Enhanced Intracellular Delivery by Twisted CC-Loop Conformation in Cyclic Cell-Penetrating Peptides.

Area of Science:

• Biochemistry
• Molecular Biology
• Drug Delivery Systems

Background:

• Biological drugs offer therapeutic potential but face challenges with cellular uptake.
• Cell-penetrating peptides (CPPs) are investigated to enhance the delivery of biomacromolecules.
• Optimizing CPP structure is crucial for improving delivery efficiency.

Purpose of the Study:

• To design and evaluate novel cyclic CPPs for enhanced cellular delivery.
• To investigate the structural basis for improved membrane penetration of cyclic CPPs.
• To demonstrate the utility of a novel cyclic CPP for delivering therapeutic payloads like siRNA.

Main Methods:

• Synthesis of three cyclic CPPs with varying ring sizes via disulfide bond formation.
• Assessment of membrane penetration and delivery efficiency using siRNA, GFP, and plasmids.
• Conformational analysis using computational methods to understand structure-activity relationships.

Main Results:

• The cyclic peptide Y2-13-OX adopted a distinct twisted CC-loop conformation.
• Y2-13-OX exhibited enhanced membrane penetration compared to linear and other cyclic CPPs.
• Y2-13-OX efficiently delivered functional siRNA targeting METTL3, achieving significant knockdown.

Conclusions:

• A novel cyclic CPP conformation (CC-loop) enhances therapeutic delivery efficiency.
• Y2-13-OX represents a promising platform for delivering nucleic acids and other biological drugs.
• This study provides new insights into CPP design for advanced drug transport strategies.