SERS optrode for human thyroglobulin detection in liquid biopsy

In this work, we propose a novel immunoassay platform for the detection of human Thyroglobulin (Tg) to be integrated with fine-needle aspiration biopsy for early identification of lymph node metastases in thyroid cancer patients. The sensing platform detects Tg (a well-known biomarker for the classification of metastatic lymph nodes related to thyroid cancer) by a sandwich immunoassay involving a self-assembled surface-enhanced Raman scattering (SERS) substrate assisted and empowered by functionalized gold nanoparticles enabling additional Raman signal amplification and improved molecular specificity. The sandwich assay platform was preliminary validated in a planar configuration and a detection limit as low as 7 pg/mL was successfully achieved. The sandwich assay was successfully demonstrated on washout fluids of fine needle aspiration biopsies from cancer patients and confirmed the high specificity of the proposed methodology when complex biological matrices are considered. Finally, optical fiber SERS optrodes were fabricated and successfully used to detect Tg concentration by applying the same bio-recognition strategy. This opens the possibility of transferring the Tg detection approach to the optical fiber tip to develop point-of-care platforms that can be directly integrated into fine needle aspiration biopsies.