Cytotoxicity of 1-15 was evaluated via CellTiter-Blue assay on KB, MCF7 and HEK293 cells. KB cells are derived from cervical cancer with high-levels of folate receptor α on the cell surface. This feature is of particular relevance in anticancer applications, as it can be exploited for selective targeting and delivery. MCF7 is a cell line derived from human breast cancer with low-levels of folate receptor α. Therefore, these cells can serve as the negative control for folate receptor α mediated tumor-targeted drug delivery systems. HEK293 is a non-cancer cell line and was chosen to evaluate the specificity of the tested compounds towards cancer cells. Cell viability assay results are summarized in Table .