Abstract
Biosensor technology has great potential for the detection of cancer through tumor-associated molecular biomarkers. In this work, we describe the immobilization of the recombinant humanized anti-HER2 monoclonal antibody (trastuzumab) on a silver nanostructured plate made by pulsed laser deposition (PLD), over a thin film of Au(111). Immobilization was performed via 4-mercapto benzoic acid self-assembled monolayers (4-MBA SAMs) that were activated with coupling reagents. A combination of immunofluorescence images and z-stack analysis by confocal laser scanning microscopy (CLSM) allowed us to detect HER2 presence and distribution in the cell membranes. Four different HER2-expressing breast cancer cell lines (SKBR3 +++, MCF-7 +/−, T47D +/−, MDA-MB-231 −) were incubated during 24 h on functionalized silver nanostructured plates (FSNP) and also on Au(111) thin films. The cells were fixed by means of an ethanol dehydration train, then characterized by atomic force microscopy (AFM) and surface-enhanced Raman scattering (SERS). SERS results showed the same tendency as CLSM findings (SKBR3 > MCF-7 > T47D > MDA-MB-231), especially when the Raman peak associated with phenylalanine amino acid (1002 cm−1) was monitored. Given the high selectivity and high sensitivity of SERS with a functionalized silver nanostructured plate (FSNP), we propose this method for identifying the presence of HER2 and consequently, of breast cancer cells.
Highlights
Breast cancer is the second cancer cause of death in the United States and it is estimated that 1.7 million new cancer cases will be diagnosed and 609,640 Americans will die of cancer in 2018 [1]
Trastuzumab is a recombinant humanized anti-HER2 monoclonal antibody that selectively binds with high affinity to HER2 extracellular domain, inhibits cell proliferation, attacks HER2-dependent tumors and blocks shedding of HER2 extracellular domain [9,10]
We are not the first to point out an increase in Raman intensity of the vibrational modes associated with phenylalanine, to the best of our knowledge, we are the first to point out that phenylalanine Raman peak could be used as a label associated with cancer cells and monitored by surface-enhanced Raman scattering (SERS) through a functionalized silver nanostructured plate (FSNP), for their identification
Summary
Breast cancer is the second cancer cause of death in the United States and it is estimated that 1.7 million new cancer cases will be diagnosed and 609,640 Americans will die of cancer in 2018 [1]. Increased Raman peaks that correspond to phenylalanine (Phe) vibrational modes have been found in various cancer types, such as prostate, lung, breast, oral and esophageal tissue samples. In this regard, different researches were reported in the scientific literature. In addition to the aforementioned examples, Chaturvedi et al [27] monitored the biomolecular changes associated with the transformation of a normal cell into an invasive breast cancer cell using Raman microspectroscopy and showed the suitability of this technique as non-invasive and label-free, having the potential to probe changes in the biomolecular composition of living cells as well as fixed cells All these data demonstrate that Raman spectroscopy has potential for cancer sample diagnostics and reduces times, cost and traumas of surgical operations. We are not the first to point out an increase in Raman intensity of the vibrational modes associated with phenylalanine, to the best of our knowledge, we are the first to point out that phenylalanine Raman peak could be used as a label associated with cancer cells and monitored by SERS through a FSNP, for their identification
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