Single-Cell Analysis with Silver-Coated Pipette by Combined SERS and SICM

The study of individual cell processes that occur both on their surface and inside is highly interesting for the development of new medical drugs, cytology and cell technologies. This work presents an original technique for fabricating the silver-coated pipette and its use for the cell analysis by combination with surface-enhanced Raman spectroscopy (SERS) and scanning ion-conducting microscopy (SICM). Unlike the majority of other designs, the pipette opening in our case remains uncovered, which is important for SICM. SERS-active Ag nanoparticles on the pipette surface are formed by vacuum-thermal evaporation followed by annealing. An array of nanoparticles had a diameter on the order of 36 nm and spacing of 12 nm. A two-particle model based on Laplace equations is used to calculate a theoretical enhancement factor (EF). The surface morphology of the samples is investigated by scanning electron microscopy while SICM is used to reveal the surface topography, to evaluate Young's modulus of living cells and to control an injection of the SERS-active pipettes into them. A Raman microscope-spectrometer was used to collect characteristic SERS spectra of cells and cell components. Local Raman spectra were obtained from the cytoplasm and nucleus of the same HEK-293 cancer cell. The EF of the SERS-active pipette was 7 × 105. As a result, we demonstrate utilizing the silver-coated pipette for both the SICM study and the molecular composition analysis of cytoplasm and the nucleus of living cells by SERS. The probe localization in cells is successfully achieved.

A rapid sap-direct reverse transcription-polymerase chain reaction method for detection of dendrobium viroid in Dendrobium plants

Dendrobium viroid (DVd) was first reported in China in 2020, and it is the only viroid known to infect Orchidaceae family plants. In this study, we developed a simple reverse transcription-polymerase chain reaction (RT-PCR) method for the rapid detection of DVd in Dendrobium plants. When extracting the sap template from the leaves, they are first clamped between two layers of plastic film, and the sap is pressed out and collected with a pipette. Using this sap, DVd was detected by dot-blot and RT-PCR methods and, the expected amplicons were confirmed by sequencing analysis. The batch analysis of field samples revealed that this method can be used to detect DVd rapidly. The detection method also reduces cross-contamination between different samples and minimizes false positives. Thus, this sap-direct RT-PCR method allows effective and rapid DVd detection in the study of Orchidaceae plants.

In Situ Nanopore Fabrication and Single-Molecule Sensing with Microscale Liquid Contacts

In this article, we introduce a flexible technique for high-throughput solid-state nanopore analysis of single biomolecules. By confining the electrolyte to a micron-scale liquid meniscus at the tip of a glass micropipette, we enable automation and reuse of a single solid-state membrane chip for measurements with hundreds of distinct nanopores per day. In addition to overcoming important experimental bottlenecks, the microscale liquid contact dramatically reduces device capacitance, which is a key limiting factor to the speed and fidelity of solid-state nanopore sensor recordings.

Novel methodology to determine the accuracy of the OmniPod insulin pump: a key component of the artificial pancreas system

BACKGROUND

This article describes two novel and easy approaches for assessing the accuracy of insulin pumps as implemented within the artificial pancreas system. The approaches are illustrated by data testing the OmniPod Insulin Management System at its lowest delivery volume (0.05 U) and at doses of 0.1, 0.2, 1, and 6U.

METHOD

In method 1, a pipette, digital microscope, and imaging software were used to measure average bolus delivery on a linear scale for multiple volumes. In method 2, a digital microscope and imaging software were used to measure the volume of a spherical bolus of 0.05 U of insulin.

RESULTS

Bench testing results using the two novel methods demonstrated that the OmniPod is extremely accurate, with a relative error ranging from -0.90% to +0.96% for all measured doses (0.05, 0.1, 0.2, 1, and 6 U). In method 1, at target bolus dose of 0.05 U, the mean delivered dose (± standard deviation) was 0.0497 ± 0.003 U, 0.099 ± 0.005 U at 0.1 U, 0.2 ± <1e-5 U at 0.2 U, 1.001 ± 0.018 U at 1 U, and 6.03 ± 0.04 U at 6 U. In method 2, at target bolus dose of 0.5 ml, the mean delivered dose for both OmniPods was 0.505 ± 0.014.

CONCLUSIONS

Both methods confirmed a high degree of accuracy for the OmniPod insulin pump. These techniques can be used to estimate delivery volume in other infusion pumps as well.