Partial poly(glutamic acid) <--> poly(aspartic acid) exchange in layer-by-layer polyelectrolyte films. Structural</-->...

Area of Science:

• Materials Science
• Biomaterials Engineering
• Polymer Chemistry

Background:

• Layer-by-layer (LBL) assembly is a versatile technique for fabricating multilayered polyelectrolyte films.
• Understanding the secondary structure of polyelectrolyte films is crucial for controlling their interactions with biomolecules.
• Poly(L-glutamic acid) (PGA), poly(L-aspartic acid) (PAA), and poly(L-lysine) (PLL) are common polyelectrolytes used in LBL films.

Purpose of the Study:

• To investigate the secondary structures of PGA/PLL and PAA/PLL polyelectrolyte films.
• To determine how the secondary structure of these films affects the adsorption and structural integrity of human serum albumin (HSA).
• To explore the incorporation and structural consequences of mixing PGA and PAA within LBL films.

Main Methods:

• Fabrication of LBL polyelectrolyte films using PGA, PAA, and PLL.
• Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy to analyze film secondary structures.
• Adsorption studies using human serum albumin (HSA) as a reporter molecule.
• Infrared spectroscopy analysis of the amide I region to monitor polyanion domain distribution.

Main Results:

• PGA/PLL films predominantly featured extended beta-sheets, while PAA/PLL films showed alpha-helices and intramolecular beta-sheets.
• HSA retained its native secondary structure on PGA/PLL films but was deformed on PAA/PLL films.
• Mixing PGA and PAA in LBL films resulted in coexisting domains with distinct secondary structures, with evidence of free diffusion of polyanions.

Conclusions:

• The secondary structure of LBL polyelectrolyte films significantly impacts protein adsorption and structural preservation.
• PGA/PLL films offer a more favorable environment for maintaining protein native structure compared to PAA/PLL films.
• LBL film composition can be tuned to create heterogeneous structures with predictable biomolecular interaction properties.