JOURNAL OF COSMETIC SCIENCE 256 toxicity and environmental compatibility. For further understanding on green surfac- tants, their interfacial properties have to be investigated in the comparison with conven- tional petroleum based surfactants. More importantly, the synergistic effect when mixed with other green surfactants or conventional ones is the key property towards higher effi - ciency at lower dosage. For e.g., acyl glutamate surfactants have shown unique interfacial properties such as high surface activity when mixed with conventional surfactants such as dodecyl maltoside (36). Acyl amino acid surfactants, such as myristoyl glutamate, are popular with consumers because these surfactants interact favorably with skin and hair (37), are hypoallergenic (38), do not cause eye irritation (39), and are readily biodegradable (40). In collaboration with modular genetics a new green surfactant was synthesized by using an engineered Bacillus strain. The engineered synthetase produces an acyl amino acid composed of a beta- hydroxy fatty acid linked to glutamate, referred to as FA-Glu (fatty acid-glutamate) (41). Due to the similarity in structure of FA-Glu to myristoyl glutamate, the water sol- ubility and CMC of these surfactants were measured (Figure 4). It was found that FA-Glu is more water soluble than myristoyl glutamate. In addition, FA-Glu has higher surface activity, as refl ected by its lower CMC (41) (1.3 mM for FA-Glu versus 14.1 mM for myristoyl glutamate). A lower relative CMC indicates that less FA-Glu should be re- quired in a formulation to achieve a particular desired reduction in surface tension. In addition, a lower CMC is correlated with an increased effectiveness in removing soils in cleaning formulation (39). CONCLUDING REMARKS Nanomaterials, such as nanogel particles, hybrid polymer nanodomains, nanoemulsions and liposomes have shown good applications in cosmetic science. The present article dis- cusses the mechanisms of development and understanding of these the nano-sized sys- tems. Hybrid polymers and their nanoemulsions can be used a delivery systems as well as for cosmetic effect (shine, glossiness, softness) on a given substrate. Figure 4. Comparison of critical micelle concentration for Fa-GLU (fi lled circle) and myristoyl glutamate (empty diamond), adapted from Gabriel O. Reznik et.al.

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