Scientists at Osaka University have developed a new sensing method, which has the potential to detect both cancer and diabetes earlier than ever possible before.
The use of terahertz (THz) waves for biosensing is currently of great interest to scientists and is receiving considerable attention. The team in Osaka have developed a THz microfluidic chip with arrays of meta-atoms that can be used for microanalysis. It is highly sensitive, and label-free, for measurements of biological samples. The new chip can detect trace amounts of known materials and minimal changes in optical constants. The research was published in APL Photonics.
THz radiation lies in between infrared and microwave radiation. The terahertz region provides essential information that clarifies biological reaction dynamics, including the hydrogen bonds and hydrophobic interactions, and it is at comparatively lower energy than that of infrared absorption. They can detect molecular vibrations and rotations, without using labels that can affect the properties of the substances of interest.
Microfluidic devices only need a very low sample volume for measurements, so they are seen as very promising analytical systems. The group from Osaka University have now developed a nonlinear optical crystal (NLOC) chip, combining the THz waves with a microfluidic device, meaning that the proximity of the THz wave source and the solution of interest in a microchannel can be combined.
The early and rapid detection of common diseases is set to be a major application of the technique. There is the potential that cancer, diabetes, and even the influenza virus would be able to be detected with very small volumes of bodily fluid. The sample volume needed allows for the patients to have their pain and discomfort from exploratory procedures reduced. The new technique also has another major benefit of allowing living cells to be analyzed in a non-destructive way.
The technique has been limited previously due to the diffraction limit of THz waves and their strong absorption by water. The new research has shown that THz time-domain spectroscopy (THz-TDS) is a technique that can give new insights into the functional expression and structural change of water, biopolymers, and DNA. When THz methods can be combined with microfluidic devices, it allows for the development of compact THz sensors, as well as new analytical THz devices that have a higher sensitivity.
Using our technique, we have been able to detect solution concentrations of several femtomoles in volumes of less than a nanoliter. Such high-sensitivity detection without the need for labeling moieties has great potential for future low-invasivity clinical techniques.
Professor Masayoshi Tonouchi, Professor of the Tonouchi lab at Osaka University
The sensor chip compared frequency shifts resulting from the presence of ions to those of pure water to analyze mineral concentrations. The chip was tested by using both distilled water and commercial mineral water, and when observing the amount of shift from the resonance frequency of pure water, they found that the solute can be detected with a sensitivity of up to 31.8 femtomoles. The sensitivity of the technique is comparable to standard fluorescence systems, but it can be improved by further optimization of the structure and the arrangement of meta-atoms. Altering the channel depth to reduce the THz absorption into the water can also optimize results.
Achieving high sensitivity without the need for a high-power optical or THz source, near-field probes or prisms opens up a number of possibilities.
Kazunori Serita, Co-Author
Serita explains how their potential findings could lead to rapid detection and compact device designs. He believes the results will lead to an acceleration in the development of THz lab-on-a-chip devices. The new adaptable technology has the potential to have a wide range of uses across many areas, including biochemistry, analytical chemistry, cell biology, and clinical medicine. The low cost of NLOC chips would also allow for disposable and compact sensors, which would be highly beneficial to both fields of medicine and biology.
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