Surfactants make up the bulk of most personal cleansing products and are primarily responsible for products' properties such as for lathering and basically removing oily residues without causing any damage to the skin. The cleanser segment has grown over the years with increasing interest in achieving skin functional benefits, especially moisturisation, from wash-off systems. However, most surfactant-based systems do not retain many of the active ingredients on the skin. Normally, the actives which are supposed to give skin functional benefits will be washed away after cleansing. Numerous improvements and advancements have been done on active ingredients delivery through the skin, but the challenges were always on how to deliver active ingredients in a wash-off personal care product that won't be removed by surfactants. The fact that skin's surface is negatively charged has led to the development of charged vesicles as the delivery vehicle for personal cleansing products.
Aquea Scientific Corporation has created a delivery system which enables efficacious active ingredients to remain on skin and hair even after thorough cleansing. Wash-OnTM (US Patent 7025952), is a patented technology that encapsulate active ingredients into micron sized positively charged particles (Traynor et al, 2006) that enables the encapsulated active ingredients to remain attracted to the skin and hair throughout the day, even after patting dry. It leverages concepts based on Sol-Gel Chemistry, the same technology used in fiber optics and semiconductors. The active ingredients are encapsulated in silica shells which are then incorporated in an emulsion that causes the external shell of silica to become positively charged. They are then further incorporated into a polymer matrix (Polyquaternium-4) which creates a semi-occlusive barrier on skin. By controlling the particle size, molecular weight and other physical and chemical conditions, the specific delivery mode can be targeted. This technology can be found in products such as Freeze 24-7 Ice Shield Facial Cleanser, which utilizes the delivery system to incorporate sunscreen with a SPF of 15.
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Cationic polymer can be used as a delivery system based on its electrostatic interaction with negatively charge substrates. In fact, many studies have been done on cationic polymer especially in hair products formulation as conditioning agents because they can electrostatically interact with the negative charged sites on hair. Gruber et al (2001) has examined the deposition of cationic polysaccharide onto keratin surfaces of hair through biopolymer fluorescent labeling and found out that the deposition efficiency is influenced by several factors such as charge level and molecular weight. It is shown that deposition of high molecular weight polymer is higher than low molecular weight polymer in surfactant-based solutions while charge level does not affect deposition to the same extent as molecular weight. For the influence of surfactants on the sorption of a cationic polymer by hair, Faucher and Goddard (1976) reported that surfactants decreased the uptake of polymer but the effect varied widely. Cationic surfactants strongly decreased the sorption while little effect is observed with nonionic surfactants probably because of its low affinity for keratin and polymer.
Among available polymers, chitosan, a natural, non toxic, bioadhesive, biocompatible, and biodegradable polymer has the potential ability to be used as the vesicle to encapsulate active ingredients. It has been widely used in pharmaceutical, cosmetics, food, and other industries as a functional biopolymer. The uniqueness of chitosan is that it possesses both nonionic hydrophobic functionality as well as a hydrophilic cationic charge. It can interact with keratin, an anionic protein found in skin through its cationic glucosamine groups (Cattaneo, 2005). Guo et al. (2003) proved that the interaction between net positive charge of the chitosan's polymeric chain and the generally negative surface charge of the skin promoted its bioadhesive ability. Biocompatibility of chitosan with living tissues is another advantage as it caused no allergic reactions or rejection by the body as reported by Chen et al. (2006). Chitosan too is safe for use in cosmetics as it degrades in the body through the action of chitosanase and lysozyme unlike most synthetic polymers (Pangburn et al, 1982).
Nevertheless, the use of chitosan is limited by its poor solubility in water or organic solvents because of its stable, crystalline structure. The free amino groups of chitosan are protonated in dilute aqueous acids and they become fully soluble at pH < 6.5. Since the pKa of amino group of glucosamine residues is about 6.3, chitosan is extremely positive in acidic medium. This kind of solubility limits the application of bioactive agents such as peptide or protein drugs, genetic material and anticancer drugs that may be affected by the acid. Due to this solubility problem, many studies have been done on developing water soluble chitosan which involves modification with water soluble derivatives (Lim and Hudson, 2004), chemical (Chung et al, 2005) and enzymatic processes (Qin et al, 2002). By reducing the molecular weight, chitosan can be dissolved directly in water without the need of an acid (Kim et al, 2006).
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However, chitosan with lower molecular weight, especially below 300, have shorter polymer chain thus lowering the local charge density and decreasing the strong positive charge. This may prevent the polymer from desirably interacting with the negative sites at the surface of the skin. Therefore, when using low molecular weight chitosan, it should not be too low as it may affect the effectiveness of chitosan. Several other factors that affect the positive charge and the effectiveness of chitosan are the degree of deacetylation, purity, pH and interaction with other cosmetic ingredients in the formulation. By controlling all the parameters which influences the cationic charge on the molecule, it is possible to obtain the desired chitosan based delivery system.
Kacip Fatimah or Labisia Pumila extract is a traditional herbal medicine which has been used by many generations of Malay women to induce and facilitate childbirth as well as a post-partum medicine. They are widely available commercially as health supplements. Recently, Kacip Fatimah has been demonstrated to be potentially used in skin care products as an anti-aging ingredient. Choi et al (2009) has demonstrated in their study the efficacy of L.Pumila to specifically protect skin against photoaging while Norhaiza et al (2009) has showed the presence of high antioxidative activities in L.Pumila. From these studies, it is suggested that L.Pumila can be a novel anti-aging cosmetic ingredient but the efficacy for skin has not yet been fully studied.
Since the effect of anti-aging ingredients take action in the deeper layers of the skin, nanoparticles delivery system are suggested to be used as it has the potential to penetrate deeper. Chitosan has many advantages in developing micro or nanoparticles such as its ability to control the release of active agents, its cationic nature that makes it available for ionic crosslinking, its bioadhesive character and low toxicity (Agnihotri et al, 2004). Works by Yoksan et al. (2009) demonstrated the encapsulation of ascorbyl palmitate in chitosan nanoparticles by oil-in-water emulsion and ionic gelation process while Kim et al. (2006) reported the successive encapsulation of retinol in low molecular water soluble chitosan nanoparticles. Several factors need to be considered in order to develop the effective nanoparticles encapsulating active ingredients which include the stability of the active ingredients encapsulated and the release from the nanoparticles. Diffusion of actives from chitosan nanoparticles might be enhanced at high pH due to the deprotonation of chitosan that affects the electrostatic interaction between the cationic material and the anionic substrates. (Yoksan et al, 2009).
To develop a stable and effective wash-off personal cleansing formulation
based on charged delivery system.
Scope of Study
Preparation and characterization of Kacip Fatimah-Chitosan nanoparticles.
Nanoparticles with varying pH values are prepared with ultrasonication. Characterization includes particle size & zeta potential determination, morphology analysis, structure determination as well as stability & encapsulation efficiency studies.
Proof of principle studies.
Deposition and penetration studies on human skin and hairless rat skin will be done to prove the charged nanoparticles are deposited on skin after washing application and further penetrated through the skin.