Comparison between dynamic versus static models and real-time monitoring of neuronal dysfunction in an amyloid-ß induced neuronal toxic model on a chip platform.

Microfluidics-based organs-on-a-chip offer a promising method for dynamic and 3-dimensional (3D) cell culture to evaluate the cell behaviors within the biomimetic environment. The purpose of this study was to establish neural network connections in a 3D neural stem cell (NSC)-based system with an interstitial level of flow for simulating the brain microenvironment toward a dynamic amyloid-ß (Aß) induced neuronal toxic model on a chip and to compare the biological effects and neurite dysfunction between static and dynamic systems. The brain-on-a-chip system consisted of an impedance analyzing layer, a structured well with a connected channel, and an interface coating with polypeptide films fabricated with modification based on our previous study. The cytotoxicity and percentage of neuron/astrocyte differentiation were all compared in both static and dynamic brain-on-a-chip systems. Reactive oxygen species production, neuron marker expression and neurotransmitter-acetylcholine release were all compared to evaluate functional neurite losses in both static and dynamic systems with/without Aß addition. Moreover, real-time impedance recording was used to consecutively monitor the neurite connection/disconnection in both static and dynamic brain-on-a-chip systems. The NSC-based dynamic brain-on-a-chip may enable the application of different neurodegenerative disease in vitro models for pathogenesis studies, drug discovery and novel therapeutic method development.

Cation-Induced Assembly of Conductive MXene Fibers for Wearable Heater, Wireless Communication, and Stem Cell Differentiation.

Emerging wearable electronics, wireless communication, and tissue engineering require the development of conductive fiber-shaped electrodes and biointerfaces. Ti3C2Tx MXene nanosheets serve as promising building block units for the construction of highly conductive fibers with integrated functionalities, yet a facile and scalable fabrication scheme is highly required. Herein, a cation-induced assembly process is developed for the scalable fabrication of conductive fibers with MXene sheaths and alginate cores (abbreviated as MXene@A). The fabrication scheme of MXene@A fibers includes the fast extrusion of alginate fibers followed by electrostatic assembly of MXene nanosheets, enabling high-speed fiber production. When multiple fabrication parameters are optimized, the MXene@A fibers exhibit a superior electrical conductivity of 1083 S cm-1, which can be integrated as Joule heaters into textiles for wearable thermal management. By triggering reversible de/hydration of alginate cores upon heating, the MXene@A fibers can be repeatedly contracted and generate large contraction stress that is >40 times higher than the ones of mammalian skeletal muscle. Furthermore, the MXene@A springs demonstrate large contraction strains up to 65.5% and are then fabricated into a reconfigurable dipole antenna to wirelessly monitor the surrounding heat sources. In the end, with the biocompatibility of MXene nanosheets, the MXene@A fibers enable the guidance of neural stem/progenitor cells differentiation and the promotion of neurite outgrowth. With a cation-induced assembly process, our multifunctional MXene@A fibers exhibit high scalability for future manufacturing and hold the prospect to inspire other applications.

Dual-frequency ultrasound enhances functional neuron differentiation from neural stem cells by modulating Ca2+ dynamics and the ERK1/2 signaling pathway.

Our previous study demonstrated that ultrasound is able to promote differentiation on neural stem cells (NSCs), and dual-frequency ultrasound promotes this effect due to enhanced acoustic cavitation compared with single-frequency ultrasound. However, the underlying biological reasons have not been well disclosed. The purpose of this study was to investigate the underlying bioeffects, mechanisms and signaling pathways of dual-frequency ultrasound on NSC differentiation. The morphology, neurite outgrowth, and differentiation percentages were investigated under various dual-frequency simulation parameters with exposure periods varying from 5 to 15 min. Morphological observations identified that dual-frequency ultrasound stimulation promoted ultrasound dose-dependent neurite outgrowth. In particular, cells exposed for 10 min/2 days showed optimal neurite outgrowth and neuron differentiation percentages. In addition, live cell calcium images showed that dual-frequency ultrasound enhanced the internal calcium content of the cells, and calcium ions entering cells from the extracellular environment could be observed. Dual frequency ultrasound exposure enhanced extracellular calcium influx and upregulated extracellular signal-regulated kinases 1/2 (ERK1/2) expression. Observations from immunostaining and protein expression examinations also identified that dual-frequency ultrasound promoted brain-derived neurotrophic factor (BDNF) secretion from astrocytes derived from NSCs. In summary, evidence supports that dual-frequency ultrasound effectively enhances functional neuron differentiation via calcium channel regulation via the downstream ERK1/2 pathway and promotes BDNF secretion to serve as feedback to cascade neuron differentiation. The results may provide an alternative for cell-based therapy in brain injury.

A Real-Time Sensing System for Monitoring Neural Network Degeneration in an Alzheimer's Disease-on-a-Chip Model.

Stem cell-based in vitro models may provide potential therapeutic strategies and allow drug screening for neurodegenerative diseases, including Alzheimer's disease (AD). Herein, we develop a neural stem cell (NSC) spheroid-based biochip that is characterized by a brain-like structure, well-defined neural differentiation, and neural network formation, representing a brain-on-a-chip. This system consisted of microelectrode arrays with a multichannel platform and allowed the real-time monitoring of network formation and degeneration by impedance analysis. The parameters of this platform for the real-time tracking of network development and organization were established based on our previous study. Subsequently, ß-amyloid (Aß) was added into the brain-on-a-chip system to generate an AD-on-a-chip model, and toxic effects on neurons and the degeneration of synapses were observed. The AD-on-a-chip model may help us to investigate the neurotoxicity of Aß on neurons and neural networks in real time. Aß causes neural damage and accumulates around neurites or inside neurospheroids, as observed by immunostaining and scanning electron microscopy (SEM). After incubation with Aß, reactive oxygen species (ROS) increased, synapse function decreased, and the neurotransmitter-acetylcholine (ACh) concentration decreased were observed. Most importantly, the real-time analysis system monitored the impedance value variation in the system with Aß incubation, providing consecutive network disconnection data that are consistent with biological data. This platform provides simple, real-time, and convenient sensing to monitor the network microenvironment. The proposed AD-on-a-chip model enhances the understanding of neurological pathology, and the development of this model provides an alternative for the study of drug discovery and cell-protein interactions in the brain.