Layer-by-layer films with bioreducible and nonbioreducible polycations for sequential DNA release

Area of Science:

• Biomaterials Science
• Nanotechnology
• Gene Delivery

Background:

• Layer-by-layer (LbL) films composed of cationic polyelectrolytes and anionic bioactive molecules like DNA show promise for localized gene delivery.
• Bioreducible LbL films, utilizing disulfide-containing poly(amido amine)s (PAAs) and plasmid DNA, are designed for degradation via thiol-disulfide exchange, releasing DNA into the extracellular environment.

Purpose of the Study:

• To investigate the degradation mechanism and released species of bioreducible PAA/DNA LbL films.
• To explore strategies for controlling film degradation and enhancing DNA release for gene delivery applications.

Main Methods:

• Atomic force microscopy (AFM), fluorescence spectroscopy, and dynamic light scattering (DLS) were employed to study film degradation in reducing agent solutions.
• Comparative analysis of PAA/DNA LbL films with and without inserted poly(ethylenimine) (PEI) layers was performed.

Main Results:

• Unmodified PAA/DNA LbL films exhibited rapid bulk degradation.
• Sequential insertion of non-bioreducible PEI layers into PAA/DNA LbL films resulted in arrested bulk degradation, leading to sequential film disassembly.
• PEI-containing LbL films demonstrated sustained DNA nanoparticle release over extended periods and enabled transfection of human embryonic kidney 293 cells.

Conclusions:

• The PEI layer acts as a crucial barrier, preventing interlayer diffusion during assembly and disassembly, thereby controlling degradation.
• The high mobility of cleaved PAA fragments without a barrier layer causes bulk degradation, hindering gene delivery potential.
• This study provides a method to design bioreducible LbL films for sequential, long-term DNA release and successful gene transfection by controlling film structure.