Evaluation of Breast Cancer Gene Type 1 (BRCA1) Protein Levels in Cancer Tissue Using Surface-Enhanced Raman Spectroscopy.

Raman spectroscopy is a chemical process that utilizes the interaction between light and matter to get significant insights into the structure or characteristics of matter. Raman spectroscopy techniques, such as quantitative evaluation, early diagnostic capabilities, and elucidation of the spectral properties of tissues, are excellent candidates for use in research. In cancer, changes in genes and proteins expressed by related genes are associated with a poor prognosis and aggressive tumor characteristics. Due to modifications and regulatory steps in protein translation, the results of the messenger RNA (mRNA) expression of genes may not correctly reflect the results of protein expression. For this reason, the mRNA and protein expressions of genes are studied in parallel in molecular studies on cancer. In our study, the breast cancer gene type 1 (BRCA1) gene, which is frequently studied in breast cancer and is relatively more difficult to measure by traditional methods due to its high molecular weight, was selected, and protein quantification was performed in tissue samples by Raman spectroscopy. With Raman spectroscopy, it is possible to obtain rapid and precise quantitative results even with a small amount of sample, so it is quite advantageous compared to traditional methods. In our study, we performed surface-enhanced Raman spectroscopy (SERS) to analyze the quantitative protein amount. SERS is a highly sensitive method for detecting compounds at low concentrations. For this purpose, magnetic nanoparticles modified with protein antibodies were used, and the target protein was withdrawn from the complex environment and transferred to an appropriate buffer environment. The calibration curve for BRCA1, which plots Raman intensity against concentration, was derived by calculating the average response reading from duplicate assays conducted under identical conditions. The BRCA1 protein levels of cells were determined from the regression curve of the BRCA1 protein. The relation between the concentration of BRCA1 protein and SERS spectrum intensity was determined to be logarithmic in the range of 300 µg·mL^-1 to 292 ng·mL^-1 (R² = 0.9928, limit of detection = 10.41 µg·mL^-1, and limit of quantitation = 31.24 µg·mL^-1).