Properties of in situ generated gold nanoparticles in the cellular context

Abstract

Gold nanostructures that serve as probes for nanospectroscopic analysis of eukaryotic cell cultures can be obtained by the in situ reduction of tetrachloroauric acid (HAuCl). To understand the formation process of such intracellularly grown particles depending on the incubation medium, the reaction was carried out with 3T3 fibroblast cells in three different incubation media, phosphate buffer, Dulbecco's Modified Eagle Medium (DMEM), and standard cell culture medium (DMEM with fetal calf serum). The size, the optical properties, the biomolecular corona, and the localization of the gold nanoparticles formed in situ vary for the different conditions. The combination of surface-enhanced Raman scattering (SERS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) microscopic mapping and transmission electron microscopy (TEM) provides complementary perspectives on plasmonic nanoparticles and non-plasmonic gold compounds inside the cells. While for the incubation with HAuCl in PBS, gold particles provide optical signals from the nucleus, the incubation in standard cell culture medium leads to scavenging of the toxic molecules and the formation of spots of high gold concentration in the cytoplasm without formation of SERS-active particles inside the cells. The biomolecular corona of nanoparticles formed in situ after incubation in buffer and DMEM differs, suggesting that different intracellular molecular species serve for reduction and stabilization. Comparison with data obtained from ready-made gold nanoparticles suggests complementary application of in situ and ex situ generated nanostructures for optical probing.

Intratumoral generation of photothermal gold nanoparticles through a vectorized biomineralization of ionic gold

“…For intracellular gold nanoparticle formation, all of the constituents (sans chloroauric acid) are innately present in cellular systems. This intracellular gold nanoparticle formation has been demonstrated previously in mammalian cells, however, only through bulk diffusive treatments, lasting more than 24 h, and typically those are in solutions which contain no cell nutrients (such as DPBS) [35][36][37][38][39][40][41][42][43][44][45][46][47] . These treatment scenarios are non-ideal for minimizing the impact on cellular health.…”

“…Previous applications for generating gold nanoparticles intracellularly, typically apply 1 mM of ionic gold over time periods >24 h [36][37][38][39][40][41][42][43][44][45][46][47] . However, the amount of formed plasmonic gold nanoparticles were negligible or considerably reduced when the ionic gold was applied diffusively in the previous literature reports either at lower concentrations (0.1 mM 43,44 , 0.25 mM 42 ) or for shorter time periods (12 h 42 , 15 h 45 ). From our application, we were able to confirm the transition of ionic to plasmonic gold through the spectral library obtained from the enhanced darkfield hyperspectral imaging of Au-PEG clusters reduced through the interactions with MCF-7 cells ( Fig.…”

Critical evaluation of fast and highly resolved elemental distribution in single cells using LA-ICP-SFMS

“…These results suggest that NPs aggregate in the perinuclear region in the course of endosomal maturation and multivesicular fusion, but not inside the cell nucleus. These findings agree with previous results on the distribution of Au NPs in cells [11,12,14]. It is noteworthy that the low signal intensity that was found in the cell nucleus region might be originated from Au NPs located in the cytosol volume above or below the cell nucleus.…”

“…laser raster mode). Laser spot sizes are usually equal to or bigger than 4 µm (nominal value of the crater spot size) and laser scan speeds equal to or lower than 15 µm/s [11][12][13][14]. The image is then constructed by ablating parallel lines on the sample surface.…”

Effective targeting of breast cancer cells (MCF7) via novel biogenic synthesis of gold nanoparticles using cancer-derived metabolites

“…Control synthesis of biocompatible metal nanoparticles using yeast, fungi, bacteria and plants [4,5], encourage the use of mammalian cells to develop nanoparticles. It has been reported that AuNPs can be generated in situ after incubation of Au 3+ with mammalian cell cultures [6]. Furthermore, it has been observed that nanoparticles can be generated inside the epithelial cells and in intact tumor tissues [6].…”