Wetting characteristics of media emulating gastric fluids.

A variety of dissolution media have been used to simulate the physiological environment of the gastric region. The objective of this study was to formulate and examine the wetting properties of dispersions composed of the dominant surface active species found in the stomach at physiologically relevant concentrations. Systems representing the fed and fasted states were studied and compared to other media that have been considered for use as simulated gastric fluids. Dilute bile salt/phospholipid solutions and bile salt-lipid emulsions were formulated on the basis of available physiologic data to represent the fasted and fed states, respectively. Wetting was evaluated through the determination of the surface tension and contact angle of the various solutions using poly(methyl methacrylate) (PMMA) as a model surface. Additional surfactant solutions and other biorelevant media were also tested. Data were evaluated in terms of contact angle, surface tension and the thermodynamic stages of wetting. The results indicate that solutions patterned after the composition of the GI tract have significantly different wetting properties relative to the fed and fasted states. The surfactant solutions tested were significantly better wetting agents for the surface than the physiologically representative formulations. The implications for the formulation of surfactant-based biorelevant media are discussed.