71 ENCAPSULATED TTO IN FACIAL CREAMS more common than allergies and constitute more than 90% of reported adverse reactions to cosmetic products (2,3). Common components in cosmetic products that cause these side effects are preservatives, fragrances, and dyes. Generally, these groups may be natural or synthetic, with the latter being more likely of side effects but having some major advantages over natural components that makes them more attractive in cosmetic industry (e.g., purity, compatibility, cost, quality control, etc.) (3). To avoid these side effects the newest trend in cosmetics has been to formulate innovative products that minimize the use of synthetic compounds by replacing them. Materials like herbal extracts, essential oils, and in general plant origin raw materials are effective against microorganisms and have other desirable effects like antiaging properties (4–7). Essential oils are aromatic plants known to produce a large array of secondary metabolites that produce volatile oils (8). Essential oils exhibit antibacterial and anti-inflammatory traits that have made them very popular in the cosmetic, pharmaceutical, and food industries, among others (9). In terms of composition, purity, and the extraction process, there are significant differences between crude plant extracts and essential oils, which is also responsible for the high price variation (8). Tea tree oil (TTO) is an essential oil, extracted using steam-distillation from the Australian Melaleuca alternifolia plant of the Myrtaceae family of aromatic plants (10–12). In the 1920s, the medical properties of TTO were reported in a large survey on Australian essential oils with economic potential. Following this, TTO was successfully introduced to the cosmetics industry. However, the commercialization of TTO began many years later when the industry could produce a consistent product in large quantities (11). TTO contains more than 100 components, mainly monoterpenes and related alcohols (minimum content of 30% of terpinen-4-ol), that are responsible for its proven medicinal properties (e.g., antimicrobial and antioxidant activity, anti-inflammatory properties, etc.) (12–16). It has been used for many years in the pharmaceutical industry due to its effective action against a variety of bacteria, fungi, viruses, and mites (15,17,18). Several dermatological studies have been conducted that show the excellent effects of TTO in numerous skin infections and diseases (e.g., seborrheic dermatitis, acne chronic gingivitis, vulgaris, head lice, dandruff, wound healing, recurrent herpes labialis, etc.), typically found to be either similar or better than traditional treatment and often with fewer side effects (12,19– 22). TTO is an increasingly popular ingredient in a variety of cosmetic products (e.g., shampoos, facial creams, cosmetic oils, and more). The unique properties of TTO makes it a desirable component for cosmetic products because it can be an antioxidant factor and offer other complementary actions (e.g., acne treatment as a component in a facial cosmetic cream). However, TTO presents a significant disadvantages from its sensory characteristics, namely the sharp camphoraceous odor, the menthol-like cooling sensation, and the pale yellow color (20). Generally, incorporating TTO and natural plant extracts or their derived products has resulted in unwanted deterioration phenomena, including change of color, odor, and emulsion instability (6,23). Thus, the challenge to developing such cosmetic products is to deliver a desirable formulation and concentration. Although there are several technologies that develop cosmeceutical products, nanotechnology can be applied to produce elegant and effective products and overcome the possible side effects of several incorporated compounds (24). Specifically, the micro- and nanoencapsulation of cosmetic ingredients (e.g., antioxidants, unsaturated fatty acids, vitamins, etc.) can improve their stability, ability to target a desired site, and controlled release, as well as smooth their undesirable sensory characteristics and more (7,25,26). The use of the nanoencapsulation

72 JOURNAL OF COSMETIC SCIENCE method in the cosmetics industry improves some basic products’ properties (e.g., efficiency and skin penetration). However, the existing encapsulation techniques may be destructive for the thermosensitive ingredients due to high temperatures needed during encapsulation (24). The electrohydrodynamic process is an inexpensive, nondestructive, and scalable technique used to produce particles (electrospraying) or fibers (electrospinning) from both natural and synthetic materials. The fibers produced through electrospinning present larger surface area than the ones obtained by traditional spinning methods as they have a thin diameter, ranging from a few nanometers to many micrometers (27,28). The coaxial electrospinning technique is a new, innovative process for encapsulation in micro- and nanoscale. With this technique, bioactive ingredients can be encapsulated in selected polymeric matrixes to develop micro- and nanofibers with specific morphology (fiber thickness and diameter, concentration of compounds, etc.) to achieve the desirable properties (e.g., controlled release, solubility, etc.) (29). To commercialize development, the cosmetic industry must ensure that products maintain some basic quality characteristics. Thus, several tests regarding their stability, safety, sensory characteristics, and reported actions have to be performed (14). One major concern when a new cosmetic product is introduced to the market is the alterations that may occur after its manufacturing (e.g., physicochemical, chemical, physical, and microbiological) that determine its expiration date. Microbial contamination and growth may cause infection on the skin. In addition, these alterations may also destroy the nature of cosmetics due to changes in viscosity and characteristics such as color, odor, and emulsion stability (7,30). Cosmetic formulations are mainly contaminated from Staphylococcus aureus, Salmonella species (spp.), Pseudomonas aeruginosa, and Escherichia coli (31). Cosmetic creams exhibit a slightly acidic pH near normal skin surface pH, ranging between 4 and 6. It has been reported that facial skin product pH has a big impact on its efficacy. The formulation of more neutral pH products present decreased efficacy but can be useful when formulating for sensitive skin types. There are limitations regarding the range of acceptable pH value, since it is a crucial parameter that affects the incorporated ingredients. In a cosmetic system, the incorporated ingredients may be incompatible when mixed together and may be easily affected by changes in pH (e.g., polymeric thickeners, dyes, and certain preservatives). Thus, pH is an important parameter that should be stable during the whole life of the product (32). Α cosmetic product should remain stable thought its life time, meaning the expected period of usage by the consumer as well as to fulfill the user’s requirements. To ensure that a product fulfills the required criteria of safety, quality, and effectiveness, cosmetics should be tested at various recommended temperatures and time periods to observe and measure property changes over time (33). This study examined the incorporation of encapsulated TTO in a cosmetic facial cream (incorporation in basic formulation) and the quality characterization and shelf-life evaluation of the formulated product to ensure the newly proposed formulation would not affect the cream in a negative way. The encapsulation of antiseptic TTO extract in β-cyclodextrin’s polymeric matrix nanofibers was performed through the electrohydrodynamic process. Cosmetic facial creams without (control samples) TTO and with TTO nanofibers were stored at three different temperatures. Subsequently, microbiological analysis, color and pH measurements were measured for the control cream and the cream containing TTO nanofibers.