Optical Properties of Crystalline Lactose Fluidized with Dilutions of Various Substances in the Terahertz Frequency Range

Baranova, Anna, Anastasiya Lykina, Daria Antonova, and Olga Smolyanskaya. "Optical Properties of Crystalline Lactose Fluidized with Dilutions of Various Substances in the Terahertz Frequency Range." Pharmaceutics 14, no. 1 (2022): 32.

For full paper see https://www.mdpi.com/1999-4923/14/1/32

Abstract: 
Lactose is a commonly used component of pharmaceutical medications in tablet form. It was previously shown that lactose changes conformationally after saturation in fluidized beds with active pharmaceutical ingredients obtained by repeated dilution of antibodies to interferongamma in combination with an external intensive vibration treatment. Moreover, it was revealed that these solutions are self-organized dispersed systems in which nano-objects are formed. Their biological activity and mechanism of action were previously established as well. The current work was dedicated to investigating the optical properties of fluidized lactose powders in the terahertz frequency range. Spectral analyses of powders of crystalline lactose saturated in fluidized beds with a diluted solution of either glycine buffer, antibodies to interferon-gamma, or water were carried out, intact lactose served as a control. All powders were tableted before testing. In the course of the study, the macroscopic parameters of the tablets were established, at which they had a stable shape and their THz optical properties had no parasitic diffraction losses. These tablets were analyzed using terahertz time-domain spectroscopy in the frequency range of 0.2–2.6 THz. The differentiation between the spectra was conducted using a principal component analysis. The differences between intact lactose and the lactose saturated with any of studied solutions were demonstrated. Additionally, lactose saturated with solutions of multiple dilutions of a substance (antibodies or glycine buffer) differed not only from intact lactose, but also from lactose saturated with a diluted solution of water. Moreover, discrimination of lactose formulations saturated with different substances (antibodies or glycine buffer) was also possible. Additionally, intact lactose differed from lactose saturated with diluted water. The methods reported could be useful for the quality control of the medications based on the technology of repeated dilution of an original substance.

2.2. Experimental Setup 

Terahertz transmission spectra of the tablets were measured using a TeraPulse 3000 time-domain spectroscopy system from TeraView (UK). The system uses a Ti:Sapphire laser with a wavelength of 800 nm, a frequency of 80 MHz, and an optical pulse duration of 90 fs. The pump pulse is incident on a photoconductive emitter on a GaAs substrate to create electron-hole pairs, which are then accelerated by an electric field applied to the electrodes. During the relaxation of charge carriers, terahertz pulses of bandwidth of 0.1–3.0 THz are emitted. The THz radiation pulses pass through the sample and hit the photoconductive detector (similar to the emitter), which also is irradiated by the incident pulse of 800 nm 90 fs, obtained by splitting the beam of the previously mentioned laser after passing through the delay line. In this study, a transmission module installed in a special chamber of the THz spectrometer was used. The space through which the THz beam passes is purged with nitrogen to reduce the absorption caused by water vapor in the air.

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