Rheological investigation of the shear strength, durability, and recovery of alginate rafts formed by antacid medication in varying pH environments

Abstract

The mechanical response of alginate rafts formed by mixing liquid alginate antacid medication (Gaviscon Extra Strength Liquid Antacid) with acidic solutions was investigated by deforming isolated rafts in a shear rheometer. As rafts were deformed to varying magnitudes of applied strain, rheological parameters were identified and related to the overall strength, durability, and recoverability of rafts formed at different pH (1.1-1.7) and aging conditions (0.5-4 h). Rafts formed in the lowest acidity solutions (pH 1.4, 1.7) were elastically weak ( G'₀ = 60 , 42 Pa for un-aged raft) yet maintained their elasticity during applied shear deformation to large values of strain (γc∼90%, 50%, where G'≈G″), and displayed a low-to-moderate level of elastic recovery following large-strain deformation. Rafts formed in the highest acidity solution had the greatest strength ( G'₀ = 500 Pa for un-aged raft and 21.5 kPa for rafts after 0.5 h of aging), reduced durability (γc∼2.5%, independent of aging), and displayed the greatest recoverability. A trade-off existed between un-aged raft strength and durability while recovery was dependent on durability, solution pH, and age. Rheometry-based evaluations of alginate rafts could be used for the informed design of future gastric retention and antacid products.

pH responsive alginate polymeric rafts for controlled drug release by using box behnken response surface design

“…Elliot et al studied the effect of different pH medium on raft forming alginate-antacids combined formulations. [ 12 ]…”

“…Prepared tablets were added into 900 ml of simulated gastric fluid (SGF) having pH 1.2, 5.8, 1.0 N HCl pH 1.2 and 0.1 N HCl pH 5.7 and effect of pH on raft formation was observed. [ 12 ]…”

Removal of yttrium (III) ions from water solutions by alginate compounds

“…In the study with natural polysaccharides, pH of solution should be taken to account. This is an important parameter because the sorption system is strongly pHdependent due to the properties of both alginate compounds changing their charge and potential at different pH and the solution composition, i.e., metal ion speciation (Lofgren et al 2002;Schiewer and Patil 2008;Elliott et al 2013). The number of active binding sites presented with carboxyl group residues of the alginate molecule may also change due to varying pH.…”

Dynamics of Supramolecular Self-Healing Recovery in Extension

“…The properties of some self-healing polymers allow for solid mechanical testing, 12,14 however, viscoelastic materials display more complex rheology which requires more robust characterization techniques. Various measures of recovery have been made using shear rheology of entangled polymers, 37 self-assembled gels, [38][39][40][41] block copolymers, 42 telechelic polymers, 43,44 and ionomers, 45 however application of damage is difficult to interpret and measurements are often only characteristic of the applied flow. In contrast to typical shear measurements, extensional rheology allows for a definitive rupture of the material prior to robust, nonlinear rheological characterization.…”

“…Typically self-healing dynamics are measured via mechanical testing. , However, these are not standard techniques, and therefore the results are mostly qualitative. Various measures of recovery have been made using shear rheology of entangled polymers, self-assembled gels, − block copolymers, telechelic polymers, , and ionomers; however, application of damage is difficult to interpret, measurements are often only characteristic of the applied flow, and systematic choices of parameters are seldom used. The field is in need of a controlled, reproducible technique to measure self-healing dynamics after controlled fracture as a function of material and process parameters.…”