Highly Sensitive Amperometric Sensor Based on Laccase-Mimicking Metal-Based Hybrid Nanozymes for Adrenaline Analysis in Pharmaceuticals

Nanozymes are nanomaterials which exhibit artificial enzymatic activities and are considered as alternatives to natural enzymes. They are characterized by good catalytic activity and high stability, as well as ease and low cost of preparation. In this study, the mimetics of laccase or “nanolaccases” (NLacs) were synthesized by a simple method of chemical reduction of transition metal salts. The NLacs were tested for their catalytic activity in solution and on the electrode surface. The most effective NLacs, namely nAuCePt and nPtFe, were found to possess excellent laccase-like activities capable of oxidizing the endocrine hormone adrenaline (AD). These NLacs were characterized in detail and used for the development of amperometric sensors for AD determination. The amperometric sensors containing the best NLacs, as well as a natural fungal laccase, were constructed. The most effective nAuCePt-containing sensor had good specificity in relation to AD and improved analytical characteristics. It possessed a 384-fold higher sensitivity than adrenaline (230,137 A·M−1·m−2), a 64-fold lower limit of detection (0.025 µM), and a broader linear range (0.085–45 µM) in comparison with the sensor based on natural laccase. The constructed nAuCePt-containing sensor was successfully used for AD analysis in pharmaceutical formulation.

Exocytotic vesicle fusion classification for early disease diagnosis using a mobile GPU microsystem

This work addresses monitoring vesicle fusions occurring during the exocytosis process, which is the main way of intercellular communication. Certain vesicle behaviors may also indicate certain precancerous conditions in cells. For this purpose we designed a system able to detect two main types of exocytosis: a full fusion and a kiss-and-run fusion, based on data from multiple amperometric sensors at once. It uses many instances of small perceptron neural networks in a massively parallel manner and runs on Jetson TX2 platform, which uses a GPU for parallel processing. Based on performed benchmarking, approximately 140,000 sensors can be processed in real time within the sensor sampling period equal to 10 ms and an accuracy of 99$$\%$$ % . The work includes an analysis of the system performance with varying neural network sizes, input data sizes, and sampling periods of fusion signals.

Sulfur Dioxide Sensors

Recent progress on the sensing and monitoring of sulfur dioxide in the environment is presented. The sensing materials covered include potentiometric gas sensors, amperometric sensors, optical sensors involving colorimetric and fluorescence changes, sensors based on ionic liquids, semiconducting metal-oxide sensors, photoacoustic detectors and biosensors.

Recent developments in voltammetric and amperometric sensors for cysteine detection

This review article aims to provide an overview of the recent advances in the voltammetric and amperometric sensing of cysteine (Cys).

Amperometric Biosensor Based on Coimmobilization of Multiwalled Carbon Nanotubes and Horseradish Peroxidase-Gold Nanocluster Bioconjugates for Detecting H2O2

An enzyme-based amperometric biosensor was fabricated for detecting hydrogen peroxide (H2O2). Horseradish peroxidase (HRP) was modified using functionalized fluorescent gold nanoclusters (AuNCs) via biomineralization. HRP-AuNCs were successfully immobilized on multiwalled carbon nanotube- (MWCNT-) coated carbon fiber ultramicroelectrodes (CFUMEs). The AuNCs, which act as molecular electric wires, effectively promote the electron transfer between the enzyme active center and the electrode. Additionally, the HRP conjugated with the AuNCs retains its biological activity, which enables the catalytic reaction of H2O2. The HRP-AuNCs/MWCNTs/CFUMEs have been proven as excellent amperometric sensors for H2O2. The sensitivity of the H2O2 biosensor is 3.0×10−4 A/M, and the detection limit is estimated to be 443 nM. Furthermore, the biosensor exhibited long-term stability and good reproducibility. Moreover, the biosensor has been tested by determining the H2O2 concentration in calf serum samples.

Atomic oxygen number densities in the mesosphere–lower thermosphere region measured by solid electrolyte sensors on WADIS-2

Absolute profiles of atomic oxygen number densities with high vertical resolution have been determined in the mesosphere–lower thermosphere (MLT) region from in situ measurements by several rocket-borne solid electrolyte sensors. The amperometric sensors were operated in both controlled and uncontrolled modes and with various orientations on the foredeck and aft deck of the payload. Calibration was based on mass spectrometry in a molecular beam containing atomic oxygen produced in a microwave discharge. The sensor signal is proportional to the number flux onto the electrodes, and the mass flow rate in the molecular beam was additionally measured to derive this quantity from the spectrometer reading. Numerical simulations provided aerodynamic correction factors to derive the atmospheric number density of atomic oxygen from the sensor data. The flight results indicate a preferable orientation of the electrode surface perpendicular to the rocket axis. While unstable during the upleg, the density profiles measured by these sensors show an excellent agreement with the atmospheric models and photometer results during the downleg of the trajectory. The high spatial resolution of the measurements allows for the identification of small-scale variations in the atomic oxygen concentration.