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| Issue 44 |  |
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| Category | Title | Authors | ||
| Guest Article | Eco-friendly cosmetic delivery systems based on natural biopolymers | Juan-Antonio Asensio (1), Philippe Grisoni (2), Yolanda Gómez (1), Sílvia Martínez (1), Salvatore Gargano (1, 2), Andreas Rathjens (2) |
Introduction
Since the simple microcapsules with gelatine and arabic gum in the 50s, hundreds of polymers have been developed for the microencapsulation of active ingredients, with the purpose of stabilization, triggered and sustained release or even for obtaining an aesthetic effect [1-2]. While the demand of delivery systems with special performances for various applications is continuously increasing, the consumer's eco-ethical principles drive the investigation towards natural and eco-friendly encapsulating polymers.
Our laboratories have accumulated a vast experience in the use of biopolymers, such as chitosan, lecithin, xanthan gum and derivatives like modified starch and carboxymethylcellulose (CMC) as encapsulating agents [3-4]. Different technologies including complex coacervation, thermal gelation, ionotropic gelation and polymer/ polymer interaction are applied for the encapsulation process. Here we shortly describe some of the Cognis delivery systems for cosmetic applications using natural biopolymers or polymers obtained from natural sources, including novelties like for instance coated liposomes.
Description of Technologies
Primasponge® (Visible Beads) can be prepared by thermal gelation of Agar, ionotropic gelation of polysaccharides (e.g. Alginate) in CaCl2 solutions, complex coacervation for instance Alginate and Chitosan, or wax beads.
One of our approaches combines the above mentioned technologies and is based on polymers from natural sources. In a typical example (described in detail elsewhere [3]), agar and alginate are dissolved in water together with the active ingredient, pigments, the preservative systems and eventually other components above the gelation temperature of the agar. Once this melt is prepared, millicapsules can be produced following different procedures.
In the easiest procedure, this melt can be added dropwise to a CaCl2 solution. Thus, alginate reacts with the Ca+2 cations and the drops are hardened. As there is agar in the formulation, once these drops fall into the receiving bath, their temperature decreases and the agar gelation contribute to harden the beads. A third mechanism involves the addition of a cationic polymer such as chitosan to the receiving bath. Alginate reacts with the Ca+2 cations and in addition chitosan by ionic interaction.
Drops can be formed by different ways, from a simple syringe to a more sophisticated vibrating nozzle. For instance, vibrating nozzles allow obtaining homogeneous drops, in a more automatic way, increasing the yield of beads in a better quality and of a desired particle size. Figure 1 (right) shows typical Agar/Alginate/Chitosan 3 mm beads
Figure
1
Up, left: Primasphere®
based on carboxymethylcelullose/ chitosan (SEM image). Up, right:
Visible beads (Primasponge®) based on agar/ alginate/ chitosan.
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Microcapsules and nanocapsules (Primasphere® and Primasys® )
Primasphere® (microcapsules) and Primasys® (nanocapsules) can be obtained by complex coacervation. Complex coacervation involves the interaction of an anionic polymer (alginate, carboxymethylcellulose, polyacrylates), with a cationic polymer (chitosan, modified starch, some polyquaterniums). A typical example are retinol microcapsules (1-10 µm) which are prepared by complex coacervation of carboxymethylcellulose (CMC) and chitosan [4]. The preparation of these capsules starts with the emulsification of retinol, dissolved in soybean oil, in a CMC solution. After decreasing the pH to below 4, a chitosan solution is added dropwise. Thus, both polymers interact and precipitate around the retinol forming the capsule shell. A typical chitosan/CMC based microcapsule of 1-10 µm containing vitamin E (Vitamin E Primasphere®) can be observed in Figure 1 (left).
The capsule size depends on the emulsion size, ranging from microcapsules obtained from a simple emulsion to nanocapsules prepared when the oil is nanoemulsified (Primasys® nanocapsules).
The typical gelatine complex coacervation is carried out for instance by using CMC as anionic polymer. This procedure starts with the emulsification of an oil or fragrance in a CMC/gelatine solution. The droplet size can be adjusted through the stirring speed. The coacervation is induced by setting the pH around 4 - 4.5 and, if afterwards the shell is hardened with for instance glutaraldehyde, the capsules can be dried.
Primasys® (Nanocapsules and Liposomes)
One of our nanocapsule approaches is based on the use of liposomes which are coated with cationic polymers. A very easy technique to prepare liposomes is to dissolve lecithin and the active matter in e.g. propyleneglycol. This solution is afterwards dispersed into a buffered water solution and forms a multilamellar liposome dispersion with a typical size of around 200 nm. The anionic character of these liposomes was confirmed by Z-potential measurements. In the case of cationic polymers, such as chitosan, modified starches, some polyquaternium polymers, etc. The interaction with the liposome surface induces a positive Z-potential. These coated cationic liposomes are nanocapsules with a size of around 200 mm. Figure 1 (down, right) shows a typical TEM (Transmission Electron Microscope) image of Lecithin-based liposomes.
Discussion
Primasponge® (Agar/Chitosan/Alginate based Millicapsules, Visible Beads)
Primasponge® (agar/ chitosan/ alginate based millicapsules, visible beads) can carry a variety of active ingredients mostly lipophilic or solid, such as oils, vitamins, fragrances, scrubbing particles or botanical extracts. These beads have been incorporated in many different market products. Among others, these are shower gels, creams, scrubbing creams and manual liquid dishwashers. For instance, Primasponge® type capsules allow the incorporation of active ingredients with a certain incompatibility to other components which are also part of the final formulation. Moreover, Primasponge® containing an oil can be formulated into a transparent gel without emulsifying the oil into this gel, always having in mind the aesthetic effect of these colored beads once suspended into a cosmetic product.
The release of the active ingredients is mainly triggered by rubbing the capsules during the application of for instance a cream. For a skin care product, it is very important that once the beads are on the skin and they are rubbed, they disappear without leaving any residue. This can be achieved by well balancing the ratio of the three main components (agar/ chitosan/ alginate). This ratio can vary depending on the amount and nature of the other components (actives, oils) and how the capsules are hardened (mainly Ca+2 concentration).
Primasphere® based on Chitosan/ CMC (Microcapsules)
Primasphere® based on chitosan/CMC (microcapsules) can be filled with lipophilic actives. A representative example are Retinol microcapsules. Retinol is an anti-aging active ingredient with anti-wrinkle performance which protect furthermore against UV photodamage. Retinol (all-trans-retinol) is a very sensitive vitamin which is easily oxidated or thermally degradated by isomerization of the trans double bonds. Retinol esters (e.g. palmitate) are much more stable than the pure all-trans isomer, however, show the disadvantage of being less active [4].
An encapsulation of Retinol (Retinol Primasphere®) using our approach enhances the thermal stability in cosmetic creams up to 10 times, as shown in Figure 2. The release is induced by skin enzymes which degradate the shell and deliver retinol gradually, so a sustained and long lasting release is achieved. [4]
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Figure 2
Enlarged
version |
Primasphere® based on Gelatine/CMC (Microcapsules)
Primasphere® based on gelatine/CMC (microcapsules) loaded with fragrances can be dried over several supports (glass, paper, fabrics, etc.), yielding dry capsules. When scratching, the oil or fragrance is released (scratch and sniff effect).
These capsules have negative Z-Potentials that can be modified by coating with cationic polymers as described above for cationic coated liposomes, thus becoming cationic. This could be of interest for skin or fabric care applications due to the negative surface charge of those substrates, in order to improve the affinity of the capsule and the skin or the fabric.
Primasys® based on Chitosan/CMC (Nanocapsules)
As Chitosan/CMC microcapsules are based on the coating of an O/W emulsion, the logical further step is the development of nanocapsules based on a similar technology, by nanoemulsifying an oily active or oily solution. An example is the nanoencapsulation of triclosan. Once triclosan (pure or dissolved into suitable oils) is nanoemulsified, the procedure is the same as described above for chitosan/CMC microcapsules. The following plots (Figure 3) show the size distribution of 1, 2 and 5 % triclosan nanocapsules suspensions measured by Photon Correlation Spectroscopy (PCS). The capsule size varies from ca. 50 to 250 nm, depending on the Triclosan loading. When we try to encapsulate a higher amount of triclosan, the obtained nanocapsules are bigger, following a linear trend.
Figure
3 Enlarged version PCS analysis of the size of CMC-Chitosan nanocapsules. As Triclosan % increases, the nanoparticles are bigger. |
Primasys® (Cationic Coated Liposomes)
Cationic liposomes have a positive charge that enhances their affinity to skin and hair. Figure 4 (Z-Potential plots) shows how the anionic liposomes become cationic by adding the coating cationic polymer. When raw Lecithin based liposomes containing hydrolyzed milk protein were coated with PEG-15 Cocopolyamine, they loose their anionic potential, first being neutralized, and later getting cationic Z-potential.
Figure
4 Enlarged version Z-Potential distribution of lecithin liposomes coated with different amounts of PEG-15 Cocopolyamine. The concentration of PEG-15 Cocopolyamine increases from left to right. |
In another example, Lecithin based liposomes loaded with Ginkgo Biloba extract were coated with PEG-15 Cocopolyamine. The particle size increased from 300 to 385 nm, due to the polymer coating, which proves that the liposomes are coated by the cationic polymer.
This technology allows the encapsulation of both lipophilic and water soluble actives, such as botanical extracts, proteins, or triclosan.
Conclusions
The use of environment-friendly chemicals is a strong trend in every segment of the cosmetic market. Thus, end users and formulators are aware of the need to focus all our efforts towards sustainable raw materials for cosmetic formulations.
During the last years we have developed several delivery systems for the cosmetic industry, successfully introduced to many market products. Primasponge® (visible beads), Primasphere® (microcapsules), Primasys® (nanocapsules), Lipocutin® and Primasys®) liposomes or Primasys® (cationic liposomes ) are examples of delivery systems provided by Cognis.
Our delivery systems are mainly based on biopolymers or biomolecules (such as chitosan, agar, alginate, or lecithin), or polymers obtained totally or partially from natural sources (like CMC which is a modified cellulose polymer, or for instance PEG-15 Cocopolyamine which is partially derived from coconut / palm kernel oil).
Many different active ingredients can be encapsulated (vitamins, fragrances, botanical extracts having a wide range of cosmetic properties, oils, moisturizing actives, proteins, antioxidants, biocides, antiperspirants, etc.) into the above described delivery systems.
These delivery systems are able to enhance different attributes, from simply aesthetic appearance (e.g. colored suspended beads, empty Primasponge®) to the stabilization of very sensitive active ingredients like pure retinol (Retinol Primasphere®), or other vitamins (e.g. vitamin E Primasphere®).
This wide range of delivery systems has been used successfully in many different cosmetic products (e.g. shower gels formulated with a number of encapsulated actives, peeling gels and creams, slimming or anticellulite formulations, anti-aging and anti-wrinkle creams, moisturizing products), and even home care products (e.g. manual dishwashers liquids).
Note 1
Primasponge®, Primasphere® , Primasys® are registered trademarks of the Cognis group.
Note 2
This topic was presented by Juan-Antonio Asensio as a poster entitled "Eco-friendly cosmetic delivery systems based on natural biopolymers" at the 25th IFSCC Congress, Barcelona, Spain (October 6-9, 2008).
References
[1] Arshady R. Microcapsule Patents and Products, London: Citus Books, 2003.
[2] Rosen MR. Delivery Systems Handbook for Personal Care and Cosmetic Products, Norwich, NY: William Andrew Inc., 2005.
[3] Viladot JL, de Moragas M (2002). Advances in Chitin Science 2002. 6; 181-184.
[4] Viladot JL, Gómez Y, Asensio JA, Hernández A, de Moragas M, Martínez S, Gargano S. IFSCC Magazine 2007. 10(3); 215-223.
Author
Dr. Juan-Antonio Asensio joined Cognis in 2002. Since then he has worked in the field of delivery systems for cosmetic applications at Cognis Iberia S.A.U (Care Chemicals Business Unit). In 2007 he became the technical responsible for the Primacare product line. Dr. Asensio obtained his PhD in Chemistry at the Institut Quimic de Sarrià (Barcelona, Spain) in 2003.
Cognis Iberia S.A.U.,
Polígon Industrial Sant Vicenç, s/n,
E-08755 Castellbisbal, Barcelona, Spain
Phone + 34 93 773 00 55
Fax + 34 93 773 00 43
E-mail: juanantonio.asensio@cognis.com
Addresses of co-authors
(1) Cognis Iberia S.A.U., Polígon Industrial Sant Vicenç, s/n, E-08755 Castellbisbal (Barcelona, Spain)
(2) Laboratoires Sérobiologiques (Division de Cognis France), 3 Rue de Seichamps, F-54425 Pulnoy (France)
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