Stratum corneum surfactants

Fulmer, A.W., and G.J. Kramer. 1986. Stratum corneum lipid abnormalities in surfactant-induced dry scaly skin. J Invest Dermatol 86 598. 

A number of works investigated the interaction between niosomes and human skin. With niosomes prepared from Ci2 alcohol polyoxyethylene ether and cholesterol, vesicular structures of about 100 nm size have been observed between the first and second layers of human corneocytes 48 h after incubation as well as in the deeper strata of the skin [37], The authors concluded that the structures visualized in the deeper regions could be vesicles reorganized from individual molecules that penetrated the skin. In another study, electron micrographs illustrated that niosomes containing surfactants and cholesterol affected only the most superficial corneocytes. Moreover, two-photon fluorescence microscopy confirmed that fluorescent probe encapsulated in niosomes was confined to the intercellular spaces within the apical stratum corneum layers [56]. 

Occlusion is a condition that could affect drug transport from niosomes and through the stratum corneum. Such an effect was reported for saturated estradiol niosomal formulations composed of polyoxyethylene alkyl ether surfactants and sucrose ester surfactants with cholesterol and dicetyl phosphate, for which occlusion enhanced the drug human stratum corneum transport [43]. 

Holland, H.E., et al. 1994. Estradiol permeation from nonionic surfactant vesicles through human stratum corneum in vitro. Pharm Res 11 659. 

Hofland, H.E., et al. 1991. Interactions of non-ionic surfactant vesicles with cultured keratinocytes and human skin in vitro A survey of toxicological aspects and ultrastructural changes in stratum corneum. J Control Release 16 155. 

H. E. J. Holland, R. van der Geest, H. E. Bodde, H. E. Junginger, and J. A. Bouwstra. Estradiol permeation from nonionic surfactant vesicles through human stratum corneum in vitro, Pharma. Res. 11 659-664 (1994). 

Chemical PEs have recently been studied for increasing transdermal delivery of ASOs or other polar macromolecules [35]. Chemically induced transdermal penetration results from a transient reduction in the barrier properties of the stratum corneum. The reduction may be attributed to a variety of factors such as the opening of intercellular junctions due to hydration [36], solubilization of the stratum corneum [37, 38], or increased lipid bilayer fluidization [39, 40]. Combining various surfactants and co-solvents can be used to achieve skin penetration, purportedly resulting in therapeutically relevant concentrations of ASO in the viable epidermis and dermis [41]. In summary, it appears feasible to deliver ASO to the skin using a number of different delivery techniques and formulations. 

Another class of surfactants that are used in cosmetics and personal care products is the phosphoric acid esters. These molecules are similar to the phospholipids that are the building blocks of the stratum corneum (the top layer of the skin, which is the main barrier for water loss). Glycerine esters, in particular, triglycerides, are also frequently used. Macromolecular surfactants of the A-B-A block type [where A is PEO and B is polypropylene oxide (PPO)] are also frequently used in cosmetics. Another important naturally occurring class of polymeric surfactants is the proteins, which can be used effectively as emulsifiers. 

Experimental evidence that protein structures are involved in stratum corneum cell cohesion was presented by Bisset et al.9 They induced cell dissociation in pig and human nonpalmo-plantar stratum corneum by means of incubation of the tissue in the presence of the zwitterionic surfactant 6-octadecyldimethyl ammoniohexanoate. Cell dissociation could not be induced when the tissue had been pretreated with the serine protease inhibitor phenylmethylsulfonyl fluoride (PMSF). The fact that cell dissociation was found only in the presence of EDTA suggested a role also for calcium in stratum corneum cell cohesion. 

There is evidence that protein structures are also responsible for cell cohesion in nonpalmo-plantar stratum corneum. When punch biopsies of normal human gluteal skin were incubated in a buffer containing a mixture of the zwitterionic surfactant /V,/V,-dimethyldodecylamine and the anionic surfactant sodium dodecyl sulfate,11 there was dissociation of cells in the stratum corneum but not in the rest of the epidermis. The cell dissociation took place only in the presence of EDTA and was inhibited by the serine protease inhibitor aprotinin.12 Suzuki et al.13,14 presented evidence that spontaneous cell dissociation in nonpalmo-plantar stratum corneum could be inhibited by a combination of inhibitors of trypsin-like and chymotrypsin-like enzymes. Thus, nonpalmo-plantar stratum corneum contains endogenous proteases that mediate cell dissociation. 

Wilhelm, K.P., Cua, A.B., Wolff, H.H., and Maibach, H.I. (1993) Surfactant-induced stratum corneum hydration in vivo prediction of the irritation potential of anionic surfactants. J. Invest. Dermatol. 101 310-315. 

Imokawa, G. et al. Importance of intercellular lipids in water retention properties of the stratum corneum induction and recovery study of surfactant dry skin, Arch. Dermatol. Res., 281, 45, 1989. 

Rhein, L., Robbins, C., Kernee, K., and Cantore, R., Surfactant structure effects on swelling of isolated human stratum corneum. J. Soc. Cosmet. Chem. 37 125-139, 1986. 

Ionic surfactants are thought to enhance transdermal absorption by disordering the lipid layer of the stratum corneum and by denaturation of keratin. The use of penetration enhancers in general, and surfactants in particular, in transdermal therapeutic systems has been reviewed by Walters. 

Warner, R.R. Boissy, Y.L. Lilly, N.A. Spears, M.J. McKillop, K. Marshall, J.L. Stone, K.J. Water disrupts stratum corneum lipid lamellae damage is similar to surfactants. J. Invest. Dermatol. 1999, 113, 960-966. 

The relationship observed for the swelling of stratum corneum and skin irritation and the existence of a large amount of data on skin swelling provided encouragement to explore the possibility of a mathematical model to predict skin irritation of mixed surfactant systems or products based on skin-swelling data. 

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