Stability studies on colloidal suspensions of polyurethane nanocapsules

Area of Science:

• Materials Science
• Colloid and Surface Chemistry
• Polymer Chemistry

Background:

• Nanocapsule suspensions are often metastable, prone to aggregation due to inter-particle forces.
• The integrity of the polymeric membrane is crucial for protecting encapsulated active ingredients from external degradation factors.

Purpose of the Study:

• To evaluate the protective role of polymeric membranes in nanocapsules against external damaging agents.
• To identify the optimal monomer for creating stable nanocapsule formulations with high active drug payload.

Main Methods:

• Nanocapsules were synthesized using interfacial polycondensation and spontaneous emulsification to encapsulate alpha-tocopherol.
• Stability was assessed through visual inspection, particle size analysis, transmission electron microscopy (TEM), and drug loss measurements after 6 months at varying temperatures (4, 25, 45°C).
• Different hydrophilic monomers (1,2-ethanediol, 1,4-butanediol, 1,6-hexanediol) were used to form polyurethane membranes.

Main Results:

• Nanocapsule sizes before storage ranged from 232 nm (ED) to 312 nm (HD).
• Polyurethane nanocapsules exhibited good physical stability against aggregation at 4°C and 25°C after 6 months.
• The formulation utilizing 1,6-hexanediol (HD) provided the best protection for alpha-tocopherol against temperature and UV-induced degradation.

Conclusions:

• Polyurethane nanocapsules demonstrate good colloidal stability and protective capabilities for encapsulated alpha-tocopherol.
• The choice of monomer significantly impacts nanocapsule stability and the payload's protection.
• 1,6-hexanediol is identified as a promising monomer for developing stable and protective polyurethane nanocapsule formulations.