A comparison between interactions of triglyceride oil and mineral oil with proteins and their ability to reduce cleanser surfactant-induced irritation.
OBJECTIVE
Skin irritation in personal cleansing has been correlated with surfactant binding with stratum corneum proteins. Polar and non-polar oils are increasingly being used in cleansing formulations which contain high (10-15%) level of anionic and non-ionic surfactants. However, the effects of oils in modulating skin damage from a cleansing product have not been studied in any detail. The objectives of this study are to determine whether low-viscosity polar and non-polar oils differ in their ability to reduce surfactant-induced skin irritation and, if so, how it might be related to their interactions with proteins.


METHODS
Surfactant-induced skin irritation was measured by a 14-day in vivo cumulative patch irritation test. The methodology was similar to the well-known soap chamber test. Surfactant interactions with the water-soluble protein, bovine serum albumin (BSA), in the presence of oils were measured by conductometric titration. The effects of low-viscosity polar and non-polar oils on stratum corneum protein dynamics in the sulfhydryl group region were studied by electron paramagnetic resonance (EPR) using the covalently bound spin-label 3-maleimido-proxyl (5-MSL). EPR measurements were performed with stratum corneums obtained from discarded skins of 3- to 4-week-old female pigs. Simulation of the complex spectra provided insights on the environment and mobility of the protein-bound spin label.


RESULTS
Addition of 1% polar sunflower seed oil (viscosity 42 centipoise) reduced in vivo irritation of 1% sodium lauryl ether sulphate with two ethoxylate/cocamidopropyl betaine (SLES/CAPB) by 20%, whereas 1% non-polar mineral oil (viscosity 15 centipoise) had no effect. Polar oil glyceryl trioleate (a major component in sunflower seed oil) at 10% level reduced surfactant binding to BSA protein in water by 40%, whereas the non-polar oil dodecane (a major component of mineral oil) at a similar level did not have any effect. The mobility of the spin label in a dry corneum was very low and was increased significantly with the addition of water and glycerol trioleate but less so with mineral oil.


CONCLUSION
Sunflower seed oil reduces surfactant-induced in vivo skin irritation more than mineral oil. This is possibly due to stronger interaction of polar oil with proteins, thus protecting it from surfactant binding.
['Mukherjee|S|S|', 'Yang|L|L|', 'Vincent|C|C|', 'Lei|X|X|', 'Ottaviani|M F|MF|', 'Ananthapadmanabhan|K P|KP|']
D004578:Electron Spin Resonance Spectroscopy D006801:Humans D007509:Irritants D008899:Mineral Oil D011485:Protein Binding D012710:Serum Albumin, Bovine D012867:Skin D013501:Surface-Active Agents D014280:Triglycerides
EPR/ESR spectroscopy cleanser-induced skin irritation conductivity oil-corneum protein interaction surfactant-protein binding