Spatially resolved polymer mobilization revisited - Three-dimensional, UltraShort Echo Time (3D UTE) magnetic resonance imaging of sodium alginate matrix tablets

Ewelina Baran; Artur Birczyński; Przemysław Dorożyński; Piotr Kulinowski

doi:10.1016/j.jcis.2023.06.139

Spatially resolved polymer mobilization revisited - Three-dimensional, UltraShort Echo Time (3D UTE) magnetic resonance imaging of sodium alginate matrix tablets

J Colloid Interface Sci. 2023 Nov:649:626-634. doi: 10.1016/j.jcis.2023.06.139. Epub 2023 Jun 20.

Authors

Ewelina Baran¹, Artur Birczyński², Przemysław Dorożyński³, Piotr Kulinowski⁴

Affiliations

¹ Institute of Technology, The Pedagogical University of Kraków, Podchorążych 2, 30-084 Kraków, Poland. Electronic address: ewelina.baran@up.krakow.pl.
² Institute of Technology, The Pedagogical University of Kraków, Podchorążych 2, 30-084 Kraków, Poland. Electronic address: artur.birczynski@up.krakow.pl.
³ Department of Drug Technology and Pharmaceutical Biotechnology, Medical University of Warsaw, Banacha 1, 02-097 Warszawa, Poland. Electronic address: mfdorozy@cyf-kr.edu.pl.
⁴ Institute of Technology, The Pedagogical University of Kraków, Podchorążych 2, 30-084 Kraków, Poland. Electronic address: piotr.kulinowski@up.krakow.pl.

PMID: 37364462
DOI: 10.1016/j.jcis.2023.06.139

Abstract

Hypothesis: Three-dimensional ¹H UltraShort Echo Time magnetic resonance imaging (¹H 3D UTE MRI) of the matrix tablet made of hydrophilic polymer hydrated in heavy water (D₂O) will allow investigation of the hydration-induced spatiotemporal evolution of the material originally included in the matrix tablet during manufacturing (i.e., polymer chains and bound water).

Experiments: The oblong-shaped sodium alginate matrix tablets were used to verify the hypothesis. The matrix was measured before and during hydration in D₂O for up to 2 h using the ¹H 3D UTE MRI. Five echo times (first at 20 μs) were used, resulting in five three-dimensional images (one image for each echo time). In chosen cross-sections, two parametric images, i.e., amplitude and T₂* relaxation time maps, were calculated using "pixel-by-pixel" mono-exponential fitting.

Findings: The regions of the alginate matrix with T₂* shorter than 600 μs were analyzed before (air-dry matrix) and during hydration (parametric, spatiotemporal analysis). During the study, only hydrogen nuclei (protons) pre-existing in the air-dry sample (polymer and bound water) were monitored because the hydration medium (D₂O) was not visible. As a result, it was found that morphological changes in regions having T₂* shorter than 300 μs were the effect of fast initial water ingress into the core of the matrix and subsequent polymer mobilization (early hydration providing additional 5% w/w hydration medium content relating to air-dry matrix). In particular, evolving layers in T₂* maps were detected, and a fracture network was formed shortly after the matrix immersion in D₂O. The current study presented a coherent picture of polymer mobilization accompanied by local polymer density decrease. We concluded, that the T₂* mapping using 3D UTE MRI can effectively be applied as a polymer mobilization marker.

Keywords: Alginates; Hydrophilic polymers; Magnetic resonance imaging (MRI); Mass transport; Polymer hydration; Polymer relaxation; Short T(2) relaxation times; Swelling, polymer mobilization; Ultrashort Echo Time (UTE).