(272e) Barrier-Mediated Pulsed Release

Many drugs are most effectively administered in pulses, ranging from hourly secretion of master hormones to vaccine cycles with weeks between boosters. Recent studies have shown the utility of administering daily pulses of bone growth factors by isolating each dose beneath an erodible polymer layer and stacking the layers to effect sequential erosion and release. It is unclear, however, the extent to which such a system could be adapted to different time scales.

Inspired by Ed Cussler's work on barrier membranes, we are developing a model system for exploring the parameter space of this release phenomenon. By loading a permeable polymer film with an insoluble base, we have constructed barriers which block acid permeation for a prescribed period of time. The underlying layer is a pH-sensitive hydrogel, also familiar to followers of Ed's work, which is triggered by the acid to swell and release a solute payload. By varying the thickness and concentration of the base, we can vary the release over a wide time scale.