Surface phosphorylation of nanoparticles by hexokinase: A powerful tool for cellular uptake improvement.

The aim of the study was to develop zeta potential changing nanoparticles (NPs) via surface phosphorylation in order to improve their uptake by epithelial cells. Polymeric NPs were formed via in situ gelation between chitosan (CS) and chondroitin sulphate (ChS). Phosphorylation of these NPs was carried out by using hexokinase. The resulting phosphorylated NPs (p-NPs) were characterized in respect of their size and zeta potential. Phosphate release was quantified by incubating the particles with isolated as well as cell-associated intestinal alkaline phosphatase (AP). In parallel, resulting change in zeta potential was monitored. In-vitro mucus permeation of these particles was evaluated on porcine intestinal mucus. Furthermore, toxicity and cellular uptake studies were performed on Caco-2 cells. p-NPs exhibited a mean size of 412 ± 3.24 nm and a zeta potential of -12.4 mV. When these p-NPs were incubated with isolated as well as cell-associated AP, a significant amount of phosphate was released within 4 h and zeta potential raised up to -1.2 mV. p-NPs showed improved mucus permeation in comparison to unmodified NPs. Due to de-phosphorylation by AP, cellular uptake of p-NPs increased almost 2-fold. Moreover, particles displayed no toxicity. Findings of this study show that zeta potential changing p-NPs provide effective mucus permeation and enhanced cellular uptake.