Preparation and characterization of Sipunculus nudus peptide-calcium chelate: Structural insights and osteogenic bioactivity assessment

• Calcium chelate of Squarrosus nudus peptide (SNP-Ca) was successfully prepared. • The chelating conditions was optimized by single factor test. • SNP-Ca could significantly improve calcium uptake in Caco-2 cells. • SNP-Ca could significantly increase the osteogenic capacity of MC3T3-E1 cells. • SNP-Ca could significantly enhance the bone formation of zebrafish larvae. In order to prepare calcium supplements for efficient absorption and utilization in the human body, this study focused on synthesizing SNP-Ca by chelating Squarrosus nudus peptide (SNP) with calcium. We characterized its structure, stability, and calcium uptake properties in Caco-2 cells and its impact on osteogenic activity in vitro. Optimal preparation conditions were determined: a peptide-calcium mass ratio of 5:1, a 30-min reaction time, a temperature of 60 °C, and a pH of 7.0. Under these conditions, a calcium chelating rate of 68.32 % was achieved. Calcium binds to the peptide primarily via carboxyl oxygen and amino nitrogen atoms, and the morphology of SNP-Ca was similar to porous nanoflowers. Our cellular experiments revealed that SNP-Ca significantly increases calcium uptake in Caco-2 cells, stimulating proliferation, differentiation, and mineralization in MC3T3-E1 cells. Additionally, zebrafish larvae models showed enhanced bone formation following SNP-Ca administration. SNP-Ca has the potential of a novel calcium supplement.