Enrichment
of the ΦX 174 DNA from a background of lambda
DNA with compound NAC. (a) TaqMan assays detect droplets containing
ΦX 174 (green) and lambda (red) DNA. (b) The microfluidic sorter
interrogates the droplets for fluorescence and sorts PCR positives.
(i) Scatter plot of fluorescence vs size of drops
from the first NAC round, with 0.24% positive. (ii) DNA from the first
round is recovered, diluted, and processed again. (iii) Scatter plot
of fluorescence vs size of drops from the second
NAC round, with 0.17% positive. (c) qPCR plots for (i) single- and
(ii) double-enriched DNA; based on curve shifts, single-round sorting
enriches ΦX 174 by ∼150-fold and double-round sorting
by ∼16,000-fold. Inset in (i) shows ΦX 174 and lambda
standard curves.