Cellular Uptake and Cytotoxicity of Gold Nanorods: Molecular Origin of Cytotoxicity and Surface Effects

TLDR

Gold nanorods of varying aspect ratios are synthesized with the surfactant CTAB, which forms a bilayer coating on their surfaces. Cellular uptake of nanorods was quantified by ICP‑MS, revealing 50–2300 rods per cell depending on surface coating. Free CTAB drives cytotoxicity of nanorods, but polymer overcoating markedly reduces it; serum protein adsorption neutralizes surface charge and alters physicochemical properties, underscoring the need to account for such changes in biological and environmental assessments.

Abstract

Gold nanorods of different aspect ratios are prepared using the growth-directing surfactant, cetyltrimethylammonium bromide (CTAB), which forms a bilayer on the gold nanorod surface. Toxicological assays of CTAB-capped nanorod solutions with human colon carcinoma cells (HT-29) reveal that the apparent cytotoxicity is caused by free CTAB in solution. Overcoating the nanorods with polymers substantially reduces cytotoxicity. The number of nanorods taken up per cell, for the different surface coatings, is quantitated by inductively coupled plasma mass spectrometry on washed cells; the number of nanorods per cell varies from 50 to 2300, depending on the surface chemistry. Serum proteins from the biological media, most likely bovine serum albumin, adsorb to gold nanorods, leading to all nanorod samples bearing the same effective charge, regardless of the initial nanorod surface charge. The results suggest that physiochemical surface properties of nanomaterials change substantially after coming into contact with biological media. Such changes should be taken into consideration when examining the biological properties or environmental impact of nanoparticles.