Paper-Based Progesterone Sensor Using an Allosteric Transcription Factor

[Image: see text] Progesterone monitoring is an essential component of in vitro fertilization treatments and reproductive management of dairy cows. Gold-standard biosensors for progesterone monitoring rely on antibodies, which are expensive and difficult to procure. We have developed an alternative transcription factor-based sensor that is superior to conventional progesterone biosensors. Here, we incorporate this transcription factor-based progesterone sensor into an affordable, portable paperfluidic format to facilitate widespread implementation of progesterone monitoring at the point of care. Oligonucleotides labeled with a fluorescent dye are immobilized onto nitrocellulose via a biotin–streptavidin interaction. In the absence of progesterone, these oligonucleotides form a complex with a transcription factor that is fluorescently labeled with tdTomato. In the presence of progesterone, the fluorescent transcription factor unbinds from the immobilized DNA, resulting in a decrease in tdTomato fluorescence. The limit of detection of our system is 27 nm, which is a clinically relevant level of progesterone. We demonstrate that transcription factor-based sensors can be incorporated into paperfluidic devices, thereby making them accessible to a broader population due to the portability and affordability of paper-based devices.