Photoresponsive, ionically cross-linked chitosan-azobenzene capsules for controlled cargo release

Area of Science:

• Soft matter physics
• Colloidal systems
• Materials science

Background:

• Photoresponsive materials enable controlled cargo release under mild conditions.
• Chitosan is a biocompatible and biodegradable material suitable for microcapsule shells.
• Azobenzene derivatives can be used as photoresponsive cross-linkers.

Purpose of the Study:

• To fabricate visible light-responsive, ionically cross-linked chitosan microcapsules.
• To investigate the controlled cargo release capabilities of these microcapsules using visible light.
• To demonstrate a scalable strategy for photo-controlled delivery systems.

Main Methods:

• Fabrication of microcapsules via oil-in-water emulsion.
• Ionic cross-linking of chitosan with disodium (E)-4,4'-(diazene-1,2-diyl)bis(3,5-difluorobenzoate) (NaFDAB).
• Characterization using optical microscopy, FE-SEM, ATR-FTIR, and UV-Vis spectroscopy.
• Cargo release studies using Nile Red monitored by fluorescence spectroscopy.

Main Results:

• Spherical, mechanically stable microcapsules were successfully prepared.
• Reversible trans-cis photoisomerisation of NaFDAB was confirmed under visible light.
• Controlled cargo release was achieved using green light irradiation, with minimal release under ambient conditions.
• Pulsed irradiation demonstrated controllable on-off release behavior, indicating light-modulated shell permeability.

Conclusions:

• A novel photoresponsive chitosan microcapsule system was developed using a visible light-responsive cross-linker.
• The system allows for mild, effective, and scalable photo-controlled cargo delivery.
• These findings present a promising platform for advanced drug delivery applications.