Comparative study for carcinogenicity of 7 different multi-wall carbon nanotubes with different physicochemical characteristics by a single intraperitoneal injection in male Fischer 344 rats

Abstract

The present study comparatively examined carcinogenicity of 7 different multi-wall carbon nanotubes (MWCNTs) with different physicochemical characteristics. Physicochemical characteristics of MWCNTs (referred to as M-, N-, WL-, SD1-, WS-, SD2-and T-CNTs in the present study) were determined using scanning electron and light microscopes and a collision type inductively coupled plasma mass spectrometer. Male Fischer 344 rats (10 weeks old, 15 animals per group) were administered MWCNTs at a single intraperitoneal dose of 1 mg/kg body weight, and sacrificed up to 52 weeks after the commencement. Fibers of M-, N-, WL-and SD1-CNTs were straight and acicular in shape, and contained few agglomerates. They were relatively long (38-59% of fibers were longer than 5 μm) and thick (33% to more than 70% of fibers were thicker than 60 nm). All of these 4 MWCNTs induced mesotheliomas at absolute incidences of 100%. Fibers of WS-, SD2-and T-CNTs were curled and tightly tangled to form frequent agglomerates. They were relatively short and thin (more than 90% of measured fibers were thinner than 50 nm). WS-CNT did not induce mesothelioma, and only one of 15 rat given SD2-or T-CNT developed tumor. Any correlations existed between the metal content and neither the size or form of fibers, nor the carcinogenicity. It is thus indicated that the physicochemical characteristics of MWCNTs are critical for their carcinogenicity. The straight and acicular shape without frequent agglomerates, and the relatively long and thick size, but not the iron content, may be critical factors. The present data can contribute to the risk management, practical use and social acceptance of MWCNTs.

Comparative carcinogenicity study of a thick, straight-type and a thin, tangled-type multi-walled carbon nanotube administered by intra-tracheal instillation in the rat

“…MWCNTs can be divided into two general subtypes: tangled and straight. Studies in rats using intraperitoneal injection of straight-type MWCNTs [15][16][17][18], an intermediate-type of MWCNT [18], and tangled-type MWCNTs [14][15][16][17] showed that in the peritoneal cavity the straight-type MWCNTs had the highest carcinogenic potential, the intermediate type MWCNT had a lower carcinogenic potential than the straight-type MWCNTs, and the tangled-type MWCNTs had the lowest carcinogenic potential. Two of these studies used MWCNTs with diameters similar to the MWCN T-A used in our present study.…”

“…The iron content of MWCNT-A and MWCNT-B is strikingly different: MWCNT-A has an iron content of approximately 0.001% while MWCNT-B has an iron content of 1.1%, a difference of more than 1000-fold. While iron content has not been found to be associated with MWCNT induction of mesothelial tumors in the peritoneal cavity [17], it is possible that iron content may have a role in MWCNT-mediated carcinogenicity in the lung [28]. Another notable difference between MWCNT-A and MWCNT-B fibers is the number of coaxial graphene cylinders that compose the fibers.…”

“…One effect would be to retain the fiber in the lung, enhancing fiber-mediated lung toxicity. The second effect would be to decrease interaction of MWCNT-B fibers with macrophages, thereby decreasing tissue damage and reducing fiber-mediated lung toxicity: enclosure of MWCNT fibers in granulation tissue also inhibits MWCNT-mediated carcinogenicity in the peritoneal cavity [17]. Importantly, MWCNT-B associated iron can theoretically generate oxygen radicals via the Fenton reaction in the absence of fiber interaction with macrophages.…”

<p>Toxicity of Carbon Nanotubes as Anti-Tumor Drug Carriers</p>

“…The carcinogenic rates of four needle-shaped MWCNTs were as high as 100% while tangled MWCNTs did not induce mesothelioma. 190 Comprehensive findings from multiple studies thus suggest that different shapes of CNTs exert differing levels of cytotoxicity, with the greatest toxicity induced by needle-shaped CNTs.…”

Flexible and transparent silver nanowire structures for multifunctional electrical and optical biointerfacing

“…[17] CNTs also suffer from controversial results and concerns associated with their cytotoxicity as biointerfaces. [18][19][20] The sheet resistance (Rsh) of graphene and CNTs is typically 1-2 orders of magnitude higher than that of ITO. [12,14] As a result, graphene and CNTs microelectrodes require additional metal interconnects which complicates the device manufacturing process.…”