High Throughput Digital Droplet ELISA for Ultrasensitive Multiplexed Diagnostics

Abstract public domain (NIH RePORTER)

Abstract: Digital assays — in which ultra-sensitive molecular measurements are made by performing millions of parallel experiments in picoliter droplets — have generated much recent enthusiasm due to their single molecule resolution of RNA, DNA, and proteins, and their robustness to reaction conditions. These assays have enormous untapped potential for point of care disease diagnostics, but are currently mainly confined to laboratory settings due to the cumbersome instrumentation necessary to generate, control, and measure tens of millions of independent droplets. To overcome this challenge, we propose a hybrid microelectronic / microfluidic chip to `unlock' droplet-based assays for clinical use. Our microdroplet megascale detector (µMD) can generate and detect the fluorescence of millions of droplets per second (1000× faster than existing digital approaches), while achieving a 1000x greater sensitivity than conventional ELISA, using only a conventional cell phone camera. The key innovation of our approach is borrowed from the telecommunications industry, wherein we modulate the excitation light with a pseudorandom sequence that enables individual droplets to be resolved that would otherwise overlap due to the limited frame rate of digital cameras. To demonstrate the power of our approach, we focus our attention on the diagnosis of pancreatic cancer.

Public health relevance public domain (NIH RePORTER)

Project Narrative: Droplet-based assays, in which microscale emulsions are used as isolated compartments to run many independent chemical reactions, have demonstrated enormous utility in recent years as a platform for the ultrasensitive detection of small molecules, proteins, and nucleic acids. These assays have enormous untapped potential for point of care disease diagnostics, but are currently mainly confined to laboratory settings due to the cumbersome instrumentation necessary to generate, control, and measure tens of millions of independent droplets. To overcome this challenge, we propose a hybrid microelectronic / microfluidic chip to `unlock' droplet-based assays for clinical use. Our microdroplet megascale detector (µMD) can generate and detect the fluorescence of millions of droplets per second (1000× faster than existing digital approaches), while achieving a 1000x greater sensitivity than conventional ELISA, using only a conventional cell phone camera.