Label-Free Measurement of CD63 Positive Extracellular Vesicles Using Terahertz Chemical Microscopy

Extracellular vesicles (EVs) are small cellular organelles involved in intracellular signaling and cell-to-cell interactions. Recent studies suggested that exosomes may have potential applications in the diagnosis and treatment of cancer and neurodegenerative diseases. In this study, extracellular vesicles of the human nonsmall cell lung cancer cell line H1299 and the unlabeled antiCD63 antibody were imaged using a new label-free terahertz chemical microscopy (TCM) technique to detect changes in the terahertz wave amplitude. To verify the high specificity of the protein biomarkers and the sensitivity of the biosensor surface, we also confirmed the selective binding of the antibody to the antigen, bovine serum albumin, and cancer cells. We also performed real-time measurements of the interaction between EVs from the H1299 cell and the antiCD63 antibody, which showed that the amount of change in the terahertz intensity increased with increasing concentration and the time to saturation decreased. Finally, to reuse the used biosensors (sensing plates), plasma-oxygen cleaning was used, and the activity of the biosensor surface was confirmed by terahertz microscopy and atomic force microscopy and was found to be reusable after less than 3 min of cleaning. Consequently, terahertz chemical microscopy was able to detect the presence or absence of antigen-antibody binding and its reaction rate and binding strength.