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  • 1.
    Girgis, E.
    et al.
    Natl Res Ctr, Giza, Egypt .
    Khalil, W. K. B.
    Natl Res Ctr, Giza, Egypt .
    Emam, A. N.
    Natl Res Ctr, Giza, Egypt .
    Mohamed, M. B.
    Cairo Univ, Cairo, Egypt .
    Rao, K. Venkat
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Nanotoxicity of Gold and Gold-Cobalt Nanoalloy2012In: Chemical Research in Toxicology, ISSN 0893-228X, E-ISSN 1520-5010, Vol. 25, no 5, p. 1086-1098Article in journal (Refereed)
    Abstract [en]

    Nanotoxicology test of gold nanoparticles (Au NPs) and gold-cobalt (Au-Co) nanoalloy is an important step in their safety evaluation for biomedical applications. The Au and Au-Co NPs were prepared by reducing the metal ions using sodium borohydride (NaBH4) in the presence of polyvinyl pyrrolidone (PVP) as a capping material. The average size and shape of the nanoparticles (NPs) were characterized using high resolution transmission electron microscopy (HRTEM). Cobalt presence in the nanoalloy was confirmed by energy dispersive X-ray spectroscopy (EDX) analysis, and the magnetic properties of these particles were determined using a vibrating sample magnetometer (VSM). The Gold and gold-cobalt NPs of average size 15 +/- 1.5 nm were administered orally to mice with a dose of 80, 160, and 320 mg/kg per body weight (bw) using gavages. Samples were collected after 7 and 14 days of the treatment. The results indicated that the Au-Co NPs were able to induce significant alteration in the tumor-initiating genes associated with an increase of micronuclei (MNs) formation and generation of DNA adduct (8-hydroxy-2-deoxyguanosine, 8-OHdG) as well as a reduction in the glutathione peroxidase activity. This action of Au-Co NPs was observed using 160 and 320 mg/kg bw at both time intervals. However, Au NPs had much lower effects than Au-Co NPs on alteration in the tumor-initiating genes, frequency of MNs, and generation of 8-0HdG as well as glutathione peroxidase activity except with the highest dose of Au NPs. This study suggests that the potential to cause in vivo genetic and antioxidant enzyme alterations due to the treatment by Au-Co nanoalloy may be attributed to the increase in oxidative stress in mice.

  • 2. Goldstein, S.
    et al.
    Czapski, G.
    Lind, Johan
    KTH, Superseded Departments, Chemistry.
    Merenyi, Gabor
    KTH, Superseded Departments, Chemistry.
    Carbonate radical ion is the only observable intermediate in the reaction of peroxynitrite with CO22001In: Chemical Research in Toxicology, ISSN 0893-228X, E-ISSN 1520-5010, Vol. 14, no 9, p. 1273-1276Article in journal (Refereed)
    Abstract [en]

    The reaction of ONOO- with CO2 at alkaline pH was recently reported to form a transient absorption with a maximum at 640 nm and a half-life of ca. 4 ms at 10 degreesC [Meli et al. (1999) Helv. Chim. Acta 82, 722-725]. This transient absorption was hardly affected by the presence of (NO)-N-., and therefore was attributed to the adduct ONOOC(O)O-. This conclusion contradicts all current experimental results as it suggests that the decomposition of this adduct via homolysis of the O-O bond into CO3.- and . NO2 is a minor pathway. In the present work the observations of Meli et al. will be shown to be artifacts resulting from light coming from the UV region. When these experiments are carried out in the presence of appropriate cutoff filters, the only observable intermediate formed in the reaction of ONOO- with CO2 at alkaline pH is the carbonate radical ion with a maximum at 600 nm. This transient absorption is not observed in the presence of (NO)-N-. or ferrocyanide. In the latter case ferricyanide is formed, and its yield was determined to be 66 +/-2% of the initial concentration of peroxynitrite. The reaction of ONOO- with 16 mM CO2 with and without ferrocyanide was also studied at pH 5.6-7.7 in the presence of 0.1 M phosphate, where both the initial pH and [CO2] remain constant. Under these conditions the rate constant of the decay of peroxynitrite was found to be identical to that of the formation of ferricyanide, indicating that ONOOC(O)(-) does not accumulate. These results confirm our earlier observations, i.e., the reaction of peroxynitrite with excess CO2 takes place via the formation of about 33% CO3.- and (NO2)-N-. radicals in the bulk of the solution.

  • 3. Goldstein, S.
    et al.
    Czapski, G.
    Lind, Johan
    KTH, Superseded Departments, Chemistry.
    Merenyi, Gabor
    KTH, Superseded Departments, Chemistry.
    Gibbs energy of formation of peroxynitrate-order restored2001In: Chemical Research in Toxicology, ISSN 0893-228X, E-ISSN 1520-5010, Vol. 14, no 6, p. 657-660Article in journal (Refereed)
    Abstract [en]

    In a recent publication [Nauser et al. (2001) Chem. Res. Toxicol. 14, 248-350], the authors estimated a value of 14 +/- 3 kcal/mol for the standard Gibbs energy of formation of ONOO- and argued that the experimental value of 16.6 kcal/mol [Merenyi, G., and Lind, J. (1998) Chem. Res. Toxicol. 11, 243-246] is in error. The lower value would suggest that the yield of free radicals during decomposition of ONOOH into nitrate is negligibly low, i.e., less than 0.5%, though within the large error limit given, the radical yield might vary between 0.003% and ca. 80%. The experimental value of 16.6 +/- 0.4 kcal/mol was based on the determination of the rate constant of the forward reaction in the equilibrium ONOO- reversible arrow (NO)-N-. and O-2(.-) by use of C(NO2)(4), an efficient scavenger of O-2(.-) which yields C(NO2)(3)(-). Nauser et al. reported that addition of.NO has no significant effect on the rate of formation of C(N02)3-, and therefore the formation of C(No-2)(3-) is due to a process other then reduction of C(NO2)(4) by O-2 (.-) In addition, they argued that Cu(II) nitrilotriacetate enhances the rate of peroxynitrite decomposition at pH 9.3 without reduction of Cu(II). In the present paper, we show that the formation of C(N02)3- due to the presence peroxynitrite is completely blocked upon addition of . NO, Furthermore, the acceleration of the rate of peroxynitrite decomposition at pH 9 in the presence of catalytic concentrations of SOD ([ONOO-]/[SOD] > 30) results in the same rate constant as that obtained in the presence of C(NO2)4. These results can only be rationalized by assuming that ONOO- homolyses into (NO)-N-. and O-2(.-) With k = 0.02 S-1 at 25 degreesC. Thus, the critical experiments suggested by Nauser et al. fully support the currently accepted thermodynamics as well as the mode of decomposition of the ONOOH/ONOO- system.

  • 4. Goldstein, S.
    et al.
    Samuni, A.
    Merenyi, Gabor
    KTH, Superseded Departments, Chemistry.
    Reactions of nitric oxide, peroxynitrite, and carbonate radicals with nitroxides and their corresponding oxoammonium cations2004In: Chemical Research in Toxicology, ISSN 0893-228X, E-ISSN 1520-5010, Vol. 17, no 2, p. 250-257Article in journal (Refereed)
    Abstract [en]

    Cyclic nitroxides effectively protect biological systems against radical-induced damage. However, the mechanism of the reactions of nitroxides with nitrogen-derived reactive species and carbonate radicals is far from being elucidated. In the present study, the reactions of several representative piperidine- and pyrrolidine-based nitroxides with (NO)-N-., peroxynitrite, and CO3.- were investigated, and the results are as follows: (i) There is no evidence for any direct reaction between the nitroxides and the (NO)-N-.. In the presence of oxygen, the nitroxides are readily oxidized by (NO2)-N-., which is formed as an intermediate during autoxidation of (NO)-N-.. (ii) (NO)-N-. reacts with the oxoammonium cations to form nitrite and the corresponding nitroxides with k(1) = (9.8 +/- 0.2) x 10(3) and (3.7 +/- 0.1) x 10(5) M-1 s(-1) for the oxoammonium cations derived from 2,2,6,6-tetramethylpiperidine-1-oxyl (TPO) and 3-carbamoyl-proxyl (3-CP), respectively. (iii) CO3.- oxidizes all nitroxides tested to their oxoammonium cations with similar rate constants of (4.0 +/- 0.5) x 10(8) M-1 s(-1), which are about 3-4 times higher than those determined for H-abstraction from the corresponding hydroxylamines TPO-H and 4-OH-TPO-H. (iv) Peroxynitrite ion does not react directly with the nitroxides but rather with their oxoammonium cations with k(10) = (6.0 +/- 0.9) x 10(6) and (2.7 +/- 0.9) x 10(6) M-1 s(-1) for TPO+ and 3-CP+, respectively. These results provide a better insight into the complex mechanism of the reaction of peroxynitrite with nitroxides, which has been a controversial subject. The small effect of relatively low concentrations of nitroxides on the decomposition rate of peroxynitrite is attributed to their ability to scavenge efficiently (NO2)-N-. radicals, which are formed during the decomposition of peroxynitrite in the absence and in the presence Of CO2. The oxoammonium cations, thus formed, are readily reduced back to the nitroxides by ONOO-, while forming (NO)-N-. and O-2. Hence, nitroxides act as true catalysts in diverting peroxynitrite decomposition from forming nitrating species to producing nitrosating ones.

  • 5. Khalil, W. K. B.
    et al.
    Girgis, E.
    Emam, A. N.
    Mohamed, M. B.
    Rao, K. Venkat
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Genotoxicity Evaluation of Nanomaterials: DNA Damage, Micronuclei, and 8-Hydroxy-2-deoxyguanosine Induced by Magnetic Doped CdSe Quantum Dots in Male Mice2011In: Chemical Research in Toxicology, ISSN 0893-228X, E-ISSN 1520-5010, Vol. 24, no 5, p. 640-650Article in journal (Refereed)
    Abstract [en]

    Quantum dots (QDs) are a novel class of inorganic fluorophores which are gaining widespread recognition as a result of their exceptional photophysical properties and their applications as a biomarker and in molecular biomedical imaging. The aim of this study was to evaluate the in vivo genotoxicity in mice exposed to CdSe quantum dots of average size 5.0 +/- 0.2 nm and CdSe doped with 1% cobalt ions of similar size. The quantum dots are surface modified using mercaptoacetic acid (MAA) in order to be biocompatible and water-soluble. The MAA-QDs were given to the mice orally at doses of 500, 1000, and 2000 mg/kg by weight of MAA-QDs. Bone marrow and liver samples were collected after two and seven days of treatment. The results indicated that after two days of treatment, the high dose of doped MAA-QDs was significantly able to induce DNA damage, formation of micronuclei (MNs), and generation of DNA adduct (8-hydroxy-2-deoxyguanosine, 8-OHdG). However, increasing DNA damage and the frequency of MNs formation as well as the generation of DNA adducts were observed with both the undoped MAA-QDs (2000 mg/kg) and doped MAA-QDs (1000 and 2000 mg/kg) after seven days of treatment. The results of our study indicate that exposure to high doses of pure MAA-QDs or MAA-QDs doped with cobalt has the potential to cause indirect in vivo genetic damage, which may be attributed to free radical-induced oxidative stress in mice.

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