Figure 7: C20-18 lipoplex cytotoxicity. ARPE-19 cell viability for C20-18 lipoplexes with either Chol or DOPE as colipid at various N/P ratios incubated up to 72 h. Horizontal line at 75% viability represents the threshold according to the ISO standard for in vitro testing of biological devices. C+ represents untreated cells and C− represents cells treated to induce cell death. Statistical significance ( ) of 95% ( ).