Blood and material interaction

Property of a material/device that permits it to function in contact with blood without inducingadverse reactions

• Proteins are a major constituent of plasma

• Cell adhesion is mediated by protein adsorption

• Adhesive proteins: fibrinogen, von Willebrand factor (vWF)

• Activation of coagulation cascade and the complement system

• The coagulation cascade is a complex system responsible for the formation blood clots

  • Activation of clotting factors (I, II, II…)

  • Each factors is an enzyme that speeds up the breakdown of a protein

• Extrinsic pathway: initiates when there is injury to the endothelial tissue

• Intrinsic pathway: initiates when blood is exposed to negatively charged surfaces leading to theactivation complex of factor XII, high-molecular-weight kininogen, and prekallikrein

• Common pathways

• General:

  • 1st Protein surface adhesion

  • Cells bind via cell receptor to the proetin complexes

• Thombosis: Red blood cells adhere to fibrin and platelet

• Biofilm formation: Pathogens adhere to an extracellular polymeric substance

• Fibrosis: Fibroblasts and immune cells adhere to an extracellular matrix

Low shear rate regime: Stagnation or low shear can promote accumulation of coagulation factors, leukocytes, and RBCs

High shear rate regime: Shear induced activation of platelets and coagulationproteins, High shear stress and turbulence, can cause membraneof red blood cells to rupture and release hemoglobin(hemolysis)

The complement system refers to a group of plasma proteins called the complement proteins,which are produced in the liver, and act collectively to help destroy pathogens

• Non polar

• polar

• + charged

• - charged

• Folded polypeptides in a aqueous envorinment have a core region with non polar groups and an outside with polar groups

• only applicable for a reversible adsorption processes

Defined by contact angle

• Protein adsorption can only occur spontaneously (at constant pressure and temperature) if theGibbs energy G of the system decreases

Coagulation and complement activation are minimized at charge-neutral, strongly water-binding surfaces