Fluorescence-activated droplet sorting (FADS): efficient microfluidic cell sorting based on enzymatic activity.
We describe a highly efficient microfluidic fluorescence-activated droplet sorter (FADS) combining many of the advantages of microtitre-plate screening and traditional fluorescence-activated cell sorting (FACS). Single cells are compartmentalized in emulsion droplets, which can be sorted using dielectrophoresis in a fluorescence-activated manner (as in FACS) at rates up to 2000 droplets s(-1). To validate the system, mixtures of E. coli cells, expressing either the reporter enzyme beta-galactosidase or an inactive variant, were compartmentalized with a fluorogenic substrate and sorted at rates of approximately 300 droplets s(-1). The false positive error rate of the sorter at this throughput was <1 in 10(4) droplets. Analysis of the sorted cells revealed that the primary limit to enrichment was the co-encapsulation of E. coli cells, not sorting errors: a theoretical model based on the Poisson distribution accurately predicted the observed enrichment values using the starting cell density (cells per droplet) and the ratio of active to inactive cells. When the cells were encapsulated at low density ( approximately 1 cell for every 50 droplets), sorting was very efficient and all of the recovered cells were the active strain. In addition, single active droplets were sorted and cells were successfully recovered.
Baret
Jean-Christophe
JC
Institut de Science et d'Ingénierie Supramoléculaires (ISIS), Université de Strasbourg, CNRS UMR 7006, 8 allée Gaspard Monge, BP 70028, F-67083, Strasbourg Cedex, France.
Miller
Oliver J
OJ
Taly
Valerie
V
Ryckelynck
Michaël
M
El-Harrak
Abdeslam
A
Frenz
Lucas
L
Rick
Christian
C
Samuels
Michael L
ML
Hutchison
J Brian
JB
Agresti
Jeremy J
JJ
Link
Darren R
DR
Weitz
David A
DA
Griffiths
Andrew D
AD
D004655:Emulsions / Q000737:chemistry; D004867:Equipment Design; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification*; D005434:Flow Cytometry / Q000191:economics / Q000295:instrumentation* / Q000379:methods*; D005456:Fluorescent Dyes; D005690:Galactose / Q000378:metabolism; D044085:Microfluidics / Q000191:economics / Q000295:instrumentation* / Q000379:methods; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism*
D004655:Emulsions; D005456:Fluorescent Dyes; D001616:beta-Galactosidase; D005690:Galactose