Igor Sizov

Highly Resolved Sub-Terahertz Vibrational Spectroscopy of Biological Macromolecules and Cells

Sub-terahertz (sub-THz) vibrational spectroscopy for biosensing is based on specific resonance features, vibrational modes or group of modes at close frequencies, in the absorption (transmission) spectra of large biological molecules and entire bacterial cells/spores. Further improvements in sensitivity, especially in the discriminative capability of sub-THz vibrational spectroscopy for detection, characterization, and identification of bacterial organisms, require spectral resolution adequate to the width of spectral features. Evidences exist for long-lasting relaxation processes for atomic dynamics (displacements) resulting in narrow spectral lines and justifying the development and application of highly resolved vibrational spectroscopy. Here we describe a new continuous-wave frequency-domain spectroscopic sensor with imaging capability operating at room temperature in the sub-THz spectral region between 315 and 480 GHz. We present experimental spectra from biological macromolecules and species obtained using this spectrometer and compare some spectra with simulation results using molecular dynamics. Observed multiple intense and specific resonances in transmission/absorption spectra from nano-gram samples with spectral line widths as small as 0.1 cm-1 provide conditions for reliable discriminative capability, potentially to the level of the strains of the same bacteria, and for monitoring interactions between biomaterials and reagents in near real-time.

Sub-terahertz vibrational spectroscopy for microRNA based diagnostic of ovarian cancer

The purpose of this research is to introduce and validate novel sub-THz resonance spectroscopy combined with molecular dynamics (MD) computation as a promising approach for optical analysis and potential quantification of molecular biomarkers in ovarian (OC) cancer cells. The ability of sub-THz spectroscopy to identify and quantify biological molecules is demonstrated by interrogation of resonance features caused by atomic vibrations within biological molecules in cancer and normal samples. In vitro human cell cultures of two ovarian cancer subtypes, SK-OV-3 human epithelial and ES-2 human clear cell carcinoma, were characterized in comparison with a normal nontransformed cell line (FT131-human fallopian tube epithelial cell line). A dramatic difference between the THz absorption spectra of cancer and normal cells and cell free samples is observed with much higher absorption intensity and a strong absorption peak at frequency of ~13 cm−1 dominating the spectra from cancer samples. Comparison of experimental spectra with MD predictions of spectroscopic signatures of microRNA molecules from the miR-200 family, known to be overexpressed in ovarian cancer, suggests an origin for this pronounced spectral peak. The rest of the cancer samples’ signature is in part similar to the signatures of normal cells and represents contributions from proteins and nucleic acid polymer molecules. Even though ovarian cancer is utilized for this proof of concept, the sub-THz spectroscopy method is very general and can be as well applied to other cancer types. PAPER

Sub-terahertz resonance spectroscopy of biological macromolecules and cells

Recently we introduced a Sub-THz spectroscopic system for characterizing vibrational resonance features from biological materials. This new, continuous-wave, frequency-domain spectroscopic sensor operates at room temperature between 315 and 480 GHz with spectral resolution of at least 1 GHz and utilizes the source and detector components from Virginia Diode, Inc. In this work we present experimental results and interpretation of spectroscopic signatures from bacterial cells and their biological macromolecule structural components. Transmission and absorption spectra of the bacterial protein thioredoxin, DNA and lyophilized cells of Escherichia coli (E. coli), as well as spores of Bacillus subtillis and B. atrophaeus have been characterized. Experimental results for biomolecules are compared with absorption spectra calculated using molecular dynamics simulation, and confirm the underlying physics for resonance spectroscopy based on interactions between THz radiation and vibrational modes or groups of modes of atomic motions. Such interactions result in multiple intense and narrow specific resonances in transmission/absorption spectra from nano-gram samples with spectral line widths as small as 3 GHz. The results of this study indicate diverse relaxation dynamic mechanisms relevant to sub-THz vibrational spectroscopy, including long-lasting processes. We demonstrate that high sensitivity in resolved specific absorption fingerprints provides conditions for reliable detection, identification and discrimination capability, to the level of strains of the same bacteria, and for monitoring interactions between biomaterials and reagents in near real-time. Additionally, it creates the basis for the development of new types of advanced biological sensors through integrating the developed system with a microfluidic platform for biomaterial samples.

Portable sub-terahertz resonance spectrometer combined with microfluidic sample cell

Radiation in the Terahertz frequency range interacts with vibrations in the weakest molecular couplings such as hydrogen bonding, van der Waals forces, and hydrophobic interactions. The work presented demonstrates our efforts towards the development of a microfluidic device as the sample cell for presenting liquid samples within the detection region of a novel sub-THz spectrometer. The continuous-wave, frequency-domain spectrometer, operating at room temperature between 315 and 480 GHz with spectral resolution of 0.3 GHz, already demonstrated highly intense and specific signatures from nanogram samples of dry biological molecules and whole bacterial cells. The very low absorption by water in this sample cell will allow for the use of liquid samples to present cells and molecules in their natural environment. The microfluidic device design utilizes a set of channels formed with metal sidewalls to enhance the interaction between the THz radiation and the sample, increasing the sensitivity of the system. Combined with near field effects, through use of a detection probe close to the surface of the sample cell, spatial resolution less than the diffraction limit can be achieved, further reducing the amount of sample required for analysis. This work focuses on the design, and fabrication methods, which will allow implementation of the microfluidic sample cell device within the THz spectrometer. The device will be utilized for characterization of different cell types, showing that THz interrogation of liquid samples is possible.