EBME 306 LECTURES 12-14-FALL-2023-ZIATS.pptx

BIOLOGICAL CONSTRAINTS in USING BIOMATERIALS: HEMOSTASIS & THROMBOSIS Readings for October 11, 13, 16: Biomaterials: The Intersection of Biology and Materials Science, J.S. Temenoff and A.G. Mikos, Pearson/Prentice Hall, 2008, pp. 228-231, 280-284, 428-441 Blood Components Normal Blood Smear Pla...

BIOLOGICAL CONSTRAINTS in USING BIOMATERIALS: HEMOSTASIS & THROMBOSIS Readings for October 11, 13, 16: Biomaterials: The Intersection of Biology and Materials Science, J.S. Temenoff and A.G. Mikos, Pearson/Prentice Hall, 2008, pp. 228-231, 280-284, 428-441 Blood Components Normal Blood Smear Platelet Eos PMN Lympho Baso Mono Hematopoeisis EPO TPO CSF CSF INTERLEUKINS INTERLEUKINS Platelets Hemostasis & Thrombosis Hemostasis- “the stopping of hemorrhage or bleeding” Thrombosis- “hemostasis in the wrong place”, really a pathological state of hemostasis due to intravascular clot (thrombus) formation Hemostasis  Factors contributed by: Endothelium Biomaterial surface Platelets Blood Clotting Factors Hemostasis & Thrombosis Virchow’s Triad BLOOD FLOW SURFACE (Biomaterials) Hemostasis & Thrombosis BIOMATERIAL SURFACE or Virchow’s Triad Fluid Dynamic Factors Hemostasis & Thrombosis EC is Nonthrombogenic! is prothrombogenic is prothrombogenic Platelets Adhesion Activation Aggregation Release /RELEASE Platelets & Biomaterials ADHESION Adhesion RELEASE ACTIVATION Aggregation AGGREGATION Platelets and Biomaterials ADHESION GpIb vWF, collagen, Biomaterials Release Many things released: Thrombin, Txb2 ADP, fibrinogen, PF4, bTG, Ca+2 ACTIVATION AGGREGATION Fibrinogen GpIIb/IIIa Platelets & Biomaterials Platelet-Material Interactions PDMS Adherent, round= “unactivated” Dacron Adherent, spread= “activated” Translational Question Design an experiment to show that platelets are or are not activated on a material surface. What controls would you use? Arachidonic Acid Pathway Thromboxanes vs. Prostacyclin Blood and Materials Interactions Albumin IgG Fibrinogen Others Blood Clotting Factors Made in Liver Endothelium Liver Fibrinogen-----------Fibrin Fibrin Blood Clotting Biomaterials Prekallikrein HMWK Biomaterials Blood Clotting FIBRINOGEN FIBRIN Blood Clotting PROTHROMBIN FIBRINOGEN THROMBIN FIBRIN Other Factors Necessary for Clotting  Calcium  Vitamin K  Phospholipids Blood Clotting factor X factor Xa PROTHROMBIN FIBRINOGEN THROMBIN FIBRIN Blood Clotting Biomaterials Prekallikrein HMWK Biomaterials Control of Clotting  Antithrombins (eg. ATIII)    Proteins C and S     inhibits the activity of thrombin and other serine protease activated by heparin-like molecules on endothelial cells vitamin K dependent inactivates Va and VIIIa protein C activated by thrombomodulin Plasminogen-plasmin system    breaks down fibrin and interferes with fibrin polymerization Urokinase-like plasminogen activators- uPA Tissue-type plasminogen activators- tPA Fibrinolysis tPA or uPA Streptokinase Urokinase Contact Factors  factor XII  factor XI  High Molecular Weight Kininogen (HMWK)  Prekallikrein (see also protein adsorption) Blood “Contact” Factors Blood Coagulation/Fibrinolysis Intrinsic Pathway Extrinsic Pathway Biomaterials factor Xa factor X Prothrombin Fibrinogen Plasminogen Thrombin Fibrin Degradation Products Fibrin tPA Plasmin Laboratory Tests Blood-Biomaterials Evaluation  Blood Smear  Platelet count  Prothrombin time  Partial Thromboplastin Time  D-dimer Test Hemostasis Testing Activated (APTT) 24-30 sec is normal (PT) 9.5-11.3 sec is normal D-Dimers & DVT D-dimers measured in lab by various methods D-dimers Anticoagulant & Antithrombotic Therapy  DRUGS   Aspirin, Reopro, Plavix Heparin/Hirudin     THROMBOLYTICS   Porcine mucosa LMWH (Lovenox) Leeches, recombinant Plasminogen Activators (Activase) COATING of SURFACES  Released from Surfaces Heparin Heparin-Antithrombin Heparin binds to Antithrombin which inactivates Thrombin and acts catalytically, potentiates the action of Antithrombin Heparin-Releasing Polymers Translational Question In what way(s) might does modification of a surface with immobilized heparin do to the surface and how could you test this? Hirudin Derived from leeches More potent inhibitor of thrombin Blood Contacting Devices Thrombosis  Solid mass formed on dysfunctional blood vessels, heart chambers, valves, major cause of device failure, deep vein thrombosis (DVT) and also leading to embolism (pulmomary embolism)  Causes Injury (or dysfunctional) to endothelium  Flow changes- stasis  Blood changes- hypercoagulable state  Why Does Thrombosis Occur on Biomaterials?  Flow Effects ► ►  Protein Adsorption ► ► ► ►  Shear Stress, Vessel size Virchow’s Triad Major and Minor proteins Monolayer versus Multilayer Vroman Effect Material Surface Platelets and Leukocytes ► ► Platelet Glycoproteins Integrins/Ligands Protein Adsorption Vroman Effect  Major and Minor proteins  Monolayer versus Multilayer  Vroman Effect ► Albumin, then Fibrinogen, then IgG, finally fXII and HMWK  Material Surface Protein Adsorption & Biomaterials Another Hypothesis Translational Question You are to design a biomaterial that inhibits complement activation and blood coagulation activation by preventing adsorption of proteins. Explain with how you might do this? ? Blood-Material Interactions Ex Vivo Testing Biomaterial ANIMAL Blood-Material Interactions Evaluation Blood Surface Interactions Pulmonary Embolism A pulmonary thromboembolus travels from a large vein in the leg up the inferior vena cava to the main pulmonary arteries as they branch. Such thrombi embolize most often from veins in the legs and pelvis where thrombi form with stasis. from WebPath 7.0 Thrombosis and Infarcts “Downstream” effect of thrombosis in lungs called Pulmonary Infarct, tissue is necrotic Pulmonary Embolism Use of Greenfield filters Mechanical Valves Occluder Cage/Strut Sewing Ring Thrombosis on Mechanical Valves Vascular Grafts Why Do Vascular Grafts Fail? Hyperplasia  Intimal  Anastomotic  Thrombosis  Infection  KEY: Lack of an endothelial lining in humans Thrombosis on a Vascular Graft Vascular Graft Pseudointima in humans (no endothelium!!!), intimal thickening seen, also at anastomoses, called intimal hyperplasia Graft Material Vascular Grafts Endotheliu m? Stenosis Intimal Hyperplasia or Anastomotic hyperplasia Common in femoral, popliteal vessels Graft Coronary Artery Disease Lumen Thrombus Scar Lipid Angioplasty (PTCA) and Stenting DISEASED VESSEL Stents Failure of Stents ► ► ► ► Intimal Hyperplasia Elastic recoil Thrombosis Infection Stent Coatings * Drug Eluting Stents Rapamycin (Sirlomus) Eluting Stent Key Concepts: Drug bound to metallic stent, Barrier coating Release of Drug Biologic Effect:   Inhibits SMC proliferation Reduces inflammation Failure: ► ► Restenosis Late-state thrombosis Stent Study Day 30 Day 90 Stent Translational Question How might you improve the hemo/blood compatibility of materials? How would you evaluate hemocompatibilty of biomaterials? Summary  Normal hemostasis vs. thrombosis  Virchow’s triad  Platelets and coagulation proteins  Contact factors or proteins  Heparins, hirudins  Blood contacting devicesg  Vroman effect, adsorbed proteins  Blood compatibility analysis