ε-Polylysine and β-Cyclodextrin assembling as delivery systems for gastric protection of proteins and possibility to enhance intestinal permeation

An electrostatic nanocomplex between naturally occurring ε-poly-L-lysine (εPL) and β-cyclodextrin sulfate (sCD) was designed, and its capacity to entrap four model proteins with high or low molecular weight and isoelectric point, i.e., lactoferrin, albumin, actinidin, and lysozyme, was investigated. The optimal formulations gave nanocomplexes with an average diameter around 276 ± 16 nm, a ζ-potential of ‒39 ± 1.5 mV, and a spherical shape with a core-shell structure. Different strategies were pursued to increase the entrapment efficiency for selected proteins, which led to 40‒100% entrapment depending on the protein type. Under simulated gastric conditions with pepsin, the complexes protected lactoferrin and albumin against proteolysis, whereas actinidin and lysozyme were intrinsically stable. In Caco-2 cells, these complexes transiently decreased the trans-epithelial electrical resistance, indicating the potential to enhance the paracellular permeability of bioactive macromolecules. Thus, these εPL‒sCD complexes would be a promising system for loading diverse proteins for gastric protection and enhancing intestinal absorption.