Reaction mass of zinc oxide and zinc peroxide

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study is well documented and meets generally accepted scientific principles.

Data source

Reference

Reference Type:

publication

Title:

Organ biodistribution, clearance, and genotoxicity of orally administered zinc oxide nanoparticles in mice

Author:

Li C-H, Shen C-C, Cheng Y-W, Huang S-H, Wu C-C, Kao C-C, Liao,J-W and Kang J-J

Year:

2012

Bibliographic source:

Nanotoxicology, 6(7):746-56

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Male ICR mice were administered ZnO nanoparticle and ZnO microparticle in an identical manner, orally by intragastric gavage. Peripheral blood (10–20 mL) was sampled from the tail vein at 24, 48, and 72 h post-dosing, smeared on a glass microscope slide and stained with acridine orange (40 mg/ mL). The prepared slides were immediately examined by fluorescence microscopy for chromosomal abberation.

GLP compliance:

not specified

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

Zinc oxide

EC Number:

215-222-5

EC Name:

Zinc oxide

Cas Number:

1314-13-2

Molecular formula:

OZn

IUPAC Name:

oxozinc

Test material form:

solid: nanoform

Details on test material:

uncoated ZnO nanoparticle:
- Diameter: 50 nm approximately
- Hydrodynamic diameter: 93.35 ± 14.53 nm

ZnO microparticles:
- Diameter: >100 nm
- Hydrodynamic diameter 1226.2 ± 120.4 nm

Other information: The suspensions of ZnO particles (stock concentration: 50 mg/mL) were prepared using anhydrous dimethyl sulfoxide (DMSO). ZnO-nanoparticle and ZnO-microparticle were diluted with sterile water plus 1% hydroxypropyl methyl cellulose (HPMC) or culture medium, then mixed vigorously, sonicated, and then immediately applied to mice or human cells to minimize agglomeration. Finally, the DMSO concentration was less than 1% (in vivo study).

Test animals

Species:

mouse

Strain:

ICR

Sex:

male

Details on test animals or test system and environmental conditions:

Male Crl:CD-1 (ICR) mice (6-week-old) were obtained from the Animal Center of National Taiwan University (Taipei, Taiwan) and acclimated for 1 week in the housing room under 12 h of light/dark cycle, 23 ± 1⁰C, and 39~43% relative humidity; water and food were available ad libitum. All procedures involving the use of animals were in compliance with Guide for the Care and Use of Laboratory Animals (National Academy of Sciences Press, 1996) and approved by the Institutional Animal Care and Use Committee (approval number: NTUIACUC-20090024).

Administration / exposure

Route of administration:

other: intragastric gavage

Vehicle:

- Vehicle(s)/solvent(s) used: DMSO
- Dosing volume: 10 mL/kg bw

Details on exposure:

The dosing volume was 10 mL/kg bw

Duration of treatment / exposure:

Single exposure

Frequency of treatment:

Once

Post exposure period:

24, 48, and 72 h

Doses / concentrations

Remarks:

Doses / Concentrations:
1250, 2500 and 5,000 mg/kg bw
Basis:
nominal conc.

No. of animals per sex per dose:

5/dose

Control animals:

yes

Positive control(s):

cyclophosphamide

Examinations

Tissues and cell types examined:

Peripheral blood (10–20 mL) was sampled from the tail vein at 24, 48, and 72 h post-dosing.

Details of tissue and slide preparation:

Peripheral blood (10–20 mL) was sampled from the tail vein at 24, 48, and 72 h post-dosing, smeared on a glass microscope slide and stained with acridine orange (40 mg/ mL). The prepared slides were immediately examined by fluorescence microscopy. The ratio (%) of polychromatic erythrocytes (PCEs) to total erythrocytes and the frequency of micronucleated polychromatic erythrocytes (MNPCEs) (%) were calculated by counting a total of 1000 erythrocytes or PCEs per animal, respectively

Statistics:

All data were expressed as the mean ± SD from at least three independent experiments (N ‡ 3). The significance of the difference between the control and each experimental test condition was analysed by Student’s t-test. Statistically significant differences among groups were determined using one-way analysis of variance (ANOVA). A value of p < 0.05 was taken as statistically significant.

Results and discussion

Test results

Sex:

male

Genotoxicity:

negative

Toxicity:

not specified

Negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

The proportion of PCEs and the frequency of MNPCEs in ZnO nanoparticles and ZnO microparticles treated groups were not statistically different from that of the negative control animals. Reduction in the ratio of PCEs to total erythrocytes (%) and an increase in frequency of MNPCEs (%) were found in the positive control group.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative
Based on the study details, both ZnO nanoparticles and ZnO microparticles were not considered to be clastogenic in the in vivo micronucleus assay.

Executive summary:

The study was conducted to examine the clastogenic effect of both ZnO nanoparticles and ZnO microparticles in an in vivo micronucleus assay in mice.

Male ICR mice were administered test substances in an identical manner, orally by intragastric gavage. Peripheral blood (10–20 mL) was sampled from the tail vein at 24, 48, and 72 h post-dosing, smeared on a glass microscope slide and stained with acridine orange (40 mg/ mL). The prepared slides were immediately examined by fluorescence microscopy. The ratio (%) of polychromatic erythrocytes (PCEs) to total erythrocytes and the frequency of micronucleated polychromatic erythrocytes (MNPCEs) (%) were calculated by counting a total of 1000 erythrocytes or PCEs per animal, respectively

The proportion of PCEs and the frequency of MNPCEs in ZnO nanoparticles and ZnO microparticles treated groups were not statistically different from that of the negative control animals. Reduction in the ratio of PCEs to total erythrocytes (%) and an increase in frequency of MNPCEs (%) were found in the positive control group.

Based on the study details, both ZnO nanoparticles and ZnO microparticles were not considered to be clastogenic to mice in the in vivo micronucleus assay.