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Evaluation and characterization of Melo Bentonite clay for cosmetic applications
Applied Clay Science 175 (2019) 40–46
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Research Paper
Evaluation and characterization of Melo Bentonite clay for cosmetic applications
T
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Juliana da Silva Faveroa, Venina dos Santosa, , Valeria Weiss-Angelia, Lucas Bonan Gomesb, Diego Gusmão Verasb, Norberto Danib, André Sampaio Mexiasb, Carlos Pérez Bergmannb a b
University of Caxias do Sul (UCS), 1130 Francisco Getúlio Vargas Street, 95070-560 Caxias do Sul, RS, Brazil Federal University of Rio Grande do Sul (UFRGS), 9500 Bento Gonçalves Avenue, 91501-970 Porto Alegre, RS, Brazil
A R T I C LE I N FO
A B S T R A C T
Keywords: Clay Bentonite Physical-chemical characterization Cosmetic formulation Microbiological evaluation
Clays are used in cosmetology with different applications, which are conditioned to the chemical and mineralogical composition and physical-chemical characteristics of these materials. Therefore, the aim of this work was to evaluate the potential application of Melo Bentonite (BEM), clay from Uruguay through different tests. Initially, it was performed the characterization of BEM by X-ray Diffraction (XRD), X-ray fluorescence spectroscopy (XRF), thermal analysis (TGA/DTG), particle size distribution and surface area. The microbial content of natural Melo Bentonite clay was also verified. Two calamine suspensions were formulated with bentonite clay, one containing BEM and the other containing bentonite clay (BE), both at concentration of 5% w/w in glycerin. Bentonite clay was used in accordance to standard. The suspensions were characterized through tests of sedimentation rate, viscosity and pH determination. The physical-chemical characterization of BEM indicated compatible characteristics with those of clay; it was observed only smectite and quartz reflections as crystalline phases and in terms of chemical composition the major presence of silicon, aluminum and magnesium was verified. The microbiological evaluation showed that microbial content of Melo Bentonite presents acceptable limits, according to the Brazilian legislation for cosmetic products. BE was tested by a suspending agent. The sedimentation amount obtained for the suspention that was prepared with BEM was (0.73 mL/min) and with BE (0.63 mL/min). BEM is a better agent suspensor than BE. The viscosity presented by the sample containing BEM was lower than that containing BE; both of them showed non-Newtonian behavior and pseudoplastic flow. The pH of the sample containing BEM was close to neutral (7.72 ± 0.005), while the pH of the sample containing BE was 8.17 ± 0.026. The results showed a possible application of BEM in cosmetic products.
1. Introduction Suspensions are thermodynamically unstable formulations and phases tend to separate over time, so they require precise rheological control and stability. Suspension agents are used to retard sedimentation by affecting the rheological behavior of the suspension (Zatz, 1985; Viseras et al., 2007). Clays are often used in pharmaceutical formulations for this purpose, by the different properties they present, such as: large surface area, adsorptive capacity, rheological properties, chemical purity and low or inexistent toxicity in humans (Carretero, 2002). Clay minerals have two main functions in semi-solid pharmaceutical formulations: they stabilize dispersed systems and adjust the rheological patterns of the preparations (Iwasaki et al., 1989). These tasks are closely related to the presence of charges on the surface of the clay mineral particles, by their colloidal dimension and their ability to form
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different structures when dispersed in polar media (López-Galindo and Viseras, 2004). The stabilization of both suspensions and dispersions, and emulsions is the result of the gel formation ability that clay minerals have, as well as their presence in the interface boundaries due to their colloidal size, surface loads and large surface areas. However, the rheological properties of the clay dispersions are strongly influenced by the type of clay minerals, concentration and the presence of other molecules and ions (López-Galindo and Viseras, 2004). A dispersion is stable when the potential energy of repulsion arising from the approach of charged particles exceeds the attractive energy inherent among the particles over a given separation distance (Viseras et al., 2007). Bentonite is used as a suspending agent in concentrations ranging from 0.5 to 5% (w/w), producing good flocculation in bismuth subnitrate suspensions. The gelling properties of bentonite are reduced by
Corresponding author. E-mail address: [email protected] (V. dos Santos).
https://doi.org/10.1016/j.clay.2019.04.004 Received 29 August 2018; Received in revised form 25 March 2019; Accepted 5 April 2019 0169-1317/ © 2019 Elsevier B.V. All rights reserved.
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Fig. 1. Geological map and location of A and B Camps at Bañado de Medina region – Uruguay (Adapted from Gomez et al., 1980; Bossi et al., 1998, Calarge et al., 2003a; Calarge et al., 2003b; Calarge et al., 2006; Albarnaz et al., 2009).
fluvial and aeolian sandstones with intercalations of mudstone deposits (red beds) typically formed by lagoon systems during the Late Permian regression (Andreis et al., 1996). Great volcanic activity in the region of Patagonia during the Triassic and Early Jurassic age (Andreis et al., 1996) is remarkable due to generation of large amounts of silica-rich ash deposits (Axelrod, 1981). The bentonite deposit itself is 1.6 m thick, pinkish, massive, soft rock bed, interlaid in sandstone formations. Besides these were also used, calamine (Alpha Química, Brazil), zinc oxide (Alpha Química, Brazil), glycerin (Alpha Química, Brazil), methylparaben (Alpha Química, Brazil) and distilled water. The other materials used are particularly described in each of the specific methods.
acids and increased by bases, such as magnesium oxide. A bentonite used commercially under the name Veegum® HS is applied in several pharmaceutical formulations, with the function of suspending agent in combination with xanthan gum to promote proper viscosity (Vanderbilt Report, 1984). Thus, the goal of this work consists in the evaluation of potential application of Melo Bentonite as a suspensor agent in cosmetology products, through physical and chemical characterization as well as evaluating the suspending capacity of these clays.
2. Materials and methods 2.1. Geologic context and materials
2.2. Bentonite characterization
The raw bentonite sample was obtained from the Banãdo de Medina deposit located in the north of Uruguay, in Cerro Largo district, municipality of Melo, with central coordinates 32°24′39″ south latitude and 54°22′04″ west latitude (Fig. 1) (Albarnaz et al., 2009). The Melo Bentonite bed belongs to the Upper Permian Yaguary Formation of the Paraná basin (Andreis et al., 1996). The lithology is mostly composed of
The studied Melo bentonite sample (BEM) was characterized before and after the microbial decontamination method. The decontamination method consisted in drying the natural samples in an oven (Fanem 315SE/Brazil) at 120 °C for 24 h (Favero et al., 2016).
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2.2.4. Microbiological evaluation The microbiological evaluation of Melo Bentonite clay (BEM) was carried out with natural clay and after the process of decontamination with dry heat, using a stove at 120 °C for 24 h. The test was done using previous work methodology Favero et al. (2016).
Table 1 Composition of the calamine suspensions containing BE and BEM. Common name
INCI
(%)
(%)
Suspension of BE 5% Suspension of BEM 5% Calamine Zinc oxide Glycerin Methylparaben Distilled water
Bentonite Clay Calamine Zinc oxide Glycerin Methylparaben Aqua
25.0 – 2.0 14.0 7.0 0.1 51.9
– 25.0 2.0 14.0 7.0 0.1 51.9
2.3. Evaluation of the suspensory capacity of Melo Bentonite 2.3.1. Preparing the calamine/bentonite suspensions In order to evaluate the suspensory capacity of BEM, a suspension containing calamine was prepared. The aim of this preparation was to assess the influence of BEM on the sedimentation rate and on the volume of sediment formed in the calamine suspension. BE was used as standard. The calamine suspension was prepared as it follows: the zinc oxide and calamine were weighed and the mixture was stirred until homogeneous; glycerin was added to this initial mixture; the methylparaben was weighed by adding hot water under stirring for its solubilization; Subsequently, dispersions of BE at 5% and BEM at 5%, previously prepared, were added into the calamine suspensions. The proportions of each component used in the preparation of the calamine/bentonite suspensions are described on Table 1.
2.2.1. X-ray diffraction Mineralogical analysis was carried out by X-ray diffraction (XRD). XRD patterns were obtained with a Siemens (BRUKER-AXS) D-5000 diffractometer (Germany) operating at 40 kV and 40 mA using Cu-Kα monochromatic radiation (λ = 0.15406 nm), divergence and antiscattering slits of 1°and 0.2 mm detector slit. It was used the angular range from 2 to 72°2θ for total rock analysis, scan speed of 0.02/1 s. For the oriented slides the angular range from 2 to 28° 2θ was chosen, scan speed of 0.02/2 s for natural (N) and heated (H) samples and 0.02/3 s for glycolated sample (G). The samples were prepared as it follows: natural Melo Bentonite was disaggregated by mechanical grinding to a talc-like powder with the use of agate mortar and pestle. Then, the disaggregated material was sieved through 74 μm. Finally, the obtained powder was mounted on a sample holder for subsequent analysis. After primary disaggregation of natural sample, the preparation procedure was followed by: (1) powdered material was dispersed in deionized water and stirred for continued 14 h; (2) for further disaggregation ultrasonic probe was used for approximately 6 min; (3) the clay fraction < 2 μm was separated following the Stokes's law which relates the settling velocity of a particle to its size and specific gravity. The sample was placed in a settling vessel and filled up with deionized water to complete the settling zone, then the temperature of the dispersion was measured (24 °C) and the vessel agitated. According to the calculation of the fluid viscosity, the sample was decanted for 4 h and 21 min; at the end of the settlement time, the supernatant clay particles was quickly syphoned out to a beaker; (4) the supernatant material obtained from decantation was pipetted onto glass slides. It was used the just amount of sample to cover each slide; (5) the glass slides were allowed to dry at room temperature overnight. After dried the slides were ready for the XRD analysis. For both samples, natural and dried at 120 °C for 24 h, 3 oriented mounts (natural, glycolated, and heated) were prepared to be analyzed by XRD.
2.3.2. Physical-chemical evaluation of bentonite/calamine suspensions with bentonite clay 2.3.2.1. Sedimentation rate analysis. The sedimentation rate analysis was performed, measuring 25 mL of the suspension and adding 25 mL of distilled water in 50 mL beaker. Subsequently, it was shaken vigorously for 5 min on a magnetic stirrer and the whole contents were poured into a 50 mL beaker with a diameter of 2.5 cm. The sedimentation volume was read for 60 min. In the first 10 min the readings were performed every minute, between minutes 10 and 40 the readings were performed every 3 min and in the remaining 20 min the readings were taken every 5 min. The sedimentation rate was calculated according to Eq. (1) (Sinko, 2010).
Sedimentation rate (V . S.) =
Final sediment volume (mL) Total time (min)
(1)
2.3.2.2. Determination of viscosity. The viscosity of calamine suspensions BE and BEM was determined in a Brookfield Viscometer, at rotations 20, 50 and 100 rpm in ascending and descending mode with spindle S63. The test was done in triplicate. 2.3.2.3. pH determination. The pH determination of calamine suspensions was carried out by dispersing the suspension in distilled water (10%, m/v) at 25 °C in a potentiometer (Digimed), calibrated with solutions pH 4.0 and 7.0 (Davis, 1977). The test was done in triplicate.
2.2.2. Chemical analysis Elemental chemical analysis was performed by X-ray fluorescence spectrometry (XRF) on a Rigaku RIX2000 (Japan) sequential spectrometer equipped with Rh X-ray Tube. Loss on ignition (LOI) was determined in accordance with ASTM D7348–08 method (ASTM, 2008).
3. Results and discussion 2.2.3. Thermal analysis, particle size distribution and surface area Thermo gravimetric analysis of Melo Bentonite was performed on a Netzsch STA 449F3 (Germany) thermo balance from ambient temperature until 800 °C using a heating rate of 10 °C∙min−1 under N2 atmosphere. Particle size distribution was performed on a CILAS, 1180 Liquid laser dispersion granulometer (France) while the specific surface area was obtained by the BET (Brunauer, Emmet & Teller) method by multimolecular nitrogen adsorption-desorption experiments on a Quantachrome, NOVA 1000e instrument (USA). The samples were outgassed for 24 h at 350 °C. Sample preparation and analysis followed the procedures and cares recommended by Brazilian Technical Standards NBR 8289 (Associação Brasileira de Normas Técnicas: ABNT NBR 8289, 1983), NBR 8291 (Associação Brasileira de Normas Técnicas: ABNT NBR 8291, 1983) and NBR 8292 (Associação Brasileira de Normas Técnicas: ABNT NBR 8292, 1983).
3.1. Characterization of clay samples The XRD results of the oriented slides (fraction < 2 μm) showed the expected behavior for Ca-Smectites, Fig. 2(a) and (b). At natural (untreated) the (001) peak was around 1.5 nm. After solvation with ethylene glycol the smectite expanded to 1.6–1.7 nm. When heated at 550 °C the (001) peak shifted to ~1.0 nm. It was also possible to verify the presence of quartz (SiO2). The decontamination method did not affect the XRD patterns. The Si, Al, Fe Mg and Ca were the elements constituting the major amount of Melo Bentonite (Table 2). In the field of cosmetics, the application of clays is directly related to their chemical and mineralogical composition. According to Carretero and Pozo (2010), high amounts of Si mean that the clay 42
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Fig. 2. XRD analysis: (a) Total Rock XRD patterns: natural (as received) x 120 °C/24 h (“d” values are given in Å); (b) Melo Bentonite XRD patterns of fine fraction (< 2 μm) oriented slides: natural, glycolated and calcined. A comparison between air dried samples and dried at 120 °C/24 h (“d” values are given in Å).
and melanin adsorption. Clays having Si, Al, Fe, Ca, Ti and K contents can be employed for bactericidal, regenerative and antiseptic action contributing to cell renewal, impurity adsorption, invigoration of tissues and activation of circulation (Carretero and Pozo, 2010). The metals found in most of the BEM sample are metals that are
should be used in the reconstruction of skin tissues, besides providing tissue hydration and mitigation of possible skin inflammatory processes. Al was the second element found in highest amount on the clays. This metal is relevant in raw materials for cosmetics application since it is well-known for its healing activity, pigment dispersion, hydration
Table 2 Chemical composition for Melo Bentonite clay (oxide wt%). Oxide
SiO2
Al2O3
TiO2
Fe2O3
MnO
MgO
CaO
Na2O
K2O
P2O5
LOI
TOTAL
(%) (w/w)
67.73
15.95
0.10
2.27
0.15
4.52
2.12
–
0.16
–
7.41
100.41
43
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permitted by European Parliament Regulation 1223/2009 and are found largely in colouring used in cosmetics (Borowska and Brzóska, 2015). The use of color cosmetics is very popular daily and among these products are applied to the mucous membrane such as of lipsticks and lip gloss. In this situation is there the risk of their oral ingestion. The clay in study did not show high toxicity metals Sb, As, Cd, Pb, Ni and Tl, in your composition. These kind of metals are banned by the European community and have established strict limits on their maximum concentration by the FDA and Canada. Facial and cosmetic masks for ocular use may facilitate the absorption of metals through the skin, so once again the importance of the chemical characterization of the clay under study is highlighted once it has a high potential of use in the composition of facial masks. Studies show that the metals found in cosmetics, resulting from the raw materials used in their preparation can accumulate in the skin and be absorbed by the skin. Some cases of topical and systemic effects are related in the literature because of the use of cosmetics containing havy metals, including allergic reactions (Travassos et al., 2011) and unfavorable effects, including internal organs damage (Hg and Pb) (Dickenson et al., 2013). Al, a metal found in the BEM, has the ability to penetrate through the skin reaching the blood circulation and accumulating in different organs exerting toxic effects (CDC, 2012; Lin et al., 2012). However, the absorption of these metals by the skin is less than that by oral ingestion of these metals. This metal as a function of continuous exposure may accumulate in the bones causing osteomalacia and in the brain contributing to the development of Alzheimer's disease (Exley and Vickers, 2014). There is no regulation that establishes an acceptable minimum quantity of Al in cosmetic products as the performance of deodorant and antiperspirant products. There is a concern with the associated use of products containing aluminum or other heavy metals of the same category as aluminum in its composition, since this associated can generate a cumulative effect of these components on blood and tissues. BEM TGA curves (Fig. 3) showed weight loss in the temperature range between 100 °C and 250 °C of the order of 3.91%, suggesting that this loss was due to release of water molecules trapped at the clay surface. In this study the maximum temperature used was 120 °C, so the observed results from thermal analysis of water loss corresponded to adsorbed water loosely bound on particle surfaces (Mielenz et al., 1953). The particle size diameter of BEM (Table 3) was lower than 10 μm, while the average particle size for clay II was 24.1 μm. Knowledge of particle size distribution features of the raw materials is essential for the
Table 3 Melo Bentonite particle diameters. D10% (μm)
D50% (μm)
D90% (μm)
Daverage (μm)
3.0
20.22
45.53
22.60
right pre-formulation steps of cosmetic and pharmaceutical products. Based on the literature (Poensin et al., 2003) the powder particle size distribution applicability can vary. Finer powders have higher skin adhesion and provide better softness when applied on skin. One example showing that particle size influences powder properties is the research published by Poensin et al. (2003), which demonstrated that products for topical application containing in their composition clay of average particle size around 74 μm provided promising results related to augmented blood flow toward the treated skin region. The analyzed clays showed particle size between 3.6 and 24.1 μm. This reduced particle size range suggests the application of clays in cosmetics. According to literature, particles smaller than 63 μm may have anti-inflammatory effects and may assist in the skin hydration, retaining moisture due to the high skin adhesiveness (Dário et al., 2014). In regards to surface area evaluation, it was observed for BEM the value of 13.905 m2∙g−1. From the point of view of cosmetology, powder absorption properties are required for the retention of skin oiliness, thus contributing to drying and healing capacity (Carretero and Pozo, 2009). The adsorption capacity of skin exudates may be related to the porosity of the particles. Minerals with large surface area have porous or rough particles that adhere to the skin forming a film that provides mechanical protection and is able to retain skin oils (Carretero and Pozo, 2010).
3.2. Microbiological evaluation Table 4 shows the microbiological results obtained for BEM according to the initial bioburden, before and after the decontamination process, as well as the parameters accepted by the Brazilian cosmetics legislation, Resolution 481/99 (Brazil, 1999), that are the same accepted by the British Pharmacopeia (British Pharmacopeia, 2008). Before the decontamination, the sample was in compliance with the specifications for the parameters of mesophilic bacteria, molds and yeasts and fecal coliforms, but it showed growth of a pathogenic bacterium, Klebsiella spp. Klebsiella spp. is a bacterium from the Enterobacteriaceae family (EARSS, 2008; Souli et al., 2008) and is considered an important pathogen involved in different infections, mainly in the hospital
Fig. 3. TGA and DTG analysis of Melo Bentonite. 44
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Table 4 Microbiological results for BEM. Assay
Specificationb
Result1
Result2
Mesophile bacteria Molds and yeasts Fecal coliforms Total coliforms Escherichia coli Pseudômonas aeruginosa Staphylococcus aureus
Maximum 5,0 × 103 CFUa/g
1,3 × 102 CFUa/g < 1,0 × 101 CFUa/g Absence in 1 g Absence in 1 g Absence in 1 g Absence in 1 g Absence in 1 g
1,2 × 101 CFUa/g < 1,0 × 101 CFUa/g Absence in 1 g Absence in 1 g Absence in 1 g Absence in 1 g Absence in 1 g
Absence Absence – Absence Absence
in 1 g in 1 g in 1 g in 1 g
Note: Presence of Klebsiella spp. Growth before decontamination. CFU = Colony forming units. a Estimated value. b Resolution n° 481/1999. 1 Before decontamination. 2 After decontamination.
made the appliance of a decontamination method imperative before the application of BEM clay in cosmetics. It was verified that the dry heat method used was effective since there was no growth of the bacterium in the microbiological test performed after its application (Table 4), demonstrating that the method can also be applied for the elimination of pathogenic bacteria such as Klebsiella spp. found in the sample.
3.3. Physical-chemical evaluation of calamine suspensions containing suspending agents In the evaluation of the suspensory activity, a sedimentation rate of 0.63 mL/min was obtained for the suspension of calamine containing BE and 0.73 mL/min for the suspension of calamine containing BEM. Considering that in this experiment the height of the sediment formed at the same time was measured and that the relation between sedimentation rate and time is inversely proportional, the obtained results showed that BEM presented a superior suspending activity to the one of BE, since the sedimentation rate was higher, thus demonstrating the ability of this clay to keep more particles in suspension. Consequently, BEM presented a suspensor activity superior to BE, since its speed of sedimentation was higher, which means, the particles remain in suspension for a longer time. In Fig. 4, it is found the rheogram of calamine suspension samples containing BE and BEM. The sample tested with BEM had a lower viscosity than BE. Therefore, considering the tested formulation and the test standards used, BE presented better results in relation to the increase of viscosity in the calamine suspension. Calamine suspensions containing BE and BEM presented nonNewtonian behavior, with variation of viscosity as a function of the applied voltage, with no linear relationship between these values (Viseras et al., 2006). The samples under study show a pseudoplastic flow (Fig. 2), which is characterized by the decrease of apparent viscosity as the shear stress increases. This type of behavior is desired in pharmaceutical formulations. High apparent viscosity at low shear stresses is necessary to prevent the mobility of the dispersed phase. In addition, when stirred, they must exhibit free flow with low viscosity and under high shear stresses, as long as these changes are reversible after some resting time, delaying coalescence or caking (Guaratini et al., 2006). The results of the pH determination averages for the calamine suspension tested within BEM indicated a value close to neutrality (7.72 ± 0.005), being lower than the pH of the suspension containing BE, which was more basic (8.17 ± 0.026). The pH of the samples presented a value above the adequate for cosmetic products (5.5–6.5). The pH of the skin surface in the facial region (5.5–6.5) depends on external and internal factors and normal pH values may increase or decrease after applying topical products, returning to baseline in a few minutes (Modabberi et al., 2015). In face
Fig. 4. Rheograms of calamine suspension.
environment, in intensive care units (ICUs), where it affects immunocompromised patients, which are subject to numerous risk factors, such as administration of large amounts of antibiotics, chronic diseases, invasive procedures and immunosuppressive treatments. It is a bacterium that over the years has created resistance to several antibiotics such as aminoglycosides and carbapenems, given this reality and different mechanisms of resistance acquired by the bacteria, several research groups have followed the distribution and susceptibility profile of the genus Klebsiella spp. with the aim of monitoring possible outbreaks and assembling the sensitivity profile in the different regions (Albrich et al., 1999; EARSS, 2008). Therefore, the decontamination of these samples must follow a critical step in the process of suitability of clays for cosmetology use, assuring the number of samples and test done with the samples are in accordance to what is recommended in the law. After the decontamination with dry heat, the reduction of mesophilic bacteria levels was observed and the remaining parameters kept the same obtained in the sample without decontamination (Table 4). There were no pathogens, fecal and total coliforms, and the sample was totally in accordance with the requirements of the Brazilian cosmetics legislation (Brazil, 1999) and the British pharmacopeia (British Pharmacopeia, 2008). The dry heat method was used in previous work (Favero et al., 2016), being effective in the decontamination of clays containing mesophilic bacteria, molds and yeasts above the specifications already mentioned. The presence of the pathogenic bacterium Klebsiella spp. 45
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of the above, the pH found in the addition of BEM was better when compared to BE, under the conditions tested. It should be pointed out that these pH values were obtained when the clays were incorporated in water, making relevant studies to evaluate if these raw materials will be able to alter the pH of a cosmetic vehicle such as gels, emulsions, among others. Alterations in pH values may occur due to chemical modifications of the formulation components, for this reason their determination together with the evaluation of the product stability becomes extremely relevant. During the storage of cosmetic products, oxidation reactions may occur, which generate chemical changes in the formula components. The rate at which these reactions occur may not be the same for the different substances present in the cosmetic product, thereby, oxidations may occur even before the antioxidant action of the formulation begins (Weiss-Angeli et al., 2008).
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Lead powder use for skin care and elevated blood lead level among children in a Chinese ruralarea. J. Expo. Sci. Environ. Epidemiol. 22, 198–203. https://doi.org/10.1038/jes.2011.46. López-Galindo, A., Viseras, C., 2004. Pharmaceutical and cosmetic applications of clays. In: Wypych, F., Satyanarayana, K.G. (Eds.), Clay Surfaces: Fundamentals and Applications. Elsevier, Granada, pp. 267–289. Mielenz, R.C., Schieltz, N.C., King, M.E., 1953. Thermogravimetric analysis of clay and clay-like minerals. In: Second National Conference on Clays and Clays Minerals. University of Missouri, pp. 285–314. Modabberi, S., Namayandeh, A., López-Galindo, A., Viseras, C., Setti, M., Ranjbaran, M., 2015. Characterization of Iranian bentonites to be used as pharmaceutical materials. Appl. Clay Sci. 116–117, 193–201. https://doi.org/10.1016/j.clay.2015.03.013. Poensin, D., Carpentier, P., Féchoz, C., Gasparini, S., 2003. Effects of mud pack treatment on skin microcirculation. Joint Bone Spine 70, 367–370. https://doi.org/10.1016/ S1297-319X(03)00064-2. Sinko, P.J., 2010. Martin's Physical Pharmacy and Pharmaceutical Sciences, Sixth, North American edition. Lippincott Williams and Wilkins. Souli, M., Galani, I., Giamarellou, H., 2008. Emergence of extensively drug-resistant and pandrug-resistant Gram-negative bacilli in Europe. Euro Surveill. 13 (47). https:// doi.org/10.1128/AAC.01823-12. pii: 19045. Travassos, A.R., Bruze, M., Dahlim, J., Goossens, A., 2011. Allergic contact dermatitis caused by nickel in a green eye pencil. Contact Dermatitis 65, 307–308. https://doi. org/10.1111/j.1600-0536.2011.01960. Vanderbilt Report, 1984. Technical Information: “VEEGUM- the Versatile Ingredient for Pharmaceutical Formulations”. In: Vanderbilt Company Bulletin No. 91R, 1984 (www.rtvanderbilt.com). R.T. Vanderbilt Company, Inc, Norwalk, CT (USA). Viseras, C., Cultrone, G., Cerezo, P., Aguzzi, P., Baschini, M.T., Valles, J., López-Galindo, A., 2006. Characterisation of northern Patagonian bentonite for pharmaceutical uses. Appl. Clay Sci. 31, 272–281. https://doi.org/10.1016/j.clay.2005.11.002. Viseras, C., Aguzzi, C., Cerezo, P., Lopez-Galindo, A., 2007. Uses of clay minerals in semisolid health care and therapeutic products. Appl. Clay Sci. 36, 37–50. https:// doi.org/10.1016/j.clay.2006.07.006. Weiss-Angeli, V., Poletto, F.S., Zancan, L.R., Baldasso, F., Pohlmann, A.R., Guterres, S.S., 2008. Nanocapsules of octyl methoxycinnamate containing quercetin delayed the photodegradation of both components under ultraviolet a radiation. J. Biomed. Nanotechnol. 4 (1), 80–89. https://doi.org/10.1166/jbn.2008.004. Zatz, J.L., 1985. Physical stability of suspensions. J. Soc. Cosmet. Chem. 36, 393–411.
4. Conclusion On the basis of the obtained results it was possible to conclude, from physical-chemical characterization, that the samples features were compatible with those of clay. The major reflections of all samples were typical smectite and quartz. The presence of Si, Al and Mg as most abundant elements was evidenced smectite and quartz). The microbiological load of BEM was within the specifications of the legislation, but with the presence of a pathogenic bacterium. Thus, for application in cosmetic products a decontamination process is suggested prior to use. The evaluation of suspensory capacity and increase in viscosity indicated that BEM did not promote better results when compared to BE, clay already used in the pharmaceutical and cosmetic sectors. However, regarding pH, BEM presented a better result when compared to BE. From the results obtained, it is possible to see that the application of Melo Bentonite clay in cosmetic products has the same performance that the BE for the testes performed in this work. Additional, but not less important, tests such as the assessment of cytotoxicity and the skin hydration capacity of the clay under study should be performed to assess the safety and efficacy of this clay in the skin. Acknowledgements Authors are beholden to the University of Caxias do Sul (UCS), to Federal University of Rio Grande do Sul (UFRGS) and to the Research Support Foundation of the Rio Grande do Sul State (FAPERGS) for financial support. References Albarnaz, L.D., Dani, N., Formoso, M.L.L., Mexias, A.S., Lisboa, N.A., 2009. A jazida de bentonita de Bañado de Medina, Melo, Uruguai. Geologia, meneralogia e utilização tecnológica. Pesquisas em Geociências 36 (3), 263–281 (ISSN 1807-9806). Albrich, W.C., Angstwurm, M., Bader, L., Gärtner, R., 1999. Drug resistance in intensive care units. Infect 27, S19–S23. https://doi.org/10.1007/BF02561665. American Society for Testing Materials: ASTM D7348-08, 2008. Standard Test Methods for Loss on Ignition (LOI) of Solid Combustion Residues. Andreis, R.R., Ferrando, L., Herbst, R., 1996. Terrenos Carboníferos y Pérmicos de la República Oriental del Uruguay. In: El Sistema Pérmico en la República Argentina Y en la República Oriental del Uruguay. Academia Nacional del Uruguay, Cordoba, Argentina, pp. 309–343. Associação Brasileira de Normas Técnicas: ABNT NBR 8289, 1983. Carvão Mineral Determinação Do Teor de Cinzas - Método de Ensaio. Associação Brasileira de Normas Técnicas: ABNT NBR 8291, 1983. Amostragem de carvão Mineral Bruto e/Ou Beneficiado – Procedimento. Associação Brasileira de Normas Técnicas: ABNT NBR 8292, 1983. Preparação de Amostra de carvão Mineral Para análise e Ensaios – Procedimento. Axelrod, D.I., 1981. Role of volcanism in climate and evolution. Geol. Soc. Am. Spec. Paper 185, 59. Borowska, S., Brzóska, M.M., 2015. Metals in cosmetics: implications for human health. J. Appl. Toxicol. 35, 551–572. https://doi.org/10.1002/jat.3129. Bossi, J., Ferrando, L., Montaña, J., Campal, N., Morales, H., Gancio, F., Schipilov, A., Piñero, D., Sprechmann, P., 1998. Carta geológica Del Uruguay. In: Montivideo. Faculdad de Agronomia, Escala (1:500.000). Brazil, 1999. Resolução RDC N° 481, de 23 de setembro de 1999. In: Establishes the
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Research Paper
Evaluation and characterization of Melo Bentonite clay for cosmetic applications
T
⁎
Juliana da Silva Faveroa, Venina dos Santosa, , Valeria Weiss-Angelia, Lucas Bonan Gomesb, Diego Gusmão Verasb, Norberto Danib, André Sampaio Mexiasb, Carlos Pérez Bergmannb a b
University of Caxias do Sul (UCS), 1130 Francisco Getúlio Vargas Street, 95070-560 Caxias do Sul, RS, Brazil Federal University of Rio Grande do Sul (UFRGS), 9500 Bento Gonçalves Avenue, 91501-970 Porto Alegre, RS, Brazil
A R T I C LE I N FO
A B S T R A C T
Keywords: Clay Bentonite Physical-chemical characterization Cosmetic formulation Microbiological evaluation
Clays are used in cosmetology with different applications, which are conditioned to the chemical and mineralogical composition and physical-chemical characteristics of these materials. Therefore, the aim of this work was to evaluate the potential application of Melo Bentonite (BEM), clay from Uruguay through different tests. Initially, it was performed the characterization of BEM by X-ray Diffraction (XRD), X-ray fluorescence spectroscopy (XRF), thermal analysis (TGA/DTG), particle size distribution and surface area. The microbial content of natural Melo Bentonite clay was also verified. Two calamine suspensions were formulated with bentonite clay, one containing BEM and the other containing bentonite clay (BE), both at concentration of 5% w/w in glycerin. Bentonite clay was used in accordance to standard. The suspensions were characterized through tests of sedimentation rate, viscosity and pH determination. The physical-chemical characterization of BEM indicated compatible characteristics with those of clay; it was observed only smectite and quartz reflections as crystalline phases and in terms of chemical composition the major presence of silicon, aluminum and magnesium was verified. The microbiological evaluation showed that microbial content of Melo Bentonite presents acceptable limits, according to the Brazilian legislation for cosmetic products. BE was tested by a suspending agent. The sedimentation amount obtained for the suspention that was prepared with BEM was (0.73 mL/min) and with BE (0.63 mL/min). BEM is a better agent suspensor than BE. The viscosity presented by the sample containing BEM was lower than that containing BE; both of them showed non-Newtonian behavior and pseudoplastic flow. The pH of the sample containing BEM was close to neutral (7.72 ± 0.005), while the pH of the sample containing BE was 8.17 ± 0.026. The results showed a possible application of BEM in cosmetic products.
1. Introduction Suspensions are thermodynamically unstable formulations and phases tend to separate over time, so they require precise rheological control and stability. Suspension agents are used to retard sedimentation by affecting the rheological behavior of the suspension (Zatz, 1985; Viseras et al., 2007). Clays are often used in pharmaceutical formulations for this purpose, by the different properties they present, such as: large surface area, adsorptive capacity, rheological properties, chemical purity and low or inexistent toxicity in humans (Carretero, 2002). Clay minerals have two main functions in semi-solid pharmaceutical formulations: they stabilize dispersed systems and adjust the rheological patterns of the preparations (Iwasaki et al., 1989). These tasks are closely related to the presence of charges on the surface of the clay mineral particles, by their colloidal dimension and their ability to form
⁎
different structures when dispersed in polar media (López-Galindo and Viseras, 2004). The stabilization of both suspensions and dispersions, and emulsions is the result of the gel formation ability that clay minerals have, as well as their presence in the interface boundaries due to their colloidal size, surface loads and large surface areas. However, the rheological properties of the clay dispersions are strongly influenced by the type of clay minerals, concentration and the presence of other molecules and ions (López-Galindo and Viseras, 2004). A dispersion is stable when the potential energy of repulsion arising from the approach of charged particles exceeds the attractive energy inherent among the particles over a given separation distance (Viseras et al., 2007). Bentonite is used as a suspending agent in concentrations ranging from 0.5 to 5% (w/w), producing good flocculation in bismuth subnitrate suspensions. The gelling properties of bentonite are reduced by
Corresponding author. E-mail address: [email protected] (V. dos Santos).
https://doi.org/10.1016/j.clay.2019.04.004 Received 29 August 2018; Received in revised form 25 March 2019; Accepted 5 April 2019 0169-1317/ © 2019 Elsevier B.V. All rights reserved.
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Fig. 1. Geological map and location of A and B Camps at Bañado de Medina region – Uruguay (Adapted from Gomez et al., 1980; Bossi et al., 1998, Calarge et al., 2003a; Calarge et al., 2003b; Calarge et al., 2006; Albarnaz et al., 2009).
fluvial and aeolian sandstones with intercalations of mudstone deposits (red beds) typically formed by lagoon systems during the Late Permian regression (Andreis et al., 1996). Great volcanic activity in the region of Patagonia during the Triassic and Early Jurassic age (Andreis et al., 1996) is remarkable due to generation of large amounts of silica-rich ash deposits (Axelrod, 1981). The bentonite deposit itself is 1.6 m thick, pinkish, massive, soft rock bed, interlaid in sandstone formations. Besides these were also used, calamine (Alpha Química, Brazil), zinc oxide (Alpha Química, Brazil), glycerin (Alpha Química, Brazil), methylparaben (Alpha Química, Brazil) and distilled water. The other materials used are particularly described in each of the specific methods.
acids and increased by bases, such as magnesium oxide. A bentonite used commercially under the name Veegum® HS is applied in several pharmaceutical formulations, with the function of suspending agent in combination with xanthan gum to promote proper viscosity (Vanderbilt Report, 1984). Thus, the goal of this work consists in the evaluation of potential application of Melo Bentonite as a suspensor agent in cosmetology products, through physical and chemical characterization as well as evaluating the suspending capacity of these clays.
2. Materials and methods 2.1. Geologic context and materials
2.2. Bentonite characterization
The raw bentonite sample was obtained from the Banãdo de Medina deposit located in the north of Uruguay, in Cerro Largo district, municipality of Melo, with central coordinates 32°24′39″ south latitude and 54°22′04″ west latitude (Fig. 1) (Albarnaz et al., 2009). The Melo Bentonite bed belongs to the Upper Permian Yaguary Formation of the Paraná basin (Andreis et al., 1996). The lithology is mostly composed of
The studied Melo bentonite sample (BEM) was characterized before and after the microbial decontamination method. The decontamination method consisted in drying the natural samples in an oven (Fanem 315SE/Brazil) at 120 °C for 24 h (Favero et al., 2016).
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2.2.4. Microbiological evaluation The microbiological evaluation of Melo Bentonite clay (BEM) was carried out with natural clay and after the process of decontamination with dry heat, using a stove at 120 °C for 24 h. The test was done using previous work methodology Favero et al. (2016).
Table 1 Composition of the calamine suspensions containing BE and BEM. Common name
INCI
(%)
(%)
Suspension of BE 5% Suspension of BEM 5% Calamine Zinc oxide Glycerin Methylparaben Distilled water
Bentonite Clay Calamine Zinc oxide Glycerin Methylparaben Aqua
25.0 – 2.0 14.0 7.0 0.1 51.9
– 25.0 2.0 14.0 7.0 0.1 51.9
2.3. Evaluation of the suspensory capacity of Melo Bentonite 2.3.1. Preparing the calamine/bentonite suspensions In order to evaluate the suspensory capacity of BEM, a suspension containing calamine was prepared. The aim of this preparation was to assess the influence of BEM on the sedimentation rate and on the volume of sediment formed in the calamine suspension. BE was used as standard. The calamine suspension was prepared as it follows: the zinc oxide and calamine were weighed and the mixture was stirred until homogeneous; glycerin was added to this initial mixture; the methylparaben was weighed by adding hot water under stirring for its solubilization; Subsequently, dispersions of BE at 5% and BEM at 5%, previously prepared, were added into the calamine suspensions. The proportions of each component used in the preparation of the calamine/bentonite suspensions are described on Table 1.
2.2.1. X-ray diffraction Mineralogical analysis was carried out by X-ray diffraction (XRD). XRD patterns were obtained with a Siemens (BRUKER-AXS) D-5000 diffractometer (Germany) operating at 40 kV and 40 mA using Cu-Kα monochromatic radiation (λ = 0.15406 nm), divergence and antiscattering slits of 1°and 0.2 mm detector slit. It was used the angular range from 2 to 72°2θ for total rock analysis, scan speed of 0.02/1 s. For the oriented slides the angular range from 2 to 28° 2θ was chosen, scan speed of 0.02/2 s for natural (N) and heated (H) samples and 0.02/3 s for glycolated sample (G). The samples were prepared as it follows: natural Melo Bentonite was disaggregated by mechanical grinding to a talc-like powder with the use of agate mortar and pestle. Then, the disaggregated material was sieved through 74 μm. Finally, the obtained powder was mounted on a sample holder for subsequent analysis. After primary disaggregation of natural sample, the preparation procedure was followed by: (1) powdered material was dispersed in deionized water and stirred for continued 14 h; (2) for further disaggregation ultrasonic probe was used for approximately 6 min; (3) the clay fraction < 2 μm was separated following the Stokes's law which relates the settling velocity of a particle to its size and specific gravity. The sample was placed in a settling vessel and filled up with deionized water to complete the settling zone, then the temperature of the dispersion was measured (24 °C) and the vessel agitated. According to the calculation of the fluid viscosity, the sample was decanted for 4 h and 21 min; at the end of the settlement time, the supernatant clay particles was quickly syphoned out to a beaker; (4) the supernatant material obtained from decantation was pipetted onto glass slides. It was used the just amount of sample to cover each slide; (5) the glass slides were allowed to dry at room temperature overnight. After dried the slides were ready for the XRD analysis. For both samples, natural and dried at 120 °C for 24 h, 3 oriented mounts (natural, glycolated, and heated) were prepared to be analyzed by XRD.
2.3.2. Physical-chemical evaluation of bentonite/calamine suspensions with bentonite clay 2.3.2.1. Sedimentation rate analysis. The sedimentation rate analysis was performed, measuring 25 mL of the suspension and adding 25 mL of distilled water in 50 mL beaker. Subsequently, it was shaken vigorously for 5 min on a magnetic stirrer and the whole contents were poured into a 50 mL beaker with a diameter of 2.5 cm. The sedimentation volume was read for 60 min. In the first 10 min the readings were performed every minute, between minutes 10 and 40 the readings were performed every 3 min and in the remaining 20 min the readings were taken every 5 min. The sedimentation rate was calculated according to Eq. (1) (Sinko, 2010).
Sedimentation rate (V . S.) =
Final sediment volume (mL) Total time (min)
(1)
2.3.2.2. Determination of viscosity. The viscosity of calamine suspensions BE and BEM was determined in a Brookfield Viscometer, at rotations 20, 50 and 100 rpm in ascending and descending mode with spindle S63. The test was done in triplicate. 2.3.2.3. pH determination. The pH determination of calamine suspensions was carried out by dispersing the suspension in distilled water (10%, m/v) at 25 °C in a potentiometer (Digimed), calibrated with solutions pH 4.0 and 7.0 (Davis, 1977). The test was done in triplicate.
2.2.2. Chemical analysis Elemental chemical analysis was performed by X-ray fluorescence spectrometry (XRF) on a Rigaku RIX2000 (Japan) sequential spectrometer equipped with Rh X-ray Tube. Loss on ignition (LOI) was determined in accordance with ASTM D7348–08 method (ASTM, 2008).
3. Results and discussion 2.2.3. Thermal analysis, particle size distribution and surface area Thermo gravimetric analysis of Melo Bentonite was performed on a Netzsch STA 449F3 (Germany) thermo balance from ambient temperature until 800 °C using a heating rate of 10 °C∙min−1 under N2 atmosphere. Particle size distribution was performed on a CILAS, 1180 Liquid laser dispersion granulometer (France) while the specific surface area was obtained by the BET (Brunauer, Emmet & Teller) method by multimolecular nitrogen adsorption-desorption experiments on a Quantachrome, NOVA 1000e instrument (USA). The samples were outgassed for 24 h at 350 °C. Sample preparation and analysis followed the procedures and cares recommended by Brazilian Technical Standards NBR 8289 (Associação Brasileira de Normas Técnicas: ABNT NBR 8289, 1983), NBR 8291 (Associação Brasileira de Normas Técnicas: ABNT NBR 8291, 1983) and NBR 8292 (Associação Brasileira de Normas Técnicas: ABNT NBR 8292, 1983).
3.1. Characterization of clay samples The XRD results of the oriented slides (fraction < 2 μm) showed the expected behavior for Ca-Smectites, Fig. 2(a) and (b). At natural (untreated) the (001) peak was around 1.5 nm. After solvation with ethylene glycol the smectite expanded to 1.6–1.7 nm. When heated at 550 °C the (001) peak shifted to ~1.0 nm. It was also possible to verify the presence of quartz (SiO2). The decontamination method did not affect the XRD patterns. The Si, Al, Fe Mg and Ca were the elements constituting the major amount of Melo Bentonite (Table 2). In the field of cosmetics, the application of clays is directly related to their chemical and mineralogical composition. According to Carretero and Pozo (2010), high amounts of Si mean that the clay 42
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Fig. 2. XRD analysis: (a) Total Rock XRD patterns: natural (as received) x 120 °C/24 h (“d” values are given in Å); (b) Melo Bentonite XRD patterns of fine fraction (< 2 μm) oriented slides: natural, glycolated and calcined. A comparison between air dried samples and dried at 120 °C/24 h (“d” values are given in Å).
and melanin adsorption. Clays having Si, Al, Fe, Ca, Ti and K contents can be employed for bactericidal, regenerative and antiseptic action contributing to cell renewal, impurity adsorption, invigoration of tissues and activation of circulation (Carretero and Pozo, 2010). The metals found in most of the BEM sample are metals that are
should be used in the reconstruction of skin tissues, besides providing tissue hydration and mitigation of possible skin inflammatory processes. Al was the second element found in highest amount on the clays. This metal is relevant in raw materials for cosmetics application since it is well-known for its healing activity, pigment dispersion, hydration
Table 2 Chemical composition for Melo Bentonite clay (oxide wt%). Oxide
SiO2
Al2O3
TiO2
Fe2O3
MnO
MgO
CaO
Na2O
K2O
P2O5
LOI
TOTAL
(%) (w/w)
67.73
15.95
0.10
2.27
0.15
4.52
2.12
–
0.16
–
7.41
100.41
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permitted by European Parliament Regulation 1223/2009 and are found largely in colouring used in cosmetics (Borowska and Brzóska, 2015). The use of color cosmetics is very popular daily and among these products are applied to the mucous membrane such as of lipsticks and lip gloss. In this situation is there the risk of their oral ingestion. The clay in study did not show high toxicity metals Sb, As, Cd, Pb, Ni and Tl, in your composition. These kind of metals are banned by the European community and have established strict limits on their maximum concentration by the FDA and Canada. Facial and cosmetic masks for ocular use may facilitate the absorption of metals through the skin, so once again the importance of the chemical characterization of the clay under study is highlighted once it has a high potential of use in the composition of facial masks. Studies show that the metals found in cosmetics, resulting from the raw materials used in their preparation can accumulate in the skin and be absorbed by the skin. Some cases of topical and systemic effects are related in the literature because of the use of cosmetics containing havy metals, including allergic reactions (Travassos et al., 2011) and unfavorable effects, including internal organs damage (Hg and Pb) (Dickenson et al., 2013). Al, a metal found in the BEM, has the ability to penetrate through the skin reaching the blood circulation and accumulating in different organs exerting toxic effects (CDC, 2012; Lin et al., 2012). However, the absorption of these metals by the skin is less than that by oral ingestion of these metals. This metal as a function of continuous exposure may accumulate in the bones causing osteomalacia and in the brain contributing to the development of Alzheimer's disease (Exley and Vickers, 2014). There is no regulation that establishes an acceptable minimum quantity of Al in cosmetic products as the performance of deodorant and antiperspirant products. There is a concern with the associated use of products containing aluminum or other heavy metals of the same category as aluminum in its composition, since this associated can generate a cumulative effect of these components on blood and tissues. BEM TGA curves (Fig. 3) showed weight loss in the temperature range between 100 °C and 250 °C of the order of 3.91%, suggesting that this loss was due to release of water molecules trapped at the clay surface. In this study the maximum temperature used was 120 °C, so the observed results from thermal analysis of water loss corresponded to adsorbed water loosely bound on particle surfaces (Mielenz et al., 1953). The particle size diameter of BEM (Table 3) was lower than 10 μm, while the average particle size for clay II was 24.1 μm. Knowledge of particle size distribution features of the raw materials is essential for the
Table 3 Melo Bentonite particle diameters. D10% (μm)
D50% (μm)
D90% (μm)
Daverage (μm)
3.0
20.22
45.53
22.60
right pre-formulation steps of cosmetic and pharmaceutical products. Based on the literature (Poensin et al., 2003) the powder particle size distribution applicability can vary. Finer powders have higher skin adhesion and provide better softness when applied on skin. One example showing that particle size influences powder properties is the research published by Poensin et al. (2003), which demonstrated that products for topical application containing in their composition clay of average particle size around 74 μm provided promising results related to augmented blood flow toward the treated skin region. The analyzed clays showed particle size between 3.6 and 24.1 μm. This reduced particle size range suggests the application of clays in cosmetics. According to literature, particles smaller than 63 μm may have anti-inflammatory effects and may assist in the skin hydration, retaining moisture due to the high skin adhesiveness (Dário et al., 2014). In regards to surface area evaluation, it was observed for BEM the value of 13.905 m2∙g−1. From the point of view of cosmetology, powder absorption properties are required for the retention of skin oiliness, thus contributing to drying and healing capacity (Carretero and Pozo, 2009). The adsorption capacity of skin exudates may be related to the porosity of the particles. Minerals with large surface area have porous or rough particles that adhere to the skin forming a film that provides mechanical protection and is able to retain skin oils (Carretero and Pozo, 2010).
3.2. Microbiological evaluation Table 4 shows the microbiological results obtained for BEM according to the initial bioburden, before and after the decontamination process, as well as the parameters accepted by the Brazilian cosmetics legislation, Resolution 481/99 (Brazil, 1999), that are the same accepted by the British Pharmacopeia (British Pharmacopeia, 2008). Before the decontamination, the sample was in compliance with the specifications for the parameters of mesophilic bacteria, molds and yeasts and fecal coliforms, but it showed growth of a pathogenic bacterium, Klebsiella spp. Klebsiella spp. is a bacterium from the Enterobacteriaceae family (EARSS, 2008; Souli et al., 2008) and is considered an important pathogen involved in different infections, mainly in the hospital
Fig. 3. TGA and DTG analysis of Melo Bentonite. 44
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Table 4 Microbiological results for BEM. Assay
Specificationb
Result1
Result2
Mesophile bacteria Molds and yeasts Fecal coliforms Total coliforms Escherichia coli Pseudômonas aeruginosa Staphylococcus aureus
Maximum 5,0 × 103 CFUa/g
1,3 × 102 CFUa/g < 1,0 × 101 CFUa/g Absence in 1 g Absence in 1 g Absence in 1 g Absence in 1 g Absence in 1 g
1,2 × 101 CFUa/g < 1,0 × 101 CFUa/g Absence in 1 g Absence in 1 g Absence in 1 g Absence in 1 g Absence in 1 g
Absence Absence – Absence Absence
in 1 g in 1 g in 1 g in 1 g
Note: Presence of Klebsiella spp. Growth before decontamination. CFU = Colony forming units. a Estimated value. b Resolution n° 481/1999. 1 Before decontamination. 2 After decontamination.
made the appliance of a decontamination method imperative before the application of BEM clay in cosmetics. It was verified that the dry heat method used was effective since there was no growth of the bacterium in the microbiological test performed after its application (Table 4), demonstrating that the method can also be applied for the elimination of pathogenic bacteria such as Klebsiella spp. found in the sample.
3.3. Physical-chemical evaluation of calamine suspensions containing suspending agents In the evaluation of the suspensory activity, a sedimentation rate of 0.63 mL/min was obtained for the suspension of calamine containing BE and 0.73 mL/min for the suspension of calamine containing BEM. Considering that in this experiment the height of the sediment formed at the same time was measured and that the relation between sedimentation rate and time is inversely proportional, the obtained results showed that BEM presented a superior suspending activity to the one of BE, since the sedimentation rate was higher, thus demonstrating the ability of this clay to keep more particles in suspension. Consequently, BEM presented a suspensor activity superior to BE, since its speed of sedimentation was higher, which means, the particles remain in suspension for a longer time. In Fig. 4, it is found the rheogram of calamine suspension samples containing BE and BEM. The sample tested with BEM had a lower viscosity than BE. Therefore, considering the tested formulation and the test standards used, BE presented better results in relation to the increase of viscosity in the calamine suspension. Calamine suspensions containing BE and BEM presented nonNewtonian behavior, with variation of viscosity as a function of the applied voltage, with no linear relationship between these values (Viseras et al., 2006). The samples under study show a pseudoplastic flow (Fig. 2), which is characterized by the decrease of apparent viscosity as the shear stress increases. This type of behavior is desired in pharmaceutical formulations. High apparent viscosity at low shear stresses is necessary to prevent the mobility of the dispersed phase. In addition, when stirred, they must exhibit free flow with low viscosity and under high shear stresses, as long as these changes are reversible after some resting time, delaying coalescence or caking (Guaratini et al., 2006). The results of the pH determination averages for the calamine suspension tested within BEM indicated a value close to neutrality (7.72 ± 0.005), being lower than the pH of the suspension containing BE, which was more basic (8.17 ± 0.026). The pH of the samples presented a value above the adequate for cosmetic products (5.5–6.5). The pH of the skin surface in the facial region (5.5–6.5) depends on external and internal factors and normal pH values may increase or decrease after applying topical products, returning to baseline in a few minutes (Modabberi et al., 2015). In face
Fig. 4. Rheograms of calamine suspension.
environment, in intensive care units (ICUs), where it affects immunocompromised patients, which are subject to numerous risk factors, such as administration of large amounts of antibiotics, chronic diseases, invasive procedures and immunosuppressive treatments. It is a bacterium that over the years has created resistance to several antibiotics such as aminoglycosides and carbapenems, given this reality and different mechanisms of resistance acquired by the bacteria, several research groups have followed the distribution and susceptibility profile of the genus Klebsiella spp. with the aim of monitoring possible outbreaks and assembling the sensitivity profile in the different regions (Albrich et al., 1999; EARSS, 2008). Therefore, the decontamination of these samples must follow a critical step in the process of suitability of clays for cosmetology use, assuring the number of samples and test done with the samples are in accordance to what is recommended in the law. After the decontamination with dry heat, the reduction of mesophilic bacteria levels was observed and the remaining parameters kept the same obtained in the sample without decontamination (Table 4). There were no pathogens, fecal and total coliforms, and the sample was totally in accordance with the requirements of the Brazilian cosmetics legislation (Brazil, 1999) and the British pharmacopeia (British Pharmacopeia, 2008). The dry heat method was used in previous work (Favero et al., 2016), being effective in the decontamination of clays containing mesophilic bacteria, molds and yeasts above the specifications already mentioned. The presence of the pathogenic bacterium Klebsiella spp. 45
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of the above, the pH found in the addition of BEM was better when compared to BE, under the conditions tested. It should be pointed out that these pH values were obtained when the clays were incorporated in water, making relevant studies to evaluate if these raw materials will be able to alter the pH of a cosmetic vehicle such as gels, emulsions, among others. Alterations in pH values may occur due to chemical modifications of the formulation components, for this reason their determination together with the evaluation of the product stability becomes extremely relevant. During the storage of cosmetic products, oxidation reactions may occur, which generate chemical changes in the formula components. The rate at which these reactions occur may not be the same for the different substances present in the cosmetic product, thereby, oxidations may occur even before the antioxidant action of the formulation begins (Weiss-Angeli et al., 2008).
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Clay minerals and their beneficial effects upon human health. A review. Appl. Clay Sci. 21, 155–163. https://doi.org/10.1016/S0169-1317(01) 00085-0. Carretero, M.I., Pozo, M., 2009. Clay and non-clay minerals in the pharmaceutical industry: part I. Excipients and medical applications. Appl. Clay Sci. 46 (1), 73–80. https://doi.org/10.1016/j.clay.2009.07.017. Carretero, M.I., Pozo, M., 2010. Clay and non-clay minerals in the pharmaceutical and cosmetic industries Part II. Active ingredients. Appl. Clay Sci. 47, 171–181. https:// doi.org/10.1016/j.clay.2009.10.016. CDC (Centers for Disease Control and Prevention), 2012. Mercury exposureamong household users and nonusers of skin-lightening creams produced in Mexico – California and Virginia, 2010. MMWR Morb. Mort. Wkly. Rep. 61, 33–36. Dário, G.M., Da Silva, G.G., Gonçalves, D.L., Silveira, P., Junior, A.T., Angioletto, E., Bernardin, A.M., 2014. Evaluation of the healing activity of therapeutic clay in rat skin wounds. Mater. Sci. Eng. 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4. Conclusion On the basis of the obtained results it was possible to conclude, from physical-chemical characterization, that the samples features were compatible with those of clay. The major reflections of all samples were typical smectite and quartz. The presence of Si, Al and Mg as most abundant elements was evidenced smectite and quartz). The microbiological load of BEM was within the specifications of the legislation, but with the presence of a pathogenic bacterium. Thus, for application in cosmetic products a decontamination process is suggested prior to use. The evaluation of suspensory capacity and increase in viscosity indicated that BEM did not promote better results when compared to BE, clay already used in the pharmaceutical and cosmetic sectors. However, regarding pH, BEM presented a better result when compared to BE. From the results obtained, it is possible to see that the application of Melo Bentonite clay in cosmetic products has the same performance that the BE for the testes performed in this work. Additional, but not less important, tests such as the assessment of cytotoxicity and the skin hydration capacity of the clay under study should be performed to assess the safety and efficacy of this clay in the skin. Acknowledgements Authors are beholden to the University of Caxias do Sul (UCS), to Federal University of Rio Grande do Sul (UFRGS) and to the Research Support Foundation of the Rio Grande do Sul State (FAPERGS) for financial support. References Albarnaz, L.D., Dani, N., Formoso, M.L.L., Mexias, A.S., Lisboa, N.A., 2009. A jazida de bentonita de Bañado de Medina, Melo, Uruguai. Geologia, meneralogia e utilização tecnológica. Pesquisas em Geociências 36 (3), 263–281 (ISSN 1807-9806). Albrich, W.C., Angstwurm, M., Bader, L., Gärtner, R., 1999. Drug resistance in intensive care units. Infect 27, S19–S23. https://doi.org/10.1007/BF02561665. American Society for Testing Materials: ASTM D7348-08, 2008. Standard Test Methods for Loss on Ignition (LOI) of Solid Combustion Residues. Andreis, R.R., Ferrando, L., Herbst, R., 1996. Terrenos Carboníferos y Pérmicos de la República Oriental del Uruguay. In: El Sistema Pérmico en la República Argentina Y en la República Oriental del Uruguay. Academia Nacional del Uruguay, Cordoba, Argentina, pp. 309–343. Associação Brasileira de Normas Técnicas: ABNT NBR 8289, 1983. Carvão Mineral Determinação Do Teor de Cinzas - Método de Ensaio. Associação Brasileira de Normas Técnicas: ABNT NBR 8291, 1983. Amostragem de carvão Mineral Bruto e/Ou Beneficiado – Procedimento. Associação Brasileira de Normas Técnicas: ABNT NBR 8292, 1983. Preparação de Amostra de carvão Mineral Para análise e Ensaios – Procedimento. Axelrod, D.I., 1981. Role of volcanism in climate and evolution. Geol. Soc. Am. Spec. Paper 185, 59. Borowska, S., Brzóska, M.M., 2015. Metals in cosmetics: implications for human health. J. Appl. Toxicol. 35, 551–572. https://doi.org/10.1002/jat.3129. Bossi, J., Ferrando, L., Montaña, J., Campal, N., Morales, H., Gancio, F., Schipilov, A., Piñero, D., Sprechmann, P., 1998. Carta geológica Del Uruguay. In: Montivideo. Faculdad de Agronomia, Escala (1:500.000). Brazil, 1999. Resolução RDC N° 481, de 23 de setembro de 1999. In: Establishes the
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