title: Sickling of red blood cells through rapid oxygen exchange in microfluidic drops.
abstract: We have developed a microfluidic approach to study the sickling of red blood cells associated with sickle cell anemia by rapidly varying the oxygen partial pressure within flowing microdroplets. By using the perfluorinated carrier oil as a sink or source of oxygen, the oxygen level within the water droplets quickly equilibrates through exchange with the surrounding oil. This provides control over the oxygen partial pressure within an aqueous drop ranging from 1 kPa to ambient partial pressure, i.e. 21 kPa. The dynamics of the oxygen exchange is characterized through fluorescence lifetime measurements of a ruthenium compound dissolved in the aqueous phase. The gas exchange is shown to occur primarily during and directly after droplet formation, in 0.1 to 0.5 s depending on the droplet diameter and speed. The controlled deoxygenation is used to trigger the polymerization of hemoglobin within sickle red blood cells, encapsulated in drops. This process is observed using polarization microscopy, which yields a robust criterion to detect polymerization based on transmitted light intensity through crossed polarizers.
authors.affiliation: Laboratoire d'Optique et Biosciences (LOB), Ecole Polytechnique, INSERM U696, CNRS, 91128 Palaiseau, France.
authors.forename: Paul
authors.initials: P
authors.lastname: Abbyad
authors.forename: Pierre-Louis
authors.initials: PL
authors.lastname: Tharaux
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Martin
authors.forename: Charles N
authors.initials: CN
authors.lastname: Baroud
authors.forename: Antigoni
authors.initials: A
authors.lastname: Alexandrou
mesh_terms: D018929:Cell Culture Techniques / Q000295:instrumentation*; D002478:Cells, Cultured; D004867:Equipment Design; D019544:Equipment Failure Analysis; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D017022:Flow Injection Analysis / Q000295:instrumentation*; D006451:Hemoglobin, Sickle / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D010100:Oxygen / Q000008:administration & dosage* / Q000493:pharmacokinetics*
chemical_list: D006451:Hemoglobin, Sickle; D010100:Oxygen