Microelectrode Array-Based Neurotoxin Biosensor with Chick Embryo CNS Neurons

In recent years, several compelling forces have emerged that drive the development of fast, effective, reliable, high-throughput, neurotoxicity assays. First, the expanding use of thousands of chemicals that are commercially available but have not been assessed for their potential toxicity has become a serious concern (Betts, 2010). Second, the rapid increase in the occurrence of neurodevelopmental diseases and in the environmental pollution has been correlated recently (Landrigan et. al., 2012). Third, the growing requirement for toxicity assessment has been hindered by conventional approaches that are animal-intensive, time-consuming, often structural, and not designed to detect the physiological and functional changes of living neurons before structural changes occur (Johnstone, 2010). Thus, there is a critical need for neurotoxicity assays that are in vitro, rapid screening based, neurophysiological, functional, highly sensitive, and cost-effective (Collins et, al., 2008). Dissociated vertebrate neurons cultured in vitro form vital neuronal networks, which retain many basic developmental and physiological features of living neural tissues such as synaptogenesis and synaptic transmission, spontaneous electrical spikes/bursts firing, network-wide firing synchronization, and synaptic plasticity. These basic physiologically functional features and their changes insulted by neurotoxins can be easily assessed with high throughput sensitive endpoint data using a microelectrode array (MEA). The reliability of MEA based tests for neurotoxicity has been recently assessed (Johnstone et. al., 2010; Novellino et. al., 2011). As the MEA technology turns to be a powerful component of and is being integrated into the toxicity testing paradigms, a vast majority of MEA experiments are done using dissociated neurons from the central nervous system (CNS) of rats or mice that are mammalian and expensive. Except for the functional differences at higher cognitive level of brain functions, common basic physiological features such as the excitability, conductivity, synaptic transmission, as well as the types of neurotransmitters used by CNS neurons are shared by mammalian and avian. Based on this fact, we hypothesize that at the very basic physiological level, in vitro neuronal networks formed by chick neurons respond to the environmental chemicals (such as agonists and antagonists of various types of neurotransmitter receptors and neurotoxins) in similar or comparable manners as those from their mammalian counterparts (e.g., rat or mice), and thus can be used as a handy and much economic resource to rapidly screen neurotoxins. We are pioneering a systematic research to characterize basic physiological features of in vitro neuronal networks formed by chick embryo CNS neurons on an MEA platform and exploring the feasibility of producing handy neurotoxin biosensors using chick CNS neurons. This paper reports our preliminary data that support our hypothesis above qualitatively.