Glycine Composition and Ion Valency Tune Phase Behavior and Drug Encapsulation in Designer Peptide Condensates

Area of Science:

• Biomaterials Science
• Drug Delivery Systems
• Peptide Engineering

Background:

• Nano- and microencapsulation for therapeutic delivery faces challenges in achieving high loading capacity and stimulus-responsive release.
• Liquid-liquid phase separation of designed peptide condensates presents a promising, biocompatible platform for advanced drug delivery.

Purpose of the Study:

• To systematically investigate how backbone flexibility and ion identity influence the phase behavior, material properties, payload encapsulation, and release kinetics of peptide condensates.
• To establish design principles for engineering peptide condensates with tunable properties for targeted therapeutic delivery.

Main Methods:

• Systematic modification of minimalistic cationic-aromatic peptides by varying glycine content to alter backbone flexibility and charge density.
• Analysis of phase behavior, condensate dynamics, and material properties under different ionic conditions (monovalent vs. divalent anions).
• High-performance liquid chromatography (HPLC) partitioning to assess encapsulation of FDA-approved small molecules and protease-triggered (trypsin) disassembly.

Main Results:

• Glycine-poor peptide sequences formed highly packed condensates, while divalent sulfate ions increased peptide concentration and droplet size.
• Increasing glycine content enhanced condensate dynamics (faster diffusion) and influenced protease-triggered disassembly.
• Payload encapsulation was compound-specific and salt-mediated, dependent on hydrophobicity, polarity, and charge state of small molecules.

Conclusions:

• Peptide sequence, particularly glycine content, and ion valency are critical factors in controlling peptide condensate formation, payload encapsulation, and release.
• These findings provide practical design rules for engineering peptide condensates for targeted sequestration and controlled release of therapeutics.
• The study advances the rational design of peptide-based materials for sophisticated drug delivery applications.