A study was undertaken to review C60 / mixture toxicity related publications.
To review publications related to C60/mixture toxicity and to summarize the results. Various parties, within the C60 health community, make various statements with respect to the safety of C60 in vegetable oil carriers. Some web sites will point to one (or maybe a few) relevant papers, but non are comprehensive. The C60/mixture community (consumers, researchers, venders and manufactures) need an accessible, unified, update-able source of this information.
Research paper selection for this study was derived from several sources. The majority of the material was obtained from a Toxnet report. Toxnet is on online database of toxicology, hazardous chemicals, environmental health and toxic releases. This report obtained is dated 2013.09.19 and a full copy is available here.
Relevant papers published since this report (that I have come across) were also included as a second source. These additional papers stem from various sources including Google Scalar searches, Pubmed searches and from discussions and links in other publications.
Papers were interpreted as being either beneficial, detrimental or were excluded. If the substance being given consideration was deemed harmful to cells or organisms it was categorized as negative. Likewise, helpful substances were categorized as being positive. Papers were excluded if considered out of scope. Examples would be papers that offer no new experimental findings or focused on mechanisms.
For papers deemed to have beneficial or detrimental evidence, the specific compound of interest was identified along with the delivery media. Overall findings were summarized in the results section.
|PBS.C60||1||phosphate buffered saline|
|PBS.CNT||1||phosphate buffered saline|
|CNT||1||carbon nano tubes|
|SWCNT||1||1||single wall CNT|
|MWCNT||1||multi wall CNT|
Table 1. Results for C60 non-oil based mixtures.
|CO.C60||1||1 ||corn oil|
|CO.SWCNT||1 ||corn oil|
Table 2. Results for C60 oil based mixtures.
 In this publication, the corn oil was found to have generated more genotoxicity than the particles ref
The toxnet report provided the following statement wrt risk…
No data on the potential for fullerenes to produce toxic effects in humans were not available. Several national agencies are conducting research to determine whether nanoparticles pose a threat to exposed workers or consumers. Skin irritation and allergic skin reactions did not occur in laboratory animals following direct skin exposure to fullerenes. Minimal eye irritation occurred. Toxic effects were not observed in laboratory animals in several studies following direct injection of fullerenes into the airways. Decreased activity and altered brain chemicals were observed in laboratory animals following injection of fullerenes directly into the brain. Embryo abnormalities and death were observed in laboratory mice injected with a high dose of fullerene C60 during pregnancy. Data for the potential for fullerenes to cause infertility were not available. The potential for fullerenes to cause cancer has not been directly evaluated in humans or laboratory animals. The potential for fullerenes to cause cancer in humans has not been assessed by the U.S. EPA IRIS program, the International Agency for Research on Cancer, or the U.S. National Toxicology Program 13th Report on Carcinogens.
This report only reviewed papers where pure C60 crystals or (pure or functionalized) C60 in aqueous based solutions were under review. None of the research papers reviewed were based on C60 dissolved in vegetable oil based mixtures.
In summary …
- no human based testing has been done
- no toxicity when C60 is exposed to skin, eye or with direct lung exposure
- decreased/altered brain chemistry if C60 injected directly into the brain
- embryo abnormalities/death reported with high dose injections
- data wrt infertility is not available
- C60 has not been assessed by any of the cancer institutions
The intent of this study was to expand upon the initial toxnet report findings. Table 1 details results from studies where the carrier is non-oil based or there was no carrier. Table 2 summarizes findings from studies where the fullerene was infused in a oil based carrier. The first column in each of these tables identifies the solution and specific C60 variation. To illustrate by example, H2O.C60(OH)x is a hydroxylated C60 fullerene in a aqueous suspension. The x value represents the number of attached hydroxyl groups.
Results summarized in table 1 identify a few mixtures having more toxic than non toxic findings. Specifically, pure C60 crystals (C60), colloidal C60 (H20.C60) and hydroxylated C60 in water (H20.(OH)x) all demonstrate toxic profiles.
A number of papers report pure C60 as being hydrophobic. Work done by Chi-cheng et al. provides some clarification on C60 in H2O behavior. Their investigation demonstrates that smaller particles are hydrophobic and larger particles are hydrophilic. The behavior is actually a result of the curvature of the particle size. Small (hydrophobic) particles will tend to aggregate until a critical size is reached and the behavior will then become hydrophilic.
Andrievsky et al. discuss colloidal C60 dispersion's as ordered water structures. They suggest that the hydrated shells act to isolate C60 from oxygen thus minimizing pro-oxidant behavior. They also state that no toxic effects have been reported for studies where the concentrations less than 100 uM/l or 25 mg/kg total dose have been applied.
Saves et al. report cytotoxicity for low concentrations of C60 aggregates in water. They attribute the damage to disrupted cellular function due to lipid peroxidation.
The underlying mechanisms in play are inconclusive at this point.
The other entries (in table 1) are somewhat balanced wrt good vs. bad counts. Again, keep in mind that this data was incidentally included and should be considered informative.
The amount of research work done on vegetable oil based fullerene mixtures is noticeably less (table 2). There is some concern with the use of corn oil. This GMO based oil product has a high polyunsaturated fatty acid content and a low nutrient profile. A closer look at the research work shows that the high polyunsaturated oil itself can be a source of genotoxicity if sonicated.
If the corn oil result is excluded then the results do clearly indicate that C60 in vegetable oil is a different and viable mode of delivery.
The method by which C60 is prepared, surface modification, size, carrier media are all important factors wrt toxicity. There doesn't appear to be any data suggesting that using quality vegetable oil as a carrier is detrimental. There is ample evidence indicating that non oil based solutions are a risk and should be avoided. More work will be undertaken in the future now that the efficacy of oil based delivery of C60 fullerene has been stated. The Baati/Paris study marks the turning point.