Surface immobilization chemistry influences peptide-based detection of lipopolysaccharide and lipoteichoic acid

Antimicrobial peptides (AMPs) have recently gained attention as potentially valuable diagnostic and therapeutic agents. The utilization of these peptides for diagnostic purposes relies on the ability to immobilize them on the surface of a detection platform in a predictable and reliable manner that facilitates target binding. The method for attachment of peptides to a solid support is guided by peptide length, amino acid composition, secondary structure, and the nature of the underlying substrate. While immobilization methods that target amine groups of amino acid sequences are widely used, they can result in heterogeneous conjugation at multiple sites on a peptide and have direct implications for peptide presentation and function. Using two types of commercial amine-reactive microtiter plates, we described the effects of analogous immobilization chemistries on the surface attachment of AMPs and their differential binding interaction with Gram-specific bacterial biomarkers, lipopolysaccharide and lipoteichoic acid. As might be expected, differences in overall binding affinities were noted when comparing AMPs immobilized on the two types of plates. However, the two-amine-targeted linking chemistries also affected the specificity of the attached peptides; lipopolysaccharide generally demonstrated a preference for peptides immobilized on one type of plate, while (when observed at all) lipoteichoic acid bound preferentially to AMPs immobilized on the other type of plate. These results demonstrate the potential for tuning not only the binding affinities but also the specificities of immobilized AMPs by simple alterations in linking strategy.