Liposome encapsulation for casein-derived peptides: Release behavior, in vitro digestibility, nutrient absorption, and gut microbiota

Protein-derived bioactive peptides hold great potential for promoting health while face significant challenges during digestion, including structural degradation by gastrointestinal enzymes and limited stability, which hinder their effective utilization. Encapsulation technology offers a promising solution to protect bioactive peptides and ensure their targeted delivery. In this study, casein peptides (CP) were encapsulated into liposomes (CPL) prepared using the thin-film hydration method. The preparation conditions were optimized through response surface methodology, with the following parameters identified: a lecithin-to-cholesterol mass ratio of 3.0, a peptide solution concentration of 0.65 mg/mL, and a wall-to-core material volume ratio of 4.0. Validation experiments confirmed the optimized CPL formulation, resulting in liposomes with an average particle size of 86.13 ± 0.62 nm and an encapsulation efficiency at 87.29 ± 0.82 %. Comprehensive characterization of CPL was conducted using transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and fourier transform infrared spectroscopy (FTIR) techniques. The results demonstrated that CPL provided strong protection for CP against degradation by gastrointestinal enzymes, allowing controlled release in the intestine. This targeted release facilitated interactions with gut microbiota, leading to improved nutrient absorption and modulation of gut health. These findings highlight the potential of liposomal encapsulation to enhance the bioavailability and functional properties of bioactive peptides, paving the way for their broader application in health-related formulations.