Reductively Responsive Gel Capsules Prepared Using a Water-Soluble Zwitterionic Block Copolymer Emulsifier

Area of Science:

• Polymer Chemistry
• Materials Science
• Biotechnology

Background:

• Poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) exhibits unique solubility in water and alcohol.
• Block copolymers offer versatile properties for advanced material applications.
• Responsive materials are crucial for controlled drug delivery systems.

Purpose of the Study:

• To synthesize a novel water-soluble block copolymer emulsifier using PMPC and poly[oligo(ethylene glycol) methacrylate] (POEGMA).
• To create reductively responsive poly[poly(ethylene glycol) methacrylate] (PPEGMA) gel capsules.
• To evaluate the drug release characteristics of these PPEGMA gel capsules in response to a reducing agent.

Main Methods:

• Reversible addition-fragmentation chain transfer (RAFT) polymerization was employed to synthesize PMPC-b-POEGMA block copolymers.
• Inverse miniemulsion periphery RAFT polymerization was used to form PPEGMA gel capsules with disulfide cross-linkers.
• Water-in-oil (W/O) emulsions were stabilized by the PMPC-b-POEGMA emulsifier.
• Drug release studies were conducted using fluorescein-conjugated dextran (FITC-Dex) as a model drug in the presence and absence of dithiothreitol (DTT).

Main Results:

• PMPC-b-POEGMA successfully stabilized W/O emulsions in a chloroform phase.
• Colloidally stable PPEGMA gel capsules were formed, stable in both chloroform and water.
• The PPEGMA gel capsules demonstrated significantly faster release of FITC-Dex in the presence of DTT compared to its absence.
• Disulfide bond cleavage due to DTT was identified as the mechanism for accelerated drug release.

Conclusions:

• The synthesized PMPC-b-POEGMA block copolymer is an effective emulsifier for creating W/O emulsions.
• The PPEGMA gel capsules exhibit responsive behavior to reducing agents, enabling controlled drug release.
• These PPEGMA gel capsules represent a promising platform for drug delivery, protein and gene delivery, and nanobioreactors.