Responsive hydrogels for microfluidic flow reactors
Application of supra- und macromolecular chemistry in microscale hydrogel dots for enzymatic cascade reactions and pharmaceutical precursors.
For the establishment of complex reaction compartments in microfluidic (multi)chamber reactors, we focus on the integration of double crosslinked hydrogel-protein/enzyme-dots and enzymatic nanoreactors in microfluidic devices: For this response hydrogels are reached either using responsive units with the gel itself or by a consecutive functionalization with responsive hydrogels. Within the hydrogels the responsive units can be integrated using functional (side) chains or by including reversible crosslinking points. Both, reversible disulfide bonds and supramolecular chemistry, are applied to achieve the latter goal. Such double crosslinked hydrogels have an additional characteristic swelling once the responsive cross-linking points are broken and return (i.e. shrink) to their original state upon the reformation of crosslinking points or network chains (Figure 1). Using this principle for hydrogel arrays in microfluidics, one can reversibly bind and release additional functional (macro)molecules (e.g. proteins, drugs). In microfluidics such hydrogel dots or other non-functional hydrogel dots can be incorporated to form an enzymatic nanoreactor. it is possible to switch on and off enzymatic nanoreactors by changing pH environment (Figure 2). The reaction of the enzyme in the first chamber then enables the reaction in the second chamber. Cross-reactivities and inhibitions of the enzymes can be excluded in this spatially separated approach.
Fig. 1: The hydrogels can be functionalised in several ways. Main chains, grafted side chains as well as cross-linking points and end-groups are possible points for an additional functionalisation.
Fig. 2: The entire cascade can only work if the reaction of the first chamber is producing enough substrate for the enzyme localised in the second chamber. The design was optimised so that no dead zones arise in the entire chip.