Contact-phase activation

It inhibits plasmin and kallikrein, thus directly affecting fibrinolysis. It also inhibits the contact phase activation of coagulation which both initiates coagulation and promotes fibrinolysis. 

The in vitro study of the hemocompatibility of biomaterials requires the consideration of many parameters, static or dynamic contact, flow rate, wall shear rate, form of biomaterial to be tested, pathway to consider (platelet adhesion, platelet activation, complement activation, contact phase activation etc..) and duration of contact(39). It has previously been demonstrated t t hemodynamic circumstances play a significant role in determining localization, growth and fiagmentation of thrombi and platelet adhesion in vivo, and that flow rate controls platelet transport to a surface and their adhesion (40). This evidence is siqtpoited by observed differences in platelet activity predominance in venous and arterial flow (41). Qearly, defining the blood compatibility of a material is a conqrromise between a number of these factors. 

Thomas M, Valette P, Mausset AL, Dejardin P. High molecular weight kininogen adsorption on hemodialysis membranes influence of pH and relationship with contact phase activation of blood plasma, influence of pretreatment with poly(ethyleneimine). Int J Artif Organs 2000 23 20-6. 

Rhodes NP, Wilson DJ, Williams RL. (2007) The effect of gas plasma modification on platelet and contact phase activation processes. Biomateriak 28 4561-4570. 

Drug-Mediated Amplification of Contact-Phase Activation... 

For the chemical reactor, the researchers used a nanoparticle catalyst deposited on metallic micro-structured foils. They tested Cu/ZnO and Pd/ZnO catalysts deposited on the microstructured foils. The Cu/ZnO catalyst was more active than the Pd/ZnO catalyst and had a lower selectivity to undesired carbon monoxide. However, because the Pd/ZnO catalyst was more stable, it was selected for use in their fuel processor. The Pd/ZnO carbon monoxide selectivity of the powder catalyst pressed into a pellet was lower than that of the nanoparticle catalyst deposited on the microstructured foils. This effect was attributed to contact phases between the catalyst and the metal foils. ... 

In another case, depending on the reaction conditions, thermodynamic phase separation of the active-site-containing phase might occur during the polymerization process. In this case, active sites would be separated from the polymer, would not be covered by the polymer produced, and would be directly accessible on the surface of polymer particles, see Fig. 5.4-4(d). In this case, the surface concentration of the monomer, instead of the monomer concentration in the swollen polymer, is to be considered as the driving force of the polymerization process. If such a separation process is combined with capillary condensation then a direct contact of active sites with, for example, liquid monomer is enabled yielding high polymerization rates. 

Functional evaluation of the intrinsic and final common pathways. Activation of the contact phase is by addition of a surface reagent to a plasma sample. 

Herwald, H., et ah, Activation of the contact-phase system on bacterial surfaces — a clue to serious complications in infectious diseases. Nat Med 1998, 4. 298-302. 

In some cases under the conditions similar to those corresponding to the formation of lyophilic colloidal systems, a spontaneous formation of emulsions, the so-called self-emulsification, may take place. This is possible e.g. when two substances, each of which is soluble in one of the contacting phases, react at the interface to form a highly surface active compound. The adsorption of the formed substance under such highly non-equilibrium conditions may lead to a sharp decrease in the surface tension and spontaneous dispersion (see, Chapter III, 3), as was shown by A.A. Zhukhovitsky [42,43], After the surface active substance has formed, its adsorption decreases as the system reaches equilibrium conditions. The surface tension may then again rise above the critical value, acr. Similar process of emulsification, which is an effective method for preparation of stable emulsions, may take place if a surfactant soluble in both dispersion medium and dispersed liquid is present. If solution of such a surfactant in the dispersion medium is intensively mixed with pure dispersion medium, the transfer of surfactant across the low surface tension interface occurs (Fig. VIII-10). This causes turbulization of interface... 

---