Charge-converting nanocarriers: Phosphorylated polysaccharide coatings for overcoming intestinal barriers

For the design of charge-converting nanocarriers (NCs), cationic lipid-based NCs containing curcumin as model drug were coated with phosphorylated starch (NC-SP) and phosphorylated dextran (NC-DP). NCs showed a drug encapsulation efficiency of 94 % and had a mean size of 175 to 180 nm. The recorded zeta potential of the core NC (cNC) was +8.3 mV, whereas it reversed to -10.6 mV and -7.4 mV after decorating with SP and DP, respectively. Furthermore, a 3-fold higher amount of curcumin having been incorporated in these NCs remained stable within 2 h of UV exposure indicating a photoprotective effect of this delivery system. Charge-converting properties were confirmed by cleavage with intestinal alkaline phosphatase (IAP) and resulted in a zeta potential shift of Δ15.4 mV for NC-SP and Δ11.2 mV for NC-DP. NC-SP and NC-DP showed enhanced mucus permeating properties compared to cNC, that were additionally confirmed by an up to 2.2-fold improved cellular uptake on mucus secreting Caco-2/HT29-MTX cells. According to these results, NC-SP and NC-DP coatings hold promise as a viable and efficient strategy for charge-converting NCs.