In the current scenario, a reliable liquid biopsy method for predicting outcomes in solid tumors, especially among breast cancer patients, is lacking. Circulating Tumor Cells (CTCs) serve as crucial indicators of metastasis, and their early detection could significantly enhance patient stratification and facilitate the customization of personalized treatments. However, detecting CTCs in breast cancer patients presents complexities due to their substantial phenotypic heterogeneity and typically low concentration. Numerous approaches have been developed for CTC detection. Nonetheless, the currently available technologies remain intricate, time-consuming, and costly. The BioCellPhe Project is dedicated to the development of a novel device capable of isolating and characterizing individual CTCs. This innovative device relies on the identification of specific cell membrane proteins with remarkable precision, achieved through the application of novel orthogonal techniques. On one hand, engineered bacteria are utilized to precisely bind to membrane proteins of interest on CTCs. On the other hand, Surface Enhanced Raman Spectroscopy (SERS) is employed for the detection of individual molecules. Specifically, the BioCellPhe Project focuses on comprehensively studying CTCs in breast cancer patients, encompassing both metastatic and non-metastatic cases.