Advanced micro/nano-scale system for modulating neural activities in vitro and in vivo
Student thesis: Doctoral Thesis
Related Research Unit(s)
Due to the complex organization and highly interconnected cellular structure of nervous system, it is important to locally investigate and manipulate neuronal activities for investigating different aspects of the nervous system, including axonal pathfinding, synaptogenesis and drugs screening targeting neurobiological diseases. This dissertation presents a series of studies in which advanced micro/nano-scale systems are interfaced with neuron cells in vitro or in vivo, to study the neural circuitry, neurites pathfinding, and synaptic plasticity. First, in order to investigate neural circuitry in the complex tissue and understand neural processes at the level of small neuron networks, we introduced NeuroArray interface in micro-scale to pattern primary neurons in vitro with single cell resolution to interrogate neuronal circuitry. Taking advantage of this platform, neuron cells could be patterned in any arbitrary format without restricting the outgrowth of neurites and thus allowed the formation of freely designed, well-connected and spontaneously active neural network. When combined with optical microscopy of intracellular Ca2+ indicators, dynamic activities of patterned neurons in the well-organized and active network could be tracked and analyzed, which provided great potential for neurobiological applications in future. With little adaption, this universal interface combined with other interrogation could be readily used for high-throughput drug testing and building neuron culture based live computational devices. Second, neural activities could be further investigated and modulated with subcellular resolution by using the microfluidic compartmentalized system. This microfluidic platform consisted of one cell body compartment and two neurites compartments, connecting with an array of microgrooves. Gradient of chemotactic factors, such as Netrin and Semaphorin 3A, could be generated in the microgrooves to guide the outgrowth of axons and dendrites towards two different directions, resulting in isolation of neurites from cell bodies, which facilitated the investigation of effects of some peptides on neurons under subcellular structure. For example, Amyloid beta peptide (Aβ1-42) is toxic peptide, mainly responsible to Alzheimer’s disease (AD) which is an age-related, neurodegenerative disorder and affects a great number of people in the world. Even though many studies have demonstrated its neural toxicity, the cytotoxicity of Aβ1-42 peptide to neurons with subcellular resolution is still not well understood. By utilizing the designed microfluidic compartmentalized chamber, isolated neurites could be locally treated with Aβ1-42 peptide and the toxicity of this peptide could be investigated with subcellular resolution by tracking neural activities. Third, neural activities can be manipulated not only in vitro, but also in vivo by taking advantage of the localized delivery system, which has attracted much attention due to the capability to remotely control the release of biomolecules from delivery systems to regulate neural activities. Recently there have been various strategies for localized delivery to modulate neural activities, but it is still challenging to adopt them in many experiment contexts that require a straightforward but versatile loading-releasing mechanism. In this study, we developed a photosensitive composite hydrogel embedded with polypyrrole nanoparticles as light-transducer, to achieve local manipulation of neural activities. Besides the demonstration of modulating neural activities in vitro by photo-controlled release of biomolecules from the hydrogel based delivery system, such as Netrin and Semaphorin 3A which could induce turning or collapsing response of neurons, neural activities could also be regulated in vivo by taking advantage of the hydrogel system to locally release neurotransmitters (e.g. glutamate) around rat auditory cortex, and light-triggered delivery of glutamate could significantly increase synchronized spiking activity in the cortex area, demonstrating great versatility and ease-of-use of the hydrogel system to modulate neural activities. In summary, this presented dissertation has developed micro/nano-scale systems for studying and modulating neural activities, which can potentially be adopted as general tools for a wide range of neuroengineering applications, including basic research of neuronal functions such as synaptic connection and plasticity, high-throughput drug screening and localized drug testing.
- Neural networks (Neurobiology), Brain-computer interfaces