Unusual behaviour induced by phase separation in hydrogel microspheres.

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Drug Delivery Systems

Background:

• Hydrogel microspheres are vital for biomedical applications, particularly in drug delivery via ion-exchange.
• Existing systems primarily use anionic hydrogels for cationically charged drugs in treatments like drug-eluting bead chemoembolization (DEB-TACE).

Purpose of the Study:

• To investigate the synthesis and properties of novel cationic hydrogel microspheres.
• To explore the unusual behavior induced by phase-separation during microsphere synthesis.

Main Methods:

• Synthesis of cationic hydrogel microspheres.
• Induction of phase-separation during synthesis, leading to core-shell structures.
• Swelling studies in aqueous environments and ion-exchange interactions with anionic compounds.

Main Results:

• Phase-separation during synthesis resulted in a cationic polymer-enriched core and a polyvinyl alcohol (PVA)-based outer phase.
• Swelling in water caused separation of the PVA-rich skin from the charged core in some formulations.
• Ion-exchange with multi-anionic compounds induced differential contraction, creating a "golf-ball" surface morphology.

Conclusions:

• The observed phase-separation and subsequent structural changes represent a novel phenomenon in hydrogel microsphere synthesis.
• These findings suggest potential for new drug delivery systems that respond to drug loading by altering their structure or surface area.