Structural determination of Enzyme-Graphene Nanocomposite Sensor Material.

State-of-the-art ultra-sensitive blood glucose-monitoring biosensors, based on glucose oxidase (GOx) covalently linked to a single layer graphene (SLG), will be a valuable next generation diagnostic tool for personal glycemic level management. We report here our observations of sensor matrix structure obtained using a multi-physics approach towards analysis of small-angle neutron scattering (SANS) on graphene-based biosensor functionalized with GOx under different pH conditions for various hierarchical GOx assemblies within SLG. We developed a methodology to separately extract the average shape of GOx molecules within the hierarchical assemblies. The modeling is able to resolve differences in the average GOx dimer structure and shows that treatment under different pH conditions lead to differences within the GOx at the dimer contact region with SLG. The coupling of different analysis methods and modeling approaches we developed in this study provides a universal approach to obtain detailed structural quantifications, for establishing robust structure-property relationships. This is an essential step to obtain an insight into the structure and function of the GOx-SLG interface for optimizing sensor performance.

Aquaporin-graphene interface: relevance to point-of-care device for renal cell carcinoma and desalination.

The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels essential to the movement of water across the cell membrane, maintaining homeostatic equilibrium. During the passage of water between the extracellular and intracellular sides of the cell, aquaporins act as ultra-sensitive filters. Owing to their hydrophobic nature, aquaporins self-assemble in phospholipids. If a proper choice of lipids is made then the aquaporin biomimetic membrane can be used in the design of an artificial kidney. In combination with graphene, the aquaporin biomimetic membrane finds practical application in desalination and water recycling using mostly Escherichia coli AqpZ. Recently, human aquaporin 1 has emerged as an important biomarker in renal cell carcinoma. At present, the ultra-sensitive sensing of renal cell carcinoma is cumbersome. Hence, we discuss the use of epitopes from monoclonal antibodies as a probe for a point-of-care device for sensing renal cell carcinoma. This device works by immobilizing the antibody on the surface of a single-layer graphene, that is, as a microfluidic device for sensing renal cell carcinoma.

Cross-linked glucose oxidase clusters for biofuel cell anode catalysts.

The efficient localization of increased levels of active enzymes onto conducting scaffolds is important for the development of enzyme-based biofuel cells. Cross-linked enzyme clusters (CEC) of glucose oxidase (GOx) constrained to functionalized carbon nanotubes (CEC-CNTs) were generated in order to evaluate the potential of using CECs for developing GOx-based bioanodes functioning via direct electron transfer from the GOx active site to the CNT scaffold. CEC-CNTs generated from several weight-to-weight ratios of GOx:CNT were examined for comparable catalytic activity to free GOx into the solution, with CEC-CNTs generated from a 100% GOx solution displaying the greatest enzymatic activity. Scanning transmission electron microscopic analysis of CEC-CNTs generated from 100% GOx to CNT (wt/wt) ratios revealed that CEC clusters of ∼78 µm2 localized to the CNT surface. Electrochemical analysis indicates that the enzyme is engaged in direct electron transfer, and biofuel cells generated using GOx CEC-CNT bioanodes were observed to have a peak power density of ∼180 µW cm(-2). These data indicate that the generation of nano-to-micro-sized active enzyme clusters is an attractive option for the design of enzyme-specific biofuel cell powered implantable devices.

In vitro anti-Helicobacter pylori effects of medicinal mushroom extracts, with special emphasis on the Lion's Mane mushroom, Hericium erinaceus (higher Basidiomycetes).

Although the medicinal mushroom Hericium erinaceus is used extensively in traditional Chinese medicine to treat chronic superficial gastritis, the underlining pharmaceutical mechanism is yet to be fully understood. In this study, minimum inhibitory concentration (MIC) values of extracts prepared from the fruiting bodies of 14 mushroom species (H. erinaceus, Ganoderma lucidum, Cordyceps militaris, Pleurotus eryngii, P. ostreatus, Agrocybe aegerita, Lentinus edodes, Agaricus brasiliensis, A. bisporus, Coprinus comatus, Grifola frondosa, Phellinus igniarius, Flammulina velutipes, and Hypsizygus marmoreus) were determined against Helicobacter pylori using laboratory strains of ATCC 43504 and SS1 as well as 9 clinical isolates via an in vitro microplate agar diffusion assay. Ethanol extracts (EEs) of 12 mushrooms inhibited the growth of H. pylori in vitro, with MIC values <3 mg/mL. EEs of H. erinaceus and G. lucidum also inhibited Staphylococcus aureus (MIC 7360;10 mg/mL) but had no effect on the growth of two Escherichia coli test strains (MIC >10 mg/mL). MIC values of ethyl acetate fractions (EAFs) of H. erinaceus against 9 clinical isolates of H. pylori ranged between 62.5 and 250 µg/mL. The bacteriostatic activity of EAFs was found to be concentration-dependant, and the half maximal inhibitory concentration and minimum bactericidal concentration values for H. pylori ATCC 43504 were 73.0 and 200 µg/mL, respectively. The direct inhibitory effect of EEs and EAFs of H. erinaceus against H. pylori could be another pharmaceutical mechanism of medicinal mushrooms-besides the immunomodulating effect of polysaccharides, suggested previously-in the treatment of H. pylori-associated gastrointestinal disorders. Further research to identify the active component(s) is currently undertaking in our laboratory.

Protein-carbon nanotube sensors: single platform integrated micro clinical lab for monitoring blood analytes.

Design of a unique, single-platform, integrated, multichannel sensor based on carbon nanotube (CNT)-protein adducts specific to each one of the major analytes of blood, glucose, cholesterol, triglyceride, and Hb1AC is presented. The concept underlying the sensor, amperometric detection, is applicable to various disease-monitoring strategies. There is an urgent need to enhance the sensitivity of glucometers to <5% level instead of greater than the present 15% standard in these detectors. CNTs enhance the signals derived from the interaction of the enzymes with the different analytes in blood. Fabricated sensors using the new methodology is a point-of-care device that is targeted for home, clinical, and emergency use and can be redesigned for continuous monitoring for critical care patients.

Expression of recombinant proteins in Pichia pastoris.

Pichia pastoris has been used extensively and successfully to express recombinant proteins. In this review, we summarize the elements required for expressing heterologous proteins, and discuss various factors in applying this system for protein expression. These elements include vectors, host strains, heterologous gene integration into the genome, secretion factors, and the glycosylation profile. In particular, we discuss and evaluate the recent progress in optimizing the fermentation process to improve the yield and stability of expressed proteins. Optimization can be achieved by controlling the medium composition, pH, temperature, and dissolved oxygen, as well as by methanol induction and feed mode.

Rational design of thermally stable proteins: relevance to bionanotechnology.

Design of thermally stable proteins is spurred by their applications in bionanotechnology. There are three major issues governing this: first, the upper limit on the temperature at which proteins remain physiologically active and are available for technological applications (answers may emerge from the discovery of new, natural hyperthermophilic enzymes that are active above 125 degrees C or from the selection of mutants of hyperthermophilic enzymes that are more stable); second, the use of hyperthermophilic enzymes as molecular templates to design highly stable enzymes that have high activity at low temperatures; third, the link between rigidity and flexibility to thermostability and activity, respectively. We review progress in these areas.