Reducing Small Molecule Adsorption in a PDMS-Based Microphysiological System of the Female Reproductive Tract via Parylene-C Coating to Improve Mechanistic Studies

Microphysiological systems (MPS) have been extensively developed in the past decade and are now used in mechanistic studies, as well as in drug and chemical toxicity testing. The utility of MPS for studies of a broad range of molecules is becoming ever more important. Many MPS models utilize polydimethylsiloxane (PDMS) as the material of choice. Despite its advantages, including biocompatibility, optical transparency, and gas permeability, PDMS exhibits significant molecular adsorption due to its hydrophobic surface properties, which is a well-known phenomenon. Although some MPS can be made from low-adsorbance materials, not all models can easily transition away from PDMS. Here, we investigated the potential of Parylene-C, a widely used coating for medical devices, for surface modification of a PDMS-based feto-maternal interface (FMi) MPS device. The impact of this coating on molecular adsorption was tested with five different chemicals (four drugs and one environmental pollutant) using a two-chambered microchannel-interconnected MPS device. We showed that the Parylene-C coating did not obstruct the microchannels, allowed chemical diffusion between chambers, did not compromise cell viability, and minimized molecular adsorption. The beneficial effect of Parylene-C coating was most prominent for highly adsorbed drugs (lipophilic)─celicoxib and tamoxifen─while the low-adsorbed compounds (amphiphilic or hydrophilic) like aspirin, sofosbuvir, and perfluorooctanoic acid were unaffected. Importantly, by limiting molecular adsorption, we were able to demonstrate chemical effects in the FMi MPS device even when using highly PDMS-adsorbed compounds. Collectively, our results demonstrate an easily adoptable strategy to increase the toxicological utility of PDMS-made MPS devices by modifying surface properties and adsorption behavior through the use of a Parylene-C coating.