Coupling of Semiconductor Nanowires with Neurons and Their Interfacial Structure

We report on the compatibility of various nanowires with hippocampal neurons and the structural study of the neuron–nanowire interface. Si, Ge, SiGe, and GaN nanowires are compatible with hippocampal neurons due to their native oxide, but ZnO nanowires are toxic to neuron due to a release of Zn ion. The interfaces of fixed Si nanowire and hippocampal neuron, cross-sectional samples, were prepared by focused ion beam and observed by transmission electron microscopy. The results showed that the processes of neuron were adhered well on the nanowire without cleft

Capturing complex tumour biology in vitro: Histological and molecular characterisation of precision cut slices

Precision-cut slices of in vivo tumours permit interrogation in vitro of heterogeneous cells from solid tumours together with their native microenvironment. They offer a low throughput but high content in vitro experimental platform. Using mouse models as surrogates for three common human solid tumours, we describe a standardised workflow for systematic comparison of tumour slice cultivation methods and a tissue microarray-based method to archive them. Cultivated slices were compared to their in vivo source tissue using immunohistochemical and transcriptional biomarkers, particularly of cellular stress. Mechanical slicing induced minimal stress. Cultivation of tumour slices required organotypic support materials and atmospheric oxygen for maintenance of integrity and was associated with significant temporal and loco-regional changes in protein expression, for example HIF-1α. We recommend adherence to the robust workflow described, with recognition of temporal-spatial changes in protein expression before interrogation of tumour slices by pharmacological or other means

Nanoscale surface topography reshapes neuronal growth in culture

International audienceNeurons are sensitive to topographical cues provided either by in vivo or in vitro environments on the micrometric scale. We have explored the role of randomly distributed silicon nanopillars on primary hippocampal neurite elongation and axonal differentiation. We observed that neurons adhere on the upper part of nanopillars with a typical distance between adhesion points of about 500 nm. These neurons produce fewer neurites, elongate faster, and differentiate an axon earlier than those grown on flat silicon surfaces. Moreover, when confronted with a differential surface topography, neurons specify an axon preferentially on nanopillars. As a whole, these results highlight the influence of the physical environment in many aspects of neuronal growth

Mapping the Complex Morphology of Cell Interactions with Nanowire Substrates Using FIB-SEM

Using high resolution focused ion beam scanning electron microscopy (FIB-SEM) we study the details of cell-nanostructure interactions using serial block face imaging. 3T3 Fibroblast cellular monolayers are cultured on flat glass as a control surface and on two types of nanostructured scaffold substrates made from silicon black (Nanograss) with low- and high nanowire density. After culturing for 72 hours the cells were fixed, heavy metal stained, embedded in resin, and processed with FIB-SEM block face imaging without removing the substrate. The sample preparation procedure, image acquisition and image post-processing were specifically optimised for cellular monolayers cultured on nanostructured substrates. Cells display a wide range of interactions with the nanostructures depending on the surface morphology, but also greatly varying from one cell to another on the same substrate, illustrating a wide phenotypic variability. Depending on the substrate and cell, we observe that cells could for instance: break the nanowires and engulf them, flatten the nanowires or simply reside on top of them. Given the complexity of interactions, we have categorised our observations and created an overview map. The results demonstrate that detailed nanoscale resolution images are required to begin understanding the wide variety of individual cells' interactions with a structured substrate. The map will provide a framework for light microscopy studies of such interactions indicating what modes of interactions must be considered

Comparison of Two Impulse Calibrators with a High Resolution Digitizer

Abstract The lightning impulse voltage calibrators, developed at NML and MIKES-HUT, and a recently developed commercial digitiser were compared. With this three-way comparison, not only the accuracies of the devices were compared, but also the linearity of both peak voltage and time parameters of the devices was investigated. The results demonstrated that the linearity of the calibrators is superior to that of the digitiser. Measurement Arrangements Calibrators for impulse voltages can be used for calibrating digital recorders and other components of impulse voltage measurement systems The MIKES-HUT calibrator [3] is a single stage impulse Marx generator of high output impedance. The generation circuitry is housed in a compact box that can be attached directly to the input terminal of a digitiser. The analytical solutions of the circuit formulae are used to calculate the output values from the DC input voltage, component values of the generation circuit and the input impedance of the external load (e.g. the digitiser). The peak voltage range is 50 mV to 320 V. Output values of the calibrator are traceable to Finnish national standards of resistance, capacitance, and direct voltage. The estimated uncertainty (k=2) for the impulse peak value is 0.05% and for the time parameters 0.5%. The digitiser used in the comparison has a 14-bit resolution and a sampling rate of 200 MS/s. The digitiser has its own in-build software to calculate the parameters of the applied impulses. The manufacturers default scale factors were used in the measurements. The scale factor of digitiser in the 10 V range was also measured at PTB using step voltages, and the scale factor in the 320 V range was calibrated against PTB's impulse voltage standards, with maximum uncertainty of 0.4 % and 1.5% for peak voltage and time parameters respectively. The comparison measurements were performed at PTB, in an air-conditioned laboratory with its ambient temperature maintained between 22 and 23 C. The measurements lasted two days, with the MIKES-HUT calibrator being compared with the digitiser first. Various impulse attenuators of 50 input impedance were used with the NML calibrator to attenuate the output peak voltage to match the measurement range of the digitiser. The impulse waveform from the NML calibrator was 0.81/60 s and that from the MIKES-HUT calibrator was 0.84/60 s. In each comparison measurement, 10 impulses from the calibrator were applied to the input of the digitiser, and the digitiser calculated the average values of the measured impulses. The standard deviations were low, typically below 0.03% for the peak value and 0.2% for the time parameters. Measurement Results Figure 1 an