Microgrippers to handle Organoids and pancreatic Islets for Precision Measurements of biological Function

The model of the cultured single cell is considered insufficient to explain the physiological regulation taking place at the organ level. The same is true for the prediction of drug action at the organ level or at the level of the intact organism. For these reasons 3D cell culture models are in increasing demand. It is thus necessary to develop the instruments to handle such cell aggregates and organoids in a controlled, precise and gentle manner. Here, a microgripper is presented which is able to work in aqueous solutions and which is compatible with electrophysiological recordings of the cells immobilized by it. It was successfully employed to position isolated pancreatic islets and a 3D cell culture model of insulin-secreting cells, the so-called MIN6-pseudoislet. As required it was possible to measure the membrane potential of cells within these aggregates without any interference from the microgripper

A Disposable Pneumatic Microgripper for Cell Manipulation with Image-Based Force Sensing

A new design for a single-use disposable pneumatic microgripper is presented in this paper. It enables very cost-eective batch microfabrication in SU-8 with a single lithography mask by shifting manufacturing complexity into reusable components. An optically readable force sensor with potential to be used in a feedback loop has been integrated in order to enable gripping with a controlled force. The sensors are first examined separately from the gripper and exhibit good linearity. The gripper function utilizes the disposable gripper element together with a reusable gripper fixture. During experiments, the pneumatically actuated microgripper can vary the gripping force within a range of a few mN (up to 5.7 mN was observed). This microgripper is planned to be used in a liquid environment for gripping larger aggregates of cells in combination with the patch clamp technique. This approach will allow Langerhans islets suspended in an electrolyte solution to be grasped and held during electrophysiological measurements without cell damage

Overview of 3D Micro- and Nanocoordinate Metrology at PTB

Improved metrological capabilities for three-dimensional (3D) measurements of various complex micro- and nanoparts are increasingly in demand. This paper gives an overview of the research activities carried out by the Physikalisch-Technische Bundesanstalt (PTB), the national metrology institute of Germany, to meet this demand. Examples of recent research advances in the development of instrumentation and calibration standards are presented. An ultra-precision nanopositioning and nanomeasuring machine (NMM) has been upgraded with regard to its mirror corner, interferometers and angle sensors, as well as its weight compensation, its electronic controller, its vibration damping stage and its instrument chamber. Its positioning noise has been greatly reduced, e.g., from 1σ = 0.52 nm to 1σ = 0.13 nm for the z-axis. The well-known tactile-optical fibre probe has been further improved with regard to its 3D measurement capability, isotropic probing stiffness and dual-sphere probing styli. A 3D atomic force microscope (AFM) and assembled cantilever probes (ACPs) have been developed which allow full 3D measurements of smaller features with sizes from a few micrometres down to tens of nanometres. In addition, several measurement standards for force, geometry, contour and microgear measurements have been introduced. A type of geometry calibration artefact, referred to as the “3D Aztec artefact”, has been developed which applies wet-etched micro-pyramidal marks for defining reference coordinates in 3D space. Compared to conventional calibration artefacts, it has advantages such as a good surface quality, a well-defined geometry and cost-effective manufacturing. A task-specific micro-contour calibration standard has been further developed for ensuring the traceability of, e.g., high-precision optical measurements at microgeometries. A workpiece-like microgear standard embodying different gear geometries (modules ranging from 0.1 mm to 1 mm) has also been developed at the Physikalisch-Technische Bundesanstalt

An Immersible Microgripper for Pancreatic Islet and Organoid Research

To improve the predictive value of in vitro experimentation, the use of 3D cell culture models, or organoids, is becoming increasingly popular. However, the current equipment of life science laboratories has been developed to deal with cell monolayers or cell suspensions. To handle 3D cell aggregates and organoids in a well-controlled manner, without causing structural damage or disturbing the function of interest, new instrumentation is needed. In particular, the precise and stable positioning in a cell bath with flow rates sufficient to characterize the kinetic responses to physiological or pharmacological stimuli can be a demanding task. Here, we present data that demonstrate that microgrippers are well suited to this task. The current version is able to work in aqueous solutions and was shown to position isolated pancreatic islets and 3D aggregates of insulin-secreting MIN6-cells. A stable hold required a gripping force of less than 30 μN and did not affect the cellular integrity. It was maintained even with high flow rates of the bath perfusion, and it was precise enough to permit the simultaneous microfluorimetric measurements and membrane potential measurements of the single cells within the islet through the use of patch-clamp electrodes

A new test specimen for the determination of the field of view of small‐area X‐ray photoelectron spectrometers

Small-area/spot photoelectron spectroscopy (SAXPS) is a powerful tool for the investigation of small surface features like microstructures of electronic devices, sensors or other functional surfaces, and so forth. For evaluating the quality of such microstructures, it is often crucial to know whether a small signal in a spectrum is an unwanted contamination of the field of view (FoV), defined by the instrument settings, or it originated from outside. To address this issue, the d80/20 parameter of a line scan across a chemical edge is often used. However, the typical d80/20 parameter does not give information on contributions from the long tails of the X-ray beam intensity distribution or the electron-optical system as defined by apertures. In the VAMAS TWA2 A22 project “Applying planar, patterned, multi-metallic samples to assess the impact of analysis area in surface-chemical analysis,” new test specimen was developed and tested. The here presented testing material consists of a silicon wafer substrate with an Au-film and embedded Cr circular and square spots with decreasing dimensions from 200 μm down to 5 μm. The spot sizes are traceable to the length unit due to size measurements with a metrological SEM. For the evaluation of the FoV, we determined the Au4f intensities measured with the center of the FoV aligned with the center of the spot and normalized to the Au4f intensity determined on the Au-film. With this test specimen, it was possible to characterize, as an example, the FoV of a Kratos AXIS Ultra DLD XPS instrument.ISSN:0142-2421ISSN:1096-991

Modulation of cortical motor networks following primed theta burst transcranial magnetic stimulation

To investigate whether priming stimulation influences the responses of intracortical inhibitory and facilitatory motor circuits to a subsequent plasticity-inducing inhibitory theta burst TMS paradigm. Using standard transcranial magnetic stimulation (TMS) procedures, MEP amplitude, short-interval intracortical inhibition (SICI), and short-interval intracortical facilitation (SICF) were assessed at baseline and 5, 20 and 30 min following continuous theta burst stimulation (cTBS), intermittent TBS (iTBS), and iTBS-primed cTBS. SICI was assessed using paired-pulse TMS at inter-stimulus intervals (ISI) of 3 ms (SICI(3)) and the latency corresponding to the latency at which SICF was minimal in each individual. SICF was assessed at ISIs corresponding to Peak 1, Trough 1, Peak 2, and Peak 3 of each individual's SICF curve. When applied alone cTBS inhibited and iTBS facilitated MEP amplitudes. iTBS-primed cTBS resulted in greater MEP inhibition than cTBS alone. There were no changes in SICF and only marginal changes in SICI following any intervention. Synapses mediating MEP generation undergo modification following iTBS-primed cTBS, possibly through mechanisms related to metaplasticity or synaptic depotentiation. A lack of substantial changes in SICI and SICF under all experimental conditions suggests that the tested rTMS paradigms may be non-optimal for inducing robust modulation of the neural elements mediating SICI and SICF across subjects. Priming stimulation may provide an approach which facilitate neuroplastic change within the human motor cortex at least in circuits responsible for MEP generation.Sebastian H. Doeltgen, Michael C. Riddin