Figure 1. Se attenuated toxic effect of CoNPs on human and rat CD34+ HSC/HPCs. (A) Human and rat CD34+ HSC/HPCs were isolated from cord blood and bone marrow, respectively, through flow cytometry. (B) CD34+ HSC/HPCs were exposed to CoNPs at concentrations from 0 to 400 μM for 24 h, followed by MTT assay. (C) Different dosages of Na2SeO3, SeMet and SeCys were added to CD34+ HSC/HPCs 15 h before treatment with 200 μM CoNPs for additional 24 h. MTT assay was conducted to assess the cell viability. (D) CD34+ HSC/HPCs were treated with 10 μM SeMet for 15 h and then subjected to 200 μM CoNPs for 24 h. Flow cytometry was conducted to evaluate apoptosis rate. *p < 0.05, **p < 0.01, and ***p < 0.001 vs. control cells that did no subjected to any treatments; ##p < 0.01 vs. cells treated with CoNPs alone.