5.3.8. Polymer Erosion on pH Change
Heller and coworkers investigated a glucose sensitive device that was composed of insulin dispersed in a polymer that was eroded by low pH. A hydrogel which contains glucose oxidase enzyme surrounds the insulin-containing polymer. When glucose interacts with the glucose oxidase, the resulting low pH erodes the polymer, and insulin is released. A schematic is given in figure 5.3.16.
Figure 5.3.16. Schematic of pH sensitive polymeric device (after Heller)
This device was tested in vitro, and dramatic release of insulin was observed at pH 5.5 and below, and at pH 5.6 no release was observed (figure 5.3.17).
Figure 5.3. 17. Effect of pH on rate of insulin release from a cross-linked polymer prepared from 3,9-bis(ethyenediene 184.108.40.206-tetraethanolamine). (After Heller)