In Vivo Real-Time Simultaneous Examination of Drug Kinetics at Two Separate Locations Using Boron-Doped Diamond Microelectrodes

Hanawa A., Ogata G., Sawamura S., et al. In Vivo Real-Time Simultaneous Examination of Drug Kinetics at Two Separate Locations Using Boron-Doped Diamond Microelectrodes. Analytical Chemistry 92(20), 13742 (2020); https://doi.org/10.1021/acs.analchem.0c01707.Methylcobalamin, which is used for the clinical treatment of patients with neuropathy, can have an impact on the sensorineural components associated with the cochlea, and it is possible that the auditory threshold in a certain population of patients with deafness may be recovered. Nonetheless, it remains uncertain whether the action site of methylcobalamin is localized inside or outside the cochlea and which cellular or tissue element is targeted by the drug. In the present work, we developed a method to realize in vivo real-time simultaneous examination of the drug kinetics in two separate locations using boron-doped diamond microelectrodes. First, the analytical performance of methylcobalamin was studied and the measurement protocol was optimized in vitro. Then, the optimized protocol was applied to carry out real-time measurements inside the cochlea and the leg muscle in live guinea pigs while systemically administering methylcobalamin. The results showed that the methylcobalamin concentration in the cochlea was below the limit of detection for the microelectrodes or the drug did not reach the cochlea, whereas the compound clearly reached the leg muscle

Redox

The book "Redox" provides vast insight into the oxidation-reduction reactions to its readers. The book consists of three sections that include redox in the coordination compounds, organic compounds and polymerization; redox in electrochemistry; and redox and fish welfare. The first section consists of three chapters that describe the role of redox reactions in several fields such as transition metal chemistry, degradation processes of toxic compounds and dyes in treatment of water and wastewater, the catalysis of oxidation of organic compounds by metal active sites, and synthesis of copolymers. The second section consists of two chapters. The role of redox reactions and reactivity description of compounds are discussed in the second section of the book. The non-aqueous redox flow batteries are described in this section. The third section extensively discusses the redox balance and fish welfare and consists of one chapter

Enzyme-material composites for solar-driven reactions

Using sunlight to drive chemical reactions has long been one of the goals in developing sustainable processes. Previous research has focused on solar fuel production in the form of H2, but this thesis demonstrates that solar-to-chemicals processes can be constructed to produce more complex compounds, using hybrid systems composed of enzymes and inorganic materials. Tetrachloroethene reductive dehalogenase (PceA), an enzyme that catalyzes the conversion of tetrachloroethene (PCE) to trichloroethene (TCE) and subsequently to cis-dichloroethene (cDCE), was shown to accept electrons from both graphite and TiO2 electrodes. Irradiation by UV light onto PceA-adsorbed TiO2 particles led to the selective production of TCE and cDCE, which was not possible without PceA as a catalyst. Ferredoxin-NADP+ reductase (FNR) is a key enzyme in photosynthesis, as it receives energetic electrons from Photosystem I and produces NADPH as an energy carrier for downstream 'Dark' reactions involving CO2 assimilation. This thesis presents the discovery of FNR activity on indium tin oxide (ITO) electrodes which led to direct electrochemical investigation of the properties of FNR, both in the absence and presence of its substrate, NADP+. The FNR-adsorbed electrode, termed 'the electrochemical leaf', rapidly interconverts NADP+/NADPH, and this was coupled to a downstream NADPH-dependent enzyme, thus demonstrating a new approach to cofactor regeneration for enzyme-catalyzed organic synthesis. The NADP+ reduction by FNR was also driven by light using a photoanode made of visible-light responsive semiconductors

Polymers and plastics modified electrodes for biosensors: a review

Polymer materials offer several advantages as supports of biosensing platforms in terms of flexibility, weight, conformability, portability, cost, disposability and scope for integration. The present study reviews the field of electrochemical biosensors fabricated on modified plastics and polymers, focusing the attention, in the first part, on modified conducting polymers to improve sensitivity, selectivity, biocompatibility and mechanical properties, whereas the second part is dedicated to modified “environmentally friendly” polymers to improve the electrical properties. These ecofriendly polymers are divided into three main classes: bioplastics made from natural sources, biodegradable plastics made from traditional petrochemicals and eco/recycled plastics, which are made from recycled plastic materials rather than from raw petrochemicals. Finally, flexible and wearable lab-on-a-chip (LOC) biosensing devices, based on plastic supports, are also discussed. This review is timely due to the significant advances achieved over the last few years in the area of electrochemical biosensors based on modified polymers and aims to direct the readers to emerging trends in this field.Peer ReviewedPostprint (published version

Hapniku elektroredutseerumine süsiniknanomaterjalidel põhinevatel katalüsaatoritel

Väitekirja eletkrooniline versioon ei sisalda publikatsioone.Doktoritöös uuriti hapniku elektrokeemilist redutseerumist erinevatel süsiniknanomaterjalidel. Süsinikmaterjalide pinda modifitseeriti ka raud- ja koobaltftalotsüaniinide ning -porfüriinidega ja uuriti nende elektrokatalüütilisi omadusi. Hapniku elektroredutseerumist uuriti happes töödeldud ning töötlemata süsiniknanotorudega modifitseeritud klaassüsinikelektroodidel 0,5 M H2SO4 lahuses. Tulemused näitasid, et süsiniknanotorude hapetes töötlemine omab materjali elektrokatalüütilistele omadustele märkimisväärset efekti ning nanotorude sünteesi käigus neisse jäävad metallide jäägid määravad paljuski nende materjalide elektrokatalüütilise aktiivsuse hapniku redutseerumisel happelises keskkonnas. Hapniku redutseerumise ekperimendid mitmeseinaliste ja kaheseinaliste süsiniknanotorudega näitasid mõlemat tüüpi nanotorude kõrget elektrokatalüütilist aktiivsust leeliselises keskkonnas. Uuriti hapniku elektrokeemilise redutseerumise pH-sõltuvust ja pindaktiivsete ainete põhjustatud efekti. Mitmeseinaliste süsiniknanotorudega modifitseeritud elektroodidel saadud hapniku redutseerumise pH-sõltuvus sarnaneb kvalitatiivselt poleeritud klaassüsinikelektroodiga saadud andmetele. Mõõtmistulemuste alusel võib väita ka seda, et pindaktiivsete ainete mõju hapniku elektrokeemilisele redutseerumisele on ilmne. Erinevate süsiniknanomaterjalidega modifitseeritud elektroodide hapniku redutseerumise uuringud näitasid, et kõik kasutatud süsinikmaterjalid omasid leeliselistes lahustes suurt katalüütilist aktiivsust. Töö ühe osana valmistati süsiniknanotorude ja metalloftalotsüaniinide ning metalloporfüriinide abil madalatemperatuurilise kütuseelemendi katalüsaatormaterjale. Leiti, et 800 °C juures pürolüüsitud katalüsaator näitab hapniku elektroredutseerumisel kõrgeimat aktiivsust. Lisaks viidi läbi ka katalüsaatormaterjalide uurimine leeliselises OH− ioonvahetusmembraaniga kütuseelemendis. Koobaltftalotsüaniin/süsiniknanotorud katalüsaatori maksimaalne võimsustihedus oli sarnane 20%-lisele Pt/C katalüsaatorile. Porfüriinid ja ftalotsüaniinid seondati redutseeritud grafeenoksiidi pinnale füüsikalise adsorptsiooni meetodil. Elektrokeemilised mõõtmised näitasid grafeenil põhinevate katalüsaatorite suurepäraseid katalüütilisi omadusi hapniku redutseerumisel leeliselises keskkonnas.The electrochemical reduction of oxygen on different nanocarbons and nanocarbon supported metallophthalocyanines and metalloporphyrins has been investigated using the rotating disk electrode (RDE) method. The oxygen reduction reaction (ORR) was studied on carbon nanotubes purified in different acids. The RDE results showed that the acid treatment of multi-walled carbon nanotubes (MWCNTs) has strong effect on the electrocatalytic activity for ORR in acid solution and clearly demonstrated the effect of catalyst impurities remained in CNTs on the kinetics of the ORR. MWCNT and double-walled carbon nanotube (DWCNT) modified electrodes were investigated as catalysts for ORR in alkaline media. The results showed that both MWCNTs and DWCNTs possess excellent electrocatalytic activity towards the ORR in alkaline solution. The pH-dependence of the ORR and the effect of surfactants on this reaction was studied using MWCNT modified glassy carbon (GC) electrodes. The pH dependence of the ORR on MWCNT-modified electrodes follows the same trend as that of bare GC. The effect of surfactants on the reduction of O2 on MWCNT/GC electrodes was evident. The electroreduction of oxygen has been studied on different carbon nanomaterials. The results obtained in this part of research indicate that these nanocarbon materials are highly active for the reduction of oxygen in alkaline solution and this activity might be caused by native quinone-type groups on their surface. Metallophthalocyanines and metalloporphyrins were studied as non-noble metal electrocatalysts for ORR in both acid and alkaline media. It was found that metal porphyrin and phthalocyanine-based electrodes heat-treated at 800 °C yielded the highest electrocatalytic activity. Metallophthalocyanine/MWCNT catalysts were also evaluated in anion-exchange membrane fuel cell. The fuel cell performance of the membrane-electrode assemblies with Co phthalocyanine was found to be similar to the commercial Pt/C catalyst. Finally, the reduced graphene oxide (rGO) nanosheets as advanced electrocatalyst supports were prepared. Metallophthalocyanines and metalloporphyrins modified rGO exhibited excellent electrocatalytic properties for ORR in alkaline media

Electrochemical Studies of Electron Transfer Proteins and Electroactive Biofilms

Bioelectrochemistry has been recognized as a very important technique to get relevant thermodynamic and kinetic information on diverse complex biological systems. From the determination of redox potentials of metallic centers in small electron carrier proteins to the resolution of more complex mechanisms in highly organised enzymes, and even whole bacteria systems, the application of dynamic electrochemical techniques has proved to be a powerful tool that has allowed to get deeper in the understanding of such systems. In the present thesis electrochemical techniques were used to study diverse biochemical systems. Different approaches have been used, namely the classic bulk systems in which the reactive species are in solution and immobilised systems where proteins are physically constrained at the electrode surface. Within these, also alternative methods were used, as membrane electrodes and physical adsorption of the biological material. Several systems of different complexity were object of study. Simple Enzymes Small non-hemic proteins, essentially related to electron transfer processes, with iron-sulfur centers, as desulforedoxin and other related iron-sulfur proteins, associated with oxidative stress protection, namely superoxide reductases, were investigated by cyclic and square wave voltammetry; its redox potentials and pH dependence were determined. Complex Enzymes and Catalytic Systems Nitrogen Cycle Enzymes Enzymes taking part in the nitrogen cycle were studied, namely the periplasmic nitrate reductase isolated from Desulfovibrio desulfuricans ATCC 27774 and nitric oxide reductase purifed from Pseudomonas nautica 617. The first one, responsible the nitrate reduction to nitrite, is the only known monomeric nitrate reductase biding an iron-sulfur center and a molybdopterin co-factor. In this work it was possible, for the first time, to observe the individual metal centers voltammetric features. The electrocatalytic activity was also evaluated. The second enzyme, nitric oxide reductase, promotes the two electrons reduction of NO to N2O. In this unique work it was possible to obtain data from a nitric oxide reductase resulting from direct electron transfer assays, accomplished by cyclic voltammetry. The demonstration of the catalytic activity towards the oxygen reduction was achieved and the reduction and catalysis of NO was also observed by direct electrochemistry. The pH dependence of the catalytic center redox process was evaluated and it was possible to show that the immobilized enzyme retained its native properties. Production and Consumption of Hydrogen Hydrogenase (Hase), isolated from Desulfovibrio gigas (Dg), is a multicenter enzyme that catalyses the interconversion between H2 and H+, and that is involved in the dissimilatory sulphate reduction pathway. In this work, the direct electrochemistry of the Dg Hase, in bulk solution and also immobilised by adsorption, in turnover and non-turnover conditions was studied. For the first time the redox features of the enzyme metallic centers in non-catalytic conditions and without the addition of any of the known enzyme inhibitors were attained. Besides, it was possible to tune the activation and inactivation of the enzyme by dynamic potential control. Approach to in vivo systems Finally, the electrochemical behaviour of biofilms formed from pure cultures of sulphate reducing bacteria, namely Desulfovibrio desulfuricans ATCC 27774 was studied. The response of the biofilm on the electrodes was evaluated by the ratio of current obtained in the presence/absence of the biofilm and its stability in time. For the first time it was possible to observe that pure culture biofilms of sulphate reducing bacteria are electroactive