We report a simple label-free electrochemical method of detecting low concentrations of botulinum neurotoxin type E light chain (BoNT/E LC) based on its peptide cleavage activity. Dual-mode cyclic voltammetry was employed to observe changes in the redox signal of ferri-/ferro-cyanide on interdigitated microelectrodes, whose surfaces were covered by peptides designed from synaptosomal-associated protein 25 to be cleaved by BoNT/E LC. With the introduction of BoNT/E LC, the redox signal showed a time-dependent increase due to cleavage of the immobilized peptide molecules. In addition to the increased redox signal intensity, its time-dependence can be considered as a strong evidence of BoNT/E sensing, since the time-dependent increase can only result from the enzymatic activity of BoNT/E LC. Using this method, BoNT/E LC, at concentrations as low as 5 pg/ml, was readily measurable with only an hour of incubation.
We successfully demonstrated
the improvement and stabilization
of the electrical properties of a graphene field effect transistor
by fabricating a sandwiched amorphous boron nitride (a-BN)/graphene
(Gr)/a-BN using a directly grown a-BN film. The a-BN film was grown via low-pressure chemical vapor deposition (LPCVD) at a
low growth temperature of 250 °C and applied as a protection
layer in the sandwiched structure. Both structural and chemical states
of the as-grown a-BN were verified by various spectroscopic and microscopic
analyses. We analyzed the Raman spectra of Gr/SiO2 and
a-BN/Gr/a-BN structures to determine the stability of the device under
exposure to ambient air. Following exposure, the intensity of the
2D/G-peak ratio of Gr/SiO2 decreased and the position of
the G and 2D peaks red-shifted due to the degradation of graphene.
In contrast, the peak position of encapsulated graphene is almost
unchanged. We also confirmed that the mobility of a-BN/Gr/a-BN structure
is 17,941 cm2/Vs. This synthetic strategy could provide
a facile way to synthesize uniform a-BN film for encapsulating various
van der Waals materials, which is beneficial for future applications
in nanoelectronics.
Liver transplantation still carries considerable risks even if the improvements in surgical and anesthetic techniques lead to a significant decrease in complications. Cardiac arrest during liver transplantation occurs most frequently immediately after the reperfusion due to the influx of hyperkalemic blood from donor liver into a recipient. Cardiac arrest caused by hyperkalemia shows a favorable response to cardiopulmonary resuscitation; however, prolonged cardiopulmonary resuscitation can damage the transplanted liver as well as brain and kidney resulting increased mortality and morbidity rates. The authors experienced repeating cardiac arrest and one hour cardiopulmonary resuscitation due to severe hyperkalemia (8.8 mmol/L) just after the reperfusion during cadaveric liver transplantation. Consciousness was returned 6 hours after operation and vital signs was stable. Transplanted liver well functioned although postoperative course was complicated with acute renal failure, pneumonia and pleural effusion. The patient recovered and discharged 97 days after operation.
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