Polyethylene-Glycol-Conjugated Peptide Coacervates with Tunable Size for Intracellular mRNA Delivery

Area of Science:

• Biomaterials Science
• Nanotechnology
• Chemical Engineering

Background:

• Coacervate microdroplets (CMs) from liquid-liquid phase separation (LLPS) show promise for biomedical uses but face challenges with size and stability.
• Existing CMs often exhibit micrometer sizes and coalesce, limiting their utility in applications like intracellular delivery or microcatalysis.

Purpose of the Study:

• To control the size and stability of peptide-based coacervates using poly(ethylene glycol) (PEG) conjugation.
• To restore and enhance the cellular uptake and mRNA delivery capabilities of these modified coacervates (CNs).

Main Methods:

• Conjugating histidine-rich beak peptides (HBpep) with PEG to create PEGylated HBpep.
• Preparing mixtures of PEGylated and non-PEGylated HBpep to form coacervate nanodroplets (CNs).
• Modifying peptide sequences with positive charges to improve mRNA recruitment and cellular delivery.

Main Results:

• PEGylation stabilized coacervates into the nanoscale range with controlled size distribution based on PEGylated-to-non-PEGylated peptide ratios.
• Incorporating positive charges restored mRNA recruitment and intracellular delivery functions of the CNs.
• PEG-stabilized CNs demonstrated enhanced cellular uptake and mRNA transfection efficiency at 37 °C.

Conclusions:

• This strategy effectively controls coacervate size and stability, creating functional nanoscale coacervate nanodroplets (CNs).
• The developed CNs offer improved cellular uptake and mRNA delivery, suitable for physiological conditions.
• This approach provides a versatile platform for designing advanced LLPS-based delivery systems for in vivo applications, catalysis, and bioreactors.