From ultrathin capsules to biaqueous vesicles

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Layer-by-layer (LbL) adsorption is a versatile technique for creating multilayered nanostructures.
• Polyelectrolyte (PE) complexes often form stiff coacervates in aqueous solutions.
• The behavior of drug-loaded nanocapsules in aqueous environments requires further investigation.

Purpose of the Study:

• To investigate the transition of polyelectrolyte/tobramycin sulfate (PE/TbS) ultrathin capsules to biaqueous vesicles.
• To explore the physicochemical properties of these transitioning systems.
• To understand the factors influencing capsule morphology and stability.

Main Methods:

• Fabrication of ultrathin capsules using LbL adsorption of anionic PE and tobramycin sulfate (TbS) on zinc oxide core particles.
• Controlled removal of the zinc oxide core to initiate capsule transformation.
• Analysis of capsule morphology, stability, and physicochemical properties under varying conditions (PE backbone hydrophilicity/hydrophobicity, PE/TbS ratio, Zn2+ concentration).

Main Results:

• LbL-assembled PE/TbS multilayers on ZnO cores transform into ultrathin capsules upon core removal.
• These capsules transition to biaqueous vesicles or emulsionlike systems, deviating from typical stiff PE coacervates.
• The transition is influenced by PE backbone properties, PE/TbS ratio, and Zn2+ concentration, leading to unique PE/TbS/H2O biphasic liquid systems.

Conclusions:

• The study demonstrates a novel transformation pathway for LbL-assembled nanostructures from capsules to biaqueous vesicles.
• The resulting PE/TbS/H2O systems exhibit unique biphasic liquid characteristics, distinct from conventional polyelectrolyte coacervates.
• Understanding this transition is crucial for designing advanced drug delivery systems and functional nanomaterials.