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 oxido-reductase flavocytochrome b2 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 electro-mediator 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 M−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.
Highlights
Artificial enzymes are stable and low-cost mimetics of natural enzymes
We reported obtaining green-synthesized PBAs or hexacyanoferrates (gHCFs) of transition metals using the purified yeast enzyme flavocytochrome b2 (Fcb2 ; L-lactate: ferricytochrome c oxidoreductase, EC 1.1.2.3)
Several gHCFs were obtained via Fcb2 from the corresponding salts (Fe, Cu, Pd, Ce, Mn, et al.) and from K4 Fe(CN)6, a product of K3 Fe(CN)6 reduction by L-lactate in the presence of an enzyme (Figure 1)
Summary
Artificial enzymes are stable and low-cost mimetics of natural enzymes. The search for effective novel artificial enzymes, especially nanozymes, and the development of simple methods for their synthesis and characterization, as well as the selection of novel branches for their application, are currently challenging problems in different fields of biotechnology, industry, and medicine [1,2,3,4,5,6,7,8,9].Peroxidase (PO) mimetics are the most frequently investigated artificial enzymes [10,11,12].One of the well-known effective PO-like artificial enzymes is Prussian blue (PB) or iron(III)hexacyanoferrate (FeHCF). PB and its analogs (PBAs) are cheap and easy to synthesize, environmentally friendly, and have potential applications for basic research and industrial purposes [12,13,14,15,16,17,18] in a large variety of fields, in medicine [13,19,20,21,22,23] Despite their multifunctionality, PBAs have complicated compositions, which are largely dependent on the synthesis methods and storage conditions [14,15,16]. Insoluble PB can be described by the formula Fe4 [Fe(CN)6 ]3 , while
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