Ultrastructural Features of Gold Nanoparticle Interactions with T47D Spheroids

In this study, we examined the effects of gold nanoparticles (AuNPs) and ultrastructural alterations on breast cancer cell line (T47D) spheroid. Tissue morphological changes, AuNP interactions, delivery, diffusion, uptake and accumulation were investigated in this tumor cell model. Transmission electron microscopy (TEM) was utilized to characterize spheroids at various culture ages prior to the introduction of AuNPs. Imaging analysis was used to observe structural changes in response to treating spheroids with 45 nm AuNPs. Considerable diversity was observed in the size of the outermost of the spheroid. The nuclei of these cells were large, irregular nuclei with distributed heterochromatin and expanded nucleoli. The innermost cells had evidence of degeneration and necrosis, including organelle enlargement, cytoplasmic vacuolation, and large, digested debris vacuoles. Signs of necrosis were observed on Day 10 and became more evident on Day 20, especially in spheroids produced from 1000 cancer cells during culture. The cells had dispersed chromatin, large irregular nucleoli and nuclei, autophagic vacuoles, lysosomes close to the nucleus, and karyolysis of the nucleus and degeneration of the cytoplasmic organelles. AuNP-treated spheroids cells demonstrated greater uptake in the outermost, peripheral cells. Spheroids exposed to AuNPs exhibited cell shrinkage, cell membrane disruption, widened intercellular spaces, and nuclear fragmentation with nuclear membrane alterations.