Drug diffusion mechanism through pH-sensitive hydrophobic/polyelectrolyte hydrogel membranes

Area of Science:

• Polymer Science
• Materials Science
• Drug Delivery

Background:

• pH-sensitive hydrogels offer tunable drug release.
• Understanding diffusion mechanisms is crucial for optimizing drug delivery systems.

Purpose of the Study:

• To investigate drug diffusion mechanisms through a methylmethacrylate/dimethylaminoethyl methacrylate based pH-sensitive hydrogel.
• To correlate drug solubility and hydrogel properties with diffusion behavior.
• To elucidate the influence of pH on drug-hydrogel interactions and release kinetics.

Main Methods:

• Utilized a pH-sensitive hydrogel cross-linked with divinylbenzene.
• Studied diffusion of a water-soluble drug (aminopyrine) at varying pH levels.
• Analyzed diffusion coefficients and swelling interface numbers to determine release mechanisms.

Main Results:

• Drug diffusion was water-content dependent and influenced by pH.
• Hydrophobic interactions increased with decreasing drug solubility and increasing polymer hydrophobicity at different pHs.
• Aminopyrine diffusion followed free-volume theory (pore mechanism) for water-soluble drugs.
• Partition or solution-diffusion mechanisms governed water-insoluble solute diffusion.
• Non-Fickian release observed in the hydrated form (pH 1.2) and Fickian in the dehydrated form (pH 7.4).

Conclusions:

• The study elucidates distinct diffusion mechanisms for drugs of varying solubilities in pH-sensitive hydrogels.
• Findings provide insights into optimizing hydrogel-based drug delivery systems by controlling pH and polymer properties.
• The pH-dependent behavior of the hydrogel significantly impacts drug release kinetics and mechanisms.