Magnetic nanoparticles (MNPs) functionalized with various enzymes (amyloglucosidase, glucose oxidase and horseradish peroxidase) were used to perform biocatalytic cascades in two different states, solute suspension or aggregated, produced in the absence or presence of an external magnetic field. The biocatalytic reactions proceeded through bulk solution diffusion of intermediate substrates or substrate channeling, when the systems were dispersed or aggregated, respectively. The both pathways have shown very similar kinetics, unless the intermediate substrate was consumed by an additional biocatalytic process called "filter" for brevity. In the presence of the "filter" process, the diffusional process in the bulk solution was significantly inhibited, while the process based on the substrate channeling was still active. The systems were switched reversibly between the inhibited dispersed state and the active aggregated state by removing and applying the external magnetic field, respectively. The signal-controlled biocatalytic cascades were considered as Boolean logic circuits with the inputs consisting of biomolecules and the magnetic field on-off.

Biocatalytic cascades involving more than one or two enzyme‐catalyzed step are inefficient inside alginate hydrogel prepared on an electrode surface. The problem originates from slow diffusion of intermediate products through the hydrogel from one enzyme to another. However, enzyme activity can be improved by surface immobilization. We demonstrate that a complex cascade of four consecutive biocatalytic reactions can be designed, with the enzymes immobilized in an LBL‐assembled polymeric layer at the alginate‐modified electrode surface. The product, hydrogen peroxide, then induces dissolution of iron‐cross‐linked alginate, which results in release process of entrapped biomolecular species, here fluorescently marked oligonucleotides, denoted F‐DNA. The enzymatic cascade can be viewed as a biocomputing network of concatenated AND gates, activated by combinations of four chemical input signals, which trigger the release of F‐DNA. The reactions, and diffusion/release processes were investigated by means of theoretical modeling. A bottleneck reaction step associated with one of the enzymes was observed. The developed system provides a model for biochemical actuation triggered by a biocomputing network of reactions.

We report an experimental realization of a biochemical XOR gate function that avoids many of the pitfalls of earlier realizations based on biocatalytic cascades. Inputs-represented by pairs of chemicals-cross-react to largely cancel out when both are nearly equal. The cross-reaction can be designed to also optimize gate functioning for noise handling. When not equal, the residual inputs are further processed to result in the output of the XOR type, by biocatalytic steps that allow for further gate-function optimization. The quality of the realized XOR gate is theoretically analyzed.

An enzyme‐based XOR logic gate was realized at interface of an alginate‐modified electrode. The biocatalytic production of H2O2 inside the alginate film was controlled by logically processed input signals. The in situ generated H2O2 was decomposed to yield free radicals in a Fenton‐type reaction catalyzed by iron cations, which were present in the alginate film as cross‐linkers stabilizing the hydrogel. The produced free radicals (•OH, •OOH) resulted in decomposition/dissolution of the alginate film removing it from the electrode surface and stimulating release process of magnetic nanoparticles (MNPs) functionalized with a fluorescent dye and entrapped in the alginate film. The release of the MNPs was analyzed by following fluorescence appearing in the solution. The release process followed the logic features of the XOR gate. The present system is the first realization of the enzyme‐based XOR gate functionally integrated with the downstream actuation process in the form of the signal‐stimulated release.

Optical properties of flawless bulk copper sample has been studied based on spectroellipsometry measurements in wide spectral interval (hν=0.18-4.87 eV) at various angles of light incidence. The main characteristics of electronic subsystem of this metal and values of main energy intervals in a band structure were determined for both oxidized and unoxidized copper sample.