Figure 4: The cytotoxicity of PEI600, PEI-β-CyD, CY11-PEI-β-CyD, and PEI25KDa against (a) COS-7, (b) HepG2, and (c) PC-3 cells. The cells were treated with polymer of different concentrations for 4 h in a serum-containing medium. Cell viability was determined using MTT assays and expressed as percentages of the control. When the concentration of the polymer was <20 nmol/mL, the toxicities of the polymers were similar ( 𝑃 > 0 . 0 5 ).