Coating of liposomes with β-glucans from the king oyster mushroom ( Pleurotus eryngii)

The aim of this study was to investigate the ability to coat liposomes with 13-glucans from Pleurotus eryngii, in order to obtain a suitable formulation for pharmaceutical purposes. After alkali extraction of the fruiting bodies of P. eryngii and solvent fractionation of the raw polysaccharide material, four polysaccharide fractions named PEA2-SS, PEA2-SP, PEA3-SS and PEA3-SP were obtained. Chemical structure analyses by methanolysis, methylation and NMR indicated that all fractions contained two types of 13-glucans: one 3-linked with some branching at O-6 and one 6-linked with branches occurring at O-3. The molar mass ranged from 7 - 36 kDa. Fraction PEA2-SP was most suitable for the coating process according to the resulting charge, hydrodynamic diameter (size) and the PDI of this formulation. This was attributed to the higher Mw displayed by this fraction. After enzymatic degradation, the ability of PEA2-SP to coat the liposomes was lost, indicating the requirement of a minimum polymer molar mass, which is suggested to be around 30 kDa. Furthermore, the presence of a positive charge on the liposome surface seemed to be essential. The novel 13-glucans coated liposomes were able to activate dectin-1b, a receptor on macrophages, and may have potential as a drug delivery platform.