(J-383) Improving Oxygenation for Endometrial Tissue Culture in Thermoplastic Microphysiological Systems

Microphysiological systems (MPS) have shown potential to improve human disease modeling and accelerate preclinical drug discovery. These “organ-on-a-chip” systems support 3D tissue culture with precise pneumatic and microfluidic control, mimicking the in vivo environment. While MPS devices are commonly made in oxygen-permeable polydimethylsiloxane (PDMS), the standard for large-scale manufacturing are thermoplastics such as polystyrene, acrylic (PMMA), cyclic olefin polymer (COP), and cyclic olefin copolymer (COC). In addition to their favorable manufacturing properties, thermoplastics do not absorb steroid hormones or lipophilic drugs, allowing for improved accuracy in disease modeling and drug discovery. As thermoplastics are not oxygen-permeable, the capacity of a novel device to supply oxygen to the cells is a critical consideration. 

The EndoChip, an MPS device developed in the Griffith Lab, is designed to model endometriosis, a complex reproductive disease involving hormone signaling, vasculature, and immune dysregulation. To support the necessary cell types to model endometrial lesions, the EndoChip must provide sufficient oxygen to the cells. As such, we designed and prototyped a compact, on-chip, open-well oxygenator in a standardized ‘patch’ format, suitable for studying the efficacy of multiple geometries with one fluidic validation platform. We are in the process of design verification through experimentation with self-assembled, perfusable microvasculature within a thermoplastic device. Perfusable vasculature indicates a suitable environment, including sufficient oxygenation, and is necessary to develop a complete and accurate model of endometrial lesions. Through these experiments, an optimized and bio-compatible oxygenator will be identified for integration with the next iteration of the EndoChip.

Oxygenators

The primary design requirements were oxygen diffusion and geometric compatibility with the EndoChip’s on-chip reservoir. Fick’s 2nd Law for diffusion, Darcy’s Law for fluid flow, and a model for oxygenation potential were used to determine acceptable values for the surface area of the media-air interface. Oxygenators were prototyped with a 3D printer (Formlabs, BioMed Clear resin) and tested for flow on the validation platform. Culture media and water were used for flow testing.

Fluidic Validation Platform

The validation system was designed as a reusable fluidic platform. To establish an interface between interchangeable oxygenator ‘patches’ and the fluidic circuit, a clear acrylic platform was machined using a desktop CNC (Bantam Tools). The fluidic channels were closed with an elastomeric COC membrane and aluminum plate with bolts. Oxygenator reservoir patches magnetically connect to the fluidic channels, and peristaltic pumps with silicone tubing allow flow. The design allows for oxygen monitoring through probes and fluorescent dyes.

Biological Validation

A compact, biocompatible, and manufacturable oxygenator that meets both the geometric constraints and oxygenation requirements will be identified through ongoing studies, including quantification of oxygenation potential and biological validation through vascularization experiments. Oxygenation potential, measured with probes and fluorescent dyes, is evaluated using oxygen concentration in the culture media at the inlet and outlet of the oxygenation element. With a deoxygenation system such as nitrogen bubbling, oxygen consumption is simulated and the efficacy of the oxygenator analyzed. Biological validation experiments will be conducted in a thermoplastic MPS device, in which sufficient oxygenation will be assessed by the self-assembly of perfusable microvasculature. A successful design will be one that is geometrically compatible with the EndoChip, meets the calculated oxygenation potential requirement, and supports perfusable vasculature.

The final optimized oxygenator will be integrated into the culture media reservoir of the next iteration of the EndoChip. Uniquely designed to support culture of endometrial lesions, the EndoChip will support research on endometriosis, a complex disease affecting roughly 10% of women of reproductive age (Source: WHO). Overall design improvements, including increased oxygen supply to the cells, will allow for more realistic models of disease tissue, which will aid in discovery of new drugs for treatment of and, possibly, a cure for endometriosis.