Sensing living cells using a terahertz split-ring resonator with reflection spectroscopy

Studies with THz split ring resonators (THz-SRRs) have revealed the possibility of using them as sensors to monitor changes in the complex dielectric constant of samples. In this regard, THz reflection spectroscopy in combination with a SRR could be used to measure even target samples in aqueous solution since the interference of water´s excessive absorption is minimized with this technique. In this letter, we demonstrate that reflectance intensity at the resonant frequency is more sensitive than frequency shift to changes in the imaginary part of the dielectric constant associated with the absorbance of the sample. Moreover, we distinguished significant changes in reflectance between a cell monolayer in a medium cultured directly onto the SRR and the SRR with medium alone. We confirmed that THz-SRR can be a highly sensitive biosensor to monitor changes in the complex dielectric constant of dielectric samples, such as living cells where abundant extracellular water is present.