Are you aware that peptides can give very low signals when immobilized? But you can also easily immobilize to much and mask any further binding!
May this publication can give anay help
1: J Mol Recognit. 2006 Jul-Aug;19(4):363-71. Links
Modular, self-assembling peptide linkers for stable and regenerable carbon nanotube biosensor interfaces.Contarino MR, Sergi M, Harrington AE, Lazareck A, Xu J, Chaiken I.