MEGAHERTZ-GENERATED FEMTOLITER MICROFLUIDIC DROPLETS FOR SINGLE-MOLECULE-COUNTING IMMUNOASSAY

This paper describes a microfluidic droplet-based approach enabling the measurement of chemical reactions of individual enzyme molecules and its application to a single-molecule-counting immunoassay. A microfluidic device is used to generate and manipulate <10-fL droplets at rates of up to 1.3 MHz. The femtodroplets produced with this device encapsulate single biomolecular complexes tagged with a reporter enzyme; their small volume enables the fluorescent product of a single enzyme molecule to be detected within 10 minutes of on-chip incubation. Our prototype system is validated by detection of a biomarker for prostate cancer down to a concentration of 46 fM.