Toxicity of cucurbit[7]uril and cucurbit[8]uril: an exploratory in vitro and in vivo study.

Cucurbit[n]urils (CB[n]) are potential stabilizing, solubilizing, activating, and delivering agents for drugs. The toxicity of the macrocyclic host molecules cucurbit[7]uril (CB[7]), the most water-soluble homologue, as well as cucurbit[8]uril (CB[8]) has been evaluated. In vitro studies on cell cultures revealed an IC(50) value of 0.53 +/- 0.02 mM for CB[7], corresponding to around 620 mg of CB[7] per kg of cell material. Live-cell imaging studies performed on cells treated with subtoxic amounts of CB[7] showed no detrimental effects on the cellular integrity as assessed by mitochondrial activity. For CB[8], no significant cytotoxicity was observed within its solubility range. The bioadaptability of the compounds was further examined through in vivo studies on mice, where intravenous administration of CB[7] showed a maximum tolerated dosage of 250 mg kg(-1), while oral administration of a CB[7]/CB[8] mixture showed a tolerance of up to 600 mg kg(-1). The combined results indicate a sufficiently low toxicity to encourage further exploration of CB[n] as additives for medicinal and pharmaceutical use.