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Faster Sickling Kinetics and Sickle Cell Shape Evolution during Repeated Deoxygenation and Oxygenation Cycles


Kinetics of cell sickling and morphological change have been recognized as important parameters that are correlated closely with altered blood rheology and vasoocclusion in microcirculation. A microfluidic transient hypoxia assay was developed to create repeated hypoxia-normoxia cycles for real time observation of repetitive sickling and unsickling of freely suspended red blood cells (RBCs) from sickle cell disease patients. Cell sickling behavior and kinetics were found to be influenced by its previous sickling-unsickling processes accumulatively, where those sickled RBCs that had a history of sickling in a previous hypoxia cycle would sickle again in subsequent hypoxia/sickling cycles and the collective sickling kinetics became progressively faster (with reduced delay time and higher sickled fraction versus deoxygenation time). Individual sickled RBCs would sickle into drastically different shapes randomly in subsequent hypoxia/sickling cycles, however, the collective shape distribution retained similar characteristics. These observations indicate a gradual worsening trend in sickling kinetics over repeated hypoxia cycles, as well as a relatively stable collective shape characteristics within a limited number of hypoxia-normoxia cycles.

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The work was supported by National Institutes of Health (NIH) Grants U01HL114476 and R01HL121386. E.D. acknowledges support by the National Science Foundation (NSF) under Grant No. 1635312 and Florida Atlantic University faculty startup grant. The authors thank Dr. John Higgins for providing sickle blood samples and for helpful discussions and Dr. Monica Diez-Silva for help with sample preparation and insightful discussions.

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Correspondence to M. Dao.

Electronic supplementary material

Supplementary Video S1

Repeated sickling and unsickling of freely suspended sickle cells induced by cyclic hypoxia in microfluidic device (16x speed). (MP4 11.2 mb)

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Du, E., Dao, M. Faster Sickling Kinetics and Sickle Cell Shape Evolution during Repeated Deoxygenation and Oxygenation Cycles. Exp Mech 59, 319–325 (2019).

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  • Microfluidics
  • Sickle cell disease
  • HbS polymerization
  • Cell morphology
  • Cyclic hypoxia-normoxia