  Bioanalytical THz sensing techniques have proven to be an interesting and
viable tool for the label-free detection and analysis of biomolecules. However,
a major challenge for THz bioanalytics is to perform investigations in the
native aqueous environments of the analytes. This review recapitulates the
status and future requirements for establishing THz biosensing as a
complementary toolbox in the repertoire of standard bioanalytic methods. The
potential use in medical research and clinical diagnosis is discussed. Under
these considerations, this article presents a comprehensive categorization of
biochemically relevant analytes that have been investigated by THz sensing
techniques in aqueous media. The detectable concentration levels of ions,
carbohydrates, (poly-)nucleotides, active agents, proteins and different
biomacromolecules from THz experiments are compared to characteristic
physiological concentrations and lower detection limits of state-of-the-art
bioanalytical methods. Finally, recent experimental developments and
achievements are discussed, which potentially pave the way for THz analysis of
biomolecules under clinically relevant conditions.
