Preparation and property of a biantenna macromolecule based on polysialic acid

Polysialic acid (PSA), an acidic polysaccharide usually exists as a double-chain structure on cell adhesion molecules in vertebrates. The available PSA produced from Escherichia coli fermentation, however, is monochain PSA. In this work, a biomimetic biantenna type PSA (biPSA) was synthesized in vitro under mild conditions, and the terminal nonreducing ends of sialic acid residue were retained. The structure of biPSA was characterized through infrared spectroscopy, and NMR, and the double-chain structure of biPSA was confirmed by the doubled molecular weight and particle size of biPSA. Analysis through circular dichroism, isothermal titration calorimetry, and thermostability experiments revealed that the obtained biPSA was more stable in aqueous solution than PSA, especially after complexation with Ca²⁺, which increased the variation in enthalpy and entropy. However, the addition of Cu²⁺ had a negligible effect on configuration of PSA and biPSA. The addition of Ca²⁺ promoted cell proliferation in a culture of microglia BV-2 cells with biPSA in medium. By contrast, the addition of Cu²⁺ had toxic effects. Supplementation with biPSA can maintain cell viability for a longer period than supplementation with monochain PSA. This work indicates that biPSA is a potential substitute for monochain PSA in practical applications.