High-throughput single copy DNA amplification and cell analysis in engineered nanoliter droplets

Abstract

A high-throughput single copy genetic amplification (SCGA) process is developed that utilizes a microfabricated droplet generator (microDG) to rapidly encapsulate individual DNA molecules or cells together with primer functionalized microbeads in uniform PCR mix droplets. The nanoliter volume droplets uniquely enable quantitative high-yield amplification of DNA targets suitable for long-range sequencing and genetic analysis. A hybrid glass-polydimethylsiloxane (PDMS) microdevice assembly is used to integrate a micropump into the microDG that provides uniform droplet size, controlled generation frequency, and effective bead incorporation. After bulk PCR amplification, the droplets are lysed and the beads are recovered and rapidly analyzed via flow cytometry. DNA targets ranging in size from 380 to 1139 bp at single molecule concentrations are quantitatively amplified using SCGA. Long-range sequencing results from beads each carrying approximately 100 amol of a 624 bp product demonstrate that these amplicons are competent for achieving attomole-scale Sanger sequencing from a single bead and for advancing pyrosequencing read-lengths. Successful single cell analysis of the glyceraldehyde 3 phosphate dehydrogenase (GAPDH) gene in human lymphocyte cells and of the gyr B gene in bacterial Escherichia coli K12 cells establishes that SCGA will also be valuable for performing high-throughput genetic analysis on single cells.