Light-driven, bias-free nitrogenase-based bioelectrochemical cell for ammonia generation.

Nitrogen fixation is a key process that sustains life on Earth. Nitrogenase is the sole enzyme capable of fixing nitrogen under ambient conditions. Extensive research efforts have been dedicated to elucidating the enzyme mechanism and its artificial activation through high applied voltage, photochemistry, or strong reducing agents. Harnessing light irradiation to minimize the required external bias can lower the process's high energy investment. Herein, we present the development of photo-bioelectrochemical cells (PBECs) utilizing BiVO4/CoP or CdS/NiO photoanodes for nitrogenase activation toward N2 fixation. The constructed PBEC based on BiVO4/CoP photoanode requires minimal external bias (200 mV) and suppresses O2 generation that allows efficient activation of the nitrogenase enzyme, using glucose as an electron donor. In a second developed PBEC configuration, CdS/NiO photoanode was used, enabling bias-free activation of the nitrogenase-based cathode to produce 100 µM of ammonia at a faradaic efficiency (FE) of 12%. The ammonia production was determined by a commonly used fluorescence probe and further validated using 1H-NMR spectroscopy. The presented PBECs lay the foundation for biotic-abiotic systems to directly activate enzymes toward value-added chemicals by light-driven reactions.

Biotic-abiotic hybrids for bioanalytics and biocatalysis.

The advances in biotic-abiotic interfaced systems open new directions toward bioanalytics and biocatalysis applications. Conjugating the unique electronic and optic properties of nanoelements with the high selectivity and extraordinary catalytic abilities of biotic materials holds great promise to gain superior new features. Herein, we present a wide scope of biotic-abiotic research, with key examples for its utilization in bioanalytics applications as well as in biocatalysis. The described configurations feature methodologies that enable extending the known scientific toolbox to gain synergy. These new nanobiohybrids may contribute to major global challenges, for example, developing alternative energy utilization or new affordable biodiagnostics and therapeutics tools.

An Oxygen-Insensitive biosensor and a biofuel cell device based on FMN l-lactate dehydrogenase.

Lactate sensing has high importance for metabolic disease diagnostics, food spoilage, sports medicine, or the construction of biofuel cell devices. Therefore, continuous lactate sensing devices which enable accurate detection should be developed. Here we present the overexpression and utilization of FMN-lactate dehydrogenase from Saccharomyces cerevisiae for oxygen-insensitive, continuous amperometric lactate biosensing. The developed sensors exhibit a high signal-to-noise ratio, low interference effect, and a wide range of linear responses using both direct and mediated electron transfer configurations. The thionine-based mediated electron transfer configuration was stable for 8 h of continuous activity and two weeks of periodic activity with storage at 4 °C. We further grafted the redox mediators on multiwall carbon nanotubes to lower the redox mediator leaching effect. The developed grafting technique improved the biosensor stability and allowed continuous operation for at least 20 h. Both the mediator-entrapped and the grafted bioanodes were further coupled with a bilirubin oxidase-based biocathode to construct a biofuel cell device. The various biofuel cells have generated a maximal power output of 110 µW/cm2 under atmospheric conditions and 200 µW/cm2 under oxygen saturation.

The Structure of Bilirubin Oxidase from Bacillus pumilus Reveals a Unique Disulfide Bond for Site-Specific Direct Electron Transfer.

Efficient oxygen-reducing biocatalysts are essential for the development of biofuel cells or photo-bioelectrochemical applications. Bilirubin oxidase (BOD) is a promising biocatalyst for oxygen reduction processes at neutral pH and low overpotentials. BOD has been extensively investigated over the last few decades. While the enzyme's internal electron transfer process and methods to establish electrical communication with electrodes have been elucidated, a crystal structure of BOD from bacterial origin has never been determined. Here we present the first crystal structure of BOD from Bacillus pumilus (BpBOD) at 3.5 Å resolution. Overall, BpBOD shows high homology with the fungal enzymes; however, it holds a unique surface-exposed disulfide bond between Cys229 and Cys322 residues. We present methodologies to orient the T1 site towards the electrode by coupling the reduced disulfide bond with maleimide moiety on the electrodes. The developed configurations were further investigated and revealed improved direct electron transfer rates with the electrodes. The work presented here may contribute to the construction of rationally designed bioanodes or biocathode configurations that are based on redox-active enzymes.

Protein-Mediated Biosynthesis of Semiconductor Nanocrystals for Photocatalytic NAD(P)H Regeneration and Chiral Amine Production.

The use of predesigned bioengineered proteins for self-grown nanomaterials is a promising strategy that opens new scientific directions for biotic-abiotic nano-bio hybrid configurations. The unique properties of nanomaterials can alter the original biological paradigm to allow novel metabolic routes or new activation triggers. In this work, we present a synthetic methodology for self-grown cadmium sulfide quantum dots in a 12-mer bioengineered stable protein 1 under ambient conditions. The sized controlled crystalline QDs are characterized and utilized for NADPH regeneration that is in turn used for the activation of the imine reductase enzyme. The presented nano-bio hybrid system enables the production of a single enantiomeric product that is required for the pharmaceutical industry. Our designed system presents superior activity and can continuously operate for at least 22 hrs with 82 % conversion efficiency. The obtained results may lay the foundations for future nano-bio hybrid systems that can operate both in vitro and in vivo.

Tailoring Quantum Dot Sizes for Optimal Photoinduced Catalytic Activation of Nitrogenase.

Many efforts have been directed towards elucidating the nitrogenase structure, its biocatalytic activity, and methods to artificially activate it by external stimuli. Here, we investigated how semiconductor nanoparticles (NPs) with sizes ranging between 2.3-3.5 nm form nano-biohybrids with the nitrogenase enzyme and enable its photoinduced biocatalytic activity. We examined two homogenously synthesized quantum dots (QDs), CdS, CdSe, and two nitrogenase variants, the wild-type and a cysteine-mutated. We show that the cysteine-mutated variant does not enhance the hydrogen generation amounts, as compared with the wild type. Nevertheless, we show that the 2.3 nm-sized CdSe NPs facilitate an eightfold increase compared with larger CdSe NPs. The obtained results were investigated using electrochemical techniques, transmission electron microscopy, and further confirmed by time-resolved spectroscopic measurements, which allow us to determine the electron tranfer rate constant (kET ) of the different configurations.

In vivo and in vitro protein mediated synthesis of palladium nanoparticles for hydrogenation reactions.

We report the biosynthesis of size confined palladium nanoparticles (Pd-NPs). The 2-3 nm size Pd-NPs were grown in 12-mer protein stable protein 1 (SP1), which serves as a template for the NP formation. We further show that by controlling the protein expression levels in the cells we can alter the cells' catalytic activity. The in vivo grown Pd-NPs were utilized in a hydrogenation reaction, converting acetylene feedstock into ethylene and ethane. The presented concept can be further used for a wide range of applications by exploiting the synergetic effect of the biotic elements with the abiotic ones.

Maternal Salvage With Extracorporeal Life Support: Lessons Learned in a Single Center.

The American Heart Association scientific statement on cardiac arrest in pregnancy did not endorse extracorporeal life support for lack of cohort data. We studied all pregnancy and peripartum cases of extracorporeal life support in 1 medical center (n = 11), including collapse due to infection (n = 6, 55%), thromboembolism (n = 3, 27%), and cardiac disease (n = 2, 18%). Half of the cases (n = 5, 45%) involved extracorporeal cardiopulmonary resuscitation. Most mothers survived (n = 7, 64% [95% confidence interval, 32%-88%]). Deaths were attributable to oxygenator blockage (n = 1) and late sepsis (n = 3). The 2 unique clinical challenges were maintenance of high peripartum cardiac outputs and balancing anticoagulation with hemostasis.

[EXTRACORPOREAL MEMBRANE OXYGENATION IN ISRAEL: 6.5 YEARS OF EXPERIENCE AT THE LARGEST ECMO TREATMENT CENTER IN ISRAEL].

AIMS: The primary purpose of the study is to evaluate the characteristics of the population treated with ECMO at Beilinson Hospital, the treatment results and a comparison of results with ECMO centers in the world. The treatment outcomes relative to the experience of the team during the years 2008-2014 were also examined. The secondary purpose of this article is to increase the awareness of the medical staff to ECMO as a treatment option for patients with appropriate indications, where indications have increased in recent years. BACKGROUND: In recent years, there has been a significant increase in extracorporeal life support as a substitute for cardiac function (VA-ECMO) and lung function (VV-ECMO) in light of technological improvements and the experience of the medical teams. The most significant increase in the use of ECMO as a replacement lung function began after the publication of the CESAR study in 2009, which demonstrated a decrease in mortality of patients with acute respiratory distress syndrome treated with ECMO, compared with conservative treatment. Furthermore, during the H1N1 epidemic in 2009-10, a number of observational studies reported good results with the use of ECMO in patients with severe respiratory insufficiency. METHODS: A retrospective gathering of information, during the period August 2008 to December 2014. Results: During this time, a total of 171 patients were connected to ECMO, 128 patients were connected to AV-ECMO and 43 patients were connected to VV-ECMO. The main causes of respiratory failure were pneumonia (mostly viral) and ARDS; 60% of patients with respiratory failure were successfully weaned from ECMO, and 51% in total were released from intensive care; 71% of patients treated with VA-ECMO were successfully weaned, and 58% in total were released from intensive care. During the six years in which the survey was conducted there was an improvement in patient survival. In 2009 only a third of the patients were released from intensive care, while in 2014 over 71% were discharged. DISCUSSION: This study reports for the first time on the morbidity characteristics, type of ECMO used and the results of all patients receiving treatment with ECMO in an intensive care unit at a tertiary hospital in Israel. The number of cases treated with ECMO is on the rise in recent years, both globally and in Israel, with good results. Therefore, this treatment option for patients with severe respiratory and/or cardiac insufficiency should be considered as a therapeutic option in appropriate situations.

Direct innominate artery cannulation for antegrade cerebral perfusion in neonates undergoing arch reconstruction.

BACKGROUND: Antegrade cerebral perfusion (ACP) is performed in neonates either by direct cannulation (DC) or indirect cannulation (IC) of the innominate artery. IC is achieved by a graft sutured to the innominate artery or advancement of a cannula through the ascending aorta into the innominate artery, whereas DC is performed by directly cannulating the innominate artery. These techniques may be limited by technical problems that can compromise perfusion. The purpose of the present study was to evaluate the flow measurements and safety of DC when compared with IC. METHODS: This was a retrospective chart review of consecutive neonates who underwent ACP from January 2007 to December 2010. Patient characteristics, surgical and hemodynamic measurements, and postoperative neurologic findings were recorded. RESULTS: Seventy neonates underwent ACP during the study period (46 using DC and 24 using IC). The groups were similar in age and weight. Operative variables were similar regarding cardiopulmonary bypass (CPB), cross-clamp times, maximal flow at full CPB, minimal temperature, ACP time, flow and flow index, and upper extremity blood pressure and proximal cannula pressure during ACP. There was a significantly higher flow index at full CPB in the DC group (217 ± 40 mL/kg/min versus 190 ± 46 mL/kg/min; p = 0.013), which correlated with higher proximal cannula pressures at full CPB (172 ± 27 mm Hg versus 158 ± 26 mm Hg; p = 0.04). Sixty-two of the 65 survivors (95%) had normal neurologic evaluations on discharge. CONCLUSIONS: ACP using DC is comparable to that using IC, with appropriate pressures in the proximal aortic line at full CPB and adequate upper extremity pressures during ACP, reflecting suitable flows in the cerebral circulation.