Biomaterials Lecture 4&5 Host Response to Implants

Biomaterials Lecture 4&5 Host Response to Implants...

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Basic stages of host reaction  following implantation of  biomaterials Activated cascade Time frame Host reactions Coagulation Seconds to  minutes Blood-material interactions Provisional matrix (proteins for cell  attachment) Complement- alternative pathway hours Acute inflammation days Chronic inflammation Granulation tissue Foreign body reaction weeks Fibrous capsule formation
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Background: concept of self and not  self CELLS + MATRIX (ECM/PROTEINS) + H2O              ALL TISSUES               ORGANS 1.BLOOD IS A TISSUE  = [CELLS] + [LIQUID ECM] 2.TISSUES/ORGANS  = [SPECIFIC CELLS] + [H2O + SOLID PROTEIN  COMPONENTS] SO WHEN YOU CUT YOURSELF YOU ARE CUTTING WHAT? CIRCULATING TISSUE (blood)  AND  RESIDENT TISSUE (site specific  tissues) Common to all implantation Unique and important. Why?  Effects tissue capacity for scarring versus regeneration: healing behavior 1.Injury and level of immune response 2.Cell proliferation capacity (example: epithelial cells versus nerve/cardiac cells)
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Components of blood
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Injured tissue response: inflammatory  response Activated cascade Time  frame Host reactions Coagulation Seconds to  minutes Blood-material interactions Provisional matrix (proteins for cell  attachment) Complement- alternative pathway hours Acute inflammation days Chronic inflammation Granulation tissue Foreign body reaction weeks Fibrous capsule formation Goal:  1.Destroy or inactivate foreign materials 2.Initiate healing Mechanism:  signal cascades Two specific cascades are activated by biomaterials  (cooperative) 1.Coagulation cascade 2.Complement-alternative pathway
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Hemostasis  Blood-biomaterials interactions:  are extremely important  since all biomaterials are implanted in vascularized tissues and  in contact with blood occurs (implantation procedure) INJURY IS THE FIRST THING TO OCCUR ALWAYS  (think  about surgical procedure/implantation-delivery of material) Examples: 1.Stent delivery in a blood vessel 2.Knee replacement
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Hemostasis  Examples: 1.Stent delivery 2.Knee replacement STENT DELIVERY TO ARTERIAL SITE DEPLOYMENT CATHETER FED  THROUGH ONE OF TWO  INSERTION POINTS “Minimally invasive”
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Hemostasis  Examples: 1.Stent delivery 2.Knee replacement A “little” more invasive
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Hemostasis  AFTER INJURY,  Hemostatic mechanisms : designed to arrest  bleeding 1.Vascular constriction at the area of insult 2.Formation of a platelet plug 1.Blood coagulation (thrombosis) Combination of these three things: decreases regional blood  flow and temporarily closes holes in vessels Key role players in the process: 1.Protein components 2.Non-protein components (platelets) 3.Endothelial lining
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Cell origins: blood and immune  cells Primary players in response to biomaterials and tissue injury
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This note was uploaded on 02/22/2010 for the course BE 2600 taught by Professor Gilbert during the Spring '08 term at Michigan Technological University.

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Biomaterials Lecture 4&5 Host Response to Implants...

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