Insulin releasing beads

Figure 5 Modulating insulin release profile from pH/temperature-sensitive beads made of terpolymers of iV-isopropylacrylamide (NIPAAm)/butyl methacrylate (BMA)/acrylic acid (AA) feed mol ratio 85/5/10 and increasing MW. Beads were placed at pH 2.0 and 37°C for 2h and then at pH 7.4 and 37°C for the remainder of the release studies in = 6). (Adapted from Ref. 76.)...

Ramkissoon-Ganorkar C, Liu F, Baudys M, Kim SW. Modulating insulin-release profile from pH/thermosensitive polymeric beads through polymer molecular weight. J Control Release 1999 59 287-298. 

Figure 4. Modulating insulin release profile from pH-/temperature-sensitive beads made of terpolymers of constant NIPAAm/BMA/AA composition 85/5/10 and increasing molecular weight.

In another approach, insulin was modified to introduce hydroxyl groups so that the hydroxylated insulin can be immobilized by forming a complex with phenylboronic acid groups on the support (Fig. 16.11). The support can be hydrogel beads made of polymers containing phenylboronic acid, e.g. poly(m-methacrylamidophenylboronic acid). The hydroxylated insulin can be displaced by the added glucose and the displaced insulin can be released. 

Rasmussen MR, Snabe T, Pedersen LH. Numerical modelling of insulin and amyloglucosidase release from swelling Ca-alginate beads. / Controlled Release 2003 91(3) 395—405. 

Taking a step further, Kim et al. have studied the loading, release, and the preservation of bioactivity of a pol3rpep-tide, insulin, entrapped in a microbead formation. The morphology of the beads studied by scanning electron microscopy (SEM) revealed that they consisted of a dense skin layer and a porous inner structure. This suggested that the critical step of bead preparation is the formation of this skin layer or... 

The bioactivity of the released insulin is shown in Figure 5. These results demonstrate that the beads protect insulin from the harsh acidic conditions and that the activity of insulin is retained after the loading procedure and on contact of the insulin vnih the polymer. 

Figure 5. Blood glucose depression activity of released insulin from polymer beads determined by TV injection in rats (n=4).

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