Publication in: Spring 2023 Issue

Synthesis and Evaluation of Antibiotics with Cleavable Guanidine Linkers to Combat Gram-Negative Antibiotic Resistance Mechanisms
Jason Dunford
Faculty Mentor(s):
Amanda Wolfe
Abstract / Summary:
Antibiotic resistance is a rising global concern with several bacteria having resistance mechanisms to many widely used antibiotics. Particularly, Gram-negative bacteria present a unique challenge because of their second, semipermeable outer membrane (OM), which offers additional protection against antibiotics. Prior studies have shown that penetration of Gram-negative OMs is dependent upon 5 separate features that most current antibiotics do not have. These features include having small molecular masses, high polar surface areas, unsubstituted amines, and low globularity. To improve antibiotic activity and facilitate OM penetration we have modified known antibiotics with guanidinium groups that follow these rules well, which should increase antibiotic effectiveness in host cells and result in cell death when paired with an antibiotic. By attaching the guanidinium through a cleavable linker, the antibiotic is theoretically able to permeabilize the membrane and then, through natural cellular environmental interactions, cleave the bond between the antibiotic and the linker. Cleaving the linkers is important as they likely would lead to reduced potency for the antibiotic. In particular, sulfamethoxazole was successfully synthesized with the guanidine linker and evaluated for activity within the cell with a cell death assay against wild-type Pseudomonas aeruginosa, a Pseudomonas aeruginosa efflux knockout strain, and wild-type Escherichia coli. There was no visible cell death recorded in any of the assays, however. Further testing with other types of antibiotics to evaluate if this method has potential further antibiotic development capabilities will be done.
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