Short Ligand, Cysteine-Modified Warnericin RK Antimicrobial Peptides Favor Highly Sensitive Detection of

Culture-based methods for the detection of Legionella pneumophila are prohibitively slow and frequently inadequate. The problem has been addressed with biosensing technology that employs a variety of ligands for the specific capture of bacteria. However, the limited success of the application of mammalian antibodies, aptamers, and nucleic acid-based probes for sensitive biosensing has generated growing interest in exploring alternative biosensing architectures, such as those based on antimicrobial peptides (AMP) that are known for their attractive therapeutic applications. We report on the successful employment of cysteine-modified warnericin RK AMP for the operation of a highly sensitive biosensor of L. pneumophila based on digital photocorrosion of GaAs/AlGaAs nanoheterostructures. The replacement of the relatively cumbersome procedure commonly applied for the attachment of antibodies to COOH-terminated mercaptohexadecanoic acid self-assembled monolayers has allowed for a significant reduction in the distance at which bacteria are immobilized above the biosensor surface. An important consequence of this approach is the attractive limit of detection of L. pneumophila estimated at 2 × 102 CFU/mL. The target bacteria were captured four times more efficiently than P. fluorescens, B. subtilis, and E. coli, which is highly promising for environmental monitoring.