Arginine-tagging of polymeric nanoparticles via histidine to improve cellular uptake

Polyarginine, a cell-penetrating peptide, has been shown to aid cellular penetration of bioactives into cells. We utilized a novel approach of using a histidine linker to produce poly(ethyl-cyanoacrylate) (PECA) nanoparticles tagged with oligoarginine and investigated cellular uptake. MALDI TOF/TOF (tandem) analysis revealed that di-arginine-histidine (RRH) covalently bound to PECA nanoparticles to form cationic particles (+18 mV), while longer oligoarginine peptides did not co-polymerize with PECA nanoparticles. Although RRH-tagged nanoparticles had similar size and FITC-dextran entrapment efficiency compared to unmodified nanoparticles, RRH-tagging of nanoparticles resulted in a greater release of FITC-dextran. As the nanoparticles were found to aggregate in Hanks Balanced Salt Solution (HBSS), the effect of phosphate on the zeta-potential of nanoparticles was studied. Treating the nanoparticles with poloxamer-407 prevented aggregation. RRH-tagged PECA nanoparticles increased cellular uptake by a further 30% compared to unmodified PECA nanoparticles and was concentration dependent. We suggest that enhanced cell uptake can be achieved using a di-arginine-histidine construct as opposed to the previously published findings that a minimum of hexa-arginine is necessary. Further, the cationic zeta-potential of the cell-penetrating peptide may not be needed to enhance uptake.