Assembly of bioactive peptide-chitosan nanocomplexes

Area of Science:

• Biomaterials Science
• Nanotechnology
• Biochemistry

Background:

• Bioactive peptides like caseinophosphopeptides (CPPs) and chitosan (CS) are promising biomaterials.
• Understanding their self-assembly into nanocomplexes is crucial for developing novel applications.

Purpose of the Study:

• To systematically investigate the assembly of CPP-CS nanocomplexes under physiological conditions.
• To characterize the physicochemical properties and binding mechanisms of these nanocomplexes at various CS/CPP mass ratios.

Main Methods:

• Utilized a combination of techniques including LC-MS/MS, turbidimetric titration, DLS, ζ-potential measurements, TEM, and fluorescence spectroscopy.
• Analyzed peptide incorporation, nanoparticle size, charge, morphology, and binding constants.

Main Results:

• Identified CPPs incorporated into CS nanoparticles with varying phosphorylated seryl residues.
• Observed shifts in critical pH values (pH(φ1) and pH(max)) with increasing CS/CPP mass ratio.
• Described a three-step process for nanocomplex formation involving absorption, bridging, and isolation, driven by electrostatic interactions (K(cs) = 4.6 × 10(4) M⁻¹).

Conclusions:

• The binding between CPPs and CS is primarily driven by electrostatic interactions.
• Phosphorylated groups and acidic amino acids (Asp, Glu) in CPPs are key interaction sites with CS.
• The study elucidates the mechanism of CPP-CS nanocomplex formation, offering insights for biomaterial design.