Hydrogels are 3D polymer networks with water content up to 90%, making an aqueous environment for the embedded enzyme. Recently, a facile method for forming tetra-PEG hydrogel was established in which a direct mixing of two macromonomer solutions led to the gelation completed within several minutes. Here we extend this method to form enzyme microgels with homogenous nanostructures.
Tetra-amine-terminated PEG (TAPEG) and tetra-NHS-glutarate-terminated PEG (TNPEG) macromonomer solutions containing proteins were mixed and dispersed into cyclohexane to form reverse micelles with diameters from 80nm to 200nm. Gelation inside micelles was triggered by tuning pH from 5.0 to 7.0, resulting in uniform enzyme-incorporated hydrogels with diameter around 1μm.
The versatility of this method was demonstrated using Cyt c, CALB, GOx and HRP, respectively, in which all enzyme hydrogels displayed catalytic activities in aqueous solutions. Moreover Cyt c hydrogel showed a 5-fold increase in peroxidase activity compared to its counterpart in free solution, in addition to an improved stability.
 Sakai T, Matsunaga T, Yamamoto Y, et al. [J]. Macromolecules, 2008, 41(14): 5379-5384.
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