*Article* **"Green" Prussian Blue Analogues as Peroxidase Mimetics for Amperometric Sensing and Biosensing †**

**Galina Z. Gayda 1,\*, Olha M. Demkiv 1,2, Yanna Gurianov 3, Roman Ya. Serkiz 1, Halyna M. Klepach 4, Mykhailo V. Gonchar 1,4 and Marina Nisnevitch 3,\***


**Abstract:** Prussian blue analogs (PBAs) are well-known artificial enzymes with peroxidase (PO)-like activity. PBAs have a high potential for applications in scientific investigations, industry, ecology and medicine. Being stable and both catalytically and electrochemically active, PBAs are promising in the construction of biosensors and biofuel cells. The "green" synthesis of PO-like PBAs using oxidoreductase flavocytochrome *b*2 is described in this study. When immobilized on graphite electrodes (GEs), the obtained green-synthesized PBAs or hexacyanoferrates (gHCFs) of transition and noble metals produced amperometric signals in response to H2O2. HCFs of copper, iron, palladium and other metals were synthesized and characterized by structure, size, catalytic properties and electromediator activities. The gCuHCF, as the most effective PO mimetic with a flower-like micro/nano superstructure, was used as an H2O2-sensitive platform for the development of a glucose oxidase (GO)-based biosensor. The GO/gCuHCF/GE biosensor exhibited high sensitivity (710 A <sup>M</sup>−1m−2), a broad linear range and good selectivity when tested on real samples of fruit juices. We propose that the gCuHCF and other gHCFs synthesized via enzymes may be used as artificial POs in amperometric oxidase-based (bio)sensors.

**Keywords:** artificial enzymes; green synthesis; hexacyanoferrates of transition and noble metals; peroxidase mimetic; amperometric (bio)sensor; glucose oxidase; glucose analysis
