Formulation-dependent stability mechanisms affecting dissolution performance of directly compressed griseofulvin tablets

 Maclean, Natalie, Ibrahim Khadra, James Mann, Alexander Abbott, Heather Mead, and Daniel Markl. "Formulation-dependent stability mechanisms affecting dissolution performance of directly compressed griseofulvin tablets." International Journal of Pharmaceutics 631 (2023): 122473.

full paper can be found at

https://www.sciencedirect.com/science/article/pii/S0378517322010286

Abstract

During drug product development, stability studies are used to ensure that the safety and efficacy of a product are not affected during storage. Any change in the dissolution performance of a product must be investigated, as this may indicate a change in the bioavailability. In this study, three different griseofulvin formulations were prepared containing microcrystalline cellulose (MCC) with either mannitol, lactose monohydrate, or dibasic calcium phosphate anhydrous (DCPA). The tensile strength, porosity, contact angle, disintegration time, and dissolution rate were measured after storage under five different accelerated temperature and humidity conditions for 1, 2, and 4 weeks. The dissolution rate was found to decrease after storage for all three batches, with the change in dissolution rate strongly correlating with the storage humidity. The changes in physical properties of each formulation were found to relate to either the premature swelling (MCC/DCPA, MCC/lactose) or dissolution (MCC/mannitol) of particles during storage. These results are also discussed with consideration of the performance- and stability-controlling mechanisms of placebo tablets of the same formulations (Maclean et al., 2021; Maclean et al., 2022).

Terahertz spectroscopy

Terahertz time-domain spectroscopy was performed using a TeraPulse Lx Spectrometer (TeraView Ltd). The sample chamber was purged with nitrogen to remove moisture from the air during analysis. Samples were analysed using an optical delay of 200 ps and 30 averages. From the terahertz measurements, the refractive index and loss coefficient were obtained. Based on the spectra obtained, a frequency of 0.8 THz was selected for comparing the change in refractive index and loss coefficient across different conditions and timepoints. This frequency was selected as this point was free from peaks (caused by the tablet components) for all formulations.

Visible-Terahertz Refractive Indices Correlation in Sodium Borosilicate Glasses

Tostanoski, Nicholas J., and S. K. Sundaram. "Visible-Terahertz Refractive Indices Correlation in Sodium Borosilicate Glasses." Journal of Infrared, Millimeter, and Terahertz Waves (2022): 1-20.

for full paper see https://link.springer.com/article/10.1007/s10762-022-00900-3

Abstract

We report visible-terahertz (THz) refractive indices correlation in the sodium borosilicate glass system along two tie lines, NaBSi and BNaSi. The NaBSi series represents the substitution of silicon dioxide for boron oxide, and the BNaSi series, the substitution of silicon dioxide for sodium oxide. Raman spectroscopy was used to provide insight into glass structure with an emphasis placed on properties including physical, e.g., density (ρ), thermal, e.g., glass transition temperature (Tg), and optical, e.g., refractive indices and dispersion at visible and THz frequencies. A prism coupler system equipped with multiple visible wavelength laser sources and terahertz time-domain spectroscopy (THz-TDS) were used to record refractive indices at visible and THz frequencies, respectively. Sodium borosilicate glasses with a depolymerized glass network, R > 0.5, consisting of charge deficient [BØ4]− borate and Q4 silicate tetrahedra forming borosilicate ring units with mixed Si–O–B bridges, and formation and increased quantities of Q3 silicate tetrahedra with more polarizable non-bridging oxygen (nbO) atoms are responsible for higher measurable refractive indices in these frequencies. This work shows that a linear correlation exists between refractive indices across these frequencies. Additionally, depolymerized glass networks record larger density, glass transition temperature, and optical basicity values. In terms of glass structure, refractive indices of depolymerized or polymerized networks measured at 0.589 μm and 0.5 THz support the correlation, which will be useful for developing active and passive components for applications across these frequencies.

Terahertz Spectroscopic Characterization and Thickness Evaluation of Internal Delamination Defects in GFRP Composites

 Nsengiyumva, Walter, Shuncong Zhong, Manting Luo, and Bing Wang. "Terahertz Spectroscopic Characterization and Thickness Evaluation of Internal Delamination Defects in GFRP Composites." Chinese Journal of Mechanical Engineering 36, no. 1 (2023): 1-21.

Abstract

The use of terahertz time-domain spectroscopy (THz-TDS) for the nondestructive testing and evaluation (NDT&E) of materials and structural systems has attracted significant attention over the past two decades due to its superior spatial resolution and capabilities of detecting and characterizing defects and structural damage in non-conducting materials. In this study, the THz-TDS system is used to detect, localize and evaluate hidden multi-delamination defects (i.e., a three-level multi-delamination system) in multilayered GFRP composite laminates. To obtain accurate results, a wavelet shrinkage de-noising algorithm is used to remove the noise from the measured time-of-flight (TOF) signals. The thickness and location of each delamination defect in the z-direction (i.e., through-the-thickness direction) are calculated from the de-noised TOF signals considering the interaction between the pulsed THz waves and the different interfaces in the GFRP composite laminates. A comparison between the actual and the measured thickness values of the delamination defects before and after the wavelet shrinkage denoising process indicates that the latter provides better results with less than 3.712% relative error, while the relative error of the non-de-noised signals reaches 16.388%. Also, the power and absorbance levels of the THz waves at every interface with different refractive indices in the GFRP composite laminates are evaluated based on analytical and experimental approaches. The present study provides an adequate theoretical analysis that could help NDT&E specialists to estimate the maximum thickness of GFRP composite materials and/or structures with different interfaces that can be evaluated by the THz-TDS. Also, the accuracy of the obtained results highlights the capabilities of the THz-TDS for the NDT&E of multilayered GFRP composite laminates.

THz-TDS and Imaging System

The THz-TDS (TeraView TPS 4000) is used to detect and characterize hidden delamination defects in GFRP composite samples. To measure the optical parameters and characterize the delamination defects of the GFRP samples, the system is configured to perform tests in reflection and transmission modes. These two modes are not simultaneously configured but rather one is configured after the other depending on which mode is needed at the different stages of the study. This THz-TDS system features a scanning range of up to 1200 ps and its resolution can reach 0.1 ps at a rapid scanning frequency of 50 Hz.

Full paper can be seen at

 https://cjme.springeropen.com/articles/10.1186/s10033-022-00829-7

Novel copper borate ceramics with lithium-based sintering aids for LTCC terahertz applications

Szwagierczak, Dorota, Beata Synkiewicz-Musialska, Jan Kulawik, Elżbieta Czerwińska, and Norbert Pałka. "Novel copper borate ceramics with lithium-based sintering aids for LTCC terahertz applications." Journal of Materials Chemistry C (2023).

Abstract

Novel CuB2O4–Cu3B2O6 substrates doped with three Li-based sintering aids, Li2WO4, LiBO2 and Li2CO3, were prepared using the LTCC (low temperature cofired ceramic) technology. The main goals of the work were to confirm the feasibility of LTCC substrates based on the developed materials and to prove their good dielectric properties in a broad terahertz frequency range. The comprehensive characterization of the thermal, compositional, microstructural, and dielectric properties of the fabricated ceramics was carried out by hot-stage microscopy, thermal analysis, dilatometry, X-ray diffractometry, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and time domain spectroscopy. The ceramic powders were used for the preparation of slurries and tape casting of proprietary green tapes. Test LTCC multilayer structures with embedded conductors were fabricated. The developed ceramics doped with Li2WO4 and LiBO2 seem to be very good candidates for LTCC substrates in THz applications. These substrates demonstrate a low sintering temperature 860–880 °C, a low dielectric permittivity 5.4–5.7 and a low loss tangent 0.008–0.01 at 1 THz, as well as a low thermal expansion coefficient of 5.7 ppm °C−1, quite well fitted to silicon, and a high flexural strength.

for full paper see 

https://pubs.rsc.org/en/content/articlelanding/2023/tc/d2tc04429c/unauth