Researchers have developed high-density microelectrode array chips (HD-MEACs) to gain unprecedented insights on the dynamics of epithelial barriers, particularly those formed by Caco-2 cells, which are commonly used to model the intestinal epithelium. This innovative technology enables real-time monitoring of cell interactions on chip, facilitating the detection of changes at both cellular and tissue levels.
The intestinal epithelial barrier plays a regulatory role, guarding against the unregulated passage of substances from the gut to underlying tissues. To understand its workings and vulnerabilities, scientists have traditionally employed techniques like transepithelial electrical resistance (TEER) measurement and permeability assays. Yet, these methods often falter when it becomes necessary to grasp the nuances of cellular behavior and the dynamic nature of tissue formation.
High-density microelectrode arrays present new avenues for tissue analysis by overcoming the spatial limitations of established techniques. "This method could enable detection of tissue barrier disrupting and modifying agents with higher specificity," say the authors of the article, showcasing the chips' enhanced sensitivity. Integrated with Complementary Metal Oxide Semiconductor (CMOS) technology, the HD-MEACs allow real-time, continuous monitoring of cellular processes without any labelling, which is often cumbersome and time-consuming.
The HD-MEACs used for this study have 16,384 electrodes, resulting in spatiotemporal resolution far surpassing earlier systems. With their 8 μm diameter electrodes configured within clusters, these arrays capture detailed electrical changes impacting barrier functions as Caco-2 cells undergo proliferation, differentiate, and respond to barrier disruption.
Using this advanced technology, the researchers monitored Caco-2 cell growth over 14 days. Their findings reveal various stages of epithelial barrier development. The first phase involves cell attachment and spreading, leading to the formation of tight junctions. During the study, at day 6, the barrier was observed to reach its peak impedance, reflecting the health and functionality of the epithelial layer.
Not only did the HD-MEACs delineate the two-dimensional growth of cells, they captured the emergence of three-dimensional structures known as domes, which play significant roles during epithelial differentiation. The researchers noted dynamic heterogeneity during these phases, as the cells responded variably to fluid dynamics and nourishment resulting from their microenvironment.
Throughout the experiment, the team introduced the chelative agent ethylene glycol-bis(2-aminoethylether)-N,N,N’,N’-tetraacetic acid (EGTA) to disrupt intercellular junctions. This illustrated how the barrier's integrity could differ, depending on the presence of the three-dimensional domes. "Epithelial barrier function assays benefit from using HD-MEA impedance sensors due to their increased informativity and resolution," explain the authors. They found dome regions experienced significantly larger decreases in impedance when exposed to EGTA compared to flatter areas.
Such findings suggest incredible potential for HD-MEAC technology across various applications, paving the way for novel organ-on-chip approaches. With the ability to conduct highly informative assays, these chips can provide significant insights not just for basic biology but also for preclinical drug testing, especially concerning gastrointestinal diseases like inflammatory bowel disease (IBD).
Continuous monitoring using these microelectrode arrays also allows researchers to bridge the gap between cellular activities and systemic responses, which is imperative for developing effective treatment strategies. The versatility and accuracy of HD-MEACs offer promising potential for advancing biomedical research and patient care.
The study concludes by recognizing the revolutionary prospects emerged from utilizing high-density microelectrode arrays for monitoring epithelial cells. Researchers are now encouraged to explore the capabilities of this technology to yield enlightening data on cell differentiation, barrier function, and responses to pharmacological and environmental stimuli.