Alginate composite hydrogels that exhibit highly sensitive stimuli-responsive behavior were used for signal-stimulated release of pre-loaded insulin. The alginate pores, particularly located at the periphery, were blocked by interpenetration of polyvinyl alcohol (PVA) cross-linked with 1,3-benzenediboronic acid (IPN), thus, significantly reducing uncontrolled leakage of the entrapped biomolecules. The beads were loaded with insulin and various enzymes mimicking different Boolean logic gates (AND, OR, NOR, IMP, INHIB). The enzymes were activated with biologically relevant input signals applied in four logic combinations: 0,0; 1,0; 0,1; 1,1, having the production of H2 O2 as the result of the biocatalytic reactions. The "successful" combination of the input signals leading to the H2 O2 production was different for different logic gates, following the corresponding truth tables of the logic gates. When H2 O2 was produced, boronate ester bonds were oxidized and the IPN was irreversibly degraded, thus re-opening the original pores of the hydrogel. This process allowed release of insulin from the alginate beads. The smart soft material that we have developed tackled well-known limitations of these systems and it may prove valuable in future medical diagnostics or treatments.
Keywords: controlled release; enzymes; insulin release; logic gates; smart material; unconventional computing.
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