Development of Tumor-Targeting 5-Fluorouracil-Loaded Hyaluronate Nanoparticles With pH-Responsive Functional Groups on Both Surface and Interior

In this study, we engineered pH-responsive nanoparticles (NPs) capable of undergoing surface charge conversion in the acidic microenvironment of tumors. These NPs were constructed from hyaluronic acid (HA) conjugated with deoxycholic acid (DOCA) and further functionalized with either 2,3-dimethylmaleic anhydride (DMA) or 3-(diethylamino)propylamine (DEAP). Self-assembly of the hydrophilic segments (HA, DMA) and hydrophobic moieties (non-protonated DEAP, DOCA) at physiological pH (7.4) yielded stable NPs encapsulating the chemotherapeutic agent 5-fluorouracil (5-FU). These constructs are herein referred to as HDOC-DMA/HDOC-DEAP NPs. At pH 7.4, the NPs maintained a net negative surface charge. Upon exposure to mildly acidic conditions characteristic of the tumor microenvironment (pH ~7.0), hydrolysis of DMA moieties triggered a surface charge reversal to positive, enhancing electrostatic interactions with negatively charged cellular membranes. Moreover, under endosomal pH conditions, protonation of DEAP induced electrostatic repulsion within the NPs, leading to structural destabilization and accelerated release of 5-FU. In vitro studies demonstrated significantly enhanced cellular uptake of the NPs under acidic conditions, resulting in improved cytotoxic efficacy against tumor cells. These findings suggest that HDOC-DMA/HDOC-DEAP NPs represent a promising platform for tumor-targeted drug delivery via pH-triggered surface charge modulation.