Biotin-Bearing pH-Sensitive Liposomes: High-Affinity Binding to Avidin Layer

A procedure is described for the preparation of biotin-bearing pH-sensitive liposomes. Liposomes were composed of phosphatidylethanolamine/oleic acid/ cholesterol/biotinaminocaproyl phosphatidylethanolamine (molar ratio 7:3:3:0.1) and contained the fluorescent dye calcein in self-quenched concentrations. these liposomes rapidly destabilized in weakly acidic media (pH 5.7). Liposomes were also readily agglutinated by acetylated avidin. Addition of biotin blocked the agglutination process. Binding of liposomes to a plastic surface coated with acetylated avidin was studied. the high-affinity binding with an apparent KD value up to 10−11 M liposomes was demonstrated by Scatchard analysis of the binding curves. A method of efficiently coating polyvinyl chloride microELisA plates with acylated avidin is also described.