Compacting hyaluronan into nanogels induces an enhanced macropinocytosis in MC38 cells

Hyaluronan (HA)-based drug delivery system including HA conjugates and nano-formulations have been intensively researched in various biomedical applications due to its excellent biocompatibility and unique biological characteristics. Currently most researches are exploring the targeted drug delivery enabled by HA receptors e.g. CD44-based cancer targeting, while the contribution of other cellular uptake pathways in HA-based delivery remains elusive especially for different HA carriers. Here, the cellular uptake of HA in linear form (HA conjugate) and nano-formulation (HA nanogels (NG)) were compared with a focus on macropinocytosis that is actively involved in nutrient scavenging for cancer cells. Considering the ease of fluorescence in evaluating cellular uptake, Rhodamine b (Rb) dye was employed as a model drug to prepare HA-Rb conjugate and HA/Rb NG. After a comprehensive physiochemical characterization, the cellular uptake of these two HA carriers were compared in MC38 cells with different transport inhibitors, HA synthesis inhibition and nutrient depletion. While macropinocytosis blockage inhibited HA/Rb NG uptake more than HA-Rb, enhancing macropinocytosis either by HA inhibition or serum starvation significantly increased HA/Rb NG uptake. These evidences clearly suggest macropinocytosis contributes differently to the cellular uptake of varied HA carriers, which provides new insights to engineer HA for different drug delivery purposes.