Controlled release of macromolecules from electrical and chemical stimuli‐sensitive hydrogels

The controlled release of drugs from hydrogels has progressed from systems that merely swell in water, to novel hydrogels with specific chemical properties which respond to various stimuli to facilitate drug release. Specifically, electro‐erodible hydrogels are synthesized by polymer chain complexation and precipitation through hydrogen or ionic bonds. The surface of the solid polymer device is eroded or dissolved in response to an applied electric current. When a constant electric current is applied, zero‐order release of entrapped drug is achieved. However, if a step‐function current is applied, the drug can be released in an on‐off pattern. Concanavalin A microspheres, a protein gel, has been synthesized to release insulin in response to glucose concentrations. This microsphere gel has specific binding affinity for glucose and mannose. A synthesized glycosylated insulin was loaded on the microspheres and then released in response to glucose concentrations via a competitive binding exchange mechanism.