Selective recognition of bacterial phospholipids by antimicrobial peptides: Employing a host-guest-mediated competitive inhibition strategy

The distinct phospholipid compositions of bacterial and mammalian cell membranes offer a promising target for the development of antimicrobial peptides (AMPs). However, distinguishing between the similarly charged anionic phospholipids-bacterial phosphatidylglycerol (PG) and mammalian phosphatidylserine (PS)-poses a significant challenge. Here we introduce a competitive inhibition strategy that leverages host-guest interactions to enable AMPs to selectively recognize PG without engaging with PS. After analyzing the binding interactions of various radially amphiphilic AMPs (RAPs), host molecules, and phospholipids, we discovered that a RAP, named C6HO, exhibited a higher affinity for cucurbit[7]uril (CB[7]) compared to PS, yet a lower affinity than for PG. Consequently, CB[7] functions as a competitive inhibitor: by forming a complex with C6HO upon simple mixing, it prevents C6HO from interacting with PS. Notably, PG can outcompete CB[7] for binding to C6HO within the complex, leading to the aggregation of PG molecules and the subsequent disruption of membranes rich in PG. Furthermore, the competitive inhibitor CB[7] effectively neutralizes C6HO's cytotoxic effects on mammalian cells while preserving the antimicrobial potency of C6HO. In vivo experiments in a subcutaneous infection model demonstrated that CB[7] reduced both systemic and local toxicity of C6HO without compromising its antimicrobial efficacy. Our study presents a strategy for the specific recognition of bacterial phospholipids and the design of highly selective AMPs.