Effect of surface-engineered AuNPs on gene expression, bacterial interaction, protein denaturation, and toxicology assay: an <i>in vitro</i> and <i>in vivo</i> model

We investigated the <i>in vitro</i> and <i>in vivo</i> uses of pamoic acid functionalized gold nanoparticles (PA@AuNPs), with a focus on determining their safety and potential toxicity in living beings. To test this theory, the bacterial interaction of PA@AuNPs was studied using <i>Escherichia coli</i>, <i>Staphylococcus aureus</i>, and <i>Pseudomonas aeruginosa</i> cultures, as well as the inhibition of the bovine serum albumin (BSA) protein. The real-time polymerase chain reaction (RT-PCR) is used to measure the expression of target genes. PA@AuNPs caused dose-dependent cell death in MDA-MB-231, a triple-negative breast cancer (BC) cell line, with an LC₅₀ of -42.23 μL mL^-1. It also caused apoptosis in BC cells. The results indicated that in the early weeks, inflammatory cells (mostly neutrophils and macrophages) penetrated the connective tissue, but in the latter weeks, a substantial number of fibroblasts and fibrocytes were identified. Changes in vascular channels, extravasated red blood cells (RBCs), and necrosis are all indicators of growing tissue pathology. These data could point to a dynamic process including an anti-inflammatory response followed by tissue remodeling or repair. These findings show that PA@AuNPs were not hazardous to the tested Sprague Dawley rats, are highly biocompatible, and can be used in a variety of biological applications.