Abstract
This thesis describes GARField magnetic resonance profiling experiments which explore skin hydration and the ingress of small molecules into the skin both in vitro and in vivo. Previous magnetic resonance imaging (MRI) studies of human skin have been severely restricted by the spatial resolution achievable on a clinical scanner as well as by the lower limit of accessible spin-spin relaxation times, T2. Our approach to overcome these limitations is to use a permanent MRI magnet, GARField, specially designed to obtain depth profiles of thin planar samples (about 100 - 800 mum thick) with a pixel resolution of the order of 10 mum, and with access to T2 times as short as a few 100 mus. In vitro human skin samples were obtained following abdominal surgery. The epidermis was removed from the dermis using the heat separation method and the samples hydrated by floatation in water. Shown in this thesis are results from in vitro experiments investigating the effect of different relative humidity environments on the skin samples. Observation of the different hydrogen mobility (arising from various water types) within the skin can also be attained using the GARField instrumentation. This is achieved by changing key NMR pulse sequence acquisition parameters. In addition, the consequence of the application of three main ingredients frequently used in care products, to the stratum corneum was investigated. The ingredients studied in the experiments were: mineral oil; Glycerine (and deuterated-glycerine); squalane; and decanol (& deuterated decanol). These ingredients were added and profiles recorded over time. In contrast to the other ingredients, the depth penetration of deuterated decanol within the skin is known to be no deeper than the junction between the stratum corneum and the viable epidermis. As such it could be used as a marker against the penetration profiles of the other ingredients. Estimations of ingress diffusion coefficients for glycerine (1x10-9 cm2s-1) and squalane (1 x 10-10 cm2s-1) was obtained. Preliminary in vivo experiments using a larger GARField magnet, working with the same principles as the smaller magnet, show that the technique can produce reproducible results.