Versatile Metasurfaces for Liquid Biopsy Applications

Liquid biopsy (LB), owing to its minimally invasive nature and ability to detect circulating tumour cells, cell-free DNA, and exosomes released by tumours into body fluids, offers unique advantages in the diagnosis, prognosis, and monitoring of cancer treatment. The quantification and analysis of cancer-related biomarkers in clinical samples, using highly sensitive sensors and trapping techniques, are essential pillars for the future progress of non-invasive liquid biopsy methods. In the framework of sensing and trapping techniques, countless electromagnetic sensors have been proposed in the literature, including interferometers, waveguides, surface plasmon resonance-based structures, cavities/resonators, and the latest all-dielectric metasurfaces. These latter offer numerous advantages for overcoming the limitations of competing technologies, although necessitating dedicated engineering for a target application. Here, after an overview of the most promising technologies in the LB framework, a versatile silicon-based metasurface is proposed. The exploitment of an anapole state leads to excellent performance of the metasurface, as an integrated multiplexed trap of vesicles (tens for several seconds) and a protein biosensor (surface sensitivity > 35 nm/RIU).