polymer, retaining 89% of the initial SNAP after ethylene oxide (EO) sterilization. The SNAP/E2As and E2As control catheters were implanted in sheep veins for 7 d to examine the effect on thrombosis and bacterial adhesion. The SNAP/E2As catheters reduced the thrombus area when compared to the control (1.56 ± 0.76 and 5.06 ± 1.44 cm², respectively). A 90% reduction in bacterial adhesion was also observed for the SNAP/E2As catheters as compared to the controls. The results suggest that the SNAP/E2As polymer has the potential to improve the hemocompatibility and bactericidal activity of intravascular catheters, as well as other blood-contacting medical devices (e.g., vascular grafts, extracorporeal circuits).

Nanocapsules for 5-fluorouracil delivery decorated with a poly(2-ethylhexyl methacrylate-co-7-(4-trifluoromethyl)coumarin acrylamide) cross-linked wall

Nanocapsules with reverse cross-linked polymer walls containing coumarin moieties are capable of encapsulating 5-fluorouracil and accomplishing a comprehensive strategy in a drug delivery system.

Biomimetic modified clinical-grade POSS-PCU nanocomposite polymer for bypass graft applications: a preliminary assessment of endothelial cell adhesion and haemocompatibility

BACKGROUND

To date, there are no small internal diameter (<5mm) vascular grafts that are FDA approved for clinical use due to high failure rates from thrombosis and unwanted cell proliferation. The ideal conditions to enhance bioengineered grafts would be the blood contacting lumen of the bypass graft fully covered by endothelial cells (ECs). As a strategy towards this aim, we hypothesized that by immobilising biomolecules on the surface of the polyhedral oligomeric silsesquioxane-poly(carbonate-urea)urethane (POSS-PCU) nanocomposite polymers, which contain binding sites and ligands for cell surface receptors similar to extracellular matrix (ECM) will positively influence the attachment and proliferation of ECs. Since, the surface of POSS-PCU is inert and not directly suitable for immobilisation of biomolecules, plasma graft polymerisation is a suitable method to modify the surface properties ready for immobilisation and biofunctionalisation.

METHODS

POSS-PCU was activated by plasma treatment in air/O2 to from hydroperoxides (-OH, -OOH), and then carboxylated via plasma polymerisation of a 30% acrylic acid solution (Poly-AA) using a two-step plasma treatment (TSPT) process. Collagen type I, a major component of ECM, was covalently immobilised to mimic the ECM structures to ECs (5mg/ml) using a two-step chemical reaction using EDC chemistry. Successful immobilisation of poly-AA and collagen on to the nanocomposites was confirmed using Toluidine Blue staining and the Bradford assay. Un-treated POSS-PCU served as a simple control. The impact of collagen grafting on the physical, mechanical and biological properties of POSS-PCU was evaluated via contact angle (θ) measurements, scanning electron microscopy (SEM), atomic force microscopy (AFM), dynamic mechanical thermal analysis (DMTA), ECs adhesion and proliferation followed by platelet adhesion and haemolysis ratio (HR) tests.

RESULTS

Poly-AA content on each of the plasma treated nanocomposite films increased on Low, Med and High samples due to more carboxylic acid (-COOH) groups at the surface forming amide (-NH2) bonds. The amount of -COOH groups on each of the Low, Med and High nanocomposites correlated with Poly-AA grafting density at 14.7±0.9, 18.9±0.9, and 34.2±2.4 μg/cm(2). Immobilisation of collagen type I on to nanocomposite surface was also found to increase significantly on the Low, Med and High samples from 22±4, 150±15, and 219±17 μg/cm(2), respectively. The level of ECs and their adhesion efficiency were improved with increasing amounts of grafted collagen I. The maximum adhesion of ECs was found on the highest collagen type I coated nanocomposites. Platelet adhesion and activation also increased with increasing collagen density. The obtained HR values for all of the treated samples were well within the acceptable standards for biomaterials (<5% HR).

CONCLUSION

Poly-AA-g-POSS-PCU surfaces offer binding sites for the covalent bonding of collagen type I and other biomolecules such as fibronectin by exposure of RGD cell binding domains and growth factors using EDC cross-linking chemistry. Collagen type I modification can yield accelerated EC growth and enhance the endothelialisation of POSS-PCU nanocomposites, and the amount of immobilised collagen can control the level of platelet adhesion on functionalized POSS-PCU via TSPT and poly acrylic acid (poly-AA) treatment. Such surface modification procedures of polymeric surfaces can improve the patency rate of POSS-PCU nanocomposites as vascular bypass grafts in the preparation of a range of medical devices ready for pre-clinical and in vivo evaluation.

Blood compatible materials: state of the art

Devices that function in contact with blood are ubiquitous in clinical medicine and biotechnology. These devices include vascular grafts, coronary stents, heart valves, catheters, hemodialysers, heart-lung bypass systems and many others. Blood contact generally leads to thrombosis (among other adverse outcomes), and no material has yet been developed which remains thrombus-free indefinitely and in all situations: extracorporeally, in the venous circulation and in the arterial circulation. In this article knowledge on blood-material interactions and "thromboresistant" materials is reviewed. Current approaches to the development of thromboresistant materials are discussed including surface passivation; incorporation and/or release of anticoagulants, antiplatelet agents and thrombolytic agents; and mimicry of the vascular endothelium.

Selective albumin-binding surfaces modified with a thrombin-inhibiting peptide

Blood-contacting medical devices have been associated with severe clinical complications, such as thrombus formation, triggered by the activation of the coagulation cascade due to the adsorption of certain plasma proteins on the surface of biomaterials. Hence, the coating of such surfaces with antithrombotic agents has been used to increase biomaterial haemocompatibility. Biomaterial-induced clotting may also be decreased by albumin adsorption from blood plasma in a selective and reversible way, since this protein is not involved in the coagulation cascade. In this context, this paper reports that the immobilization of the thrombin inhibitor D-Phe-Pro-D-Arg-D-Thr-CONH2 (fPrt) onto nanostructured surfaces induces selective and reversible adsorption of albumin, delaying the clotting time when compared to peptide-free surfaces. fPrt, synthesized with two glycine residues attached to the N-terminus (GGfPrt), was covalently immobilized onto self-assembled monolayers (SAMs) having different ratios of carboxylate-hexa(ethylene glycol)- and tri(ethylene glycol)-terminated thiols (EG6-COOH/EG3) that were specifically designed to control GGfPrt orientation, exposure and density at the molecular level. In solution, GGfPrt was able to inactivate the enzymatic activity of thrombin and to delay plasma clotting time in a concentration-dependent way. After surface immobilization, and independently of its concentration, GGfPrt lost its selectivity to thrombin and its capacity to inhibit thrombin enzymatic activity against the chromogenic substrate n-p-tosyl-Gly-Pro-Arg-p-nitroanilide. Nevertheless, surfaces with low concentrations of GGfPrt could delay the capacity of adsorbed thrombin to cleave fibrinogen. In contrast, GGfPrt immobilized in high concentrations was found to induce the procoagulant activity of the adsorbed thrombin. However, all surfaces containing GGfPrt have a plasma clotting time similar to the negative control (empty polystyrene wells), showing resistance to coagulation, which is explained by its capacity to adsorb albumin in a selective and reversible way. This work opens new perspectives to the improvement of the haemocompatibility of blood-contacting medical devices.