Biodegradation of carbon nanotubes by eosinophil peroxidase.
Kapralov-AA; Yanamala-N; Feng-WH; Fadeel-B; Star-A; Shvedova-AA; Kagan-VE
Toxicologist 2011 Mar; 120(Suppl 2):10-11
Single-walled carbon nanotubes (SWCNT) having high potential for applications in nanotechnology, electronics and medicine can have adverse effects on human health and the environment. In vitro data indicate that SWCNT may be cytotoxic, largely by inducing oxidative stress. It was shown previously, that horseradish peroxidase and human myeloperoxidase (MPO) catalyse the biodegradation of SWCNT. Biodegradation of nanotubes by another mammalian peroxidase - eosinophil peroxidase (EPO) has not been studied. EPO exocytosed by eosinophils is actively involved in increased oxidant production during lung inflammation after treatment with pollutants and cigarette smoke. We found that incubation with EPO and H2O2 caused degradation of CNT over time, and the CNT suspension turned translucent. Neither EPO alone nor H2O2 alone caused nanotube degradation. Degragation of CNT was confirmed by: 1) visible-near-infrared spectroscopy showing decrease of characteristic metallic band (M1) and semiconducting (S2) transition band and 2) Raman spectroscopy demonstrating increase of disorder-induced D-band and decrease of tangential-mode G-band. Drastic changes in nanotube morphology were demonstrated by transmission electron microscopy. Biodegradation of CNT was higher in the presence of NaBr suggesting that not only reactive radical intermediates of EPO but also generated HOBr was involved in the biodegradation process. Computer modeling was used to structurally characterize possible nanotube interaction sites with EPO. Studies are underway to assess oxidative biodegradation of CNT by EPO-rich activated human eosinophils. We conclude, that EPO can participate in enzymatic biodegradation of CNT after respiratory exposures during their production and handling.
Airborne-particles; Air-contamination; Biodegradation; Biological-effects; Cell-biology; Cellular-reactions; Computer-models; Cytotoxic-effects; Cytotoxicity; Environmental-contamination; Environmental-pollution; Exposure-levels; Health-hazards; Humans; Inhalation-studies; Lung; Lung-disease; Lung-disorders; Lung-function; Lung-irritants; Microscopic-analysis; Morphology; Nanotechnology; Oxidative-processes; Peroxidases; Physiological-effects; Pulmonary-system-disorders; Quantitative-analysis; Respiratory-hypersensitivity; Respiratory-irritants; Respiratory-system-disorders; Spectrographic-analysis; Statistical-analysis; Toxic-effects
The Toxicologist. Society of Toxicology 50th Annual Meeting and ToxExpo, March 6-10, 2011, Washington, DC
University of Pittsburgh at Pittsburgh