China
Africa
Explore chapters and articles related to this topic
Naturally Occurring Polymers—Plants
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
Above is a representative structure of heparin (9.25) that is complex containing d-glucuronic acid, l-iduronic acid, and d-glucosamine units. The glucosamine units may be N-acetylated or N-sulfonated. It is found in the lung, liver, and arterial walls of mammals. It is also found in intracellular granules of mast cells that line arterial walls and is released through injury. The glucuronic acid and iduronic acid units are not randomly present but occur in blocks. Heparin is found as free polysaccharide and bonded to protein. Heparin acts as an anticoagulant, an inhibitor of blood clotting, and is widely used for this in medicine. In nature, its purpose appears to be to prevent uncontrolled clotting.
Postsynthetic Modifications of Mesoporous MOFs for Adsorption-Based Applications
Published in Alexander Samokhvalov, Adsorption on Mesoporous Metal-Organic Frameworks in Solution for Clean Energy, Environment, and Healthcare, 2017
This is of interest to postsynthetically modify the mesoporous MOFs with biologically active molecules and use the obtained nanocomposites for emerging applications in biomedicine. Heparin is an anticoagulant (blood thinner) that prevents the formation of blood clots (Jones et al. 2011). The molecule of heparin contains several polar functional groups (sulfate, carboxylic, and hydroxyl) that are expected to strongly interact with the polar groups in the mesoporous MOFs such as the Fe(III) site in MIL-100(Fe).
European regulatory guidance
Published in Sarfaraz K. Niazi, Biosimilars and Interchangeable Biologics, 2016
This reduction of molecule size is associated with a loss of thrombin inhibition activity in comparison to standard heparin and an increased inhibition of FXa. Due to difficulties in the physical detection of LMWH, conventional PK studies cannot be done. Instead, the absorption and elimination of LMWHs are studied by using PD tests, including the measurement of anti-FXa and anti-FIIa activity. There are several authorized LMWHs that differ in their source material, manufacturing process, PK/PD properties, and therapeutic indications, which include treatment and prophylaxis of deep venous thrombosis and prevention of complications of acute coronary syndromes (unstable angina, non-ST elevation myocardial infarction [non-STEMI] and myocardial infarction with ST elevation [STEMI]). The most common adverse reactions induced by heparins are bleedings, while the most serious one is the rarely observed heparin-induced thrombocytopenia type II (HIT II). This antibody-mediated process is triggered by the induction of antibodies directed against neoantigens of platelet factor 4 (PF4)-heparin complexes. Binding of those antibody-PF4-heparin complexes may activate platelets and generate thrombogenic platelet microaggregates. Patients developing thrombocytopenia are in danger of arterial and venous thromboembolic complications (heparin-induced thrombocytopenia and thrombosis, HITT). Although the risk of these adverse reactions appears to be reduced in comparison to unfractionated heparin, it is obligatory to monitor the platelet count regularly in all patients using LMWH and to test for PF4-heparin complex antibodies in those who develop thrombocytopenia or thromboembolic complications during heparin treatment. In conclusion, the heterogeneity of LMWH is high, the structure effect relationship is presently not fully elucidated and the PD markers anti-FXa and anti-FIIa activity may not fully reflect/predict efficacy. Thus, clinical trials will usually be necessary to address remaining uncertainties resulting from the physicochemical and biological comparison.
Biomimetic materials based on zwitterionic polymers toward human-friendly medical devices
Published in Science and Technology of Advanced Materials, 2022
Heparin acts effectively on the blood coagulation system and plays a role in preventing blood clotting. Furthermore, it can be expected to reduce the effect on patients by inhibiting the reduction in cell function and activation reactions when blood encounters it. Generally, membrane oxygen-enriched devices surface-treated with heparin are used to prevent thrombus [179]. A substantial amount of heparin is administered to the blood during extracorporeal blood circulation therapy, and coagulation system activity is inhibited in the blood. However, platelet-related coagulation reactions occur on the surface of the membrane material; thus, adhesion and activation of blood cells must be prevented. Although heparinized surfaces are expected to decrease the number of blood cell adhesions due to increased hydrophilicity, they do not prevent platelet adhesion or activation [180]. Therefore, the efficacy of MPC polymers that actively inhibit platelet-based coagulation has been investigated, and poly(MPC-co-DMA) (PMD) was applied to the surface treatment of membrane oxygen-enriched devices (Figure 10(a)) [127,179–183]. The Sorin Group was the first to clinically develop it and the device has been shown to inhibit platelet coagulation on the membrane surface and maintain good blood quality in patients after treatment. Subsequently, JMS Co., Japan, also put it into practical use in Japan.
Characterization of a heparinized decellularized scaffold and its effects on mechanical and structural properties
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Ji Li, Zhiwen Cai, Jin Cheng, Cong Wang, Zhiping Fang, Yonghao Xiao, Zeng-Guo Feng, Yongquan Gu
The decellularization process necessary for the removal of cellular antigens also removes the endothelial cells (ECs) lining the lumen that is responsible for inhibiting coagulation and platelet adhesion [35]. Following the removal of ECs, the highly thrombogenic surface of exposed collagen activates platelets and the extrinsic coagulation cascade, which may contribute to unsuccessful transplantation. To improve the patency of implanted vascular grafts, avoidance of thrombus formation and early confluent endothelialization are critical. Heparin is well known to prevent thrombosis owing to its inhibition of the thrombin clotting cascade. Furthermore, heparin immobilization of the decellularized vascular grafts can promote endothelialization during implantation [36]. Thus, heparin has been applied to decellularized vessels [36–38]; however, the changes in mechanical properties caused by heparin immobilization need to be studied. It is worth noting that the mismatch of mechanical properties with respect to native vessels may cause local flow disturbance and neointimal hyperplasia at anastomosis sites, which in turn leads to thrombosis and occlusion [39].
A review on the treatment of intimal hyperplasia with perivascular medical devices: role of mechanical factors and drug release kinetics
Published in Expert Review of Medical Devices, 2023
Ankur J. Raval, Jigisha K. Parikh, Meghal A. Desai
Acute vascular graft failure within 30 days post-bypass surgery is significant because of thrombosis, in which blood clots are formed at the lesion site, thereby blocking it completely. Heparin, an anticoagulation agent, is used in surgeries to prevent clot formation. Moreover, it is used where there is a high risk of thrombus formation, such as in various heart, lung, and circulatory disorders. A controlled release of heparin from PLGA microspheres effectively inhibited the bovine vascular smooth muscle cell proliferation in vitro in a dose-dependent manner [74].