We are aware that the number of CTCs obtained from cancer patient samples will be much lower than the number of cells used in these experiments; nevertheless, we have proven the specificity of our Pept-NEs for two well-studied CTC biomarkers: EpCAM, the cell adhesion molecule used by CellSearch platform, and EGFR, which may be used as an alternative to EpCAM, as its expression has been confirmed in CTCs [48]. This evidence concerns the gene EGFR and cancer.