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In this study, polythiophene copolymers have been used as modifier for electrode surfaces in order to allow the immobilization of active pyrroloquinoline quinone dependent glucose dehydrogenase (PQQ-GDH) and to simultaneously improve the direct electrical connection of the enzyme with the electrode. Polymer films are electrosynthesized in aqueous solution without the need of surfactants onto carbon nanotubes modified gold electrodes from mixtures of 3-thiopheneacetic acid (ThCH2CO2H) and 3-methoxythiophene (ThOCH3) using a potentiostatic pulse method. Polythiophene deposition significantly improves the bioelectrocatalysis of PQQ-GDH: the process starts at − 200 mV vs. Ag/AgCl and allows well-defined glucose detection at 0 V vs. Ag/AgCl with high current density. Several parameters of the electro-polymerization method have been evaluated to maximize the anodic current output after enzyme coupling. The polymer deposited by this new procedure has been morphologically and chemically characterized by different methods (SEM, EDX, FT-IR, UV–Vis, XPS and Raman spectroscopy). The bioelectrocatalytic response towards increasing glucose concentrations exhibits a dynamic range extending from 1 μM to 2 mM. The low applied potential allows to avoid interferences from easily oxidizable substances such as uric acid and ascorbic acid. Short and long-term stability has been evaluated. Finally, the PQQ-GDH electrode has been coupled to a bilirubin oxidase (BOD)- and carbon nanotube-based cathode in order to test its performance as anode of a biofuel cell. The promising results suggest a further investigation of this kind of polymers and, in particular, the study of the interaction with other enzymes in order to employ them in building up biosensors and biofuel cells.

Cities 115, 103211 (2021). doi:10.1016/j.cities.2021.103211, Published by Elsevier Science, Amsterdam [u.a.]

The establishment of a polythiophene-supported electron transfer of PQQ-dependent glucose dehydrogenase (PQQ-GDH) at multiwalled carbon nanotubes is reported. For this purpose, thiol-functionalized MWCNTs are deposited on a gold electrode, which is further modified by on-top electropolymerization of different thiophene monomers. The enzyme is covalently bound to such an electrode by activating the carboxy groups of the polymer. The presence of the polythiophene copolymers allows for electrochemical wiring of PQQ-GDH that can subsequently transfer the electrons from the glucose oxidation to the electrode. Bioelectrocatalysis starts just at −0.2 V vs. Ag/AgCl and the anodic current reaches high values already at 0 V vs. Ag/AgCl. In order to improve the catalytic response, different parameters in the electropolymerization process are evaluated and buffer effects are investigated. The modified electrode surface is characterized by SEM-EDX, FTIR, UV–vis and XPS. The bioelectrocatalytic response towards increasing glucose concentrations is measured at 0 V vs. Ag/AgCl, showing a dynamic range extending from 1 μM to 500 μM.

Efficient direct electron transfer (DET) between cellobiose dehydrogenase from Corynascus thermophilus (CtCDH) and a novel gold electrode platform, obtained by covalent linking of green AuNPs and AgNPs modified with a dithiol self-assembled monolayer, consisting of biphenyl-4,4'-dithiol (BPDT), was presented. The green AuNPs and AgNPs were synthesized using quercetin as reducing agent at room temperature. TEM experiments showed that the AuNPs and AgNPs were circular in shape with an average diameter of 5 and 8nm, respectively. Cyclic voltammetry of CtCDH immobilized onto the AuNPs/BPDT/AuE and the AgNPs/BPDT/AuE electrode platforms were carried out and compared with naked AuE, BPDT/AuE, AuNPs/AuE, and AgNPs/AuE. A pair of well-defined redox waves in neutral pH solution due to efficient DET of CtCDH was present with both MNPs/BPDT/AuE platforms. No DET communication was found with platforms without MNPs linked to BPDT. The apparent heterogeneous electron transfer rate constants (kS) of CtCDH were calculated to be 21.5±0.8s-1 and 10.3±0.7s-1, for the AuNPs/BPDT/AuE and the AgNPs/BPDT/AuE platforms, respectively. The modified electrodes were successively used to develop an eco-friendly biosensor for lactose detection. The CtCDH/AuNPs/BPDT/AuE based biosensor showed the best analytical performances with an excellent stability, a detection limit of 3µM, a linear range between 5 and 400µM and a sensitivity of 27.5±2.5µAcm-2mM-1. Such performances were favorably compared with other lactose biosensors reported in literature. The biosensor was successively tested to quantify lactose content in real milk and cream samples. No significant interference present in the sample matrices was observed.

In this paper we address the problem of structured feature selection in a multi-class classification setting. Our goal is to select groups of features meaningful to all classes simultaneously, and to this purpose we derive a new formulation of Group LASSO - the MC-GrpLASSO - and a solution of the obtained functional based on proximal methods. We then apply the algorithm to a typical multi-class problem - face recognition. On this respect we focus on finding an effective and fast to compute (that is, sparse) representation of faces, detected in low quality videos of unconstrained environments. We start from a classical over-complete representation based on Local Binary Patterns (LBPs), descriptors endowed with a characteristic internal structure that can be preserved by selecting features in groups. We present an extensive experimental analysis on two benchmark datasets, MOBO and Choke Point, and on a more complex set of data acquired in-house over a large temporal span. We compare our results with state-of-the-art approaches and show the superiority of our method in terms of both performances and sparseness of the obtained solution.

High resolution 17O NMR spectra of 17O-labeled t-BuOOH, t-BuOOBu-t, (HMPA)MoO(O2)2 and (L)CrO(O2)2 (with L = HMPA, Py) have been measured. Significant differences were found in the peroxide bond resonances of the chromium with respect to the molybdenum peroxo complex, in that chromium(VI)oxide diperoxide showed two distinct 17O resonance signals, suggesting non-equivalence of the oxygen atoms in the O-O bond; this feature was not present in the spectra of (HMPA)MoO(O2)2. For both peroxometal complexes, no 17O NMR evidence could be found for significant exchange between oxo and peroxo oxygens.