Creative Developments (Cosmetics) Limited
Skin
Care 2000
Skin
care by the application of cosmetics includes cleansing and toning, solar
protection and anti-free radical activity; it includes moisturising, acne
treatments, and the treatment of hyper-pigmentation, skin peels and other means
of wrinkle reduction. The active ingredients may be natural oils and extracts
or active principals isolated from plants or they may be minerals or synthetic
chemicals. The form that these compositions can take varies from sprays to
pastes and the packaging from aerosols and bottles to jars, tubes and sachets.
Developments in skin care include improved carrier systems and time-release
mechanisms, anti-inflammatory and protective ingredients, new active
ingredients obtained from botanical sources, the use of microfine oxides for
safe sun protection, of AHAs for skin rejuvenation and of advances in
emulsifier and emollient systems.
This
feature will review those materials that are claimed to slow the visible
effects of ageing with particular reference to vitamins A and C and delivery
systems that enhance their activity.
The
prime purpose of skin care is to reduce the visible effects of aging. In her
paper, A Global Approach to Skin Aging presented at the IFSCC Congress 1999
[REF 1], Isabelle Benoit described the modifications that occur in cutaneous
tissue with time. Chronological changes are genetically programmed responses;
extrinsic changes are connected to environmental aggression such as photo-aging
and responses to heavy metals and other pollutants. These changes take place in
both the dermis and epidermis. They alter the dermis architecture and skin
mechanical properties of rigidity, elasticity and resilience and eventually
lead to wrinkles. Extrinsic aging is primarily a response to oxidative damage to
the skin triggered by an accumulation of reactive oxygen species as a result of
photo damage following exposure to UV radiation and it may lead to
carcinogenesis.
According
to Benoit, given the multiplicity of mechanisms involved in cutaneous aging, a
global and consistent approach to skin aging needs to be at both the extrinsic
and intrinsic level. Active ingredients should support the antioxidant
properties of the skin to protect the cells from oxidative stress and should
also boost cell metabolism. Benoit described the development of a vegetable
extract and methods that were used to prove its efficacy as an antioxidant and
anti-inflammatory ingredient that also stimulated keratinocyte metabolism and
which contributed towards the regeneration of the extra cellular matrix. The
material is a natural plant extract rich in polyphenols, amino acids, peptides,
sugars and trace elements. For further details contact Gattefosse,
France.
The
first commercial appearance of liposomes in a cosmetic product was ten years
ago in “Capture” by Christian Dior. Since then they have appeared in many
products with a variety of claims. A paper by Gabriel Blume [Ref 2] described
the development of liposomes to act as a protective carrier system for active
ingredients. If of a suitable structure, they improve skin penetration of the
active to the target site and can protect the encapsulated material from
premature oxidation. Those described by Blume are small-sized vesicules of
80-300nm with one to three bi-layers formed from phosphatidylcholine, obtained
from soybean and with a high essential fatty acid content. The benefits of such
a system were illustrated by an in-vitro experiment whereby ascorbic
acid encapsulated in liposomes achieved four times the penetration of ascorbic
acid in an emulsion. Liposomes may also be used to transport lipophilic actives
and were used to apply a mixture of vitamins A, E and C to excised skin.
Experimental results show that the mixture was an effective free-radical
scavenger and protected DNA during UV-A exposure. Similar liposomes can be used to transport AHAs with a resultant
increase in skin moisture, improved smoothness and a reduction in wrinkles
while another variation was used for the application of tyrosinase inhibitors
in skin-whitening products.
The
materials described by Blume are available from Rovi GmbH as Rovisomes.
Natterman Phospholipid provide what is arguably the most comprehensive
range of materials in liposome form supported by extensive literature and
technical application data. There are many other sources of liposomes including
LipoCeutical Complexes from Lipo Chemicals, and slow and
fast-release systems from Collaborative Laboratories, which also
supplies Catezomes, a non-phospholipid vesicle system with a cationic charge
that makes them substantive to skin. They are used to deliver oil-soluble
ingredients like UV absorbers and ceramides or water-soluble actives like
panthenol. Lucas Meyer offers Pro-Lipo and Isocell microencapsulating
systems; Lipotec supplies an extensive range of active ingredients in
liposome form and provides a number in liposomes coated in a hydrophilic
polymer that can be incorporated into emulsions, milks and gels.
Lipoid
GmbH produces Ultraspheres, which are finely dispersed nano-emulsions
with lecithin as the only emulsifier and with a lipophilic active enclosed
within a phospholipid monolayer. This can form the internal oil phase of an o/w
emulsion, without the addition of further emulsifiers. The vesicle form ensures
enhanced penetration of the lipophilic ingredient into the upper layers of the
skin. Excess lecithin passes into the water phase and spontaneously forms
liposomes, which themselves can encapsulate water-soluble actives. Kryosomes
from Lipoid are described as “dry liposomes” They are formed by freeze-drying
liposome dispersions in the presence of a polysaccharide cryoprotectant that
maintains the liposome structure as a porous sponge. This enables highly active
materials to be produced without the need for preservatives and which may be
readily hydrated to provide a liposome dispersion.
LIBIOL
provides a number of active ingredients in liposome form
including vitamin A, various enzymes and ceramides. Ultrasomes from AGI Dermatics contain
the enzyme UV-endonuclease prepared from milk by biotechnology and supplied in
liposome form for sun-repair products. The same company supplies Photosomes,
which are liposomes containing an enzyme obtained from
plankton, and Oxysomes, magnesium ascorbyl phosphate encapsulated within a
liposome membrane that contains vitamin E. Enzymes are finding increasing
application in skin care but Laminarghane from SECMA, France, is said to
control sebum production, follicular inflammation and hyperkeratinisation by
inhibiting the activity of 5-α reductase in oily skin disorders.
A
paper by Diana Smith [Ref 3] given at the IFSCC Congress described
the use of polyester technology for optimising actives. Their effect is the
opposite of liposome delivery systems. Whereas the latter assist penetration of
the epidermis, polyesters mitigate skin penetration and this is of advantage
where a protective barrier is required as with organic sun filters. According
to Smith it was found possible to design the polyester structure in order to
optimise the effect achieved with various active ingredients. This was used for
the delivery of AHAs, which because they were retained in the upper layer of
the stratum corneum, they gave the maximum effect where it was most required.
It was possible to reduce the concentration required while maintaining product
efficacy, which resulted in reduced stinging potential and less irritation.
Dihydroxyacetone was also used with a polyester delivery system and its
activity was enhanced by the increased contact time with the skin surface. The
polyesters described are available through Innolex Chemical Co., USA.
The
many different retinoids and their use in dermatology were described by
Christos Zouboulis [Ref 4] at the Cosmetic Science Conference 2000. The
term retinoid includes both naturally occurring molecules and synthetic
compounds showing biological activities, which are characteristic of vitamin A.
They affect cell growth and differentiation, sebum production and collagen
synthesis and possess anti-inflammatory properties. They are used to treat
sebum disorders, acne and psoriasis, photodamage, hyperpigmentary disorders and
skin cancers. Zouboulis described the
many different forms of retinoid available and the factors affecting their
activity. Because of adverse effects caused by retinoic acid less toxic
compounds were investigated and it was found that biological activity could be
maintained with a reduction in toxicity by altering the molecular structure.
Zouboulis investigated the mechanism of retinoid biological activity, their
effect on receptor proteins and the complex interactions between them and
hormonal signal transduction molecules.
The
use of retinoic acid in dermatology has promoted the use of retinol and retinyl
esters in cosmetics for skin care. Retinol is the alcohol form and although
substantially less effective than the acid it is significantly more effective
than the esters. It should be used at from 0.01% – 0.10% w/w
in products for topical application. At higher concentrations it is likely to
induce irritation because of its ability to penetrate into the skin. The
material is sensitive to pH, temperature, heavy metals and oxygen, which make
formulation with it difficult. Coletica, France, claims to have
overcome these problems by micro-encapsulation of retinol in a combination of
acacia and alginate polysaccharides. Termed Cylaspheres, they have a strong
affinity for the skin surface, binding to the corneocytes in the stratum
corneum and they greatly reduce the depth of penetration of the retinol. The
retinol content is released over time with a consequent improvement in its
efficacy at the site where it is most needed and there is a significant
reduction of adverse local and systemic side effects. Retinol Cylaspheres
contain 1% retinol and are incorporated into emulsions at a level between 1%
and 10%w/w. They must be added at ambient temperature and
the finished product packed in an airtight container.
Retinoids
and vitamin C are both used in skin whitening compounds. This is a major growth
area for cosmetic skin care because pigment disorders are one of the most
visible signs of ageing. Also, with the use of hydroquinone being discontinued
in most countries of the world the industry is looking for new materials.
Vitamin C has much potential as a cosmetic ingredient for topical application
as both an antioxidant and in skin whitening compounds but it is notoriously
unstable. Including it in the inner water-phase of a w/o/w emulsion is one
method of protecting it from oxidation. Using a derivative such as ascorbyl
glucosamine simplifies handling but there is a great increase in cost and it is
less effective.
A
presentation by Arun Puri [Ref 5] at the cosmetic science conference described
a method of entrapping active agents in a methyl methacrylate/glycol
dimethacrylate cross-polymer and then encapsulating this in gelatine. The
actives described in the paper were retinol and ascorbic acid. The
cross-polymer is a patented method developed by Advanced Polymer Systems
as Microsponge controlled release system and the gelatine capsules protect the
actives from light and oxygen, greatly improving stability.
An
alternative method was described by G.Fabrizi [Ref 6] whereby two derivatives
of ascorbic acid were packaged in an air-free pump. The materials were the water-soluble
magnesium L-ascorbyl-2-phosphate (VC-PMG) and the lipo-soluble
dellihexyldecanoyl-L-ascorbic acid (VC-IP). Both undergo hydrolysis by skin
enzymes to release ascorbic acid. According to the authors, because of the
differences in their penetrative powers the water-soluble form penetrated more
deeply while the liposoluble form stayed at the cutaneous level and was
hydrolysed more slowly. Further work using VC-IP described by S Ukaji [Ref 7]
showed it to reduce melanogenesis and to enhance collagen synthesis. A
different approach to improving the stability of ascorbic acid is suggested by Grant
Industries, which has incorporated it in a gel of cyclomethicone and
polysilicone-11.
Skin
care cosmetics consist of more than an active ingredient in a liposome. The
most popular carrier form remains an emulsion and improving the application
characteristics of this is one method of enhancing product efficacy. Silsoft
034 from CK Witco is caprylyl methicone that is described as a modified
trisiloxane lipophobe with surface-active properties. It is said to lower
surface tension of the oil-phase and to promote its spreading properties,
providing a uniform film that is ideal for the application of oil-soluble
ingredients. Silicone compounds have long been an active area of cosmetic
ingredient development. New introductions include the
vinylpyrrolidone/polycarbamyl polyglycol esters from Phoenix Chemicals sold
in the form of hydrogels. They are said to complex with a wide range of organic
molecules including antimicrobial compounds and UV absorbers and to dry on the
skin as a water-resistant film, making them ideal for sun protection products.
1.
Benoit, I., A global approach to skin aging; IFSCC Congress
South Africa 1999.
2.
Blume, G., Liposomal carriers; how to make an active
efficient. ibid
3.
Smith, D., Delivering the goods – Polyester technology for
optimising actives. Ibid
4.
Zouboulis, C., Retinoids: is there a new approach? Cosmetic
Science Conference 2000, Barcelona
5.
Puri, A., Unique way to stabilise retinol and vitamin C in
cosmetics using softgel technology. Ibid
6.
Fabrizi, G. et al, New perspectives on vitamin C. ibid
7.
Ukaji, S. et al, A new Vitamin C based compound for
whitening and anti aging. ibid