ABSTRACT
To date, emollients are included in skin care formulations although not much is known about their adsorption/deposition properties and/or the interactions of the constituents within these multi-component systems. The modulation of the adsorption/deposition via the use of specific surfactant and/or emollient systems could therefore help to increase performance and sensorial benefits as well as to reduce adverse effects. In this study, the effects of various tripartite systems consisting of sodium laureth sulphate (SLES), a co-surfactant and an emollient were studied. The two different emollients tested adsorbed with varying amounts although the same surfactant/co-surfactant system was used. Interestingly, the deposition of both SLES and/or the emollient is also substantially influenced by the emollient component itself as well as by the co-surfactant used. Sensory assessments showed that although SLES has a negative effect on the skin feel, adsorbed emollients improve skin softness and smoothness. These results show that optimization of performance is possible when using a co-surfactant best suited for the emollient.
Subject(s)
Cosmetics/pharmacokinetics , Emollients/pharmacokinetics , Sodium Dodecyl Sulfate/pharmacokinetics , Surface-Active Agents/pharmacokinetics , Animals , Cosmetics/chemistry , Double-Blind Method , Emollients/chemistry , Humans , In Vitro Techniques , Skin/drug effects , Skin/metabolism , Skin Absorption , Sodium Dodecyl Sulfate/chemistry , Statistics, Nonparametric , Surface-Active Agents/chemistry , SwineABSTRACT
Based on the requirements of biomolecular interaction analysis on direct optical transducers, a streptavidin surface is examined. A general protocol was developed allowing the immobilization of biotinylated compounds using the rife biotin-streptavidin system. This type of surface modification can be applied to all biosensors using glass surfaces as sensor devices. Reflectometric interference spectroscopy (RIfS), a label-free, direct optical method was used to demonstrate the quality of the transducer surfaces. The surface modification is based on an aminofunctionalized polyethylene glycol layer covalently bound to the silica surface of the transducer and shows very little nonspecific binding. Biotin molecules can be easily coupled on such layers. Streptavidin followed by a biotinylated estrone derivative was immobilized by incubation of the biotinylated transducer surface. For the streptavidin layer we obtained interference signals corresponding to a protein monolayer. Finally, using a surface prepared as described above, biomolecular interaction experiments with an antibody against estrone were carried out to show the quality of the transducer surface. With RIfS all of the affinity-based surface modifications can be detected online and time resolved.
Subject(s)
Biosensing Techniques/methods , Estrone/chemistry , Antibodies , Biotinylation , Dextrans/chemistry , Estrone/analogs & derivatives , Estrone/immunology , Glass , Polyethylene Glycols/chemistry , Solvents , Spectrum Analysis/methods , Streptavidin/chemistryABSTRACT
Since the first label-free optical biosensor was commercialized in 1990 a rising number of publications have demonstrated the benefits of direct biomolecular interaction analysis (BIA) for biology and biochemistry. This article first gives an overview of the historical development of different transducer principles used for the detection of BIA. Subsequently, the four major parts of a biosensor system: transducer, sample handling, surface/immobilization chemistry and test formats/data evaluation will be discussed, with a main focus on the test formats and data evaluation. The intention of this review is to present an introduction to the field and to point out the difficulties most frequently encountered.
