THz technologies are a powerful tool for label-free detection of biomolecules. However, significant reduction of the lower detection limit is required to apply THz-sensors in biomedical diagnosis. This paper reports an ultrasensitive THz-biosensor based on asymmetric double split ring resonators (aDSRR) for the direct label-and PCR-free detection of DNA at physiologically relevant concentrations. We introduce selective functionalization and localized electric field concentration to enhance aDSRR sensitivity and specificity. The sensor characteristics are demonstrated using the human tumor marker MIA in cDNA samples produced from total RNA without PCR-amplification. Measurements of DNA samples with concentrations as low as 1.55 × 10 −12 mol/l are presented.
Terahertz (THz) biosensing has emerged as an important research field, mainly driven by the resonant behavior of many biomolecules in this spectral range which holds potential for highly sensitive analyses. In this work, we present a detailed overview of our current research on THz biosensing, focusing on the development and analysis of THz biosensors based on frequency selective surfaces (FSS) for two different measurement scenarios: i) label-free, highly sensitive and selective analysis of dried biomolecules, and ii) sensitive and selective analysis in an aqueous environment. With our carefully designed THz biosensor for measurements in the dry state, we were able to indirectly measure tumor-marker MIA RNA in a concentration as low as 1.55 × 10−12 mol/L, without the need for biochemical amplification. Our biosensor with substrate-integrated microfluidics for terahertz measurements in an aqueous environment is validated by simulations, showing that the resonance feature in the frequency response of our sensor is maintained even for measurements in water.
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