Lactoferrin-directed self-assembly of a casein phosphopeptide–calcium delivery system: Structural, stability, and in vitro absorption studies

s: Calcium is essential for bone health, but its bioavailability is limited by its poor solubility in the intestinal environment. To overcome these challenges, this study developed a novel calcium delivery system through the self-assembly of lactoferrin and casein phosphopeptides, followed by chelation with calcium to form an LF-CPP-Ca ternary complex. The product was characterized using intrinsic fluorescence spectroscopy, Fourier transform infrared spectroscopy, and Zeta potential techniques. Results demonstrated that LF and CPP form complexes through hydrogen bonding and electrostatic interactions, inducing conformational changes in LF. The incorporation of calcium ions further drove the formation of the ternary chelate, resulting in reduced particle size, homogeneous distribution, and enhanced structural stability. In vitro simulated digestion experiments demonstrated that LF-CPP-Ca showed significantly lower calcium release rate (89.43%) during the intestinal phase compared to CPP-Ca (97.91%), demonstrating its superior capability to deliver calcium to absorption sites. In the Caco-2 cell model, LF-CPP-Ca demonstrated exceptional calcium transport efficiency. Particularly in the presence of oxalic acid and phytic acid, the reduction in calcium absorption rate of LF-CPP-Ca (PA: 32.99%; OA: 38.36%) was much lower than that of CaCl 2 (PA: 45.71%; OA: 57.33%) and CPP-Ca (PA: 41.65%; OA: 45.43%), demonstrating excellent anti-interference capacity. This work establishes a new paradigm for designing mineral delivery systems based on protein-peptide co-assembly and multi-ligand chelation.