[en] One of the objectives during designing of enzymatic biofuel cells is to avoid using of electron mediators - substances, which mediate electron transfer between the electrode surface and the active centers of enzymes. During this configuration it is not necessary to separate the cathodic and anodic space by membrane, what facilitates the transport of protons from the anode to the cathode while allowing miniaturization of the entire facility effectively. This work presents a biofuel cell based on direct electron transfer of fructose dehydrogenase and bilirubin oxidase immobilized on an electrode modified by gold nanoparticles. The device showed a maximum power of 27.4 mW · cm^-2 at 0.3 V and the value of the potential (without flowing current) 746 mV. Then for this cell an increase of the maximum performance during operation in a reduced volume of electrolyte was detected in accordance with the expected facilitated metabolism and cartridge diffusion. (authors)

[en] In this study, an assay for detection of the cancer biomarker Thomsen-nouvelle (Tn) antigen on the ELISA plates format was designed and developed. The effects of size and funcional groups of magnetic beads (MBs) on the specific sensitivity of the bioaffinity interaction were studied. Four different MBs were used in the study, i.e. carboxy-modified MBs of 250 nm, 500 nm, 1000 nm and 2800 nm. In order to evaluate which MBs are the best suited for detection of the analyte anti-Tn antibodies, sensitivities of detection (slopes from calibration curves) were calculated. Then, we evaluated the effect of size on the specific sensitivity of detection of anti-Tn antibodies in order to understand the immobilisation process on nanoscale. We obtained a limit of detection (LOD) (0.31 ± 0.01) ng mL^-1 or (2.10 ± 0.04) pM for analyte detection. In addition, the optimal assay configuration was highly selective and enabled reliable detection of the analyte in human serum with a recovery index in the range of 102 -104%. (authors)

[en] In this contribution we will describe application of various forms of nanomaterials applicable in biosensing and bioanalysis. In particular 2D nanomaterials such as graphene oxide or MXene will be presented, but also other types of nanomaterials including hybrid magnetic nanoparticles and magnetic nano/microparticles will be discussed, as well. Another aspect which will be described is to control immobilisation process at the nanoscale by carefully tuned modification of interfaces. Such devices were extensively optimized to resist non-specific interactions allowing to work with complex samples such as human serum from patients having various diseases including cancer i.e. prostate cancer, breast cancer, etc. The clinical potential of magnetic enzyme-linked lectin assays for diagnostics of prostate cancer will be discussed in detail (authors)

[en] Glycans and other saccharide moieties attached to proteins and lipids, or present on the surface of a cell, are actively involved in numerous physiological or pathological processes. Their structural flexibility (that is based on the formation of various kinds of linkages between saccharides) is making glycans superb 'identity cards'. In fact, glycans can form more 'words' or 'codes' (i. e., unique sequences) from the same number of 'letters' (building blocks) than DNA or proteins. Glycans are physicochemically similar and it is not a trivial task to identify their sequence, or-even more challenging-to link a given glycan to a particular physiological or pathological process. Lectins can recognise differences in glycan compositions even in their bound state and therefore are most useful tools in the task to decipher the 'glycocode'. Thus, lectin-based biosensors working in a label-free mode can effectively complement the current weaponry of analytical tools in glycomics. This review gives an introduction into the area of glycomics and then focuses on the design, analytical performance, and practical utility of lectin-based electrochemical label-free biosensors for the detection of isolated glycoproteins or intact cells. (author)

[en] Four different types of nanomaterials will be presented including gold nanoparticles, graphene oxide, MXene (2D nanomaterial) and human serum albumin (HSA, as a biocompatible scaffold) for construction of electrochemical sensors, biosensors and bioanodes of biofuel cells. Gold nanoparticles (AuNPs) were applied for modification of gold electrodes patterned by self-assembled monolayer. Such electrodes were utilised for affinity biosensing using electrochemical impedance spectroscopy (EIS) as a detection platform. AuNPs-modified biosensors (3D configuration) offered much lower limit of detection compared to the biosensor configuration without using AuNPs (2D configuration). Graphene oxide (GO) was successfully applied for modification of electrodes for construction of affinitybased biosensors and for preparation of a bioanode. EIS-based affinity biosensors with immobilised lectins (carbohydrate binding proteins) were successfully utilised for detection of glycoproteins down to aM level (10^-18 M). Protocol of immobilisation of bilirubin oxidase (BOD) on GO affected current density for oxygen reduction significantly from 2.6 μA cm^-2 to 280 μA cm^-2. GO flakes with a tuned density of a negative charge significantly influenced density and orientation of BOD immobilised by a passive physisorption with the highest current density of 597 μA cm^-2. Besides GO we applied in our studies another 2D nanomaterial - Mxene. Using this nanomaterial we were able to detect H₂O₂ down to 0.7 nM with one of the highest sensitivity of H₂O₂ detection observed so far i.e. 596 mA cm^-2 mM-1. The last type of nanomaterial HSA was applied in our studies as a scaffold for immobilisation of small glycan antigen. The glycan biosensor was then applied for detection of an antibody, what is an approach applicable for analysis of glycan autoantibodies, which are considered as biomarkers of various types of cancer. (authors)

[en] MXene was modified by aryldiazonium betaine derivatives terminated either in a sulfo (SB) or a carboxy (CB). Since MXene contains free electrons, betaine derivatives could be grafted to MXene spontaneously. Kinetics of spontaneous grafting of SB and CB towards MXene was electrochemically examined in two different ways and experiments confirmed quicker spontaneous SB grafting compared to CB. Electrochemical methods investigating non-Faradaic and Faradaic redox behaviour with contact angle measurements and secondary ion mass spectrometry confirmed differences in formation and interfacial presentation of betaine layers spontaneously grafted on MXene. Electrochemical grafting by a redox trigger provides denser layer of SB and CB on the interface compared to spontaneous. Electrochemically grafted SB layer offers much lower interfacial resistance and electrochemically active surface area compared to electrochemically grafted CB layer. By adjusting SB/CB ratio in the solution during electrochemical grafting it is possible to effectively tune redox behaviour of MXene modified interface. (authors)

[en] The aim of the work was preparation of thin layers of graphene oxide (GO) electrodes from low-viscosity aqueous GO dispersions by rotary coating and subsequent reduction of prepared GO electrodes by low-temperature diffuse coplanar surface barrier discharge plasma (DCSBD) in hydrogen atmosphere. The positive effect of reducing plasma in rGO electrodes resulted in a decrease in the quantitative representation of oxygen bonds and at the same time a decrease in their electrical surface resistance. (authors)

[en] We describe the preparation and characterization of a glassy carbon electrode modified with a bionanocomposite consisting of a hyaluronic acid, dispersed carbon nanotubes, and electrostatically bound toluidine blue. The electrode was used to detect NADH in the batch and flow-injection mode of operation. The electrode was further modified by immobilizing sorbitol dehydrogenase to result in biosensor for D-sorbitol that displays good operational stability, a sensitivity of 10.6 μA mM^-1 cm^-2, a response time of 16 s, and detection limit in the low micromolar range. The biosensor was successfully applied to off-line monitoring of D-sorbitol during its bioconversion into L-sorbose (a precursor in the synthesis of vitamin C) by Gluconobacter oxydans. The sample assay precision is 2.5% (an average RSD) and the throughput is 65 h^-1 if operated in the flow-injection mode. The validation of this biosensor against a reference HPLC method resulted in a slope of correlation of 1.021 ± 0.001 (R² = 0.99997). (author)