In recent years,cell-penetrating peptides (CPPs) have been proven to be a useful tool in improving the membrane translocation capacity of bioactive macromolecules via covalent linkage.The intestinal absorption of macromolecules can also be enhanced by electrostatic interaction with CPPs; however,the application of this strategy is restricted to negatively charged macromolecules.In the present study,we devised an approach utilizing CPP-functionalized poly(lactic-co-glycolic acid) (PLGA) nanoparticles as a carrier for the oral delivery of insulin.The surfaces of pegylated PLGA nanoparticles were functionalized with arginine-rich poly(arginine)8 peptide enantiomers (L-R8 and D-R8) via a maleimide-mediated covalent conjugating procedure.