Morphology, hydration, and sickling kinetics of HbSC RBCs. (A-C) SEM images of AA, SC, and SS erythrocytes. Insets show an enlarged version of a classical and representative RBCs in each group. (D-F) Representative SC erythrocytes. Specimens were imaged using a Zeiss FE-SEM (Supra 35 VP) at 2 to 5 keV with a working distance of 3 to 5 mm using the Inlens detector. The magnification scale is shown within the micrographs and insets. (G) Osmoscan curves for mRBCs, showing the RBC deformability under varying osmolarities. The EI is plotted against osmolarity for HbAA, HbSS, and HbSC RBCs, 3 samples per group. The curves illustrate the deformability of RBCs, with maximal EI occurring at iso-osmolar conditions and shifting left for dehydrated cells (xerocytosis). (H) Osmoscan curves for hRBCs under varying osmolar conditions. (I) Oxyscan curves of mRBCs in HbAA (n = 6), HbSC (n = 10), and HbSS (n = 5). (J) Oxyscan curves of hRBCs in HbAA (n = 3), HbSC (n = 10), and HbSS (n = 8). (K) O_hyper in mRBCs indicates the osmolarity in the hyperosmolar region at which the RBCs achieve half of their maximal elongation. (L) The PoS, defined as the pO2 at which a >5% decrease in EI is observed during deoxygenation, indicating the onset of sickling in mRBCs. (M) O_hyper in hRBCs. (N) PoS in hRBCs. For panels K through N: each symbol represents an individual sample, and bars represent mean ± standard error of the mean. Statistics were performed using ANOVA. ∗∗P < .01; ∗∗∗∗P < .00001. mOsm, milliosmoles.