Synthesis of bacterial cell penetrating peptoids

Abstract

The delivery of therapeutic agents into bacterial cells remains a significant challenge due to the impermeability of bacterial membranes. This study investigated the potential of peptoids, stable mimetics of cell- penetrating peptides (CPPs), for application in proka yotic systems, focusing on mitochondria-targeting peptoids (MTPs) and RXRtoid, a peptoid mimetic of the RXR4 peptide commonly used in therapeutic delivery. MTPs were hypothesized to exhibit favorable bacterial-penetrating properties due to their inherent CPP activity and structural parallels with Gram-negative bacterial membranes. While MTPs demonstrated high uptake and mitochondrial colocalization in mammalian cells, confocal microscpy revealed that these properties often resulted in bacterial membrane disruption rather than successful cytoplasmic penetration. Co-staining with DAPI and FM 4-64 confirmed that two bacterial cell penetrating peptoid (BPP) candidates localized to the bacterial cytosol, with MJJ- 1-121, a peptoid exhibiting low mammalian permeability—achieving effective bacterial internalization, whereas other peptoids predominantly caused membrane damage. The inclusion of RXRtoid further highlighted the potential of peptoid design for modulating cellular uptake and internalization, offering insights into the optimization of peptoids as delivery agents for bacterial applications.