Drug delivery assessment of an iron-doped fullerene cage towards thiotepa anticancer drug

•Features of thiotepa (TP) anticancer drug and a fullerene (F) cage were investigated.•Two configurations of complex models were recognized through relaxation of N head and S heads.•The strength of TPN@F model was higher than the strength of TPS@F model.•The F cage could work for protecting delivery of TP anticancer.•The employed F cage mode was seen suitable for working in the drug delivery process of TP anticancer.