Terahertz-Biosensorik : dielektrische long-range Moden für die THz-Analyse von Biomolekülen in stark absorbierenden Flüssigkeiten

In certain parts of the world medical care has probably never been better than it is now. Yet, in highly industrialized countries a growing number of people suffer from serious lifestyle diseases like diabetes, cardiovascular disease, various forms of cancer, dementia and Parkinson’s or Alzheimer’s disease. A great variety of bioanalytical tools is available for detecting such diseases at the molecular level. These diagnostic methods are essential for deciding on effective treatment at the earliest stage possible. Nevertheless, the overall intricacy of biochemical processes is rarely understood at a comprehensive level due to the vast physiological complexity of the human organism. One of the greatest challenges of our times is discovering disease-related disorders within the biomolecular context. As a result of recent advances in THz technologies and deeper insights into molecular resonances at THz frequencies, the THz community has begun to investigate (patho-)physiological significant analytes in the THz frequency range. In order to take the full complexity and functionality into account, analytes need to be studied in native, aqueous environments. Since THz radiation is strongly absorbed by water, traditional THz setups usually only allow for biomolecular characterization in aqueous environments under non-physiological conditions. Possible solutions to overcoming these experimental limitations will be neither simple nor quick, and none are widely available at the moment. Therefore, the THz community presently needs to develop novel strategies and schemes to make substantial progress in THz analysis of biomolecules under physiological conditions.
This thesis presents the systematic development of an alternative technological platform suitable for the THz-based recognition of biomolecules in aqueous solutions. Within the scope of this sensoric approach THz waves are coupled as long-range guided modes into µm-thin liquid films. The excitation as well as the propagation along cm-range distances will be clearly demonstrated. In comparison to the strong THz absorption in bulk water, this waveguiding approach allows for a frequency dependent increase in the interaction distance by up to four orders of magnitude between THz radiation and water. The feasibility of the mode for THz sensing will be demonstrated in an exemplary fashion through the detection of the protein bovine serum albumin. Moreover, analytically modelled resonating Bragg structures will demonstrate the potential suitability of the long-range guided mode scheme for significantly increasing sensitivity capabilities.
This thesis then, presents a comprehensive approach that can function as a basis for prospective THz detection and characterization of biomolecules at physiological concentrations. This is a decisive step for advancing THz sensing under physiological conditions.