Biocompatibility of Gold Nanoparticles and Their Endocytotic Fate Inside the Cellular Compartment: A Microscopic Overview

TLDR

Macrophages are key immune cells, and studies have linked gold nanoparticle cytotoxicity to their endocytic uptake observed with AFM, CFLSM, and TEM. This study investigates the cytotoxicity and immunogenic effects of gold nanoparticles on RAW264.7 macrophage cells. Gold nanoparticles are internalized by pinocytosis and accumulate in perinuclear lysosomal bodies, as shown by AFM, CFLSM, and TEM. Au(0) nanoparticles are noncytotoxic, reduce reactive oxygen and nitrite species, do not trigger TNF‑α or IL‑1β secretion, and are thus biocompatible for nanomedicine applications.

Abstract

Macrophages are one of the principal immune effector cells that play essential roles as secretory, phagocytic, and antigen-presenting cells in the immune system. In this study, we address the issue of cytotoxicity and immunogenic effects of gold nanoparticles on RAW264.7 macrophage cells. The cytotoxicity of gold nanoparticles has been correlated with a detailed study of their endocytotic uptake using various microscopy tools such as atomic force microscopy (AFM), confocal-laser-scanning microscopy (CFLSM), and transmission electron microscopy (TEM). Our findings suggest that Au(0) nanoparticles are not cytotoxic, reduce the production of reactive oxygen and nitrite species, and do not elicit secretion of proinflammatory cytokines TNF-α and IL1-β, making them suitable candidates for nanomedicine. AFM measurements suggest that gold nanoparticles are internalized inside the cell via a mechanism involving pinocytosis, while CFLSM and TEM studies indicate their internalization in lysosomal bodies arranged in perinuclear fashion. Our studies thus underline the noncytotoxic, nonimmunogenic, and biocompatible properties of gold nanoparticles with the potential for application in nanoimmunology, nanomedicine, and nanobiotechnology.