Imaging of High-Amylose Starch Tablets. 3. Initial Diffusion and Temperature Effects

Abstract

The penetration of water into cross-linked high amylose starch tablets was studied at different temperatures by nuclear magnetic resonance (NMR) imaging, which follows the changes occurring at the surface and inside the starch tablets during swelling. It was found that the swelling was anisotropic, whereas water diffusion was almost isotropic. The water proton image profiles at the initial stage of water penetration were used to calculate the initial diffusion coefficient. The swelling and water concentration gradients in this controlled release system show significant temperature dependence. Diffusion behavior changed from Fickian to Case II diffusion with increasing temperature. The observed phenomena are attributed to the gelatinization of starch and the pseudo-cross-linking effect of double helix formation.

NMR spectroscopy and imaging studies of pharmaceutical tablets made of starch

“…The reorganization of the starch chains was evidenced by 13 C NMR spectroscopy as discussed in the precedent section. Table 2 shows the anisotropic swelling of the CHAS tablet evidenced by a larger swelling in thickness (axial) than in diameter (radial) Thérien-Aubin et al, 2005). The phenomenon is related to the preparation process of the tablets.…”

“…In the study of solvent uptake, only the molecules of solvent contribute to the signal. However, contrast of the image could be adjusted by any factors measurable by NMR, such as changes in concentration Chowdhury, Hill, & Whittaker, 2004a;Chowdhury, Hill, Whittaker, Braden, & Patel, 2004b;Fyfe & Blazek, 1997;Thérien-Aubin, Baille, Zhu, & Marchessault, 2005;Thérien-Aubin & Zhu, 2006;Thérien-Aubin, Zhu, Ravenelle, & Marchessault, 2008), relaxation times (Chowdhury et al, 2004b;Fyfe & Blazek, 1997;Rajabi-Siahboomi, Bowtell, Mansfield, Davies, & Melia, 1996), or self-diffusion coefficients Kojima & Nakagami, 2002;Rajabi-Siahboomi et al, 1996;Thérien-Aubin et al, 2008;Tritt-Goc, Kowalczuk, & Pislewski, 2003). NMR imaging is widely used to follow water uptake and moisture diffusion and to assess the water distribution in a system in different polymeric and starch-based systems (Hopkinson, Jones, Black, Lane, & McDonald, 1997;Horigane, Takahashi, Maruyama, Ohtsubo, & Yoshida, 2006b;Horigane et al, 2006a;Kasai, Lewis, Ayabe, Hatae, & Fyfe, 2007;Russo et al, 2007;Ziegler, MacMillan, & Balcom, 2003).…”

“…The swelling observed upon immersion of the tablet in water is limited and anisotropic Thérien-Aubin & Zhu, 2006;Thérien-Aubin et al, 2005. The limited swelling, leading to the shape retention of the tablet and the prevention of tablet dissolution or erosion, is caused by the reorganization of the hydrated starch chains (Le Bail et al, 1999;Ravenelle & Rahmouni, 2006).…”

High-amylose carboxymethyl starch matrices for oral sustained drug-release: In vitro and in vivo evaluation

“…Several authors have proposed different analytical techniques, such as Calorimetry, Light Microscopy and Nuclear Magnetic Resonance (NMR), to characterize the matrix swelling process and the effects involved in drug-release (Gladden 1994;Gao, Skoug et al 1996;Richardson, Bowtell et al 2005; Thérien-Aubin, Baille et al 2005;Mikac, Kristl et al 2011;). …”

“…The technique can be easily used to monitor simultaneously different areas of interest in the tablet and qualitative/quantitative results can be obtained . The effect of factors such as pH and ionic strength , tablet size , temperature (Therien-Aubin, Baille et al 2005) and drug-loading on solvent uptake and tablet swelling, as well as on gel layer formation at the water/tablet interface (Therien-Aubin, Zhu et al 2008) in the case of cross-linked high-amylose starch tablets has been evaluated using this technique.…”