Platinum dioxide

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 May 2018 - 3 August 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Platinum dioxide

EC Number:

215-223-0

EC Name:

Platinum dioxide

Cas Number:

1314-15-4

Molecular formula:

O2Pt

IUPAC Name:

Platinum dioxide

Details on test material:

Platinum dioxide
CAS# 1314-15-4

Specific details on test material used for the study:

Purity: 100% PtO2x0.7H2O or 94.5% PtO2 (based on platinum content of 81.17%)

Method

Target gene:

Histidine

Species / strain

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102

Metabolic activation:

with and without

Metabolic activation system:

S-9 derived from Aroclor 1254-treated male Sprague-Dawley rats

Test concentrations with justification for top dose:

Mutation Experiment 1 (with and without S9)
5, 16, 50,160, 500, 1600, 5000 ug/plate

Mutation Experiment 2 (with and without S9)
51.2, 128, 320, 800, 2000, 5000 ug/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Formulations in 1% Methyl Cellulose (1% MC) at concentrations equivalent to at least 100 mg/mL provided stable suspensions, and were used for the formulations and subsequent dilutions of test article in this study. Test article stock formulations were prepared by suspending Platinum dioxide,hydrate under subdued lighting in 1% MC with the aid of Silverson mixing and stirring (where required), to give the maximum required treatment concentration. Subsequent dilutions were made using 1% MC. The test article suspensions were protected from light and used within approximately 5 hours of initial formulation.
- Justification for choice of solvent/vehicle: Preliminary solubility data indicated that Platinum dioxide,hydrate was not soluble in a variety of standard vehicles that are compatible with the assay system for this study, including Water, Ethanol, Acetone, Tetrahydrofuran, Dimethylformamide and NMethyl-2-pyrrolidone. Formulations in 1% Methyl Cellulose (1% MC) at
concentrations equivalent to at least 100 mg/mL provided stable suspensions, and were used for the formulations and subsequent dilutions of test article in this study

Controls

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

2-nitrofluorene

sodium azide

benzo(a)pyrene

mitomycin C

other: 2-aminoanthracene

Remarks:

2NF for TA98 (-S9); NaN3 for TA100 and TA1535 (-S9); AAC for TA1537 (-S9); MMC for TA102 (-S9); BaP for TA98 (+S9); AAN for TA100, TA1535, TA1537 and TA102 (+S9)

Details on test system and experimental conditions:

METHOD OF APPLICATION:
- In agar (plate incorporation); preincubation (for experiment 2 in the presence of S9).
- 0.1 mL volume additions of test article suspension were used for all treatments (positive controls were treated using 0.05 mL volume additions)

Triplicate plates for test substance and vehicle&positive controls.

Prepared test suspensions were protected from light and used within approximately 5 hours of initial formulation.

DURATION
As the results of Experiment 1 were equivocal, treatments in the presence of S-9 in Experiment 2 included a pre-incubation step. Quantities of test article, vehicle control
solution (reduced to 0.05 mL) or positive control, bacteria and S-9 mix detailed above, were mixed together and incubated for 20 minutes at 37±1°C, with shaking,
before the addition of 2 mL of supplemented molten agar at 45±1°C. Plating of these treatments then proceeded as for the normal plate-incorporation procedure.

DETERMINATION OF CYTOTOXICITY
The test item was tested for for evidence of toxicity to the background lawn using the 5 tester strains in experiment 1, using triplicate platings.

These platings were achieved by the following sequence of
additions to 2 mL of molten agar at 45±1°C:
• 0.1 mL bacterial culture
• 0.1 mL of testarticle suspension/vehicle control or 0.05 mL of positive control
• 0.5 mL 10% S-9 mix or buffer solution
followed by rapid mixing and pouring on to Vogel-Bonner E agar plates. When set, the plates were inverted and incubated at 37±1°C protected from light for 3 days.
Following incubation, these plates were examined for evidence of toxicity to the background lawn and, where possible, revertant colonies were counted.

Evaluation criteria:

Data were considered acceptable if the vehicle control counts fell within the calculated historical control ranges and the positive control plate counts were comparable with the historical control ranges.

The assay was considered to be valid if all the following criteria were met:
1. The vehicle control counts fell within the laboratory’s historical control ranges
2. The positive control chemicals induced increases in revertant numbers of ≥1.5-fold (in strain TA102), ≥2-fold (in strains TA98 and TA100) or ≥3-fold (in strains TA1535 and TA1537) the concurrent vehicle control confirming discrimination between different strains, and an active S-9 preparation.

For valid data, the test article was considered to be mutagenic if:
1. A concentration related increase in revertant numbers was ≥1.5-fold (in strain TA102), ≥2-fold (in strains TA98 and TA100) or ≥3-fold (in strains TA1535 and TA1537) the concurrent vehicle control values
2. The positive trend/effects described above were reproducible.

The test article was considered positive in this assay if both of the above criteria were met.
The test article was considered negative in this assay if neither of the above criteria were met.

Statistics:

Individual plate counts were recorded separately and the mean and standard deviation of the plate counts for each treatment were determined. Control counts were
compared with the laboratory’s historical control ranges.
The presence or otherwise of a concentration response was checked by non-statistical analysis, up to limiting levels (for example toxicity, precipitation or 5000 μg/plate).
However, adequate interpretation of biological relevance was of critical importance.

Results and discussion

Test results

Species / strain:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

True negative controls validity:

not examined

Positive controls validity:

valid

Applicant's summary and conclusion

Conclusions:

In a guideline Ames test, it was concluded that Platinum dioxide did not induce mutation in five histidine requiring strains (TA98, TA100, TA1535, TA1537 and TA102) of Salmonella typhimurium when tested at concentrations up to 5000 μg/plate for each strain, in the absence and in the presence of a rat liver metabolic activation system (S-9).

Executive summary:

Platinum dioxide ,hydrate was as sayed for mutation in five histidine-requiring strains (TA98, TA100, TA1535, TA1537 and TA102) of Salmonella typhimurium, both in the absence and in the presence of metabolic activation by an Aroclor 1254-induced rat liver post-mitochondrial fraction (S-9), in two separate experiments. As no vehicle could be identified that would dissolve the test article and was compatible with the assay system, all Platinum dioxide,hydrate treatments in this study were performed using suspensions prepared in 1% Methyl Cellulose (1% MC).

The same concentrations were retained for treatments of all the tester strains in Experiment 1 in the absence and in the presence of S-9. Following these treatments, no evidence of toxicity was observed.

Mutation Experiment 1 treatments of all the tester strains were performed in the absence and in the presence of S-9, using final concentrations of Platinum

dioxide,hydrate at 5, 16, 50, 160, 500, 1600 and 5000 μg/plate. Following these treatments, no evidence of toxicity was observed.

Experiment 2 treatments of all the tester strains were performed in the absence and in the presence of S-9. The maximum test concentration of 5000 μg/plate was retained for all strains. Narrowed concentration intervals were employed covering the ranges 51.2 - 5000 μg/plate. In addition, all treatments in the presence of S-9 were further modified by the inclusion of a preincubation step. Following these treatments, no clear evidence of toxicity was observed.

The test article was formulated and treated as a suspension in this study, and therefore any observations of precipitation are not considered relevant and are not reported.

Vehicle and positive control treatments were included for all strains in both experiments. The mean numbers of revertant colonies fell within acceptable ranges for vehicle control treatments, and were elevated by positive control treatments.

Following Platinum dioxide,hydrate treatments of all the tester strains in the absence and presence of S-9, only the Experiment 1 treatments of strains TA98 and TA100 in the presence of S-9 provided any notable increases in revertant numbers. Although these increases approached (in strain TA98) or exceeded (in strain TA100) 2-fold the concurrent vehicle control level, and appeared to provide some evidence of a concentration-relationship as they each occurred at the highest treatment concentration, in both cases the increases were almost entirely attributable to a single elevated replicate plate count. As no comparable increases were observed following either the plate incorporation or pre-incubation methodology treatments of these

strains in the presence of S-9 in Experiment 2, it was considered that the single elevated plate counts with these strain treatments in Experiment 1 were not a true compound-related effect. As no other strain treatments provided any increases in revertant numbers that were ≥1.5-fold (in strain TA102), ≥2-fold (in strains TA98 or TA100) or ≥3-fold (in strains TA1535 or TA1537) the concurrent vehicle control, this study was considered therefore to have provided no evidence of any Platinum dioxide,hydrate mutagenic activity in this assay system.