Surface Charge-Dependent Electrostatic Interactions in Cellular Uptake of Nanoparticles

SATSUKI TAKAI, Taiki Nagaya, Emi Fukuda, Yasuto Matsui, Kyoto University

     Abstract Number: 593
     Working Group: Aerosol Exposure

Abstract
Nanomaterials have significant utility in both industry and biomedical applications. However, their cellular uptake mechanisms and safety profiles remain insufficiently understood. Several studies have indicated that receptor-mediated endocytosis contributes to the cellular uptake of nanoparticles, and that surface potential may influence the extent of uptake. Nevertheless, few studies have quantitatively evaluated the uptake of nanoparticles with identical surface modification but differing surface potentials.

This study aimed to quantitatively clarify the dependence of nanoparticle uptake and kinetics on surface potential, using particles differing only in surface potential within receptor-mediated endocytic pathways. Receptor-dependent uptake of carboxyl-modified nanoparticles was assessed by flow cytometry using endocytosis inhibitors and natural ligands for low-density lipoprotein receptors (LDLR) and scavenger receptors (SR). Additionally, three types of carboxyl-modified nanoparticles with distinct surface potentials (−30.30 ± 0.88 mV, −45.13 ± 1.20 mV, −57.36 ± 1.68 mV) were exposed to A549 cells, and differences in uptake behavior were analyzed by fluorescence microscopy. Co-localization analysis with endocytic markers was performed to quantify uptake dynamics.

Inhibition of clathrin- and caveolae-mediated endocytosis significantly reduced the number of nanoparticle-positive cells. The addition of ligands also suppressed uptake, confirming the involvement of LDLR and SR. Particles with more negative surface potential exhibited faster uptake, especially within the range of −30 to −40 mV. In contrast, the maximum uptake amount was not dependent on surface potential.

These findings suggest that nanoparticle uptake occurs via receptor-mediated endocytosis and may be facilitated by electrostatic interactions between nanoparticles and cellular receptors. Notably, more negatively charged particles appear to bind more rapidly to receptors, resulting in accelerated internalization. Future studies will include aerosol-phase exposure to evaluate how airborne particle charge influences cellular uptake efficiency. Exploring how physicochemical properties of particles affect their interactions with cells will establish in vitro alveolar exposure models that can simulate realistic deposition and uptake dynamics.