Development of a biosensor based on a new marine luciferase fused to an affibody to assess Her2 expression in living cells.

The development of new diagnostic tools in tumor pathology allows the optimization of individualized therapies in cancer patients. The functional optical image provides a unique opportunity to identify the pathophysiological characteristics of each tumor in a non-invasive way. Although fluorescent recombinant affibodies and nanobodies, capable of detecting certain membrane proteins present in tumor cells, has been described, the use of bioluminescent molecules is gaining a great impact in this field due to its high sensitivity. In this work, we characterize a new luciferase from the Metridia lucens copepod (MlLuc) and develop a novel bioluminescent recombinant affibody (MlLuc-aff) capable of recognizing the HER2 receptors that are overexpressed in breast cancer tumors. For this purpose, the thermostability and pH sensitivity of MlLuc1.1 were determined, showing no significant changes in the activity among temperatures between 4 and 70 °C, and with a maximum of brightness at pH 8.0. Furthermore, MlLuc-aff was able to accurately detect HER2 receptors expressed in the SK-BR-3 cells. Future applications of this new tracer can contribute to the early diagnosis of breast cancer patients and the assessment of the efficacy of the treatment.