1College of Food Science and Technology, Nanjing Agricultural University, Nanjing, China
2State Key Laboratory of Marine Food Processing and Safety Control, Dalian Polytechnic University, Dalian, China
3National Engineering Research Center of Seafood, Collaborative Innovation Center of Seafood Deep Processing, School of Food Science and Technology, Dalian Polytechnic University, Dalian, China
With the prevalence of chronic diseases, health-promoting foods have gained increasing attention. Curcumin (Cur), one of dietary polyphenols, which is well known for its various biological activities but liable to degradation and has poor hydrophilicity and bioaccessibility. In our previous study, we employed the nanoliposomes (Lips) to encapsulate Cur (Lips-Cur). Results suggested that Cur interacted with phospholipids, which regulated the spatial rearrangements of bilayer. The system performed superiorities in delivering Cur with enhanced solubility, stability and antioxidant activity. In this study, we modified Lips with whey isolate protein (WPI-Lips) to further improve the Cur physicochemical stability and bioaccessibility. The effect of WPI mass ratios (WPI/Lips = 0.125, 0.25, 0.5, 1.0, and 2.0) on liposomal physicochemical properties, bilayer structure, and Cur stability and release behaviour were systematically investigated.
The mass ratios of WPI influenced properties of WPI-Lips. As the WPI/Lips ratio increased from 0.125 to 1.0, particle size gradually increased (from 105.26 ± 2.41 nm to 122.48 ± 1.83 nm), accompanied by a moderate rise in polydispersity index (PDI < 0.30) and enhanced surface charge magnitude. A remarkable size increase (up to 158.37 ± 3.12 nm) and PDI elevation (0.403 ± 0.009) were observed at a 2.0 ratio, indicating vesicle aggregation and reduced dispersion stability. Collectively, as 0.5 mass ratio of WPI was added, WPI-Lips presented narrow size distribution (118.12 ± 1.56 nm), small PDI values (< 0.15) and high surface charges (>|30 mV|), unravelling their excellent uniformity and preferable stability.
Spectroscopic analyses revealed that hydrogen bonding and van der Waals forces were the main driving interactions between WPI and Lips. The binding of Lips altered protein conformation and aggregation behaviour, which also affected membrane structure. Moderate WPI incorporation (0.25-1.0 ratios) allowed the hydrophobic protein regions to embed partially within the bilayer,reducing membrane fluidity by 25.2%-47.8%and enhancing bilayer order by 4.5%-23.9% . With the increase of WPI (≥ 1.0), a dense surface coating formed, providing steric hindrance and electrostatic repulsion, but overly high concentrations (2.0 ratio) imposed stress that disrupted acyl-chain order by 11% and caused structural instability.
Functional evaluations confirmed that WPI modification greatly enhanced Cur stability. The half-life of Cur increased from 10.26 h to 16.62 h under UV exposure, from 15.09 h to 29.69 h under thermal treatment, and from 15.58 day to 35.94 day during storage. Moreover, WPI-Lips-Cur exhibited sustained release and higher bioaccessibility (39.62%) during in vitrodigestion, compared with 30.91% for unmodified Lips-Cur.
In summary, WPI modification at an optimal mass ratio of 0.5 produced well-dispersed, structurally stable liposomes with reinforced bilayer rigidity and improved Cur retention. These findings demonstrate that membrane engineering is an effective strategy to enhance the physicochemical stability and gastrointestinal delivery of liposomal bioactives, providing valuable insights for developing functional foods and nutraceuticals with improved efficacy.