Biological selection of peptides for poly(L-lactide) substrates

Short peptides that recognize the a form of poly(L-lactide) (PLLA) crystalline films were identified from a phagedisplayed peptide library. An enzyme-linked immunosorbent assay (ELISA) revealed that the apparent binding constants of the phage clones for the a form of PLLA were greater than those of the unselected phage library. The specificity index for the a form of PLLA referred to a structurally similar atactic poly(methyl methacrylate) (at-PMMA), supporting the a form of PLLA specific binding of the selected phage. Amino acid residues with proton-donor lateral groups and hydrophobic alkyl groups were relatively enriched in a sequence of heptapeptides on the specific phage clones, thereby suggesting the presence of hydrogen bonding as well as hydrophobic interactions between the a form of PLLA and the peptides. Surface plasmon resonance (SPR) analysis revealed that the binding constant of the freed c22 heptapeptide (Gln-Leu-Met-His-Asp-Tyr-Arg) for the a form of PLLA was greater than those for reference at-PMMA, amorphous PLLA, and the β form of PLLA. It was found that c22 peptide can recognize slight differences in PLLA polymorphs such as a crystalline state and an arrangement of PLLA functional groups.