Pressure-induced change in permeation of insulin through a polymer alloy membrane for an implantable insulin pump

Pressure-induced change in insulin permeability through a polymer alloy membrane for an implantable insulin pump was investigated. The polymer alloy membrane was composed of a segmented polyurethane (SPU) and poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-co-2-ethylhexyl methacrylate) (PMEH). The polymer alloy membrane had a pathway for insulin permeation because the hydrophilic PMEH became the domain structure in the polymer alloy. The functions of the SPU/PMEH alloy membrane were characterized in terms of insulin permeability and water permeability with an applied pressure, mechanical properties, and strain and volume changes under the pressured condition. The insulin permeability synchronized with the applied pressure, that is, the insulin permeability increased 3.4 times with the applied pressure (pressure-on state) of 18 kPa in comparison with no applied pressure (pressure-off state). The permeability changed reversibly without lag time between the pressure-on and -off states. The phenomenon was caused by an increase in water permeation with the applied pressure. From the observation of volume change in the insulin reservoir in the pressure-on state, the effective pressure advancing water permeation was produced by the elasticity of the polymer alloy membrane. The polymer alloy membrane had excellent mechanical properties resisting the applied pressure, as was indicated by stress–strain measurements. It was concluded that the SPU/PMEH alloy membrane had a useful function for an implantable insulin pump.