Abstract: Despite numerous attempts to use human mesenchymal stem cells (hMSCs) in the field of tissue engineering, the control of their differentiation remains challenging. Here, we investigated possible applications of a non-thermal atmospheric pressure plasma jet (NTAPPJ) to control the differentiation of hMSCs. An air- or nitrogen-based NTAPPJ was applied to hMSCs in culture media, either directly or by media treatment in which the cells were plated after the medium was exposed to the NTAPPJ. The durations of exposure were 1, 2, and 4 min, and the control was not exposed to the NTAPPJ. The initial attachment of the cells was assessed by a water-soluble tetrazolium assay, and the gene expression in the cells was assessed through reverse-transcription polymerase chain reaction and immunofluorescence staining. The results showed that the gene expression in the hMSCs was generally increased by the NTAPPJ exposure, but the enhancement was dependent on the conditions of the exposure, such as the source of the gas and the treatment method used. These results were attributed to the chemicals in the extracellular environment and the reactive oxygen species generated by the plasma. Hence, it was concluded that by applying the best conditions for the NTAPPJ exposure of hMSCs, the control of hMSC differentiation was possible, and therefore, exposure to an NTAPPJ is a promising method for tissue engineering.

Abstract: Non-thermal plasma (NTP), defined as a partially ionized gas, is an emerging technology with several biomedical applications, including tissue regeneration. In particular, NTP treatment has been shown to activate endogenous biological processes to promote cell regrowth, differentiation, and proliferation in multiple cell types. However, the effects of this therapy on nervous system regeneration have not yet been established. Accordingly, the current study explored the effects of a nanosecond-pulsed dielectric barrier discharge plasma on neural regeneration. Following mechanical trauma in vitro, plasma was applied either directly to (1) astrocytes alone, (2) neurons alone, or (3) neurons or astrocytes in a non-contact co-culture. Remarkably, we identified NTP treatment intensities that accelerated both neurite regeneration and astrocyte regrowth. In astrocyte cultures alone, an exposure of 20-90 mJ accelerated astrocyte re-growth up to three days post-injury, while neurons required lower treatment intensities (<= 20 mJ) to achieve sub-lethal outgrowth. Following injury to neurons in non-contact co-culture with astrocytes, 20 mJ exposure of plasma to only neurons or astrocytes resulted in increased neurite regeneration at three days post-treatment compared to the untreated, but no enhancement was observed when both cell types were treated. At day seven, although regeneration further increased, NTP did not elicit a significant increase from the control. However, plasma exposure at higher intensities was found to be injurious, underscoring the need to optimize exposure levels. These results suggest that growth-promoting physiological responses may be elicited via properly calibrated NTP treatment to neurons and/or astrocytes. This could be exploited to accelerate neurite re-growth and modulate neuron-astrocyte interactions, thereby hastening nervous system regeneration.

Abstract: Recent advances in the development of electron and X-ray detectors have opened up the possibility to detect single events from which its time of arrival can be determined with nanosecond resolution. This allows observing time correlations between electrons and X-rays in the transmission electron microscope. In this work, a novel setup is described which measures individual events using a silicon drift detector and digital pulse processor for the X-rays and a Timepix3 detector for the electrons. This setup enables recording time correlation between both event streams while at the same time preserving the complete conventional electron energy loss (EELS) and energy dispersive X-ray (EDX) signal. We show that the added coincidence information improves the sensitivity for detecting trace elements in a matrix as compared to conventional EELS and EDX. Furthermore, the method allows the determination of the collection efficiencies without the use of a reference sample and can subtract the background signal for EELS and EDX without any prior knowledge of the background shape and without pre-edge fitting region. We discuss limitations in time resolution arising due to specificities of the silicon drift detector and discuss ways to further improve this aspect.