Quantifying and modeling loss of estrogen and progesterone in PDMS-based devices

An early study on the biological consequences of using polydimethysiloxane (PDMS) for microfluidic cell culture reported that estrogens could be sequestered by PDMS; however, the PDMS interaction parameters of specific hormones have not been reported. Without these parameters, it is not possible to assess whether such sequestration is a problem for a particular device and flow rate combination. Here we quantify chemical-PDMS interactions for a commonly used estrogen and two additional steroid-class hormones: estradiol, aldosterone, and progesterone. We find that aldosterone does not detectably interact with PDMS; estradiol interacts modestly; and progesterone interacts strongly. Based on these measured interactions, we computationally model dynamic dosing protocols based on pulsed/bolus delivery and circadian control. We show that interactions with PDMS can strongly disrupt these dynamic dosing protocols in a chemical-specific and flow-rate-dependent manner. Notably, estradiol-PDMS interactions can have significant impacts under static conditions or low flow rates, but those impacts become negligible at higher flow rates. These results have critical implications for the use of steroid hormones in PDMS-based microfluidic devices.