Abstract-Single-cell terahertz spectral characteristics in simulated scattering near-field imaging mode

Jie Wang, Shihan Yan, Zaoxia Li, Ziyi Zang, Xingxing Lu, and Hong-Liang Cui

Schematic of the coupled tip–cell model system.

https://www.osapublishing.org/osac/abstract.cfm?URI=osac-3-8-2096

Spectral imaging of a single cell with terahertz (THz) wave is valuable in determination of its physiological state for cell-based precision diagnosis, as THz photon energy is in tune with the vibration-rotation and conformation related excitations of cellular material, and THz absorption is extremely sensitive to the state and degree of hydration of a cell. Because of the severe mismatch between the cell size and the THz wavelength, such imaging has to be carried out in the near-field modality. To make the design and performance assessment of a THz near-field spectral imager effective and systematic, we simulate the scattering THz near-field signals of tumor cells by strictly controlling cell model parameters with representative physiological states. The results demonstrate that the specific physiological characteristics from intracellular hydration state, nucleocytoplasmic ratio, and cell geometric morphology of tumor cells can be characterized quantitatively by their discrepant dielectric response in the THz band, correlating THz near-field scattering signal from a cell with the latter’s corresponding physicochemical state.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Single cell imaging with near‐field terahertz scanning microscopy

Zaoxia Li, Shihan Yan, Ziyi Zang, Guoshuai Geng, Zhongbo Yang, Jiang Li, Lihua Wang, Chunyan Yao, Hong‐Liang Cui, Chao Chang, Huabin Wang

https://onlinelibrary.wiley.com/doi/full/10.1111/cpr.12788

Objectives

Terahertz (THz)‐based imaging techniques hold great potential for biological and biomedical applications, which nevertheless are hampered by the low spatial resolution of conventional THz imaging systems. In this work, we report a high‐performance photoconductive antenna microprobe‐based near‐field THz time‐domain spectroscopy scanning microscope.

Materials and methods

A single watermelon pulp cell was prepared on a clean quartz slide and covered by a thin polyethylene film. The high performance near‐field THz microscope was developed based on a coherent THz time‐domain spectroscopy system coupled with a photoconductive antenna microprobe. The sample was imaged in transmission mode.

Results

We demonstrate the direct imaging of the morphology of single watermelon pulp cells in the natural dehydration process with our near‐field THz microscope.

Conclusions

Given the label‐free and non‐destructive nature of THz detection techniques, our near‐field microscopy‐based single‐cell imaging approach sheds new light on studying biological samples with THz.

Abstract-Temperature- and pH-dependent protein conformational changes investigated by terahertz dielectric spectroscopy

Ziyi Zang, Shihan Yan, Xiaohui Han, Dongshan Wei. Hong-Liang Cui, Chunlei Du,




https://www.sciencedirect.com/science/article/pii/S1350449518305267

Polypeptides and protein drugs have received enormous attention from pharmaceutical industry, medical sector and consumer groups because of a favourable combination of their bioactivity, specificity and overall success rate for the treatment of a variety of diseases. The efficacy and safety of drugs may be degraded due to fluctuating environmental factors, accompanied by changes of the natural conformation of protein. Thus, it is necessary and meaningful to evaluate drug status before use. To that end, the evolving new and pre-existing protein activity/conformation technologies have proven to ensure the safety of drug use consistently. Recently, terahertz time-domain spectroscopy (THz-TDS) has demonstrated suitability for label-free and non-destructive detection of polypeptide and protein conformational changes. In this paper, THz optical parameters of pepsin solutions under different temperatures and with varying pH are measured to demonstrate the feasibility and the considerable potential of THz spectroscopic method in detecting protein drugs. In cases where temperature or pH change is apparent, the THz absorption coefficient, the refractive index, and the dielectric loss tangent change noticeably, independently verified by enzyme activity testing. These findings strongly support the conclusion that THz spectroscopy of pepsin solutions can be used for qualitative analysis to identify the folding or unfolding of protein drugs caused by changes of environmental factors, laying the foundation of a new label-free method for quality control of protein drugs.

Abstract-Temporal and Spatial Variability of Water Status in Plant Leaves by Terahertz Imaging

Zheyu Song,  Shihan Yan,   Ziyi Zang,  Yun Fu, Dongshan Wei,  Hong-Liang Cui,  Puxiang Lai,

https://ieeexplore.ieee.org/document/8403254/

Water and its distribution and transport dynamics in green plant leaves are vital to the growth of plants. Owing to the high sensitivity of terahertz (THz) wave to water, THz spectroscopy has great advantages in analyzing the water status of plant leaves. This paper presents a new approach to estimate the water status of plant leaves by the THz time-domain spectroscopy (THz-TDS) technique. Spatial distribution of THz transmission amplitudes located in vein xylem and mesophyll of all three kinds of leaves including wintersweet, ginkgo, and bamboo is detected by THz-TDS measurements. Based on the transmission amplitude, reconstructed THz images show that the water loss in the basal leaf region is more than that in the distal region during the natural drying process for all three plants. A good agreement is reached between the THz imaging method and the direct water weight measurement. To illustrate the accuracy and the sensitivity of the THz technique, the temporal and spatial variations of the water content in the damaged ginkgo leaf with a wound by cutting are also investigated for comparison. The water flow from the basal region to the distal region of the leaf is inferred according to the variation of THz transmission amplitude with the leaf region in different dehydration periods, which is consistent with the string-of-lakes model prediction. This paper shows the feasibility of using THz technology to monitor the temporal and spatial variability of the water status in plant leaves.

Abstract-Label-free protein detection using terahertz time-domain spectroscopy

Xiaohui Han, Shihan Yan, Ziyi Zang, Dongshan Wei, Hong-Liang Cui, and Chunlei Du

https://www.osapublishing.org/boe/abstract.cfm?uri=boe-9-3-994

Protein analysis is the foundation to understanding the mechanisms of complex biological processes. As one of the most widely used techniques to determine protein species and contents, protein dot blot aids biology research but needs corresponding antibodies for marking. A label-free detection method based on terahertz time-domain spectroscopy (THz-TDS) is proposed and demonstrated to improve this traditional technology. A membrane loaded with protein samples is directly scanned using a transmission THz-TDS system for spectral imaging. Different kinds of proteins can be distinguished by the refractive index extracted from the THz transmission spectrum. The intensity or shade imaged with the THz transmission spectrum can help detect the protein quantitatively. The feasibility of this new protein assay is demonstrated by the results of systematic testing with actual samples prepared with the dot-blot protocol.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement