Concerning the toxicity of two compounds used as mediators in biosensor devices: 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetrathiafulvalene (TTF)

Abstract

The lethal dose (LD 50) and the maximum tolerated dose (MTD) of TCNQ and TTF were determined experimentally by single-dose administration to CBA-line mice. The effect of the compounds on the blood constitution, accumulation, acute and subacute dermal and eye irritation, skin sensitization and delayed type hypersensitivity reaction were also monitored in mice and guinea pigs. The LD 50 S were found to be 1225 mg Kg −1 (6·0 mmol kg −1) for TCNQ and 710 mg kg −1 (3·5 mmol kg −1) for TTF; MTDs were 750 mg kg −1 (3·7 mmol kg −1) and 450 mg kg −1 (2·2 mmol kg −1, respectively. Mice that had received the MTD showed no significant change in their measured blood parameters after five days for TTF; however, for TCNQ a decrease in the absolute leucocyte number and changes in the leucoformula were apparent by the fifth day. Oral administration to mice for 28 days at a concentration of 10% of the LD 50 showed a super-accumulation, and the accumulation index was 0·94 and 0·53 for TCNQ and TTF, respectively. Neither compound caused acute or subacute dermal irritation of guinea pigs and there was no acute eye irritation. Skin sensitization in guinea pigs and delayed-type hypersensitivity reaction in mice indicated that TCNQ and TTF used as ethanol solutions were not allergic. This study indicates that TCNQ and TTF may be regarded as low-toxicity compounds.