Biodegradable Aurum: Gold Nanosheets Undergo Biodegradation by Neutrophil Myeloperoxidase

Though gold nanomaterials (NMs) have been largely used in biomedical applications for decades, none have been approved for clinical usage, mostly due to a lack of understanding about their long-term fate and non-biodegradability. Here, the biodegradability of 2D Au nanosheets (AuNS) by enzymatic catalysis of human myeloperoxidase (hMPO) using a test-tube model and an in vitro model with MPO-secreting neutrophil-like cells (present in the blood) differentiated from human leukemia (HL-60) cells has been reported. The results obtained from the high-resolution transmission electron microscopy (HR-TEM), selected area diffraction (SAED), X-ray photoelectron spectroscopy (XPS), and electrical impedance spectroscopy (EIS) confirm that the AuNS undergoes partial biodegradation to Au^I ions by reactive radical intermediates generated by hMPO, hypochlorous acid, including hydroxy radicals generated by AuNS. The results demonstrate the potential for AuNS biodegradation by neutrophils, which are primarily present in the blood. Therefore, these results can be crucial for understanding the long-term fate of AuNMs in humans. Further, near-infrared (NIR) photothermal therapy is successfully demonstrated using AuNS against triple-negative breast cancer cells.