The use of printing to produce 2D arrays is well established, and should be relatively facile to adapt for the purpose of printing biomaterials; however, very few studies have been published using enzyme solutions as inks. Among the printing technologies, inkjet printing is highly suitable for printing biomaterials and specifically enzymes, as it offers many advantages. Formulation of the inkjet inks is relatively simple and can be adjusted to a variety of biomaterials, while providing nonharmful environment to the enzymes. Here we demonstrate the applicability of inkjet printing for patterning multiple enzymes in a predefined array in a very straightforward, noncontact method. Specifically, various arrays of the enzymes glucose oxidase (GOx), invertase (INV) and horseradish peroxidase (HP) were printed on aminated glass surfaces, followed by immobilization using glutardialdehyde after printing. Scanning electrochemical microscopy (SECM) was used for imaging the printed patterns and to ascertain the enzyme activity. The successful formation of 2D arrays consisting of enzymes was explored as a means of developing the first surface confined enzyme based logic gates. Principally, XOR and AND gates, each consisting of two enzymes as the Boolean operators, were assembled, and their operation was studied by SECM.

A surface-localized enzymatic AND gate based on scanning electrochemical microscopy was designed and studied. The gate is composed of an insulating glass surface modified with the enzyme glucose oxidase (GOx) and another surface opposing it made of a microelectrode. The latter was modified with a second enzyme, invertase (INV). The distance separating the modified microelectrode and surface controlled the output of the AND gate produced upon the biocatalytic reaction of the confined enzymes. Specifically, as the GOx-modified glass substrate entered the diffusion layer of the microelectrode, it catalyzed the regeneration of an electron-transfer mediator, ferroceniummethanol, generated electrochemically at the tip by oxidizing glucose, also generated at the tip, by catalytic cleaving of sucrose by INV. To enhance the activity of the GOx, mutarotase was added to convert α- to β-glucose to be further consumed by GOx. Hence, an increase of the current at the microelectrode was obtained by approaching the glass surface only in the presence of all the components. This is the first micrometer-sized biomolecular logic gate, of which we are aware, that is surface-confined and shows the promise held by the localization of biomolecular information-processing species.

Biodegradable nanoparticles represent a promising platform for controlled release and other applications in medicine. To alter the interface of the medical device with the living tissue successfully, a thin coating needs to be applied onto the surface. The traits and functionality of the coating depends on its components, which in the presented work are sol-gel and biodegradable nanoparticles (NPs) deposited onto the substrate using the electrochemical sol-gel method. Aspects affecting the deposition process were investigated such as the applied potential and its duration. The properties of the deposits with emphasis on the biodegradable NPs within the deposited films were characterized and studied. Another element examined was the loading ability of the NPs. A fluorescent organic molecule was incorporated in the biodegradable NPs as a drug model, to demonstrate loading capability.

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