Surface-Enhanced Raman Spectroscopy Characterization of Breast Cell Phenotypes: Effect of Nanoparticle Geometry

Abstract

The use of surface-enhanced Raman spectroscopy (SERS) to delineate between the breast epithelial cell lines MCF10A, SK-BR-3, and MDA-MB-231 is explored utilizing varied morphologies of gold nanoparticles. The nanoparticles studied had spherical, star-like, and quasi-fractal (nanocaltrop) morphologies and possessed varying degrees of surface inhomogeneity and complexity. The efficacy of Raman enhancement of these nanoparticles was a function of their size, their surface morphology, and the associated density of "hot spots," as well as their cellular uptake. The spherical and star-like nanoparticles provided strong signal enhancement that allowed for the discernment among the three cell phenotypes based solely on the acquired Raman spectra. The presence of overlapping Raman band spectral regions, as well as unique spectral bands, suggests that the underlying biological differences between these cells can be accessed without the need for tagging the nanoparticles or for specific cell targeting, demonstrating the potential ubiquity of this technique in imaging any cancer. This work provides clear evidence for the potential application of SERS as a tool for mapping cancerous lesions, possibly during surgery and under histopathological analysis.

Evaluation of aromatic amino acids as potential biomarkers in breast cancer by Raman spectroscopy analysis

“…The Raman shift peak frequencies that we followed and analyzed correspond to those characteristic of aromatic amino acids at 657, 816, 837, 845, 965, 1006, 1012 and 1131 cm –1 29 , 54 – 58 , and to S–S bonds at 503 cm −1 29 . The assignment of the vibrational modes of these peaks is shown in Fig.…”

“…For example, a comparison between the non-malignant MCF-10A with malignant SK-BR-3 breast cell lines indicates an increase in the concentration of tyrosine-rich proteins, as evidenced by the high intensity band at 837 cm −1 , in accordance with the structure of the HER-2 receptor 29,[59][60][61][62] . In addition, it has been observed that the Raman spectra corresponding to aromatic amino acids in malignant SK-BR-3 and MDA-MB-231 breast cell lines exhibit intense bands characteristic to tyrosine, phenylalanine, and tryptophan, suggesting the enhancement in the expression of such aromatic amino acid rich proteins in malignant cells 29,[63][64][65][66][67][68] . This phenomenon is not restricted to breast cancer alone, but is prevalent in other malignancies such as pancreatic cancer, colon cancer, gastric cancer, and lung cancer.…”

“…The collection of all the normalized Raman band intensities in the spectral range of 500–1200 cm −1 for all breast tissues examined 29 – 49 are shown in Fig. 4 a.…”

“…All the peaks collected from the pertinent Raman spectra in the literature were grouped into two cell categories, cancerous and healthy, the latter category including also cells that have been deemed benign (i.e. non-cancerous) in their respective publications 29 – 49 . It is evident from this representation of the data, that at higher relative peak intensities, most of the peaks belong to the cancerous cells across all frequencies.…”

“…The enhanced expression of aromatic amino acids in breast cancer became apparent in a multitude of recent studies, in which cancer tissue characteristics was measured by Raman spectroscopy 29 – 49 . The SK-BR-3 cell lines, characterized by the overexpression of HER-2 receptor, and MDA-MB-231 cell lines, characterized by the lack of estrogen, progesterone and HER-2 receptors, exhibited intense Raman bands that correspond to aromatic amino acids such as tyrosine, phenylalanine, and tryptophan 29 , particularly when using the surface enhance Raman spectroscopy technique. Raman spectroscopy has emerged in recent years as a successful tool for the diagnosis of breast cancer tissue samples by detecting lipid and protein identity, structure and concentrations based on known samples or difference spectra.…”