The glucose responsive hydrogels developed by Horbett et al. [1, 2] are potentially useful as materials for constructing glucose sensors. The construction of microsensors presents challenges in developing processes for preparing these gels that are compatible with semiconductor fabrication technology.
We have lithographically patterned a pH-sensitive copolymer (poly-(2-hydroxyethyl methacrylate-co-dimethyl aminoethyl methacrylate) 90:10 (mole ratio) (HEMA/DMA) from a prepolymer solution of monomers, crosslinker, solvent, and a viscosity agent (p(HEMA)). Varying the spin speed and p(HEMA) concentration resulted in reproducible thicknesses between 5 and 25 μm. pH sensors produced by this method showed sensitivity ranging from 20 to 50%/pH and a response time (10%–90%) of 6.8 minutes. Sensitivity dropped by a factor of two over a 24 day testing period. The limited lifetime is thought to be due to loss of adhesion of the polymer to the substrate.
Derivatizing glucose oxidase with a photoactivatible crosslinker allowed it to be covalently immobilized onto the surface of the gel layer in a spatially specific manner. After immobilization, GOX specific staining showed that enzyme activity was preserved, however the amount of enzyme immobilized was insufficient to create a working glucose sensor.