First-generation shaped gel reactors based on photo-patterned hybrid hydrogels†
This paper reports the development of first-generation photo-patterned ring-shaped gel reactors that catalyse the hydrolysis of para-nitrophenol phosphate using a phosphatase enzyme. Encapsulation of alkaline phosphatase within a hybrid gel combining a low-molecular-weight gelator (LMWG) and a polymer gelator (PG) does not appear to inhibit its ability to turn over this reaction. The PG enables photo-patterning of the gel, facilitated by the pre-formed LMWG network which limits convection and diffusion during the patterning step. Furthermore, the rheologically weak, reversible LMWG network can be washed away, allowing straightforward release of the patterned gel reactor. By tailoring reactor design and reaction conditions, and changing the enzyme to acid phosphatase, the distribution of substrate and product between the gel and the different solution phases could be controlled. Although these first generation gel reactors have some limitations, in particular with the gel adsorbing significant amounts of substrate/product, a number of design criteria emerge with regard to choice of gelator, enzyme and assembly technique. These insights will inform the future development of this approach to reaction engineering.