title: Adsorption of complement proteins on surfaces with a hydrophobicity gradient.
abstract: Activation of the complement system is recognized as one of the major problems with respect to biocompatibility of biomaterials. The binding of C3 (central component of complement) and B (factor B, an activator of C3), and H (factor H, an inhibitor of C3 activation) plays a crucial role in the activation of the alternative pathway of complement on the surfaces of biomaterials during extracorporeal procedures. Here we report on the adsorption of C3, B or H on to the silica surface with a hydrophobicity gradient. The amount of native 125I-C3 bound to both hydrophilic and hydrophobic surfaces was very similar (0.8 and 0.9 micrograms/cm2; 4 x 10(-12) mol/cm2). Neither factor H nor factor B was able to displace already adsorbed 125I-C3 from either of the surfaces. The extent of binding of factors B and H to preadsorbed C3 was a function of the surface hydrophobicity: more 125I-B or 125I-H was bound to C3 adsorbed at the hydrophilic end than at the hydrophobic end of the gradient surface. The binding of 125I-B or 125I-H to preadsorbed C3 appeared to be influenced by the availability of their binding sites on adsorbed C3 molecules rather than by the amount of surface-bound C3. At the hydrophobic end of the gradient surface the molar binding ratio of B/C3 was considerably smaller than the molar binding ratio of H/C3. It can be speculated that the hydrophobicity of the surface determines orientation and/or conformation of adsorbed C3 molecule; when adsorbed at the hydrophobic end of the gradient, C3 molecule predominantly exposes the binding site to which only factor H can bind.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Material Science and Engineering, University of Utah, Salt Lake City 84112.
authors.forename: Y S
authors.initials: YS
authors.lastname: Lin
authors.forename: V
authors.initials: V
authors.lastname: Hlady
authors.forename: J
authors.initials: J
authors.lastname: Janatova
mesh_terms: D000327:Adsorption; D001672:Biocompatible Materials; D002482:Cellulose / Q000031:analogs & derivatives; D003176:Complement C3 / Q000378:metabolism; D003180:Complement C3b Inactivator Proteins / Q000378:metabolism; D011415:Complement Factor B / Q000378:metabolism; D017242:Complement Factor H; D003170:Complement Pathway, Alternative; D003165:Complement System Proteins / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D012822:Silicon Dioxide; D013499:Surface Properties; D014867:Water
chemical_list: D001672:Biocompatible Materials; C493495:CFH protein, human; D003176:Complement C3; D003180:Complement C3b Inactivator Proteins; D014867:Water; C005062:acetylcellulose; D012822:Silicon Dioxide; D017242:Complement Factor H; D002482:Cellulose; D003165:Complement System Proteins; C009865:cuprammonium cellulose; D011415:Complement Factor B