Single Wall Carbon Nanotubes (SWCNT)

Additional physico-chemical information

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

other: Dispersion in BSA water

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods

Qualifier:

according to guideline

Guideline:

other: Nanogentox protocol

Version / remarks:

May 18th, 2010; IN SUPPORT OF PROSPECT: Ecotoxicology Test Protocols for Representative Nanomaterials in Support of the OECD Sponsorship Programme

GLP compliance:

no

Results:

Following sonication using the NANOGENTOX dispersion protocol, the test material did not disperse in the 0.05% BSA-water solution. The test material clumped together in clearly visible agglomerates and stuck to the slides of the vial. It was obvious that the test material was not in suspension because liquid clearly moved away from the material when the vial was tilted.

Conclusions:

This study demonstrated that the test material Tuball™ is not suitable for use with the NANOGENTOX dispersion protocol as it was not possible to create a stable suspension of the test material.

Reference 2

Endpoint:

other: Prepartion of a homogenous and stable disperion for in vitro mutagenicity testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods

Qualifier:

according to guideline

Guideline:

other:

Version / remarks:

NANOGENOTOX protocol- part 4

GLP compliance:

no

Results:

Following several attempt to prepare stable homogenous solutions/dispersions of Tuball single wall carbon nanotubes (SWCNT) in test media, required to perform in vitro mutagenicity studies (see section on mutagenicity in this dossier), that all failed at the institute that was supposed to perform the in vitro studies, it was decided to consult internationally recognized specialist for handling nanomaterial in such media and establish a collaboration between these specialists and the testing facility.
To this end, a part of the test sample was shipped to the laboratory of The Talmon Group in Israel, which is well known and recognized for handling nanomaterial and cooperated in the development. Their task was to try, based on their experience with nanomaterial samples, to find a methodology to establish stable and homogenous solutions of SWCNT in BSA (bovine serum albumin) water, that could be used for performing in vitro mutagenicity tests.
However, also at the Talmon group, despite several attempts to find a way to prepare a stable solution (Jan – Jul 2019) such attempt did fail as reported here:
We used sterile filtered 0.05% w/v BSA-water as the dispersion medium (prepared by NANOGENOTOX protocol- part 4). We weighed 15.36 mg of CNTs powder and used 30 μL of 96% purity ethanol for pre-wetting of the CNTs. Then 970 μL of 0.05% w/v BSA-water was added to the pre-wetted CNTs by pipette, while slowly rotating. Then the remaining 5 ml of 0.05% w/v BSA-water was added to the vial.
The vial was placed on ice for 10 minutes. We sonicated with a probe-sonicator to deliver the requested amount of energy, according to the GENOTOX protocol (7056 Joule).
The CNTs remained aggregated at the bottom of the vial, with no visible dispersion.

Conclusions:

Attempt to prepare a stable and homogenous solution of Tuball SWCNT in BSA water, performed at the Talmon Group in Israel did fail and no dispersion/solution, suitable for in vitro mutagenicity testing could be prepared (Nanogenotox protocol).

Description of key information

Following several attempt to prepare stable homogenous solutions/dispersions of Tuball™single wall carbon nanotubes (SWCNT) in test media, required to perform in vitro mutagenicity studies (see section on mutagenicity in this dossier), that all failed at the institute that was supposed to perform the in vitro studies, it was decided to consult internationally recognized specialist for handling nanomaterial in such media and establish a collaboration between these specialists and the testing facility.

To this end, a part of the test sample was shipped to the laboratory of The Talmon Group in Israel, which is well known and recognized for handling nanomaterial and cooperated in the development. Their task was to try, based on their experience with nanomaterial samples, to find a methodology to establish stable and homogenous solutions of SWCNT in BSA (bovine serum albumin)water, that could be used for performing in vitro mutagenicity tests.

However, also at the Talmon group, despite several attempts to find a way to prepare a stable solution (Jan – Jul 2019) such attempt did fail as reported here.

In parallel equal samples of the test material were provided to the In Vitro Toxicology Group, Institute of Life Science, Swansea University Medical School, Swansea University, Singleton Park, Swansea, SA2 8PP, Wales, UK, well experienced in using the Nanogentox protocol, which was established specifically for the purpose of investigating nanomaterials in mutagenicity studies.

The NANOGENTOX dispersion protocol was developed as part of the Executive Agency for Health and Consumers (EAHC) NANOGENOTOX project. Its purpose was to provide toxicological laboratories with a Standard Operation Procedure (SOP) for batch preparation of nanomaterials for in vitro and in vivo toxicity testing. The utility of the NANOGENOTOX protocol was demonstrated in a five-laboratory interlaboratory comparison study and implemented as a mandatory protocol for in vitro studies in the EU FP7 NANoREG project. It has also been used for numerous in vivo toxicological studies in rodents where BSA may be exchanged with the species specific (e.g., mouse and rat) serum albumin.

Both labs, coordinated by In Vitro connect and in collaboration with the laboratory TOXI-COOP ZRT in Hungary, having made own investigations, in order to perform in vitro mutagenicity studies according to OECD 473 and 476, failed to prepare stable homogenous solutions of Tuball™ Single Wall Carbon Nanotubes (SWCNTs), thus, confirming the initial findings of TOXI-COOP ZRT (see section on mutagenicity). Thus, it can be concluded that it is not technically feasible to prepare stable homogenous solutions of the test material Tuball™ Single Wall Carbon Nanotubes (SWCNTs) and in conclusion, in vitro mutagenicity studies cannot be performed with this material.

Additional information

The complete summary report on the attempts to create a stable and homogenous dispersion in the different laboratories involved is attached to this endpoint summary for reference, including pictures taken.