Chitosan based micelle with zeta potential changing property for effective mucosal drug delivery.

Mucus permeation, mucoadhesion and cell membrane interaction are properties that a drug carrier needs to deliver macromolecule compounds through the mucus barrier and inside epithelial cells effectively. Herein, we prepared micelles from phosphorylated chitosan-stearic acid conjugates (CSSAP) possessing those properties. Their zeta potential can be shifted from negative to neutral once contacting with alkaline phosphatase (ALP). CSSAP micelles showed effective mucus permeation and cell association, thus could be used as a promising platform for mucosal drug delivery. CSSAP was obtained via two modifications: alkylation of CS with stearic acid (termed CSSA) followed by phosphorylation utilizing phosphorus pentoxide. CSSAP had critical micelle concentration value of 76 μg/mL and phosphate content of 1066 μmol/g polymer. Micelle hydrodynamic size was 50-60 nm. Upon contacting with ALP, the polymeric micelles showed a phosphate release of 626 μmol/g polymer (~60%) and a zeta potential shift from -20 to -9 mV within 30 min. They exhibited 6-times higher mucus permeation capacity than positively charged CSSA micelles. CSSAP micelles association to Caco-2 and HEK 293 cells depended on the ALP activity. On Caco-2 cells, cell association rate after 3 h was 2-times higher compared to association rate in the presence of 0.5% phosphatase inhibitors.