Complications in investigations of the swelling of hydrogel matrices due to the presence of trapped gas

Fyfe, C. A.; Blazek, Almira

doi:10.1016/s0168-3659(97)00217-4

Cited by 24 publications

(4 citation statements)

References 10 publications

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“…To minimize the risk of air bubbles forming in the dissolving tablet, an evacuation procedure was performed before each experiment. The procedure is based on the setup by Fyfe and Blazek (1998) . The NMR tube with the tablet was placed in a chamber and exposed to vacuum ( P < 1 mmHg) for 5 min.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Using NMR Chemical Shift Imaging To Monitor Swelling and Molecular Transport in Drug-Loaded Tablets of Hydrophobically Modified Poly(acrylic acid): Methodology and Effects of Polymer (In)solubility

et al. 2013

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A new technique has been developed using NMR chemical shift imaging (CSI) to monitor water penetration and molecular transport in initially dry polymer tablets that also contain small low-molecular weight compounds to be released from the tablets. Concentration profiles of components contained in the swelling tablets could be extracted via the intensities and chemical shift changes of peaks corresponding to protons of the components. The studied tablets contained hydrophobically modified poly(acrylic acid) (HMPAA) as the polymer component and griseofulvin and ethanol as hydrophobic and hydrophilic, respectively, low-molecular weight model compounds. The water solubility of HMPAA could be altered by titration with NaOH. In the pure acid form, HMPAA tablets only underwent a finite swelling until the maximum water content of the polymer-rich phase, as confirmed by independent phase studies, had been reached. By contrast, after partial neutralization with NaOH, the polyacid became fully miscible with water. The solubility of the polymer affected the water penetration, the polymer release, and the releases of both ethanol and griseofulvin. The detailed NMR CSI concentration profiles obtained highlighted the clear differences in the disintegration/dissolution/release behavior for the two types of tablet and provided insights into their molecular origin. The study illustrates the potential of the NMR CSI technique to give information of importance for the development of pharmaceutical tablets and, more broadly, for the general understanding of any operation that involves the immersion and ultimate disintegration of a dry polymer matrix in a solvent.

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Section: Methodsmentioning

confidence: 99%

“…The procedure is based on the setup by Fyfe and Blazek (1998). 47 The NMR tube with the tablet was placed in a chamber and exposed to vacuum (P < 1 mmHg) for 5 min. The vacuum was then broken by addition of Gd 3+ -doped D 2 O, and a low pressure was maintained for an additional 5 min to ensure that all pores of the tablet were emptied.…”

Section: Methodsmentioning

confidence: 99%

Using NMR Chemical Shift Imaging To Monitor Swelling and Molecular Transport in Drug-Loaded Tablets of Hydrophobically Modified Poly(acrylic acid): Methodology and Effects of Polymer (In)solubility

et al. 2013

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“…During the compression process, air is trapped between particles and interparticular spaces are presented as air spaces. When the dosage form is placed in aqueous media, it swells and as a result air becomes trapped in the hydrated hypromellose matrix (Fyfe & Blazek 1998). During dissolution studies, air bubbles may appear attached to the tablet surface, making the dosage form more buoyant.…”

Section: Trapped Airmentioning

confidence: 99%

The use of hypromellose in oral drug delivery

Martini

Ford

et al. 2005

Journal of Pharmacy and Pharmacology

279

149

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Hypromellose, formerly known as hydroxypropylmethylcellulose (HPMC), is by far the most commonly employed cellulose ether used in the fabrication of hydrophilic matrices. Hypromellose provides the release of a drug in a controlled manner, effectively increasing the duration of release of a drug to prolong its therapeutic effect. This review provides a current insight into hypromellose and its applicability to hydrophilic matrices in order to highlight the basic parameters that affect its performance. Topics covered include the chemical, thermal and mechanical properties of hypromellose, hydration of the polymer matrices, the mechanism of drug release and the influence of tablet geometry on drug-release rate. The inclusion of drug-release modifiers within hypromellose matrices, the effects of dissolution media and the influence of both the external environment and microenvironment pH within the gel matrix on the properties of the polymer are also discussed.

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“…Relevant to this study, MRI has been used to monitor diffusion of solvents into synthetic polymers and to track the penetration of water into swelling tablets, most commonly hydroxypropylmethylcellulose (HPMC) (Fyfe and Blazek 1998, 2000; Fyfe and others 2000; Tritt‐Goc and Pis'lewski 2002; Kowalczuk and others 2004; Dahlberg and others 2007), poly(glycolic acid‐co‐DL‐lactic acid) (Hyde and others 1995), polyethylene oxide (Hyde and Gladden 1998), and high‐amylose starch tablets (Baille and others 2002; Russo and others 2007; Therién‐Aubin and others 2008). In these studies, qualitative and quantitative descriptions of the swelling process were obtained, and solvent uptake was quantified by kinetic and diffusion expressions.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Resonance Imaging (MRI) and Relaxation Spectrum Analysis as Methods to Investigate Swelling in Whey Protein Gels

Öztop¹,

Rosenberg²,

Rosenberg³

et al. 2010

Journal of Food Science

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Effective means for controlled delivery of nutrients and nutraceuticals are needed. Whey protein-based gels, as a model system and as a potential delivery system, exhibit pH-dependent swelling when placed in aqueous solutions. Understanding the physics that govern gel swelling is thus important when designing gel-based delivery platforms. The extent of swelling over time was monitored gravimetrically. In addition to gravimetric measurements, magnetic resonance imaging (MRI) a real-time noninvasive imaging technique that quantified changes in geometry and water content of these gels was utilized. Heat-set whey protein gels were prepared at pH 7 and swelling was monitored in aqueous solutions with pH values of 2.5, 7, and 10. Changes in dimension over time, as characterized by the number of voxels in an image, were correlated to gravimetric measurements. Excellent correlations between mass uptake and volume change (R(2)= 0.99) were obtained for the gels in aqueous solutions at pH 7 and 10, but not for gels in the aqueous solution at pH 2.5. To provide insight into the mechanisms for water uptake, nuclear magnetic resonance (NMR) relaxation times were measured in independent experiments. The relaxation spectrum for the spin-spin relaxation time (T(2)) showed the presence of 3 proton pools for pH 7 and 10 trials and 4 proton pools for pH 2.5 trials. Results demonstrate that MRI and NMR relaxation measurements provided information about swelling in whey protein gels that can constitute a new means for investigating and developing effective delivery systems for foods.

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Complications in investigations of the swelling of hydrogel matrices due to the presence of trapped gas

Cited by 24 publications

References 10 publications

Using NMR Chemical Shift Imaging To Monitor Swelling and Molecular Transport in Drug-Loaded Tablets of Hydrophobically Modified Poly(acrylic acid): Methodology and Effects of Polymer (In)solubility

Using NMR Chemical Shift Imaging To Monitor Swelling and Molecular Transport in Drug-Loaded Tablets of Hydrophobically Modified Poly(acrylic acid): Methodology and Effects of Polymer (In)solubility

The use of hypromellose in oral drug delivery

Magnetic Resonance Imaging (MRI) and Relaxation Spectrum Analysis as Methods to Investigate Swelling in Whey Protein Gels

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