The novel modification of gold surfaces with a biotinylated polypeptide multilayer formed by nonspecific electrostatic adsorption was designed for the SPR sensing platform. The multilayer of polypeptides (poly-L-lysine and poly(aspartic acid)) was prepared onto a negatively charged self-assembled monolayer of 11-mercaptoundecanoic acid (MUA) on gold film. The polypeptide multilayer was functionalized with biotin by directly grafting to poly (succinimide) (PSI). The specific binding of avidin to the biotinylated polypeptide multilayer (DS 2.7%) resulted in a shift in the refractive index of 0.003 +/- 9 x 10(-4) with a surface density of 2.9 ng/mm(2). This multilayer surface was found to provide a simple and effective method for the SPR sensing.