Protein encapsulation via polyelectrolyte complex coacervation: Protection against protein denaturation

Area of Science:

• Polymer Science
• Biochemistry
• Materials Science

Background:

• Complex coacervation is a liquid-liquid phase separation process involving oppositely charged polyelectrolytes.
• This phenomenon enables the encapsulation of various molecules, including proteins, within coacervate droplets.
• Understanding protein encapsulation is crucial for applications in drug delivery, biomaterials, and stabilizing sensitive biomolecules.

Purpose of the Study:

• To investigate the encapsulation efficiency of Bovine Serum Albumin (BSA) within poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) complex coacervates.
• To determine the influence of mixing sequence, polyelectrolyte concentration, BSA concentration, and PAA/PAH ratio on protein encapsulation.
• To evaluate the protective effect of coacervates on BSA structure and function under various stress conditions.

Main Methods:

• Complex coacervation was induced using cationic PAH and anionic PAA.
• Bovine Serum Albumin (BSA) was used as a model protein for encapsulation studies.
• Encapsulation efficiency was modulated by varying parameters like mixing order and concentrations.
• Circular dichroism spectroscopy was employed to assess protein secondary structure preservation.
• BSA stability was tested under extreme pH, high temperature, and urea exposure.

Main Results:

• Efficient encapsulation of BSA was achieved by specific mixing sequences and optimized PAA-PAH coacervate conditions.
• Increased total polyelectrolyte concentration and PAA/PAH ratio enhanced BSA encapsulation.
• Decreased BSA concentration also led to more efficient protein encapsulation.
• Circular dichroism confirmed that BSA retained its secondary structure within the coacervates.
• PAA-PAH coacervates protected BSA from denaturation caused by pH, heat, and urea.
• Encapsulation effectively inhibited complexation between BSA and heavy metals.

Conclusions:

• PAA-PAH complex coacervates provide a robust system for encapsulating and stabilizing proteins like BSA.
• The coacervation process preserves protein secondary structure and protects against environmental stressors.
• This method offers a promising approach for maintaining protein stability and function in diverse applications.
• Inhibition of protein-metal complexation is a significant benefit for certain biotechnological applications.