Terahertz spectroscopy of Bisphenol "A", "AF", "S", "E" and the interrelationship between their molecular vibrations

Evaluation of the cardiotoxicity potential of bisphenol analogues in human induced pluripotent stem cells derived cardiomyocytes

The importance of evaluating the cardiotoxicity potential of common chemicals as well as new drugs is increasing as a result of the development of animal alternative test methods using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM). Bisphenol A (BPA), which is used as a main material in plastics, is known as an endocrine-disrupting chemical, and recently reported to cause cardiotoxicity through inhibition of ion channels in CMs even with acute exposure. Accordingly, the need for the development of alternatives to BPA has been highlighted, and structural analogues including bisphenol AF, C, E, F, and S have been developed. However, cardiotoxicity data for analogues of bisphenol are not well known. In this study, in order to evaluate the cardiotoxicity potential of analogues, including BPA, a survival test of hiPSC-CMs and a dual-cardiotoxicity evaluation based on a multi-electrode array were performed. Acute exposure to all bisphenol analogues did not affect survival rate, but spike amplitude, beat period, and field potential duration were decreased in a dose-dependent manner in most of the bisphenols except bisphenol S. In addition, bisphenols, except for bisphenol S, reduced the contractile force of hiPSC-CMs and resulted in beating arrest at high doses. Taken together, it can be suggested that the developed bisphenol analogues could cause cardiotoxicity even with acute exposure, and it is considered that the application of the MEA-based dual-cardiotoxicity evaluation method can be an effective help in the development of safe alternatives.

State-of-the-Art Room Temperature Operable Zero-Bias Schottky Diode-Based Terahertz Detector Up to 5.56 THz

We present the characterization of a Zero-bias Schottky diode-based Terahertz (THz) detector up to 5.56 THz. The detector was operated with both a table-top system until 1.2 THz and at a Free-Electron Laser (FEL) facility at singular frequencies from 1.9 to 5.56 THz. We used two measurement techniques in order to discriminate the sub-ns-scale (via a 20 GHz oscilloscope) and the ms-scale (using the lock-in technique) responsivity. While the lock-in measurements basically contain all rectification effects, the sub-ns-scale detection with the oscilloscope is not sensitive to slow bolometric effects caused by changes of the IV characteristic due to temperature. The noise equivalent power (NEP) is 10 pW/Hz in the frequency range from 0.2 to 0.6 THz and 17 pW/Hz at 1.2 THz and increases to 0.9 μW/Hz at 5.56 THz, which is at the state of the art for room temperature zero-bias Schottky diode-based THz detectors with non-resonant antennas. The voltage and current responsivity of ∼500 kV/W and ∼100 mA/W, respectively, is demonstrated over a frequency range of 0.2 to 1.2 THz with the table-top system.

Study of temperature-dependent terahertz spectra of isonicotinamide in the form I using the quasi-harmonic approximation

Anharmonicity of molecular vibrational motions is closely associated with the thermal property of crystals. However, the origin of anharmonicity is still not fully understood. Low-frequency vibrations, which are usually defined in the terahertz (THz) range, show excellent sensitivity to anharmonicity. In this work, anharmonicity of isonicotinamide in the form I was investigated by using temperature-dependent terahertz time-domain spectroscopy and quasi-harmonic approximation (QHA) approach at PBE-D3 and PBE-MBD levels. Both DFT calculations suggest the variation of p-p stacking conformation dominates in the thermal expansion of unit cell. The frequency shifts of the modes in THz range obtained by QHA approach are found to be qualitatively consistent with the observation, demonstrating QHA approach is a useful tool for the interpretation of frequency shifts of modes induced by temperature.

The necessity of periodic boundary conditions for the accurate calculation of crystalline terahertz spectra

Terahertz vibrational spectroscopy has emerged as a powerful spectroscopic technique, providing valuable information regarding long-range interactions - and associated collective dynamics - occurring in solids. However, the terahertz sciences are relatively nascent, and there have been significant advances over the last several decades that have profoundly influenced the interpretation and assignment of experimental terahertz spectra. Specifically, because there do not exist any functional group or material-specific terahertz transitions, it is not possible to interpret experimental spectra without additional analysis, specifically, computational simulations. Over the years simulations utilizing periodic boundary conditions have proven to be most successful for reproducing experimental terahertz dynamics, due to the ability of the calculations to accurately take long-range forces into account. On the other hand, there are numerous reports in the literature that utilize gas phase cluster geometries, to varying levels of apparent success. This perspective will provide a concise introduction into the terahertz sciences, specifically terahertz spectroscopy, followed by an evaluation of gas phase and periodic simulations for the assignment of crystalline terahertz spectra, highlighting potential pitfalls and good practice for future endeavors.

Quantitative analysis of bisphenol analogue mixtures by terahertz spectroscopy using machine learning method

Quantitative analysis of complex mixtures is a great challenge for spectral analysis. Bisphenol A (BpA) is a chemical predominantly used in manufacturing and is being replaced by other analogs due to its potential toxicity. Reliability methods is hence crucial for identification and quantification of bisphenol mixtures. In this study we present an attractive strategy for composition determination of BpA incorporated in its analogue mixtures. Terahertz spectra of four bisphenol components are analyzed using machine learning method (SVR) to learn the underlying model of the frequency against the target concentration of BpA in mixtures. The learned mode predicts the concentrations of the unknown samples with decision coefficient R² = 0.98. Absorption spectra for bisphenols mixtures were successfully reconstructed by a hold-out validation scheme. The results indicate the terahertz spectroscopy in combination with SVR is robust and accurate in mixture quantitative analysis and should play a significant role for industrial applications in the future.

Receptor-binding affinities of bisphenol A and its next-generation analogs for human nuclear receptors

An endocrine-disrupting chemical Bisphenol A (BPA) binds specifically to a nuclear receptor (NR) named ERRγ. Although the importance of receptor-binding evaluation for human NRs is often stressed, the binding characteristics of so-called next-generation (NextGen) bisphenol compounds are still poorly understood. The ultimate objective of this investigation was to evaluate BPA and its NextGen analogs for their abilities to bind to 21 human NRs, the greatest members of NRs for which tritium-labeled specific ligands were available. After establishing the detailed assay conditions for each NR, the receptor binding affinities of total 11 bisphenols were evaluated in competitive binding assays. The results clearly revealed that BPA and the NextGen bisphenols of BPAF, BPAP, BPB, BPC, BPE, and BPZ were highly potent against one or more of NRs such as CAR, ERα, ERβ, ERRγ, and GR, with IC₅₀ values of 3.3-73 nM. These bisphenols were suggested strongly to be disruptive to these NRs. BPM and BPP also appeared to be disruptive, but less potently. BPF exhibited only weak effects and only against estrogen-related NRs. Surprisingly, most doubtful bisphenol BPS was supposed not to be disruptive. The NRs to which BPA and NextGen bisphenols did not bind were RARα, RARβ, RARγ, and VDR. PPARγ, RORα, RORβ, RORγ, RXRα, RXRβ, and RXRγ, exhibited very weak interaction with these bisphenols. The ten remaining NRs, namely, ERRγ, ERβ, ERα, CAR, GR, PXR, PR, AR, LXRβ, and LXRα, showed distinctly strong binding to some bisphenols in this order, being likely to have consequential endocrine-disruption effects.