pH-induced release from P2VP-PEO block copolymer vesicles.

Area of Science:

• Polymer Science
• Materials Science
• Nanotechnology

Background:

• Polymeric vesicles offer potential for controlled release applications.
• Understanding the stimuli-responsive behavior of block copolymers is essential for designing advanced materials.
• Poly(2-vinylpyridine-b-ethylene oxide) (P2VP-PEO) is a pH-sensitive block copolymer.

Purpose of the Study:

• To investigate the pH-induced release of hydrophilic dyes from P2VP-PEO block copolymer vesicles.
• To characterize the structural changes and rupture mechanism of the vesicles upon pH decrease.
• To explore the potential of these vesicles for controlled release systems.

Main Methods:

• Small-angle neutron scattering (SANS) for structural characterization.
• Cryo-electron microscopy (cryo-TEM) for vesicle morphology analysis.
• Fluorescence video microscopy, gel electrophoresis, and high-performance ultrafiltration to study the release kinetics.

Main Results:

• Vesicle structure was confirmed using SANS and cryo-TEM.
• A decrease in pH below 5 induced protonation and dissolution of the P2VP blocks.
• This protonation led to vesicle membrane rupture and subsequent release of encapsulated hydrophilic dyes.
• The release process dynamics were detailed by fluorescence microscopy and ultrafiltration.

Conclusions:

• P2VP-PEO block copolymer vesicles exhibit pH-triggered release behavior.
• The protonation and dissolution of P2VP blocks are key mechanisms for vesicle rupture.
• These findings highlight the potential of P2VP-PEO vesicles as smart drug delivery systems sensitive to pH changes.