SRF Heavy Industries

From The prolongation of the lifespan of rats by repeated oral administration of [60] fullerene:

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3.3. Chronic toxicity and effects of C₆₀ on lifespan of rats

Fig. 3 shows the animal survival and growth. After five months of treatment (M₁₅) one rat treated with water only exhibited some palpable tumours in the abdomen region. Due to the rapid development of tumours (about 4 cm of diameter) this rat died at M₁₇. As rats are known to be sensitive to gavages, we decided to stop the treatment for all rats and to observe their behaviour and overall survival.

All remaining animals survived with no apparent sign of behavioural trouble until M₂₅ (Fig. 3a). At the end of M₂₅ the animals of the control groups showed signs of ulcerative dermatitis with ageing while C₆₀-treated animals remained normal. As the growths of all surviving animals showed no significant difference until M₃₀ (Fig. 3b) indicating that the treatment did not alter their food intake, we continued observing their survival.

At M₃₈ all water-treated control rats were dead (Fig. 3a). This agrees with the expected lifespan of this animal species that is thirty to thirty six months. At this time 67% of olive-oil-treated rats and 100% of C₆₀-treated rats were still alive.

The survival distributions for C₆₀-olive oil-treated rats and controls were estimated by the non-parametric Kaplane–Meier estimator (Fig. 3) and compared by a log-rank estimated test. The estimated median lifespan (EML) for the C₆₀-treated rats was 42 months while the EMLs for control rats and olive oil-treated rats were 22 and 26 months, respectively. These are increases of 18 and 90% for the olive-oil and C₆₀-treated rats, respectively, as compared to controls.

The log-rank test leads to Χ² values (one degree of freedom) of 7.009, 11.302, and 10.454, when we compare water-treated and olive oil-treated rats, water-treated and C₆₀-treated rats, and olive oil-treated and C₆₀-treated rats, respectively. This means that olive oil extends the lifespan of rats with respect to water with a probability of 0.99 while C₆₀-olive oil extends the lifespan of C₆₀-treated rats with a probability of 0.999 and 0.995 with respect to water and olive oil treatments, respectively.

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So I guess doubling the expected lifespan of a lab rat after seven months of daily dosing counts as no measurable levels of toxicity to C₆₀ buckyballs. Hunh.

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Baati T, et al., The prolongation of the lifespan of rats by repeated oral administration of [60]fullerene, Biomaterials (2012), doi:10.1016/j.biomaterials.2012.03.036