• Alany, Raid G.
• Thrimawithana, Thilini Rasika

Abstract

<p><b>Objectives:</b> The main objective of this study was to determine the effect of potassium and calcium ions on the microstructure and release dynamics of kappa (κ) and iota (ι) carrageenan. </p><p><b>Methods</b> The microstructure of the dispersions was imaged using a cryogenic scanning electron microscope. Franz-cell diffusion apparatus was used to determine the release kinetics of a model hydrophilic drug, sodium fluorescein, incorporated in selected polymer dispersions. Release profiles were analysed using Higuchi, Korsmeyer-Peppas and dual first-order models. </p><p><b>Key Findings</b> Cryogenic scanning electron microscope images showed that κ-carrageenan forms hexagonal structures, whereas ι-carrageenan forms rectangular pores at low cation concentrations. In-vitro release studies showed sustained release profiles for all carrageenan systems; however the model drug, fluorescein, diffusion from ι-carrageenan with 0.06% w/v calcium was significantly higher than other ι-carrageenan systems. This may be attributed to improved tortuosity of this system. However further increase in cation concentration led to a reduction in fluorescein release from the matrices. The dual first-order release model illustrated two distinct release rates, an initial rapid release followed by a slow diffusion of fluorescein from the carrageenan matrices. </p><p><b>Conclusions</b> The observed microstructural differences may account for the well known variation in mechanical properties of κ- and ι-carrageenan gels. The dual first order release model adds a new tool in the elucidation of release mechanisms from polymer matrices, where parallel processes contribute to drug release.</p>

Topics

• pore
• dispersion
• polymer
• Sodium
• Potassium
• Calcium