Redox-active materials are an attractive platform for engineering specific interactions with charged species by electrochemical control. We present nanostructured redox-electrodes, functionalized with poly­(vinyl)­ferrocene embedded in a carbon nanotube matrix, for modulating the adsorption and release of proteins through electrochemical potential swings. The affinity of the interface toward proteins increased dramatically following oxidation of the ferrocenes, and, due to the Faradaic nature of the organometallic centers, the electrodes were maintained at sufficiently low overpotentials to ensure the preservation of both protein structure and catalytic activity. Our system was selective for various proteins based on size and charge distribution, and exhibited fast kinetics (<120 s for a charge–discharge cycle) and high uptake capacities (>200 mg/g) under moderate overpotentials (+0.4 V vs Ag/AgCl), as well as remarkable stability for binding under ferrocene oxidation conditions. The preservation of bioactivity and protein structure at the interface indicates the potential for these redox-mediated surfaces to be used as heterogeneous supports for enzyme catalysis. This work draws on the molecular selectivity of ferrocene-functionalized materials toward organic anion groups, and demonstrates that these smart redox-active materials can be used for modulation of the macroscopic affinity of surfaces for charged biomacromolecules to enhance processes such as bioseparations, electrochemically controlled protein purification, biocatalysis, and electrochemically mediated drug release.

In the course of their development, industrial biocatalysis processes have to be optimized in small-scale, e. g., within microfluidic bioreactors. Recently, we introduced a novel microfluidic reactor device, which can handle defined reaction compartments of up to 250 μL in combination with magnetic micro carriers. By transferring the magnetic carriers between subsequent compartments of differing compositions, small scale synthesis, and bioanalytical assays can be conducted. In the current work, this device is modified and extended to broaden its application range to the screening and optimization of bioprocesses applying immobilized enzymes. Besides scaling the maximum compartment volume up to 3 mL, a temperature control module, as well as a focused infrared spot were integrated. By adjusting the pump rate, compartment volumes can be accurately dosed with an error <5% and adjusted to the requested temperature within less than a minute. For demonstration of bioprocess parameter optimization within such compartments, the influence of pH, temperature, substrate concentration, and enzyme carrier loading was automatically screened for the case of transferring UDP-Gal onto N-acetylglucosamine linked to a tert-butyloxycarbonyl protected amino group using immobilized β1,4-galactosyltransferase-1. In addition, multiple recycling of the enzyme carriers and the use of increased compartment volumes also allows the simple production of preparative amounts of reaction products.

A benchtop device that combines segmented flow with magnetic particle separation and active resuspension capabilities for biotechnological applications, e.g. biomolecule purification.

In the last decade, microfluidic bioreactor systems became increasingly important due to their high suitability for lab‐on‐a‐chip applications and resource‐saving experiments with small sample volumes. Here, a prototype of a microfluidic device for fast small‐scale investigations of enzymatic and biochemical reactions is introduced. Single or consecutive enzyme‐catalyzed reactions can be implemented within compartmented reaction environments separated by immiscible fluidic plugs. By immobilizing one of the reactants onto magnetic microcarriers, a fast and easy separation of the reaction products is possible allowing the realization of a sequence of different reaction steps with different enzymes and varying chemical environments. Besides permanent magnetic fields for separation processes, alternating electromagnetic fields can be applied to resuspend the carriers. This leads to an intense mixing as well as even microcarrier distribution within the compartment. In a proof of concept, kinetic studies of HRP immobilized onto polyvinyl alcohol‐magnetite composite microcarriers are presented. The results showed a specific enzyme activity of approximately 89 units per gram immobilized biocatalyst under the applied reaction conditions. In addition, results of recycling experiments point out the importance of the magnetically induced resuspension. While ten times reuse with immobilisate resuspension resulted in substrate conversion yields between 95 and 65%, the same experiment without the magnetically induced resuspension showed conversion yields below 10% over all cycles.