Citotoxicidade e genotoxicidade de nanotubos de carbon

Abstract

Recebido em 2/5/11; aceito em 6/9/11; publicado na web em 8/11/11 CYTOTOXICITY AND GENOTOXICITY OF CARBON NANOTUBES. There are many controversies regarding the cyto-and genotoxicity of carbon nanotubes (CNTs). In this work, we discuss that many of the incongruous arguments are probably associated with the poor physical-chemical characterization of the CNT samples used in many publications. This manuscript presents examples of carbon nanostructures observed under high resolution electron microscopy that can be found in typical CNT samples, and shows which roles in cyto-and genotoxicity need to be better investigated. Issues concerning chemical treatment are addressed and examples of misunderstandings that can occur during the studies of cyto-and genotoxicity of CNT samples are given.Keywords: cell viability; DNA damage; carbon nanotube samples. INTRODUÇÃOA ideia de nanotecnologia como uma ciência de manipulação molecular ou de escala nanométrica sempre foi um fascínio para muitos pesquisadores. Feynman em 1959 e Drexler em 1986 já chamavam a atenção da comunidade científica com relação à nanotecnologia. 1,2 Com os avanços da microscopia e de outras técnicas, a nanotecnologia se tornou nos últimos 10 anos uma das áreas mais importantes da ciência e da inovação tecnológica com projeções comerciais estimadas para 2015 em um trilhão de dólares. 3,4 Nesse contexto a Nanotoxicologia desempenha um papel importante, pois investiga os efeitos dos nanodispositivos e nanoestruturas em sistemas biológicos. 5 A avaliação toxicológica de partículas e fibras em escala nanométrica 6 contribui para uma série de questões ligadas à utilização de nanomateriais em produtos comerciais. Sendo assim, o entendimento dos mecanismos de cito-e genotoxicidade de um dado nanomaterial é fundamental para a definição de seu impacto ambiental e de estratégias de proteção aos trabalhadores e consumidores. 7 O presente artigo apresenta uma revisão de estudos realizados sobre a eventual indução de danos às células e ao DNA (citotoxicidade e genotoxicidade, respectivamente) por nanotubos de carbono (NTCs), conduzidos em experimentos in vitro. Na literatura existente é possível detectar várias controvérsias e questões que ainda precisam ser esclarecidas já que algumas dessas nanoestruturas se apresentam biocompatíveis. Recentes estudos demonstraram, por exemplo, que a enzima mieloperoxidase presente em neutrófilos humanos é capaz de degradar nanotubos de carbono de parede simples (NTCPS) e que os produtos da biodegradação dos NTCs não induziram inflamação quando expostos aos pulmões de camundongo. [8][9][10][11][12] Embora haja um conflito sobre o mérito do descobrimento dos NTCs, 13 o fato é que esses são um dos nanomateriais mais fascinantes e estudados nas últimas duas décadas. Um NTCPS pode ser descrito basicamente como uma folha de grafeno enrolada e fechada em cada extremidade por metade de um fulereno. Quando várias folhas de grafeno constituem a parede do tubo os mesmos são classificados como NTCs de parede múltiplas (NTCPM). 14 Os NTCs aprese...

Lack of mutagenic effect by multi-walled functionalized carbon nanotubes in the somatic cells of Drosophila melanogaster

“…Although cell viability assays performed by a few researchers have detected that SWCNT samples containing residual iron have a high cytotoxic potential (Franchi et al, 2011), the MWCNT samples used in the present study catalyzed with C, O and Fe demonstrated no cytotoxicity according to the test applied. This finding may be associated with the high levels of purity of the nanotubes used in our study: only 1.5% from iron oxide and the other 98.5% from carbon.…”

“…Results obtained in another study using single walled carbon nanotubes and graphite nanofibers (3.8-380 lg/mL), evaluated by the comet test, also demonstrated a correlation between genotoxicity and the activity of metal catalysts present in the material (Lindberg et al, 2009). The toxicity and genotoxicity mechanisms of the CNTs have not yet been fully clarified and there is a need for more research in this area (Franchi et al, 2011), but evidence suggests points of similarity between CNTs and asbestos fibers, due to the generation of reactive oxygen species and oxidative stress (Sanchez et al, 2009). Although cell viability assays performed by a few researchers have detected that SWCNT samples containing residual iron have a high cytotoxic potential (Franchi et al, 2011), the MWCNT samples used in the present study catalyzed with C, O and Fe demonstrated no cytotoxicity according to the test applied.…”

“…The toxicity and genotoxicity mechanisms of the CNTs have not yet been fully clarified and there is a need for more research in this area (Franchi et al, 2011), but evidence suggests points of similarity between CNTs and asbestos fibers, due to the generation of reactive oxygen species and oxidative stress (Sanchez et al, 2009). Although cell viability assays performed by a few researchers have detected that SWCNT samples containing residual iron have a high cytotoxic potential (Franchi et al, 2011), the MWCNT samples used in the present study catalyzed with C, O and Fe demonstrated no cytotoxicity according to the test applied. This finding may be associated with the high purity levels of the nanotubes used in our study: only 1.5% from iron oxide and the other 98.5% from carbon.…”

DFT Study on the Mechanistic, Energetic and Structural Aspects of Adsorption of Tirapazamine Onto Pristine and Functionalized Carbon Nanotubes

“…31,32 Despite some disadvantages such as low solubility and that they will not be easily discharged from the body, there has been increasing interest during the past two decades for using CNTs in drug delivery. [33][34][35][36] Using CNTs for drug delivery causes reduction in the dosage of the intended drug and consequently the reduction of its side effects. 37,38 Covalent and noncovalent (hydrogen bonds and van der Waals interactions) functionalizations perform a principle role in the drug delivery systems.…”

Cell Viability, Mitotic Index and Callus Morphology of Byrsonima verbascifolia (Malpighiaceae)

“…The mitotic index (MI) is a parameter used to assess the growth of cell populations in vitro and their regeneration capacity, and also is used to the identification of several mitotic abnormalities associated with the age of the cultures (Franchi et al 2012). This parameter can also be used as an indicator of adequate proliferation of cells, mainly applied in mutagenicity and toxicity studies (Gadano et al 2002;Rogero et al 2003).…”