Inorganic mercury in mammary cells: viability, metal uptake but efflux?

Surface-Enhanced Raman Scattering Optophysiology Nanofibers for the Detection of Heavy Metals in Single Breast Cancer Cells

Mercury(II) ions (Hg²⁺) and silver ions (Ag⁺) are two of the most hazardous pollutants causing serious damage to human health. Here, we constructed surface-enhanced Raman scattering (SERS)-active nanofibers covered with 4-mercaptopyridine (4-Mpy)-modified gold nanoparticles to detect Hg²⁺ and Ag⁺. Experimental evidence suggests that the observed spectral changes originate from the combined effect of (i) the coordination between the nitrogen on 4-Mpy and the metal ions and (ii) the 4-Mpy molecular orientation (from flatter to more perpendicular with respect to the metal surface). The relative intensity of a pair of characteristic Raman peaks (at ∼428 and ∼708 cm^-1) was used to quantify the metal ion concentration, greatly increasing the reproducibility of the measurement compared to signal-on or signal-off detection based on a single SERS peak. The detection limit of this method for Hg²⁺ is lower than that for the Ag⁺ (5 vs 100 nM), which can be explained by the stronger interaction energy between Hg²⁺ and N compared to Ag⁺ and N, as demonstrated by density functional theory calculations. The Hg²⁺ and Ag⁺ ions can be masked by adding ethylenediaminetetraacetate and Cl^-, respectively, to the Hg²⁺ and Ag⁺ samples. The good sensitivity, high reproducibility, and excellent selectivity of these nanosensors were also demonstrated. Furthermore, detection of Hg²⁺ in living breast cancer cells at the subcellular level is possible, thanks to the nanometric size of the herein described SERS nanosensors, allowing high spatial resolution and minimal cell damage.

Metalloproteomics analysis in human mammary cell lines treated with inorganic mercury

The interest in inorganic Hg toxicity and carcinogenicity has been pointed to target organs such as kidney, brain or placenta, but only a few studies have focused on the mammary gland. In this work, analytical combination techniques (SDS-PAGE followed by CV-AFS, and nanoUPLC-ESI-MS/MS) were used to determine proteins that could bind Hg in three human mammary cell lines. Two of them were tumorigenic (MCF-7 and MDA-MB-231) and the other one was the non-tumorigenic cell line (MCF-10A). There are no studies that provide this kind of information in breast cell lines with IHg treatment. Previously, we described the viability, uptake and the subcellular distribution of Hg in human breast cells and analysis of RNA-seq about the genes that encode proteins which are related to cytotoxicity of Hg. This work provides important protein candidates for further studies of Hg toxicity in the mammary gland, thus expanding our understanding of how environmental contaminants might affect tumor progression and contribute with future therapeutic methods.