LAURENZA MASSIMO (IT)
WO2020060761A2 | 2020-03-26 |
MOSKOWITZ R W ED - BREEDVELD FERDINAND CHRISTOFFEL: "ROLE OF COLLAGEN HYDROLYSATE IN BONE AND JOINT DISEASE", SEMINARS IN ARTHRITIS AND RHEUMATISM, ELSEVIER, AMSTERDAM, NL, vol. 30, no. 2, 1 October 2000 (2000-10-01), pages 87 - 99, XP009021767, ISSN: 0049-0172, DOI: 10.1053/SARH.2000.9622
DATABASE GNPD [online] MINTEL; 27 April 2021 (2021-04-27), ANONYMOUS: "Original Hydrolyzed Collagen Powder", XP055902994, retrieved from https://www.gnpd.com/sinatra/recordpage/8657549/ Database accession no. 8657549
MATHEW-STEINER SHOMITA S. ET AL: "Collagen in Wound Healing", vol. 8, no. 5, 1 January 2021 (2021-01-01), pages 63, XP055903006, Retrieved from the Internet
SUGIHARA FUMIHITO ET AL: "Ingestion of bioactive collagen hydrolysates enhanced pressure ulcer healing in a randomized double-blind placebo-controlled clinical study", vol. 8, no. 1, 1 December 2018 (2018-12-01), pages 11403, XP055903007, Retrieved from the Internet
DATABASE GNPD [online] MINTEL; 12 May 2021 (2021-05-12), ANONYMOUS: "Hydrolyzed Collagen Sachets", XP055902997, retrieved from https://www.gnpd.com/sinatra/recordpage/8701009/ Database accession no. 8701009
CLAIMS 1 , A hydrolyzed collagen powder having the following particle size distribution: at most 10% of the particles have a mean diameter lower than 2.5 microns; at least 50% of the particles have a mean diameter lower than 10 microns; at least 90% of the particles have a mean diameter lower than 20 microns. 2, The collagen powder according to claim 1, characterized in that said hydrolyzed collagen consists of oligopeptides having the following molecular weights: at least 30% of the oligopeptide molecules have a weight average molecular weight from 80 to 120 kDa; at least 25% of the oligopeptide molecules have a weight average molecular weight from 50 to 70 kDa; at least 25% of the oligopeptide molecules have a weight average molecular weight from 25 to 45 kDa; at least 85% of said collagen has a molecular weight from 25 to 120 kDa. 3, The collagen powder according to claim 1 or 2, characterized in that said collagen is of type I. 4, The collagen powder according to any one of claims 1 to 3, characterized in that said collagen is equine. 5, The collagen powder according to any one of claims 1 to 4, characterized in that it shows the particle size distribution of Figure 1. 6, A pharmaceutical, nutraceutical or cosmetic composition comprising the collagen powder according to any one of claims 1 to 5, together with at least one suitable carrier. 7, Use of the collagen powder according to any one of claims 1 to 5, as food supplement or as a cosmetic product. 8, The collagen powder according to any one of claims 1 to 5, for its use in therapy. 9, The collagen powder according to claim 8, for use in the treatment of sores, bums, wounds, joint disorders, skin ageing, interstitial cystitis and vulvovaginitis; for the regeneration and bio-revitalization of dermis and for the visco-supplementation and regeneration in synovia in case of osteo-chondral damages. 10. A process for the preparation of the collagen powder according to any one of claims 1 to 5, which comprises: (i) suspending collagen of type I, deprived of the telopeptide fractions, in acidified water and subjecting it to proteolysis; and (ii) drying said collagen in a micronized form. |
Aim of the Study
Mammalian cell culture systems are used to detect mutations induced by chemical substances. This in vitro experiment is conducted to assess the potential of the test item to induce gene mutations by means of a thymidine kinase (tk) assay using the mouse lymphoma cell line L5178Y. The thymidine kinase assay detects base pair mutations, frameshift mutations, small, large and non-lethal deletions and rearrangements of the relevant chromosomes.
The kinase catalyses the reaction of thymidine and ATP to form TMP (thymidine 5'- mono-phosphate) and ADP. However, it also phosphorylates the pyridine analogue triflurothymidine (TFT) to its cytostatic and cytotoxic trifluoro-thymidine- monophosphate derivative. By inactivating the functional allele of tk+/-, cells are resistant to TFT. Thus, mutant cells (tk-/-) are capable of proliferation in the presence of TFT, whereas normal cells (tk +/-) are not.
Cells in suspension are exposed to the test chemical, both with and without an exogenous source of metabolic activation (MA), for a suitable period of time, and then sub-cultured to determine cytotoxicity and to allow phenotypic expression prior to mutant selection.
Cytotoxicity is determined by relative total growth (RTG). The treated cultures are maintained in growth medium for a sufficient period of time, to allow near-optimal phenotypic expression of induced mutations.
Following phenotypic expression, mutant frequency (MF) is determined by seeding known numbers of cells in medium containing the selective agent to detect mutant colonies, and in medium without selective agent to determine the cloning efficiency. After a suitable incubation time, colonies are counted. Mutant frequency is calculated based on the number of mutant colonies corrected by the cloning efficiency at the time of mutant selection.
Justification for the selection of the Test System
OECD (2016), Test No. 490 (In Vitro Mammalian Cell Gene Mutation Tests Using the Thymidine Kinase Gene) and ISO/TR 10993-33:2015 (Guidance on tests to evaluate genotoxicity - Supplement to ISO 10993-3) recommend using the cell line L 5178 Y Characterisation of the Test Item
The identity of the test item was inspected upon delivery at the test facility (e.g. test item name, batch no., and additional data were compared with the label) based on the following specifications provided by the sponsor.
The following listed information applies to the sample as received.
Name: BIO ACTIVE COLL
Batch No.: 03/21
Sterility: yes
Sterilisation Procedure: g-Irradiation Type of Material: Natural Polymer Storage Conditions: Room temperature, cool dry place Expiry' Date: not applicable
Safety Precautions: The routine hygienic procedures w'ere sufficient to assure personnel health and safety.
Preparation
The preparation was carried out in compliance to ISO 10993-3: 2014 “Tests for genotoxicity, carcinogenicity and reproductive toxicity”:
. Can the test sample be dissolved/suspended in an appropriate solvent compatible with the test system?
Yes: Use method A
No: Determine the percentage of extractables in the test sample (pre-test method B - A.3.3.4).
. Is the percentage of extractables > 0.5% for devices > 0.5 g or > 1% for devices < 0.5 g?
Yes: Use method B
No: Use method C
The solvent was compatible with the survival of the cells and the S9 activity. Controls
Negative or solvent as well as positive controls are included in each experiment. Negative Control
Negative controls (RPMI) are treated the same way as all test groups. Solvent Control
Name: Water (10%) Supplier: Cayman Chemical Batch
No.: 0634617-1
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• a o The dilutions of the positive control stock solutions were prepared on the day of experiment and used immediately. The stability of the positive control substances in solution is proven by the mutagenic response in the expected range. Test System The Cells
The L5178Y tk +/- 3.7.2C cell line has been successfully used in in vitro experiments for many years. These cells are characterised by their high proliferation rate (10-12 h doubling time of the Eurofms Munich stock cultures) and their cloning efficiency, typically more than 50%. The cells obtain a near diploid karyotype (40 ± 2 chromosomes) and are heterozygous at the thymidine kinase (tk) locus.
To prevent high background counts arising from spontaneous mutation, tk -/ - cells can be eliminated by culturing in RPMI 1640 supplemented with: 9.0 μg/mL, hypoxanthine, 15.0 μg/mL thymidine, 22.5 μg/mL glycine, 0.1 μg/mL methotrexate.
The cells are resuspended in medium without methotrexate, but with thymidine, hypoxanthine, and glycine for 1-3 days.
Large stock cultures of the cleansed L5178Ytk +/- 3.7.2C cell line are stored over liquid nitrogen (vapour phase) in the cell bank of Eurofms Munich. This allows the repeated use of the same cell batch in experiments. Each cell batch i s routinely checked for an absence of mycoplasma.
Thawed stock cultures are maintained in plastic culture flasks in RPMI 1640 complete medium and sub-cultured on demand.
Post-Mitochondrial Fraction (S9) Substances may only develop mutagenic potential when they are metabolised by the mammalian organism. The cell line L5178Y tk +/ - 3.7.2C has an inadequate endogenous metabolic capacity and therefore an exogenous MA system is necessary . The most commonly used system is a co-factor- supplemented post-mitochondrial fraction (S9) prepared from livers of rodents. The S9 fraction was prepared at Eurofms Munich. Male Wistar rats were induced with phenobarbital (80 mg/kg bw) and □-naphthoflavone (100 mg/kg bw) for three consecutive days by oral route. The preparation was performed according to Ames et ah.
The following quality control determinations were performed: a) Biological activity in the Salmonella typhimurium assay using 2- aminoanthracene and benzo[a]pyrene b) Sterility test
A stock of the supernatant containing the S9 fraction was frozen in aliquots of 2 and 4 mL and stored at ≤-75 °C. The protein concentration in the S9 fraction was 35 mg/mL (Lot: 191121).
Preparation of S9 Mix
The S9 mix preparation was performed according to Ames et al..
An appropriate quantity of S9 fraction was thawed and mixed with a co-factor solution to result in a final protein concentration of 0.75 mg/mL in the cultures. In 100 mM sodium phosphate buffer pH 7.4, the following concentrations were achieved: 8 mM MgCl2, 33 mM KCl, 5 mM Glucose-6-phosphate, 5 mM NADP. During the experiment the S9 mix was stored on ice.
Experimental Design Exposure Concentrations
Criteria to determine the highest concentration were cytotoxicity, solubility in the test system, and changes in pH or osmolality. Cytotoxicity was determined with and without m etabolicactivation .
Several concentrations of the test item were set-up.
In STE (-) STE (+) LIE 5 mg/mL was selected as the highest concentration. Solvent vehicle or negative controls were tested in duplicate.
Experimental Performance
For the STE 10 7 cells were suspended in 11 mL RPMI medium with 5% horse serum
(25 flasks) and exposed to designated concentrations of the solved test item, in the presence or absence of MA. After 4 h, the solved test item was removed by centrifugation (200xg, 7min)and the cells were washed twice with PBS. Subsequently the cells were suspended in 30 mL complete culture medium and incubated for an expression and growth period of two days in total at 37 °C in 5% CO2/95% humidified air. The cell density was determined each day and, if necessary, adjusted to 3x10 5 cells/mL. For the LTE, 5x10 6 cells were suspended in 25 mL RPMI medium with 7.5% horse serum (75 cm 2 flasks) and exposed to designated concentrations of the solved test item in the absence of MA. After 24 h, the solved test item was removed by centrifugation
(200 xg, 7 min) and the cells were washed twice with PBS. Subsequently, 3x10 5 cells/mL were suspended in 14 mL complete culture medium and incubated for an expression and growth period of 2 days at 37 °C in 5% CO2/95% humidified air. The cell density was determined each day and adjusted to 3x10 5 cells/mL, if necessary. After the expression period the relative cloning efficiency (RCE; percentage cloning efficiency of the test group in relation to the vehicle controls) of the cells was determined by seeding a statistical number of 1.6 cells/well in two 96-well plates. The cells were incubated for at least seven days at 37 °C in 5% CO2/95% humidified air. Analysis of the results was based on the number of cultures with cell growth (positive wells) and those without cell growth (negative wells) compared to the total number of cultures seeded. Relative suspension growth (RSG) and RTG (RTG = [RSG x RCE] / 100) of the treated cell cultures were calculated according to the method of Clive and Specter. Additionally, cultures were seeded in selective medium. Cells from each experimental group were seeded in four 96-well plates at a density of approximately 2000 cells/well in 200 μL selective medium with TFT. The plates were scored after an incubation period of 11 to 14 days at 37 °C in 5% CO2/95% humidified air. The MF was calculated by dividing the number of TFT resistant colonies by the number of cells plated for selection, corrected for the plating efficiency of cells from the same culture grown in the absence of TFT. The Poisson distribution was used to calculate the plating efficiencies for cells clonedwithout and with TFT selection. Based on the null hypothesis of the Poisson distribution, the probable number of clones/well (P) is equal to -In (negative wells/total wells) and the plating efficiency (PE) equals P/(number of cells plated per well). MF then was calculated as MF = (PE (cultures in selective medium)/PE (cultures in non-selective medium)). The MF is usually expressed as “mutants per 10 6 viable cells” Suspension growth (SG) of the cell cultures reflects the number of times the cell number increases from the starting cell density. When conducting the STE, a two- day growth period was considered, when conducting the LTE, the treatment period of 24 h and the two-day growth period was considered. The RTG is the product of the RSG (cal culated by comparing the SG of the test groups with the SG of the control) and the RCE for each culture: RTG = RSG x RCE / 100.
To specify the GEF the international workshop on genotoxicity testing (IWGT) analysed distributions of negative/vehicle mutant frequencies from ten laboratories. The GEF is defined as the mean of the negative/vehicle MF plus one standard deviation. Applying this definition to the collected data, the GEF is 126 mutants per 10 6 cells for the microwell method.
The size of the colonies was characterised as follows: Small colonies approximately ≤ ¼ of well diameter. Large colonies approximately > ¼ of well diameter. Size is the key factor and morphology should be secondary.
Cell Culture Media Prior to the preparation of different media, horse serum (FIS) was heat-inactivated for
30 min at 56 °C.
The selective agent (TFT) was obtained from Sigma-AIdrich (Lot No.: BCCD1996). Data recording
The generated data were recorded on the experimental design protocol. The results are presented in tabular form, including experimental groups with the test item, negative and positive controls. Individual colony counts for the treated and control groups are presented for both mutation induction and survival. Small colonies and large colonies were determined for the relevant test groups.
Statistics
Only in cases where the GEF is exceeded:
The non-parametric Mann- Whitney test was applied to the mutation data to determine if there are statistical differences between the mutant frequencies of the treated test groups compared to the negative/solvent controls.
Only for full studies: A statistical trend analysis was performed.
Acceptability of the Assay
A mutation assay is considered acceptable if it meets the criteria defined in current international guidelines and the current recommendations of the IWGT . At least three out of four 96-well plates from the TFT selection experiment are analy sable.
• The cloning efficiency of the negative or solvent controls is in the range 65%- 120%,
. The spontaneous MF in the negative or solvent controls is in the range 50- 170 mutants per 10 6 cells.
• The cell number of the negative/solvent controls undergo 8-32-fold increase during a two-day growth period (STE) or 32-180-fold increase during a three-day growth period (LTE).
. The positive controls (MMS and B[a]P) for clastogenicity produce an induced
MF (total MF minus concurrent negative control MF) of at least 300 mutants per 10^ cells with at least 40% of the colonies being small colonies or with an induced small colony MF of at least 150 mutants per 10 6 cells. « The RTG must be greater than or equal to 10%.
Evaluation of Results
The test item is considered mutagenic if the following criteria are met:
. The induced MF meets or exceeds the GEF . The RTG must be greater than or equal to 10%.
• A concentration-dependent increase in MF is detected using an appropriate statistical trend analysis (not for limit study).
Besides, combined with a positive effect in the MF, an increased occurrence of small colonies (≥ 40% of total colonies) is an indicator of potentially clastogenic effects.
A test item is considered negative if the induced MF is below the GEF or the trend of the test is negative.
Interpretation of Results
There is no requirement for verification of a clear positive response. Equivocal results should be clarified by further testing preferably using a modification of experimental conditions.
Negative results need to be confirmed on a case-by-case basis.
Study parameters which might be changed are concentration spacing, duration of treatment (LTE without MA) or metabolic activation conditions. Results of STE (-)
Discussion
The test item BIO ACTIVE COLL was assessed for its potential to induce mutations at the mouse lymphoma thymidine kinase locus (tk +/- using the L5178Y cell line. For the short-term experiments (STE), the solved test item was incubated with cells for 4 hours. The STEs were performed independently: with ( STE (+) ) and without
( STE (-) ) metabolic activation. For the long-term experiment (LTE), the solved test item was incubated with cells for 24 hours. The LTE was performed without metabolic activation.
The solved test item was investigated at the following concentrations:
STE (-) · 0.25, 0.50, 1, 3 and 5 mg/mL
STE (+) : 0.25, 0.50, 1, 3 and 5 mg/mL LTE: 0.25, 0.50, 1, 3 and 5 mg/mL Test Item Properties
The measured pH value of the solved test item was within the physiological range. No precipitation of the solved test item was noted in the experiments.
Toxicity
In STE (-) STE (+) LTE 5 mg/mL was selected as the highest concentration. No growth inhibition was observed in STE (-) (Tabled).
Growth inhibition was observed in STE (+) and LTE. In STE (+) ’ the relative total growth (RTG) was 69% for highest concentration evaluated (Table 7). In LTE, the relative total growth (RTG) was 26% for highest concentration evaluated (Table 10). Mutagenicity
The induced mutant frequencies obtained from all experiments were compared to the GEF. The global evaluation factor (GEF) was not exceeded by the induced mutant frequency. The GEF is defined as the mean of the negative/vehicle mutant frequency plus one standard deviation, data are gathered from ten laboratories. For the micro well method, the GEF was defined to be 126 mutants/10 6 cells. Criterion for mutagenicity is the extension of the GEF by the induced mutant frequency as well as a concentration-dependent increase in mutant frequency. The positive controls EMS (200 and 300 μg/mL), MMS (8 and 10 μg/mL) andB[a]P (3.5 μg/mL) showed distinct responses in mutation frequency, thus demonstrating the ability of the test system to detect potentially mutagenic effects.
All criteria of validity were met (10.9), except of the mutant frequencies for the I negative control of STE (-) ; 171 and 1 solvent control of LTE:47 (acceptance range of
50-170 mutants/10 6 cells, according to the IWGT criteria). Nevertheless, the negative control and solvent control values were considered acceptable for inclusion in the historical control data set (Table 13), as they were only slightly outside of the historical range and no technical reason or human failure was determined, No biologically relevant increase of mutants was found in any experiments, the GEF was not exceeded (Table 5, Table 8, Table 11)
Clastogenicitv
The increased occurrence of small colonies (defined by slow growth and morphological alteration of the cell clone) in combination with a GEF exceeding induced mutant frequency is an indication of potentially clastogenic effects. Colony size was counted for all concentrations of the test item and for the negative and positive controls.
The positive controls MMS and B[a]P induced a significant increase in mutant frequency and a biologically significant increase of small colonies (≥ 40%), thus confirming the ability of the test system to indicate potentially clastogenic effects (Table 6, Table 9, Table 12). In all experiments the percentage of small colonies in the negative and solvent controls was lower than 40%.
Based on the non-mutagenic effects of BIO ACTIVE COLL, an assessment of clastogenicity was not feasible, Conclusion
In conclusion, in this in vitro Mammalian Cell Gene Mutation Assay (Thymidine Kinase Locus/tk+/-) in L5178 Y Mouse Lymphoma Cells, under the experimental conditions reported, the test item BIO ACTIVE COLL is considered to be non- mutagenic. EXPERIMENTAL TEST 6
REVERSE MUTATION ASSAY USING BACTERIA (SALMONELLA TYPHIMURIUM AND ESCHERICHIA COLI) WITH BIO ACTIVE COLL Summary Results
In order to investigate the potential of BIO ACTIVE COLL for its ability to induce gene mutations the plate incorporation test was performed with the Salmonella typhimurium strains TA98, TA100, TA1535, TA1537 and E. coli WP2 uvrA (pKM101).
In the experiment several concentrations of the test item were used. The assay was conducted with and without metabolic activation. The concentrations, including the controls, were tested in triplicate. The following concentrations of the test item were prepared:
31.6, 100, 316, 1000, 2500 and 5000 μg/plate
No precipitation of the test item was observed in any tester strain used (with and without metabolic activation).
No toxic effects of the test item were noted in any of the five tester strains used up to the highest dose group evaluated with and without metabolic activation.
No biologically relevant increases in revertant colony numbers of any of the five tester strains were observed following treatment with BIO ACTIVE, COLL at any concentration level, neither in the presence nor absence of metabolic activation.
All criteri a of validi ty were met (see).
Conclusion
In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, BIO ACTIVE COLL did not cause gene mutations by base pair changes or frameshifts in the genome of the tester strains used.
Therefore, BIO ACTIVE COLL is considered to be non-mutagenic in this bacterial reverse mutation assay.
Aim of the Study
Bacterial reverse mutation assays use amino acid requiring strains of Salmonella typhimurium and Escherichia coli (E. coli) to detect point mutations, which involve substitution, addition or deletion of one or a few DNA base pairs. The principle of these bacterial reversion assays is that they detect mutations which functionally reverse mutations present in the tester strains and restore the capability to synthesize an essential amino acid.
The purpose of this study is to establish the potential of the test item to induce gene mutations in bacteria by means of a S, typhimurium and E. coli reverse mutation assay, Further confirmatory testing in the case of clearly negative or positive test results is not usually needed. Equivocal results should be clarified by further testing preferably using a modification of experimental conditions. Modification of study parameters to extend the range of conditions assessed should be considered in follow-up experiments. Study parameters that might be modified include the concentrations spacing and / or the method of treatment (pre-incubation method). In case of severe toxicity of the test item or the use of e.g, ethanol, acetone or tetrahydrofuran as the most appropriate solvent, the confirmatory experiment i s carried out according to the plate incorporation method with a different spacing between dose levels. Due to clear negative results in the first experiment of this study no independent repetition was performed, as described in 10993-33.
The S. typhimurium histidine (his) reversion system and the E. coli tryptophan (trp) reversion systems measure his- ->his + reversions and trp trp + . The S. typhimurium strains are constructed to differentiate between base pair (TA100, TA1535) and frameshift (TA98, TA1537) mutations. The E. coli strain detects only base substitution mutagens.
These assays directly measure heritable DNA mutations of a type which is associated with adverse effects. Point mutations are the cause of many human genetic diseases and there is substantial evidence that somatic cell point mutations in oncogenes and tumour suppressor genes are involved in cancer in humans and experimental systems. The tester strains have several features that make them more sensitive for the detection of mutations. The specificity of the strains can provide useful information on the types of mutations that are induced by mutagenic agents.
According to the direct plate incorporation method the bacteria are exposed to the test item with and without metabolic activation and plated on selective medium. After a suitable period of incubation, revertant colonies are counted. At least five different concentrations of the test item are tested with approximately half log (i ,e. V 10) intervals between test points for an initial test. Narrower spacing between dose levels may be appropriate when a dose response is investigated. For soluble, non- toxic test compounds the recommended maximum test concentration is 5 mg/plate or 5 μL/plate.
To validate the test, reference mutagens are tested in parallel to the test item, justification for the Selection of the Test System
The OECD Guideline for Testing of Chemicals, Section 4, No. 471 - Bacterial Reverse Mutation Test - recommends using a combination of S. typhimurium strains TA98, TA100, TA1535, TA1537 and TA102 or E, coli WP2 uvrA (pKM101).
MATERIALS AND METHODS
Characterisation of the Test Item
The identity of the test item was inspected upon delivery at the test facility (e.g. test item name, batch no. and additional data were compared with the label) based on the following specifications provided by the sponsor. The following listed information applies to the sample as received.
Name: BIO ACTIVE COLL
Lot No.: 03/21
Code: TYPE 1 PROFIL
Manufacturing Date: November 2021 Expiry Date: not applicable
Storage Conditions: at room temperature, cool dry' place, protected from light Type of Material: Natural Polymer Sterility: sterile
Sterilization Procedure: γ-irradiation Safety Precautions: The routine hygienic procedures were sufficient to assure personnel health and safety. Preparation of the Test Item The test item was prepared in compliance to ISO 10993-3: 2014 “Tests for genotoxicity, carcinogenicity' and reproductive toxicity” . The sample preparation should follow the decision tree in the Figure 3. This figure diagrams the decision process used to select the extraction method (method A, B or C).
If the test sample can be dissolved or suspended in an appropriate solvent within the test system, the test sample can be applied directly to the test system (Method A) at a maximum concentration of 5 mg/niL (in vitro mammalian test system) or 5 mg/plate (bacterial reverse mutation assay).
Since the test item can be dissolved (see Eurofms Munich Study 150459 “In vitro Cytotoxicity Assay: Evaluation of Materials for Medical Devices by Extraction Method and XTT Dye with BIO ACTIVE COLL”) Method A was chosen. The test item was dissolved in A. dest, processed by ultrasound for 5 min at 37 °C and diluted prior to treatment. The solvent was compatible with the survival of the bacteria and the S9 activity.
Controls
Negative as well as positive controls were included in the experiment. Strain specific positive controls were included in the assay, which demonstrated the effective performance of the test.
Negative/Solvent Control s
Negative controls (A. dest., Eurofms Munich, Lot No. 220218, 220304) were treated in the same way as all dose groups. Positive Controls
Without metabolic activation
Tester Strains: S. typhimurium: TA100, TA1535
Name: NaN 3 ; sodium azide
CAS No.: 26628-22-8 Supplier: Sigma Batch No.: STBF8665V
Dissolved in: A. dest.
Concentration: 10 μg/plate
Tester Strains: S. typhimurium: TA98, TA1537 Name: 4-NOPD; 4-nitro-o-phenyl ene-diamine
CAS No.: 99-56-9 Supplier: Sigma
Batch No.: MKCF1418
Dissolved in: DMSQ Concentrations: 10 μg/plate for TA98, 40 μg/plate for TA1537
Tester Strain: E. coli WP2 uvrA (pKMIOl)
Name: MMS; methylmethanesulfonate
CAS No.: 66-27-3
Supplier: Sigma
Batch No.: MKCG1346
Dissolved in: A. dest. Concentration: 1 μL/plate
With metabolic activation Tester Strains: S. typhimurium: TA98, TA100, TA1535, TA1537 and
E. coli WP2 uvrA (pKMIOl)
Name: 2-AA; 2-aminoanthracene
CAS No.: 613-13-8
Supplier: Alfa Aesar
Batch No.: 102181359-A
Dissolved in: DMSO
Concentrations: 2.5 μg/plate for TA98, TA100, TA1535 and TA1537;
10 μg/plate for E. coli WP2 uvrA (pKM101)
The stability of the positive control substances in solution is unknown but a mutagenic response in the expected range is sufficient evidence of biological stability.
Test System Bacteria
Four strains of S. typhimurium and one strain of E. coli with the following characteristics are used: TA98: Tester strains TA98, TA1535 and E. coli were obtained from MOLTOX, INC., NC 28607, USA. Tester strains TA100 and TA1537 were obtained from Xenometrix AG, Switzerland. They were stored as stock cultures in ampoules with nutrient broth (OXOID) supplemented with DMSO (approx. 8% v/v) over liquid nitrogen. All Salmonella strains contain mutations in the histidine operon, thereby imposing a requirement for histidine in the growth medium. They contain the deep rough (rfa) mutation, which deletes the polysaccharide side chain of the lipopoly saccharides of the bacterial cell surface. This increases cell permeability of larger substances. The other mutation i s a deletion of the uvrB gene coding for a protein of the DNA nucleotide excision repair system resulting in an increased sensitivity in detecting many mutagens. This deletion also includes the nitrate reductase (chl) and biotin (bio) genes (bacteria require biotin for growth).
The tester strains TA98, TA100 and E. coli contain the R-factor plasmid, pkM101. These strains are reverted by a number of mutagens that are detected weakly or not at all with the non R-factor parent strains. pkM101 increases chemical and spontaneous mutagenesis by enhancing an error-prone DNA repair system which is normally present in these organisms.
The tester strain E. coli WP2 uvrA (pKM101) carries the defect in one of the genes for tryptophan biosynthesis. Tryptophan-independent mutants (revertants) can arise either by a base change at the site of the original alteration or by a base change elsewhere in the chromosome so that the original defect is suppressed. This second possibility can occur in several different ways so that the system seems capable of detecting all types of mutagens which substitute one base for another. Additionally, the strain is deficient in the DNA nucleotide excision repair system. The properties of the S. typhimurium and E. coli strains with regard to membrane permeability, ampicillin- and tetracycline-resistance as well as normal spontaneous mutation rates are checked regularly according to Ames et al. In this way it is ensured that the experimental conditions set up by Ames are fulfilled.
Preparation of Bacteria Samples of each tester strain were grown by culturing for 12 h at 37 °C in S. typhimurium medium (Nutrient Broth) and E. coli medium (Luria Bertani), respectively, to the late exponential or early stationary phase of growth (approx. 10 9 cells/mL).
The S. typhimurium medium (Nutrient Broth) contains per litre of purified water:
8 g Nutrient Broth 5 g NaCl
The E. coli medium (Luria Bertani) contains per litre of purified water:
10 g tryptone 10 g NaCl 5 g yeast extract
A solution of 125 μL ampicillin (10 mg/mL) (TA98, TA100, E. coli WP2 uvrA (pKM101)) was added in order to retain the phenotypic characteristics of the strain. Agar Plates
The Vogel-Bonner Medium E agar plates with 2% glucose used in the Ames test were prepared by Eurofins Munich or provided by an appropriate supplier. Quality controls were performed.
Vogel-Bonner-salts contain per litre of purified water:
Sterilisation was performed for 20 min at 121 °C in an autoclave. Vogel-Bonner Medium E agar plates contain per litre of purified water:
Sterilisation was performed for 20 min at 121 °C in an autoclave.
Overlay Agar
The overlay agar contains per litre of purified water:
Sterilisation was performed for 20 min at 121 °C in an autoclave.
Mammalian Microsomal Fraction S9 Mix
The bacteria most commonly used in these reverse mutation assays do not possess the enzyme system which, in mammals, is known to convert promutagens into active DNA damaging metabolites. In order to overcome this major drawback an exogenous metabolic system was added in the form of mammalian microsome enzyme activation mixture.
S9 Homogenate The S9 liver microsomal fraction was prepared at Eurofms Munich. Male Wistar rats were induced with phenobarbital (80 mg/kg bw) and b-naphthoflavone (100 mg/kg bw) for three consecutive days by oral route.
The following quality control determinations are performed: a) Biological activity in the Salmonella typhimurium assay using 2- aminoanthracene and benzo[a]pyrene b) Sterility Test
A stock of the supernatant containing the microsomes was frozen in aliquots of 2 and 4 mL and stored at ≤-75 °C.
The protein concentration in the S9 preparation (Lot: 191121) was 35.0 mg/mL. Preparation of S9 Mix
The S9 mix preparation was performed according to Ames et al.
100 mM of sodium-ortho-phosphate-buffer, pH 7.4, was ice-cold added to the following pre-weighed sterilised reagents to give final concentrations in the S9 mix of:
This solution was mixed with the liver 9000 x g supernatant fluid in the following proportion: co-factor solution 9.5 parts liver preparation 0.5 parts
During the experiment the S9 mix was stored on ice.
S9 Mix Substitution Buffer
The S9 mix substitution buffer was used in the study as a replacement for S9 mix, without metabolic activation (-S9).
Phosphate-buffer (0.2 M) contains per litre of purified water:
0.2 M NaH 2 PO 4 x H 2 O 120 ml.
0.2 MNa 2 HPO 4 880 mL
The two solutions were mixed and the pH was adjusted to 7.4. Sterilisation was performed for 20 min at 121 °C in an autoclave.
This 0.2 M phosphate-buffer was mixed with 0.15 M KCl solution (sterile) in the following proportion:
0,2 M phosphate-buffer 9,5 parts
0.15 M KCl solution 0.5 parts This S9 mix substitution buffer was stored at 4 °C.
Experimental Design Pre-Experiment for Toxicity
The toxicity of the test item was determined with tester strains TA98 and TA100 in a pre-experiment. Eight concentrations were tested for toxicity and induction of mutations with three plates each. The experimental conditions in this pre-experiment were the same as described below for the main experiment (plate incorporation test).
Toxicity may be detected by a clearing or rather diminution of the background lawn or a reduction in the number of revertants down to a mutation factor of approximately < 0.5 in relation to the solvent control.
The test item was tested in the pre-experiment with the following concentrations:
3.16, 10.0, 31.6, 100, 316, 1000, 2500 and 5000 μg/plate Exposure Concentrations
The test item concentrations to be applied in the main experiment wore chosen according to the results of the pre-experiment. 5000 μg/plate was selected as the maximum concentration. The concentration range covered two logarithmic decades. The experiment was performed with the following concentrations: 31.6, 100, 316, 1000, 2500 and 5000 gg/plate
As the results of the pre-experiment were in accordance with the criteria of validity, these were reported as a part of the main experiment.
Experimental Performance
For the plate incorporation method, the following materials were mixed in a test tube and poured over the surface of a minimal agar plate:
100 μL test solution at each dose level, solvent control, negative control or reference mutagen solution (positive control)
500 μL S9 mix(for testing with metabolic activation) or S9 mix substitution buffer (for testing without metabolic activation) 100 μl Bacteria suspension (cf. Preparation of bacteria, pre-culture of the strain)
2000 μL Overlay agar.
Due to clear negative results in the first experiment of this study no independent repetition was performed, as described in 10993-33.
For each strain and dose level, including the controls, three plates were used. After solidification the plates were inverted and incubated at 37 °C for at least 48 h in the dark.
Data Recording
The colonies were counted using a ProtoCOL counter (Meintrup DWS Laborgerate GmbH). If precipitation of the test item precluded automati c counting the revertant colonies were counted by hand. In addition, tester strains with a low spontaneous mutation frequency like TA1535 and TA1537 were counted manually. Evaluation of Cytotoxicity Cytotoxicity can be detected by a clearing or rather diminution of the background lawn (indicated as "N" or "B", respectively in the result tables) or a reduction in the number of revertants down to a mutation factor of approximately ≤ 0.5 in relation to the solvent control. Criteria of Validity A test is considered acceptable if for each strain: - the bacteria demonstrate their typical responses to ampicillin (TA98, TA100, E. coli WP2 uvrA (pKM101)) - the negative control plates (A. dest.) with and without S9 mix are within the following ranges (mean values of the spontaneous reversion frequency are within the historical control data range (January – December 2020 for all tester strains)): - corresponding background growth on negative control, solvent control and test plates is observed - the positive controls show a distinct enhancement of revertant rates over the control plate - at least five different concentrations of each tester strain are analysable. Evaluation of Mutagenicity The Mutation Factor is calculated by dividing the mean value of the revertant counts by the mean values of the solvent control (the exact and not the rounded values are used for calculation). A test item is considered as mutagenic if: - a clear and dose-related increase in the number of revertants occurs and/or - a biologically relevant positive response for at least one of the dose groups occurs in at least one tester strain with or without metabolic activation. A biologically relevant increase is described as follows: if in tester strains TA98, TA100 and E. coli the number of reversions is at least twice as high if in tester strains TA1535 and TA1537 the number of reversions is at least three times higher than the reversion rate of the solvent control.
According to OECD guidelines, the biological relevance of the results is the criterion for the interpretation of results, a statistical evaluation of the results is not regarded as necessary.
A test item producing neither a dose related increase in the number of revertants nor a reproducible biologically relevant positive response at any of the dose groups is considered to be non-mutagenic in this system Results
Pre-Experiment
Toxicity may be detected by a clearing or rather diminution of the background lawn or a reduction in the number of revertants down to a mutation factor of approximately < 0.5 in relation to the solvent control.
Discussion
The test item BIO ACTIVE COLL was investigated for its potential to induce gene mutations according to the plate incorporation test using Salmonella typhimurium strains TA98, TA100, TA1535, TA1537 and tester strain E. coli WP2 uvrA (pKM101).
In the experiment several concentrations of the test item were used. Each assay was conducted with and without metabolic activation. The concentrations, including the controls, were tested in triplicate. The following concentrations of the test item were prepared:
31.6, 100, 316, 1000, 2500 and 5000 μg/plate No precipitation of the test item was observed in any tester strain used (with and without metabolic activation).
No toxic effects of the test item were noted in any of the five tester strains used up to the highest dose group evaluated with and without metabolic activation.
No biologically relevant increases in revertant colony numbers of any of the five tester strains were observed following treatment with BIO ACTIVE COLL at any concentration level, neither in the presence nor absence of metabolic activation.
The reduction in the number of revertants down to a mutation factor of < 0.5 found in tester strain TA 1537 at a concentration of 316 μg/plate (with metabolic activation) was regarded as not biologically relevant due to lack of a dose-response relationship. The microbial contamination observed in one plate (TA98, 316 μg/plate, without metabolic activation) did not affect the quality or integrity of the results as the microbial contamination could be clearly distinguished from the Salmonella typhimurium revertants and thus did not affect the evaluation. All criteria of validity were met.
Conclusion
In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, BIO ACTIVE COLL did not cause gene mutations by base pair changes or frameshifts in the genome of the tester strains used.
Therefore, BIO ACTIVE COLL is considered to be non-mutagenic in this bacterial reverse mutation assay.
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