CD44 and cancer: One of the earliest studies that reported the utilization of SERS for in vivo multiplexed cancer detection with bioconjugated SERS nanoparticles was able to detect three intrinsic cancer biomarkers, i.e., EGFR, CD44, and TGFβ receptor II, in a breast cancer-bearing murine model, after intratumoral injection.151 The SERS contrast agents were constructed from different reporter molecules, namely Cy5, malachite green isothiocyanate, and rhodamine 6G, and conjugated with antibodies to enable targeting of the specific cell surface receptors.