Monitoring the role of enantiomers in the surface modification and adsorption process of polymers imprinted by chiral molecules: theory and practice

Woźnica, Marcin, Monika Sobiech, Norbert Pałka, and Piotr Luliński. "Monitoring the role of enantiomers in the surface modification and adsorption process of polymers imprinted by chiral molecules: theory and practice." Journal of Materials Science: 1-17.

ABSTRACT 

The objective of this study was to explore the role of enantiomers in the surface modification and adsorption process of polymers imprinted by chiral molecules. Here, R-, S- and R/S-1-aminoindanes (TR, TS and TR/S) were used as the model template molecules. Optimization of synthetic protocols facilitated preselection of the most efficient composition for a molecularly imprinted polymer (MIP)— methacrylic acid-co-ethylene glycol dimethacrylate—with satisfactory specificity and an imprinting factor equal to 3. This polymer composition was used further to analyse the effect of configuration of the template on adsorption properties. The results showed preferable adsorption of R-enantiomer, TR in the R-MIP and S-enantiomer, TS in the S-MIP but revealed variations in the binding capacities of TR and TS in the R- and S-cavity (stereoselectivity factor; k = 1.66 to 1.22, respectively). The theoretically analysed binding energies (DEB) of both TR and TS in the R-cavity (DEB = - 506.14 to - 256.77 kcal mol-1 ) and S-cavity (DEB = - 302.42 to - 347.18 kcal mol-1 ) were in agreement with empirical data. Morphology and porosity analyses revealed the impact of the template molecule on the pore system of the MIP and control (a non-imprinted polymer), but enantiomers were only found to have a negligible role. Binding characterization revealed that the physisorption-governed adsorption process and Dubinin– Radushkevich model fitted the experimental data best. Finally, terahertz spectroscopy was employed to confirm the similarity between both materials imprinted by each enantiomer.

for full paper see https://link.springer.com/content/pdf/10.1007/s10853-020-04796-z.pdf

… Terahertz spectroscopy was performed at the Military University of Technology Institute

of Opto- electronics, Warsaw, Poland. A TDS-based spec- trometer was used for terahertz

measurements (Teraview TPS Spectra 300, Cambridge, UK) in transmission …

Simultaneous Investigation of the Liquid Transport and Swelling Performance during Tablet Disintegration

Al-Sharabi, Mohammed, Daniel Markl, Theona Mudley, Prince Bawuah, Anssi-Pekka Karttunen, Cathy Ridgway, Patrick Gane et al. "Simultaneous Investigation of the Liquid Transport and Swelling Performance during Tablet Disintegration." International Journal of Pharmaceutics (2020): 119380.

Abstract

Fast disintegrating tablets have commonly been used for fast oral drug delivery to patients with swallowing difficulties. The different characteristics of the pore structure of such formulations influence the liquid transport through the tablet and hence affect the disintegration time and the release of the drug in the body. In this work, terahertz time-domain spectroscopy and terahertz pulsed imaging were used as promising analytical techniques to quantitatively analyse the impact of the structural properties on the liquid uptake and swelling rates upon contact with the dissolution medium. Both the impact of porosity and formulation were investigated for theophylline and paracetamol based tablets. The drug substances were either formulated with functionalised calcium carbonate (FCC) with porosities of 45% and 60% or with microcrystalline cellulose (MCC) with porosities of 10% and 25%. The terahertz results reveal that the rate of liquid uptake is clearly influenced by the porosity of the tablets with a faster liquid transport observed for tablets with higher porosity, indicating that the samples exhibit structural similarity in respect to pore connectivity and pore size distribution characteristics in respect to permeability. The swelling of the FCC based tablets is fully controlled by the amount of disintegrant, whereas the liquid uptake is driven by the FCC material and the interparticle pores created during compaction. The MCC based formulations are more complex as the MCC significantly contributes to the overall tablet swelling. An increase in swelling with increasing porosity is observed in these tablets, which indicates that such formulations are performance-limited by their ability to take up liquid. Investigating the effect of the microstructure characteristics on the liquid transport and swelling kinetics is of great importance for reaching the next level of understanding of the drug delivery, and, depending on the surface nature of the pore carrier function, in turn controlling the performance of the drug mainly in respect to dissolution in the body.

for full paper see https://www.sciencedirect.com/science/article/pii/S0378517320303641

"2.3. Terahertz Time-Domain Spectroscopy and Imaging. A commercial terahertz system (TeraPulse 4000, Teraview Ltd., Cambridge, UK) was used to conduct all the terahertz measurements in either transmission or reflection mode."

Terahertz-infrared electrodynamics of swingle-crystalline Ba0. 2Pb0. 8Al1. 2Fe10. 8O19 M-type hexaferrite

Ahmed, Asmaa, Anatoly S. Prokhorov, Vladimir Anzin, Denis Vinnik, Alexander Bush, Boris Gorshunov, and Liudmila Alyabyeva. "Terahertz-infrared electrodynamics of swingle-crystalline Ba0. 2Pb0. 8Al1. 2Fe10. 8O19 M-type hexaferrite." Journal of Alloys and Compounds (2020): 155462.

Abstract

Spectral response of single-crystalline Ba0.2Pb0.8Al1.2Fe10.8O19 synthesized by a modified Czochralski method is investigated using terahertz-infrared spectroscopy. Reflectivity, transmissivity, and complex dielectric permittivity spectra of the compound are studied in the temperature range from 6 to 300 K and in the frequency interval 8-8000 cm−1 for two principle polarizations of the radiation electric field relative to the crystallographic c-axis, namely E||c and E⊥c. The resonance absorption lines observed above 80 cm−1 are assigned to polar lattice vibrations basing on a factor group analysis and a comparison with a dielectric response of isostructural compounds. A set of absorption bands is observed in a range of 8–80 cm−1. To clarify their nature, a model is developed that considers electronic transitions within the fine-structured ground state of four-fold coordinated Fe2+. It is shown that the trigonal distortions of the crystal field lead to lowering of the symmetry of 4f1 and 4e tetrahedral site-positions of Fe2+ and, as a result, to further splitting of the ground state spin-orbital sub-levels. Electro-dipole transitions between the corresponding sub-levels are associated with the absorption lines observed in a low-energy response (at 8-80 cm−1) of the Ba0.2Pb0.8Al1.2Fe10.8O19 compound. The study paves the way for the development of low cost materials with high dielectric permittivity (about 30) at terahertz frequencies that are promising for the manufacture of electronic devices with enhanced characteristics.

for full see https://www.sciencedirect.com/science/article/abs/pii/S0925838820318260

Sub-lattice of Jahn-Teller centers in hexaferrite crystal

Gudkov, V. V., M. N. Sarychev, S. Zherlitsyn, I. V. Zhevstovskikh, N. S. Averkiev, D. A. Vinnik, S. A. Gudkova et al. "Sub-lattice of Jahn-Teller centers in hexaferrite crystal." Scientific Reports 10, no. 1 (2020): 1-15.

Abstract

A novel type of sub-lattice of the Jahn-Teller (JT) centers was arranged in Ti-doped barium hexaferrite BaFe₁₂O₁₉. In the un-doped crystal all iron ions, sitting in five different crystallographic positions, are Fe³⁺ in the high-spin configuration (S = 5/2) and have a non-degenerate ground state. We show that the electron-donor Ti substitution converts the ions to Fe²⁺ predominantly in tetrahedral coordination, resulting in doubly-degenerate states subject to the E⊗eE⊗e problem of the JT effect. The arranged JT complexes, Fe²⁺O₄, their adiabatic potential energy, non-linear and quantum dynamics, have been studied by means of ultrasound and terahertz-infrared spectroscopies. The JT complexes are sensitive to external stress and applied magnetic field. For that reason, the properties of the doped crystal can be controlled by the amount and state of the JT complexes.

for full paper see https://www.nature.com/articles/s41598-020-63915-7

They used a terahertz time-domain spectrometer (Teraview TPS 3000 TDS)

Terahertz-Based Porosity Measurement of Pharmaceutical Tablets: a Tutorial

Bawuah, Prince, Daniel Markl, Daniel Farrell, Mike Evans, Alessia Portieri, Andrew Anderson, Daniel Goodwin, Ralph Lucas, and J. Axel Zeitler. "Terahertz-based porosity measurement of pharmaceutical tablets: a tutorial." Journal of Infrared, Millimeter, and Terahertz Waves (2020): 1-20.

Abstract

Porosity, one of the important quality attributes of pharmaceutical tablets, directly affects the mechanical properties, the mass transport and hence tablet disintegration, dissolution and ultimately the bioavailability of an orally administered drug. The ability to accurately and quickly monitor the porosity of tablets during manufacture or during the manufacturing process will enable a greater assurance of product quality. This tutorial systematically outlines the steps involved in the terahertz-based measurement method that can be used to quantify the porosity of a tablet within seconds in a non-destructive and non-invasive manner. The terahertz-based porosity measurement can be performed using one of the three main methods, which are (i) the zero-porosity approximation (ZPA); (ii) the traditional Bruggeman effective medium approximation (TB-EMA); and (iii) the anisotropic Bruggeman effective medium approximation (AB-EMA). By using a set of batches of flat-faced and biconvex tablets as a case study, the three main methods are compared and contrasted. Overall, frequency-domain signal processing coupled with the AB-EMA method was found to be most suitable approach in terms of accuracy and robustness when predicting the porosity of tablets over a range of complexities and geometries. This tutorial aims to concisely outline all the necessary steps, precautions and unique advantages associated with the terahertz-based porosity measurement method.

for full paper see https://link.springer.com/article/10.1007/s10762-019-00659-0