In vitro effect of CTAB- and PEG-coated gold nanorods on the induction of eryptosis/erythroptosis in human erythrocytes

Gold nanorods (Au-NRs) have attracted enormous interest due to their size and unique optical properties. Many studies have demonstrated their use in biomedical systems. However, their potential toxicity is not fully understood. This study evaluated the effects of the Au-NRs (15 nM x 64 nM) coated with CTAB (cetyltrimethylammonium bromide) or PEG (polyethylene glycol) in human erythrocytes on the induction of haemolysis and erythroptosis. In our study, erythroptosis (also known as eryptosis) was determined systematically through the measurement of feature events of apoptosis by flow cytometry. We found that the CTAB-and PEG-coated Au-NRs up to 0.5 nM did not cause severe haemolysis. However, the CTAB-Au-NRs were more toxic than the PEG-Au-NRs. The toxicity of the CTAB-Au-NRs was largely due to the CTAB residues from desorption or incomplete purification. Mechanistically, cytosolic Ca2+ ions seem to be the key mediator in the eryptosis/erythroptosis mediated by the CTAB or CTAB-Au-NRs while caspase-3 and reactive oxygen species did not contribute much to the process.