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Boosting the Antimicrobial Efficiency of Multifunctional Additives by Chelating Agents


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The continuing discussion of cosmetic preservatives has limited the number of accepted actives that can be practically used. As a result, a number of different methods and materials are being used to boost the activity of the remaining acceptable substances for microbial stabilisation. Increasing the permeability of microbial cells to biocides by EDTA helps to optimise the stabilisation. To avoid the environmental discussion about chelating agents, readily biodegradable alternatives to EDTA are indispensable. The antimicrobial stabilisation of multifunctional additives in combination with chelating agents were tested in different cosmetic formulations. The readily biodegradable chelating agent Tetrasodium Glutamate Diacetate shows good performance in reducing the use concentration of sensiva® SC 10, sensiva® PA 20, sensiva® PA 30 and sensiva® PA 40 to pass antimicrobial effectiveness testing.
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English Edition
International Journal for Applied Science
• Personal Care • Detergents • Specialties
W. Siegert
Boosting the
antimicrobial efficiency of
multifunctional additives
by chelating agents
2 SOFW-Journal | 140 | 1/2-2014
number of accepted actives that can
be used. Over-dosing of antimicrobial
actives becomes more clearly a regula-
tory affair if it results in an adverse
risk assessment. The incentive to make
biocides more effective at lower con-
centrations becomes more and more
important. The efficacy of EDTA is
generally known (1), however modern
readily biodegradable alternatives can
replace it (2).
The use of chelating agents in
The chelate effect describes the en-
hanced affinity of chelating ligands for
a metal ion compared to the affinity of
a collection of similar non-chelating
(monodentate) ligands for the same
metal. The key features of chelating
agents in cosmetics are:
Chelates calcium and transition metal
ions, which helps to enhance the
shelf-life of creams
Helps to stabilise and avoid
Boosts the performance of
Boosts the performance of
W. Siegert*
Boosting the Antimicrobial Efficiency of
Multifunctional Additives by Chelating Agents
The continuing discussions surrounding cosmetic preservation has li-
mited the number of accepted actives that can be used. As a result, a
number of different methods and materials are being used to boost the
activity of the remaining acceptable substances for microbial stabilisation.
Increasing the permeability of microbial cells to biocides by EDTA helps to
optimise the stabilisation, however to avoid the environmental discussions
regarding chelating agents, readily biodegradable alternatives to EDTA are
The antimicrobial stabilisation of multifunctional additives in combination
with chelating agents were tested in different cosmetic formulations.
The readily biodegradable chelating agent Tetrasodium Glutamate Diacetate
is shown to improve performance therefore enabling the reduction in the
use concentration of sensiva® SC 10, sensiva® PA 20 , and sensiva® PA 30
and sensiva® PA 40 to pass antimicrobial effectiveness testing.
The microbial safety of cosmetic prod-
ucts is an important consideration. It is
integral to ensuring the stability of the
products for the entire shelf-life and
to preventing damage to the health of
The continuing discussions surrounding
cosmetic preservation has limited the
SOFW-Journal | 140 | 1/2-2014 3
Commonly used chelating agents
Ethylenediaminetetraacetic acid
(EDTA) and its salts are commonly used,
but this is under environmental discus-
sion in several European countries.
Glutamic acid, N,N- diacetic acid
(GLDA) and its salts are readily biode-
gradable chelating agents that can be
used as alternative for EDTA. GLDA has
an exceptionally high solubility at high
and low pH.
Trends in using chelating agents
The frequency of use of EDTA in cos-
metic products was investigated in Min-
tel GNPD (3). In the period Jan 2010 to
Dec 2012 13.8% of the products contain
EDTA or EDTA salts. The analysis of the
trend in the last three years shows an
increase in the use of EDTA salts in cos-
metic formulations (Fig. 1).
The use of GLDA is still minor but also
increasing (Fig. 2). Based on the trend
to more environmentally friendly and
natural compounds an increasing sub-
stitution of EDTA can be expected.
Boosting preservatives –
Mode of action
Chelating agents can be used to increase
the efficacy of antimicrobial substances.
They remove multivalent cations from
the cell membrane of the microbes by
forming complexes, weakening the out-
er surface by decreases membrane sta-
bility and making them more vulnerable
to biocidal attack (Fig. 3) (4)(5).
Influence of pH on the preservative
boosting effect
Overall, the chelating agents were found
to exhibit a better boosting effect at pH
5.0 for Escherichia coli and Pseudomonas
aeruginosa. For Staphylococcus aureus,
the result at pH 7.0 was better, especially
with GLDA. Finally, the efficacy for Can-
dida albicans was worse at pH 5.0 (6).
Fig. 1 Trend using EDTA and EDTA salts in cosmetics (3)
Fig. 2 Trend using GLDA in cosmetics (3)
Fig. 3 Boosting of preservatives - Mode of action (5)
4 SOFW-Journal | 140 | 1/2-2014
Fig. 4 PEG-Free Emulsion for Baby Wipes (O/W) Fig. 5 Natural O/W Cream
Tests with frame formulations
To evaluate the effect of chelating
agents cosmetic formulations without
microbial stabilisation where tested in
comparison to samples with antimicro-
bial additive and with chelating agent
(GLDA). The microbial challenge tests
where performed according KoKo Test
(7) (8) protocol. For the finished wet wipe
the FeuTuKo Test (9) was applied.
The results are shown in Fig. 4–7.
The schülke KoKo Test
In this test (the schülke KoKo Test), a
mixture of bacteria, yeast and moulds
are inoculated 6 times (once a week) into
the test material with the goal of keep-
ing the test material germ free for this
period. The inoculum contains patho-
genic microorganisms as germs which
are well known for product spoilage. All
species have to be cultivated separately
and mixed directly before the addition,
to ensure a constant composition and
germ count of the inoculum. Its germ
count is approximately 107–108cfu/ml,
which means a germ count of approxi-
mately 105cfu/ml in the sample.
A sample can be considered to be well
preserved according criteria A, if a pe-
riod of six weeks is passed under the
above described laboratory conditions
without showing microbial growth on
the test batches. This means that even
after the sixth inoculation no micro-
bial growth should be observed. From
many years of experience in the use
of this test method, these results can
equate to a microbiological stability of
30 months, as recommended for cos-
metic products.
Criteria B is fulfilled if the sample
showed slight microbial growth (+)
during the 6 inoculation cycles. If the
formulation meets criteria B, the mi-
crobiological risk analysis should dem-
onstrate the existence of control fac-
tors not related to the formulation; for
example, a protective package such as a
pump provides a higher level of protec-
tion than a jar and /or following strong
demands on Good Manufacturing Prac-
tice (GMP).
The schülke FeuTuKo Test
In this test wet tissues in flexible plastic
packaging are inoculated with a mixed
culture containing 106-107cfu/ml. The
inoculum contains pathogenic microor-
ganisms as germs which are well known
for product spoilage. All species have to
be cultivated separately and mixed di-
SOFW-Journal | 140 | 1/2-2014 5
Fig. 6 Cosmetic Wipes – Self-Preserving Fig. 7 Tutti Frutti Body Scrub
rectly before the addition, to ensure a
constant composition and germ count
of the inoculum. After inoculation the
whole packaging is kneaded properly
and, thereafter, incubated for three
weeks at 30°C. The evaluation is done by
placing pieces of tissue (approx. 3 x 3cm,
cut out of the tissue pack in one block)
on TS and SA agar. In every case double
determinations are done. The growth on
the tissues is evaluated after three days
of incubation at 30°C (for bacteria) and
seven days at 25°C (for moulds). Fungi
are classified into yeasts and the differ-
ent mould types.
A sample can be considered to be well
preserved, if it passes a period of three
weeks under the above described labo-
ratory conditions without showing mi-
crobial growth on the test batches. This
means that even after inoculation no
microbial growth should be observed.
From many years of experience in the
use of this test method, these results can
equate to a microbiological stability of
30 months, which is recommended for
cosmetic products.
Chelating agents can improve the anti-
microbial efficiency of multifunctional
additives. With GLDA even the effect
against moulds is improved (Fig. 4). This
results confirm the results achieved with
the combination of GLDA with euxyl® PE
9010 (Phenoxyethanol (and) Ethylhexyl-
glycerin) (2).
Internal challenge tests showed the ben-
efit of chelating agents with euxyl® PE
9010, sensiva® SC 10, sensiva® PA 20 ,
and sensiva® PA 30 and sensiva® PA 40
in leave-on formulations. The boosting
of preservatives with chelating agents
performs at its best in simple formula-
tions. Positive results were found in:
wet wipes (best results)
other high water-based formulations
In complex systems, the boosting effect
to preservatives is limited. The addition
of chelating agents cannot counter-
act an inactivation of preservatives by
migration into the oil phase or micelle
(1) J. E. Finch and M. R. W. Brown, The influence
of nutrient limitation in a chemostat on the
sensitivity of Pseudomonas aeruginosa to po-
lymyxin and to EDTA, Journal of Antimicrobi-
al Chemotherapy 1/1975
(2) W. Siegert, Can New Biodegradable Comple-
xing Agents Replace Tetrasodium EDTA to
boost Preservatives, SOFW Journal 1/2 2008
(3) Mintel’s Global New Products Database
(GNPD), Search criteria: »Household, Beau-
ty & Personal Care, Global (49 countries)«,
search for products where Ingredient Search
matches one or more of »EDTA, Disodium ED-
TA, Tetrasodium EDTA, Trisodium EDTA« as the
Ingredients and Date Published is between
Jan 2010 and Dec 2012.
6 SOFW-Journal | 140 | 1/2-2014
(4) E. C. Hill, Biocides for the future, International
Biodeterioration Vol. 26/1990
(5) J. Seetz, New Environmental benign che-
lating agent GLDA, International Nonwo-
vens Symposium, May 2013, St. Peters-
burg, Russia
(6) W. Siegert, Influence of pH on the Preser-
vative Boosting Effect of Chelating Agents,
(7) H.Brill, Prüfverfahren zur Bestimmung der
mikrobiologischen Wirksamkeit von che-
mischen Konservierungsmitteln für Kosme-
tika, Jahrbuch für den Praktiker 1987
(8) W. Siegert, ISO 11930, Cosmetics – Microbi-
ology – Evaluation of the antimicrobial pro-
tection of a cosmetic product, SOFW-Journal
(9) W. Siegert, Microbiological quality ma-
nagement for the production of wet-wipes,
Household and Personal Care Today 2/2008
*Author´s address:
Wolfgang Siegert
Technical Support Manager,
Schülke & Mayr GmbH
Special Additives International
Tel.: +49 40 52100 528
... Improve the skin's natural elasticity and strength. [39][40][41][42] Chelation -Heavy metal scavenging. Elimination of heavy metals and boost the performance of antioxidants. ...
... Elimination of heavy metals and boost the performance of antioxidants. [41,42] antioxidants that protect against free radicals is the essential building block for protecting the skin from environmental pollution. ...
Urban pollution is one of the main problems encountered worldwide with major impact on public health as well as the environment. Health impact of urban pollution is not limited to respiratory conditions but also encompasses major skin problems including irritation, skin ageing, and skin cancer. Toxic gases and particulate matter are the main pollutants and exhibit extensive local variability. The aforementioned pollutants are small particles that attach to the skin or penetrate into it, enhancing free radicals’ production inside the inner skin layers. This urges the need to propose cosmetic products that help prevent and/or minimise pollutants’ effects on the skin whether irritation, ageing and cancer. Furthermore, intrinsic and extrinsic factors contributed to skin irritation and ageing. Intrinsic factors are within skin factors and include genetic and physiological characteristics of individuals. Moreover, extrinsic factors comprise environmental factors such as humidity, temperature, and smoke. Subsequently active ingredients with antipollutant properties addressed the intrinsic and extrinsic factors by four mechanisms being: free radical neutralisation, film-forming ability, skin barrier enhancement and fortification. Such ingredients include vitamin A derivatives, vitamin C derivatives, carbohydrates, and plant-based products. Yet, very limited studies have evaluated the effectiveness of the aforementioned active ingredients against irritation or ageing and this should be considered in future work.
... Les émulsifiants peuvent aussi participer à la diminution de l'activité antimicrobienne en séquestrant par exemple les molécules antimicrobiennes dans des micelles(Shimamoto and Mima 1979;Pernin, Bosc, et al. 2019;Kirk-Othmer 2013).Au contraire, dans d'autres cas, les émulsifiants peuvent augmenter l'efficacité antimicrobienne des conservateurs en perturbant les membranes bactériennes, et facilitant ainsi la pénétration des conservateurs à l'intérieur des bactéries(Halla et al. 2018). Les agents chélateurs, tels que l'EDTA (acide éthylène diamine tétra acétique) ou le GLDA (diacétate de glutamate de tétrasodium) ont la capacité d'augmenter la perméabilité membranaire des bactéries, les rendant plus sensibles aux agents antimicrobiens(Siegert 2014). L'éthylhexylglycérine, généralement utilisé pour ses propriétés tensioactives, émollientes, humectantes et solubilisantes, peut également, à une certaine concentration, favoriser l'activité antimicrobienne de conservateurs tels que le caprylyl glycol, le phénoxyéthanol et le 1,2-pentanediol(Langsrud et al. 2016;Herman 2019). ...
La plupart des produits cosmétiques sont sensibles à la prolifération microbienne, notamment du fait de leur composition riche en eau, de leur conservation à température ambiante et de leur utilisation en plusieurs fois. La gamme de conservateurs utilisables se réduisant, notamment à cause du durcissement de la réglementation, il devient indispensable de déterminer avec précision la capacité de conservation des formules cosmétiques pour prévoir leur durée de vie. Ainsi, l’objectif de cette thèse est de mieux comprendre, de prévoir et d’optimiser le fonctionnement des systèmes conservateurs au sein des matrices cosmétiques. Il s’agira tout d’abord de comprendre le rôle de la matrice (composition et structure) sur la répartition spatiale des microorganismes dans les formules cosmétiques, puis de mettre en place une méthode permettant d’évaluer et de prédire l’action des conservateurs au sein de ces matrices. Le Challenge-test est aujourd’hui encore la méthode de référence pour l’évaluation de la protection antimicrobienne d’un produit cosmétique mais il présente cependant un certain nombre de limites, notamment du fait de la lourdeur des expérimentations et du délai d’obtention des résultats. Nous avons tout d’abord cherché à identifier les déterminants de la distribution spatiale de Staphylococcus aureus, artificiellement inoculés dans des formules cosmétiques, grâce à une méthode associant la microscopie confocale à balayage laser (MCBL) et l’analyse d’images. Nous avons pu montrer que plus la viscosité des formules et/ou l’hydrophobicité des bactéries augmentent, plus la distribution spatiale des bactéries est hétérogène. De plus, nous avons mis en évidence qu’une distribution spatiale hétérogène pouvait induire une variabilité des résultats de dénombrement lors des Challenge-tests. Une méthode rapide a ensuite été développée pour évaluer et prédire l’action des conservateurs dans les formules cosmétiques. Cette méthode est basée sur l’acquisition de données d’inactivation bactérienne obtenues sur des temps courts par MCBL et sur la mise en place de modèles mathématiques d’inactivation. Elle a permis de prédire le nombre de réductions logarithmiques des populations bactériennes sur des temps longs, de même ordre de grandeur que les temps définis dans les challenge-tests. Cet outil devrait ainsi permettre aux industries cosmétiques de gagner du temps dans l’optimisation de la protection antimicrobienne des formules cosmétiques.
... PEG 400 (polyethylene glycol 400) also interacts with bacteria in high concentrations by decreasing the water activity [18,19]. The addition of chelating agents increased the efficacy of antimicrobial agents through variation of the permeability of microorganisms [20]. ...
Antimicrobial testing is a time consuming and cost-intensive but essential method for evaluation of newly developed pharmaceutical formulations for topical use. In this study the correlation between free preservative concentration in emulsion gels measured by equilibrium dialysis and the successful preservative effectiveness testing for Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans and Aspergillus brasiliensis (analyzed according to Ph. Eur. and USP) was investigated. The higher the lipophilicity of the oil phase and the lower the content of the aqueous phase with regard to dissolved ingredients the more preferably distributed is phenoxyethanol to the water phase and, consequently, the higher was the efficacy against the microbes. Increased emulsifier concentrations reduced the free amount of the preservative due to micellar interactions. Aspergillus brasiliensis was the most resistant and Staphylococcus aureus the most sensitive germ towards phenoxyethanol in o/w-emulsion gels.
... Chelating agents (e.g., EDTA 'ethylenediaminetetraacetic acid', GLDA 'glutamic acid, N,N-diacetic acid, lactic acid, citric acid, and phytic acid) increase the permeability of cell membranes and make them more sensitive to antimicrobial agents. In addition, chelating agents block the iron required for metabolism and microbial growth, and can enhance the antimicrobial efficacy of the used preservatives [42,82]. Surfactants with antimicrobial properties are the 1,2-diols (from butanediol to octanediol, mainly caprylyl glycol) due to their amphiphilic character and average molecular size, exhibit viscosity modulation properties that complement their antimicrobial properties. ...
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Cosmetics, like any product containing water and organic/inorganic compounds, require preservation against microbial contamination to guarantee consumer’s safety and to increase their shelf-life. The microbiological safety has as main goal of consumer protection against potentially pathogenic microorganisms, together with the product’s preservation resulting from biological and physicochemical deterioration. This is ensured by chemical, physical, or physicochemical strategies. The most common strategy is based on the application of antimicrobial agents, either by using synthetic or natural compounds, or even multifunctional ingredients. Current validation of a preservation system follow the application of good manufacturing practices (GMPs), the control of the raw material, and the verification of the preservative effect by suitable methodologies, including the challenge test. Among the preservatives described in the positive lists of regulations, there are parabens, isothiasolinone, organic acids, formaldehyde releasers, triclosan, and chlorhexidine. These chemical agents have different mechanisms of antimicrobial action, depending on their chemical structure and functional group’s reactivity. Preservatives act on several cell targets; however, they might present toxic effects to the consumer. Indeed, their use at high concentrations is more effective from the preservation viewpoint being, however, toxic for the consumer, whereas at low concentrations microbial resistance can develop.
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The aims of this study were to determine and evaluate the results of the physicochemical characteristic of snow mushroom (Tremella fuciformis) facial wash, and to determine the acceptability of the snow mushroom (Tremella fuciformis) extract facial wash which has the best physicochemical characteristics. In this study, the extraction of snow mushroom (Tremella fuciformis) used UAE (Ultrasound-Assisted Extraction) and ethanol as solvent with various concentrations, 96% (F1), 75% (F2), and 50% (F3). Furthermore, the extract will be formulated into facial wash and evaluated for physicochemical characteristics. The parameters of physicochemical characteristics include organoleptic, pH, density, viscosity, spreadability, and foamability. The difference in the concentration of ethanol as menstruum of snow fungus (Tremella fuciformis) extraction did not significantly affect the organoleptic composition of facial wash, but it did affect the physicochemical characteristics of facial wash, where higher ethanol concentrations resulted in lower pH, higher density and viscosity, smaller spreadability, and foamability that meets specifications. The results of the evaluation of physicochemical characteristics showed that F1 had the best specifications and continued hedonic testing to determine the acceptability of snow mushroom (Tremella fuciformis) extract facial wash. The results of the hedonic test on F1 showed good acceptance regarding the parameters of appearance, foam, and effects after using facial wash; as well as sufficient acceptability related to aroma and viscosity parameters.
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Hydroxylammonium nitrate (HAN) is an energetic salt used in flight-proven green monopropellants such as ASCENT (formerly AF-M315E), flown in NASA’s 2019 Green Propellant Infusion Mission, and SHP163, flown in JAXA’s Rapid Innovative Satellite Technology Demonstration-1. The decomposition of HAN is catalyzed by metals commonly found in storage tanks, a factor limiting its use. This work investigates the ability of metal-sequestering chelating agents to inhibit the decomposition of HAN. Isothermal and dynamic thermogravimetric analysis (TGA) were used to find isothermal decomposition rates, decomposition onset temperatures, and first-order Arrhenius reaction rate parameters. In the present research, 2,2′-bipyridine (Bipy), triethanolamine (TEA), and ethylenediaminetetraacetic acid (EDTA) were studied as 0.05, 0.1, 0.5, 1, and 5% by weight additives in 90% aqueous HAN. An isothermal decomposition rate of 0.137%/h at 348 K was observed for HAN. The addition of 1% Bipy and 1% TEA reduced the isothermal decomposition rate by 20.4% to 0.109%/h, and by 3.65% to 0.132%/h, respectively, showing that Bipy can inhibit decomposition. The addition of 1% EDTA increased the isothermal decomposition rate by 12.4% to 0.154%/h. Bipy was found to increase the decomposition onset temperature from 454.8 K to 461.8 K, while the results for TEA and EDTA were inconclusive. First order reaction rates calculated by the Ozawa-Flynn-Wall method were found to be insufficient to capture the effects of the tested additives. Bipy was found to inhibit the decomposition of HAN, while TEA and EDTA produced little or negative effect, a result believed to be due to poor metal complex stability at low pH and high acidity, respectively. Spectrophotometry, used for colorimetric analysis of Bipy+iron complexes, showed that Bipy forms chelate complexes with trace iron impurities when added to HAN solutions.
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Analytical method for the quantitative determination of EDTA in Cosmetics has been developed and validated by high-performance liquid chromatography (HPLC) with UV detection at wavelength 280 nm. The analysis was performed in gradient mode on a reversed phase C18 column, 4.6mm x 250mm using mobile phase consisted of a 25mM tetrabutyl ammonium hydrogen sulphate, in water as mobile phase A and acetonitrile as mobile phase B. The developed method was validated for various parameters such as Specificity, Linearity, Precision, Recovery, Repeatability and Ruggedness by employing HPLC. A linear calibration curve was observed in the range of 0.5-10.0 mg/kg with r 2 values ≥ 0.99. The limits of detection and quantification were 0.25 mg/kg and 0.5 mg/kg respectively. Cosmetics samples were spiked at 0.5, 1.0 and 2.0mg/kg fortification levels. Better recoveries between 70% to 120% were obtained with the acceptable relative standard deviation (% RSD) i.e. <20%. The validated method has been satisfactorily applied to the analysis of EDTA in Cosmetics samples due to its high sensitivity and selectivity.
Objective: As questions on the safety of some popular preservatives are on the rise, there is a growing interest in developing 'Self Preserving' personal care products. Use of Multi-functional ingredients / actives with antimicrobial properties has been explored as replacements for conventional preservatives. This paper explores the use of combinations of multi-functional actives (MFA) and other cosmetic ingredients in various personal care formulations, to deliver microbiologically safe self-preserving products. Products studied in this paper include face wash, gel based leave-on skin care product and face mask. Methods: Minimum Inhibitory Concentration (MIC) of several cosmetic ingredients was determined to identify Multi-functional actives with antimicrobial activity. Personal care formulations made with multi-functional actives and other cosmetic ingredients were studied for preservative efficacy by challenging the product with 6 multiple cycles of microbial challenge. Results: Formulations with combinations of multi-functional actives with antioxidant (AO) and chelators (CHL) were found to work synergistically and were highly efficacious in controlling multiple microbial challenges as observed in the Preservative Efficacy Test (PET) studies. The effective combinations were able to withstand up to 6 multiple microbial challenges without product degradation. The preservative efficacy profile was similar to control formula containing preservatives. Conclusion: Self-preserving personal care / cosmetic products can be developed which are as efficacious as preserved products by a prudent selection of multi-functional actives, antioxidants, and chelators as a part of the formulation. This article is protected by copyright. All rights reserved.
New regulatory measures require greater disclosure of toxic agents including biocides and the performance of risk assessments for each specific biocide application. There is a duty to minimise risk and hence an obligation to use concentrations which are effective but not excessive. A number of strategies are discussed which could lead to enhanced anti-microbial activity at lower use concentrations.