Search Results (5)

Amperometric biosensors (ABSs) and enzymatic biofuel cells (BFCs) share several fundamental principles in their functionality, despite serving different primary purposes. Both devices rely on biorecognition, redox reactions, electron transfer (ET), and advanced electrode materials, including innovative nanomaterials (NMs). ABSs and BFCs, utilizing microbial oxidoreductases in combination with electroactive NMs, are both efficient and cost-effective. In the current study, several laboratory prototypes of BFCs have been developed with bioanodes based on yeast flavocytochrome b₂ (Fcb₂) and alcohol oxidase (AO), and a cathode based on fungal laccase. For the first time, BFCs have been developed featuring anodes based on Fcb₂ co-immobilized with redox NMs on a glassy carbon electrode (GCE), and cathode-utilizing laccase combined with gold–cerium–platinum nanoparticles (nAuCePt). The most effective lactate BFC, which contains gold–hexacyanoferrate (AuHCF), exhibited a specific power density of 1.8 µW/cm². A series of BFCs were developed with an AO-containing anode and a laccase/nAuCePt/GCE cathode. The optimal configuration featured a bioanode architecture of AO/nCoPtCu/GCE, achieving a specific power density of 3.2 µW/cm². The constructed BFCs were tested using lactate-containing food product samples as fuels. Full article

Artificial enzymes or nanozymes (NZs) are gaining significant attention in biotechnology due to their stability and cost-effectiveness. NZs can offer several advantages over natural enzymes, such as enhanced stability under harsh conditions, longer shelf life, and reduced production costs. The booming interest in NZs is likely to continue as their potential applications expand. In our previous studies, we reported the “green” synthesis of copper hexacyanoferrate (gCuHCF) using the oxidoreductase flavocytochrome b₂ (Fcb₂). Organic–inorganic micro-nanoparticles were characterized in detail, including their structure, composition, catalytic activity, and electron-mediator properties. An SEM analysis revealed that gCuHCF possesses a flower-like structure well-suited for concentrating and stabilizing Fcb₂. As an effective peroxidase (PO) mimic, gCuHCF has been successfully employed for H₂O₂ detection in amperometric sensors and in several oxidase-based biosensors. In the current study, we demonstrated the uniqueness of gCuHCF that lies in its multifunctionality, serving as a PO mimic, a chemosensor for ammonium ions, a biosensor for L-lactate, and exhibiting perovskite-like properties. This exceptional ability of gCuHCF to enhance fluorescence under blue light irradiation is being reported for the first time. Using gCuHCF as a PO-like NZ, novel oxidase-based sensors were developed, including an optical biosensor for L-arginine analysis and electrochemical biosensors for methanol and glycerol determination. Thus, gCuHCF, synthesized via Fcb₂, presents a promising platform for the development of amperometric and optical biosensors, bioreactors, biofuel cells, solar cells, and other advanced devices. The innovative approach of utilizing biocatalysts for nanoparticle synthesis highlights a groundbreaking direction in materials science and biotechnology. Full article

We report the development of amperometric biosensors (ABSs) employing flavocytochrome b₂ (Fcb₂) coupled with nanoparticles (NPs) of noble metals on graphite electrode (GE) surfaces. Each NPs/GE configuration was evaluated for its ability to decompose hydrogen peroxide (H₂O₂), mimicking peroxidase (PO) activity. The most effective nanoPO (nPO) was selected for developing ABSs targeting L-lactate. Consequently, several Fcb₂/nPO-based ABSs with enhanced sensitivity to L-lactate were developed, demonstrating mediated ET between Fcb₂ and the GE surface. The positive effect of noble metal NPs on Fcb₂-based sensor sensitivity may be explained by the synergy between their dual roles as both PO mimetics and electron transfer mediators. Furthermore, our findings provide preliminary data that may prompt a re-evaluation of the mechanism of L-lactate oxidation in Fcb₂-mediated catalysis. Previously, it was believed that L-lactate oxidation via Fcb₂ catalysis did not produce H₂O₂, unlike catalysis via L-lactate oxidase. Our initial research revealed that the inclusion of nPO in Fcb₂-based ABSs significantly increased their sensitivity. Employing other PO mimetics in ABSs for L-lactate yielded similar results, reinforcing our hypothesis that trace amounts of H₂O₂ may be generated as a transient intermediate in this reaction. The presence of nPO enhances the L-lactate oxidation rate through H₂O₂ utilization, leading to signal amplification and heightened bioelectrode sensitivity. The proposed ABSs have been successfully tested on blood serum and fermented food samples, showing their promise for L-lactate monitoring in medicine and the food industry. Full article

L-Lactate is an indicator of food quality, so its monitoring is essential. Enzymes of L-Lactate metabolism are promising tools for this aim. We describe here some highly sensitive biosensors for L-Lactate determination which were developed using flavocytochrome b₂ (Fcb₂) as a bio-recognition element, and electroactive nanoparticles (NPs) for enzyme immobilization. The enzyme was isolated from cells of the thermotolerant yeast Ogataea polymorpha. The possibility of direct electron transfer from the reduced form of Fcb₂ to graphite electrodes has been confirmed, and the amplification of the electrochemical communication between the immobilized Fcb₂ and the electrode surface was demonstrated to be achieved using redox nanomediators, both bound and freely diffusing. The fabricated biosensors exhibited high sensitivity (up to 1436 A·M⁻¹·m⁻²), fast responses, and low limits of detection. One of the most effective biosensors, which contained co-immobilized Fcb₂ and the hexacyanoferrate of gold, having a sensitivity of 253 A·M⁻¹·m⁻² without freely diffusing redox mediators, was used for L-Lactate analysis in samples of yogurts. A high correlation was observed between the values of analyte content determined using the biosensor and referenced enzymatic-chemical photometric methods. The developed biosensors based on Fcb₂-mediated electroactive nanoparticles can be promising for applications in laboratories of food control. Full article

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. Full article