Phospholipid bilayers as biomembrane-like barriers in layer-by-layer polyelectrolyte films

Area of Science:

• Materials Science
• Biophysics
• Polymer Science

Background:

• Layer-by-layer (LbL) assembly is a versatile technique for fabricating polyelectrolyte films.
• Lipid bilayers are crucial components of cell membranes and have potential applications in biomaterials.
• Integrating lipid bilayers into synthetic polymer structures presents challenges in maintaining their integrity and function.

Purpose of the Study:

• To investigate the successful fabrication of dipalmitoylphosphatidylcholine (DPPC) lipid bilayers on poly(glutamic acid)/poly(lysine) (PGA/PLL) polyelectrolyte films.
• To analyze the impact of DPPC bilayer incorporation on the growth dynamics and structural properties of the LbL film.
• To evaluate the stability and protein incorporation capabilities of the DPPC-embedded polyelectrolyte films.

Main Methods:

• Fabrication of PGA/PLL LbL films via exponential growth.
• Deposition of DPPC lipid bilayers onto the polyelectrolyte film surface.
• Characterization of film structure, surface roughness, and DPPC bilayer properties using techniques like ellipsometry and microscopy.
• Incorporation of Gramicidin A (GRA) into DPPC films.
• Thermal analysis (e.g., differential scanning calorimetry) to study DPPC phase transitions.

Main Results:

• DPPC bilayer formation reduced polyelectrolyte film surface roughness.
• The DPPC layer acted as a barrier, altering the LbL growth regime and enabling film continuation.
• DPPC bilayers exhibited structural and dynamic properties similar to hydrated multibilayers, with slightly broadened phase transitions.
• Embedded DPPC bilayers showed a decreased phase transition temperature due to interactions with the polyelectrolyte film.
• Gramicidin A (GRA) was successfully incorporated into the DPPC films.
• The resulting DPPC/PGA/PLL films demonstrated remarkable thermal stability over multiple heating-cooling cycles.

Conclusions:

• DPPC lipid bilayers can be effectively integrated into LbL polyelectrolyte films, modifying their growth and properties.
• The embedded DPPC bilayers serve as stable platforms for incorporating biomolecules like Gramicidin A.
• These hybrid materials exhibit excellent stability, suggesting potential for applications in drug delivery, biosensing, and biomimetic systems.