Investigating Penetration and Antimicrobial Activity of Vector-Bicycle Conjugates

Area of Science:

• Microbiology
• Drug Discovery
• Biotechnology

Background:

• Antibiotic resistance is a growing threat to treating Gram-negative bacterial infections.
• Bicycle molecules are a promising new class of antibiotics, but bacterial outer membrane penetration is a challenge.
• Membrane active peptides (MAPs) can facilitate outer membrane penetration when conjugated to cargo molecules.

Purpose of the Study:

• To investigate how physicochemical properties of a specific MAP influence the penetration of MAP-Bicycle conjugates into Gram-negative bacteria.
• To identify key properties for optimizing MAP-Bicycle conjugate design for enhanced antimicrobial efficacy.

Main Methods:

• Generated multiple variants of MAP-Bicycle conjugates using a membrane active peptide derived from ixosin-B.
• Systematically altered physicochemical properties of the MAP component, including charge, hydrophobicity, amphipathicity, and secondary structure.
• Assessed the penetration efficiency of these variants into the Gram-negative outer membrane.

Main Results:

• Conjugate penetration and antimicrobial potency were significantly enhanced by increasing positive charge and hydrophobicity of the MAP.
• Induction of secondary structure in the MAP was crucial for effective outer membrane penetration.
• Changes in amphipathicity alone did not significantly improve penetration.

Conclusions:

• Charge and hydrophobicity are critical physicochemical properties for designing effective membrane-penetrating vectors.
• Secondary structure induction is vital for MAP-mediated delivery through the Gram-negative outer membrane.
• These findings provide a framework for designing improved delivery systems for bicycle molecules and other therapeutic cargos across biological membranes.