Developing an organic transmembrane device to host and monitor 3-D cell cultures

Researchers have used 3D cell culture models in the past decade to translate molecular targets during drug discovery processes to thereby transition from an existing predominantly 2D culture environment. In a new report now published in Science Advances, Charalampos Pitsalidis and a research team in physics and chemical engineering at the University of Science and Technology in Abu Dhabi, UAE and the University of Cambridge describe a multi-well plate bioelectronic platform named the e-transmembrane to support and monitor complex 3D cell architectures.

The team microengineered the scaffolds using poly(3,4- ethylenedioxythiophene polystyrene sulfonate to function as separating membranes to isolate cell cultures and achieve real-time in situ recordings of cell growth and function. The high surface area to volume ratio allowed them to generate deep stratified tissues in a porous architecture. The platform is applicable as a universal resource for biologists to conduct next-generation high-throughput drug screening assays.

A new e-transmembrane platform for drug screening and drug discovery

The existing knowledge of cell growth, function and homeostasis arises from two-dimensional cell-based assays using cell monolayers grown on flat, rigid substrates. While such assays are applicable across fundamental research and toxicology screening, they do not adequately demonstrate the complex 3D microenvironment observed in vivo, as noted in cell-cell and cell-extracellular matrix interactions. While animal studies are regarded as a gold standard for preclinical studies, they are limited by marked physiological differences between species, costs and ethical concerns. Researchers have therefore shifted the focus to improve in vitro systems such as 3D cell cultures and organ-on-a-chip devices to better emulate physiological architectures of biological systems in vivo.

In recent studies, Pitsalidis and the team used conducting polymer scaffolds as architectures to host 3D cell cultures for real-time sensing. In this work, they developed a bioelectronic transmembrane device to combine a range of desirable features, including the potential to host biologically complex and physiologically relevant 3D cell co-cultures and monitor the models in real-time. The researchers propose using the "e-transmembrane" platform as a highly useful resource for drug discovery.

Developing the e-transmembrane platform in the lab

The scientists developed the e-transmembrane by engineering three key modules; the conducting polymer scaffold membrane, electrical interconnects to capture electrochemical readouts and plastic insert components. They developed an e-transmembrane system as a two-dimensional electrochemical device to conduct electrochemical impedance spectroscopy (EIS) measurements. Due to the presence of the physiological media of the cell culture, the electrochemical behavior underwent alterations; however, these variations were negligible after two weeks in cell culture media.

The team next explored the use of scaffold membranes in an organic electrochemical transistor in order to investigate the transistor mode of functionality via performance optimization studies in the future. They conducted a series of experiments to show that the mechanical properties of the 3D constructs influenced cell-substrate interactions. Thereafter, by tailoring the pore size and morphology, the researchers regulated the functionality of the constructs.

From a 3D cell culture system to a 3D human intestine on an e-transmembrane

The team then modeled the e-transmembrane electrode functionality to assess cell barrier integrity, and qualitatively observed the morphology of the measured impedance and relative changes by using 3D cell culture systems. The typical e-transmembrane model contained human fibroblasts grown in the bulk of the scaffold with a confluent monolayer of human epithelial and endothelial cells seeded on the top. The scientists cultured the electroactive substances with human fibroblasts to serve as a guide for tissue organization with subsequent integration of cell types that varied according to their tissue model of interest.

The researchers used these study outcomes to develop a 3D human intestine on an e-transmembrane device. The fibroblasts and their resultant proteins affected cell attachment, polarization and functional properties of epithelia in the triculture model. The team subsequently monitored the real-time cell tissue and barrier integrity to detect and circumvent any breaches in the intestinal barrier.

Outlook

In this way, Charalampos Pitsalidis and colleagues developed a first in-study example of a bioelectric well plate platform by using an e-transmembrane template. The porous platform facilitated 3D cell cultures and enabled them to monitor cell growth in multiculture systems. The e-transmembrane functioned both as an electrode and a transistor with the capacity to regulate the pore size and morphology of the device for specific applications. The 3D cell culture platform is capable of incubating multicultures of cells for high-throughput measurements as a drug screening and therapeutics platform. The scientists envision implementing the concept to expand interfaces of the tissue to lung and blood brain barrier for drug discovery and disease modeling applications.

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