Assembling Fibrinogen at Air/Water and Solid/Liquid Interfaces Using Langmuir and Langmuir-Blodgett Films

Langmuir films of pure fibrinogen (Fg) and Fg spread at the air/buffer interface and subphase containing electrolytes, NaCl, KCl, CaCl2, and ZnCl2, have been analyzed to understand the role of the surface/interface in mediating the organization of the protein eventually to fibrils. These films have been characterized by the surface pressure and surface potential-molecular area ((pi-A) and (Delta V-A)) isotherms and Brewster angle microscopy (BAM). The Langmuir-Blodgett (LB) films of the protein transferred to the solid substrates have been characterized by scanning electron microscopy (SEM) and circular dichroism (CD). Our results suggest that fibrils are formed during organization at air/solution interface and also in LB films. The rate of formation of the fibril is the maximum for Fg with ZnCl2. Adsorption of Fg to surfaces coated with a neutral lipid, dimyristoylphosphatidylcholine (DMPC), and a cationic lipid, dioctadecyldimethylammonium bromide (DOMA), from a range of solution concentrations has been studied using a quartz crystal microbalance (QCM). The work of adhesion of the protein on the solid surface shows fibril formation and positive adhesion for Fg in the presence of electrolytes. SEM results show that the adherent protein exhibits the widely reported nodulelike structure in the presence of CaCl2 and ZnCl2. These results provide definite evidence that specifically designed surfaces can promote adhesion of Fg and also activate fibril formation even in the absence of thrombin.