Abstract-Study on an artificial phenomenon observed in terahertz biological imaging

 

Zhongbo Yang, Muyang Zhang, Dandan Li, Ligang Chen, Ailing Fu, Yanmei Liang,  Huabin Wang, 

The THz-TDS system and the determination of the radius of the THz beam by the knife-edge method. (a) Schematic of the THz path of the THz-TDS system. (1) and (7) Photoconductive antennae; (2) and (6) High-resistance hyper hemisphere Si lenses; (3) and (5) High-density polyethylene plano convex lenses; (4) Sample. The sample was positioned in the optical path with the aid of a miniature optical clamping device installed on a two-dimensional motorized precision translation stage. A laser level was used in the installation of the sample to ensure that the sample was perpendicular to the incident direction of the terahertz beam. The focus plane is indicated by a dashed line accompanied with the character ‘F’; the green bar with the character ‘S’ indicates the sample position in the Z axis. ‘Z1’ indicates the distance between the front surface of the sample and the focus plane, namely, the defocus distance. (b) A typical time-domain spectrum and (c) the corresponding frequency-domain spectrum of the system free of samples. (d) The line profile extracted from the THz amplitude image at 1.2 THz. (e) The first derivative (black square dot) of the THz amplitude data in (d), fitted by a Gaussian function (red curve).

https://www.osapublishing.org/boe/fulltext.cfm?uri=boe-12-6-3133&id=450836

Terahertz (THz) wave-based imaging of biological samples is an emerging but promising field. In the present work, we report an artificial phenomenon observed in imaging melanoma slices, which can lead to mistakenly interpretation of the experimental results. It was observed that a structure similar to but smaller than the sample contour appeared inside the melanoma slice image. The underlying mechanism of this phenomenon was then investigated both experimentally and theoretically. By imaging a regular standard sample (vinyl coverslip) with a THz time domain spectroscopy (THz-TDS) system and reconstructing its images at 0.8 and 1.2 THz, we can clearly observe the afore-mentioned artifacts. The experimental results are highly consistent with the simulations based on the Fresnel-Kirchhoff diffraction theory in which possible optical aberrations were incorporated. It can be concluded that this artifact was caused by the frequency-dependent diffraction of the sample edge. The work demonstrated here is essential for correct interpretation of the images obtained by the THz-TDS technique.

© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Near‐Field Nanoscopic Terahertz Imaging of Single Proteins

 

Zhongbo Yang,  Dongyun Tang,  Jiao Hu,  Mingjie Tang,  Mingkun Zhang,  Hong‐Liang, Cui  Lihua Wang,  Chao Chang,  Chunhai Fan,  Jiang Li,  Huabin Wang,

https://onlinelibrary.wiley.com/doi/abs/10.1002/smll.202005814

Terahertz (THz) biological imaging has attracted intense attention due to its capability of acquiring physicochemical information in a label‐free, noninvasive, and nonionizing manner. However, extending THz imaging to the single‐molecule level remains a challenge, partly due to the weak THz reflectivity of biomolecules with low dielectric constants. Here, the development of graphene‐mediated THz scattering‐type scanning near‐field optical microscope for direct imaging of single proteins is reported. Importantly, it is found that a graphene substrate with high THz reflectivity and atomic flatness can provide high THz contrast against the protein molecules. In addition, a platinum probe with an optimized shaft length is found enabling the enhancement of the amplitude of the scattered THz near‐field signals. By coupling these effects, the topographical and THz scattering images of individual immunoglobulin G (IgG) and ferritin molecules with the size of a few nanometers are obtained, simultaneously. The demonstrated strategy thus opens new routes to imaging single biomolecules with THz

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-Detecting melanoma with a terahertz spectroscopy imaging technique

Dandan Li, Zhongbo Yang, Ailing Fu, Tunan Chen, Ligang Chen, Mingjie Tang, Hua Zhang, Ning Mu, Shi Wang, Guizhao Liang,  Huabin Wang

https://www.sciencedirect.com/science/article/abs/pii/S1386142520302079

Transmission mode terahertz time-domain spectroscopy system was employed to image BALB/c mouse skin tissue slices containing melanoma. The melanoma was unambiguously identified in the frequency region of 0.6–1.8 THz because melanoma has a higher refractive index as well as a higher absorption coefficient than the normal region of the skin tissue. Based on the results of hematoxylin-eosin staining and mass weighing, it was further suggested that the higher density of nucleic acids, higher water content, and lower fat content in the melanoma compared to the normal region are major factors responsible for melanoma's higher refractive index and absorption coefficient than normal tissue. The present work validates that terahertz time-domain spectroscopy imaging technique is possible to be used for the diagnosis of melanoma.

Abstract-Terahertz Spectroscopic Signatures of Microcystin Aptamer Solution Probed with a Microfluidic Chip

Mingkun Zhang, Zhongbo Yang, Mingjie Tang , Deqiang Wang , Huabin Wang, Shihan Yan , Dongshan Wei,  Hong-Liang Cui

https://www.mdpi.com/1424-8220/19/3/534

Terahertz signature detection of biological samples in aqueous solution remains a great challenge due to the strong terahertz absorption of water. Here we propose a new preparation process for fabricating a microfluidic chip and use it as an effective sensor to probe the terahertz absorption signatures of microcystin aptamer (a linear single-stranded DNA with 60 nucleotides) dissolved in TE buffer with different concentrations. The microfluidic chip made of silicon includes thousands of 2.4 μm × 2.4 μm square-cross-section channels. One repeatable terahertz absorption signature is detected and recognized around 830 GHz, fitted to a Lorentz oscillator. This signature is theorized to originate from the bending of hydrogen bonds formed between adjacent hydrated DNA bases surrounded by water molecules. Furthermore, the low-lying vibrational modes are also investigated by molecular dynamics simulations which suggest that strong resonant oscillations are highly probable in the 815–830 GHz frequency band

Abstract-Synthesis of novel rambutan-like graphene@aluminum composite spheres and non-destructive terahertz characterization

Zhongbo Yang, Shuanglong Feng, Wei Yao, Jiaguang Hanc, Huabin Wang

https://pubs.rsc.org/en/Content/ArticleLanding/2019/RA/C8RA09129C#!divAbstract

Graphene reinforced Al (graphene@Al) spheres were synthesized using microwave plasma chemical vapor deposition technique in which H2, CH4, and Ar were used as the reduced gas, carbon source, and plasma enhancement gas, respectively. The obtained graphene@Al spheres presented a rambutan-like structure and had a graphene shell wrapped on the sphere surface, which was proved by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The thickness of the graphene shell on the Al sphere is difficult to be characterized by conventional techniques. However, it was successfully measured with a sophisticated terahertz (THz) time-domain spectroscopic technique. To the best of our knowledge, neither have graphene@Al spheres been synthesized before nor has a THz-based technique been exploited to characterize the thickness of a shell structure. Therefore, the present work sheds useful insights on both the rational synthesis and non-destructive characterization of graphene reinforced functional structures.

Abstract-Terahertz time-domain spectroscopy of chondroitin sulfate

Changcheng Shi, Yuting Ma, Jin Zhang, Dongshan Wei, Huabin Wang, Xiaoyu Peng, Mingjie Tang, Shihan Yan, Guokun Zuo, Chunlei Du, and Hongliang Cui

https://www.osapublishing.org/boe/abstract.cfm?uri=boe-9-3-1350&origin=search

Chondroitin sulfate (CS), derived from cartilage tissues, is an important type of biomacromolecule. In this paper, the terahertz time-domain spectroscopy (THz-TDS) was investigated as a potential method for content detection of CS. With the increase of the CS content, the THz absorption coefficients of the CS/polyethylene mixed samples linearly increase. The refractive indices of the mixed samples also increase when the CS content increases. The extinction coefficient of CS demonstrates the THz frequency dependence to be approximately the power of 1.4, which can be explained by the effects of CS granular solids on THz scattering.

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