Mid-Infrared Laser Ablation of Stratum Corneum Enhances In Vitro Percutaneous Transport of Drugs

The precise removal of stratum corneum from cadaveric swine skin by a mid-infrared erbium: yttrium scandium gallium garnet laser (λ = 2.79 μm; 250 μsec pulse width) was assessed by electrical resistance measurements and documented by histology. The effects of stratum corneum removal by laser ablation and by adhesive tape-stripping on the in vitro penetration of 3H-hydrocortisone and 125I-γ-interferon were determined. Excised swine skin was irradiated with laser (1 J/cm2 31 mJ/pulse; 1 Hz; 2mm spot diameter). For skin penetration studies, laser pulses were delivered to discrete 2-mm areas to ablate up to 12.6% of the total 3-cm2 stratum corneum diffusional area. Franz in vitro skin penetration chambers were used to measure the cumulative 48-h penetration of 3H-hydrocortisone and 125I-γ-interferon in laser-treated and tape-stripped skin. Electrical resistance measurements and histologic studies demonstrated that 10-14 laser pulses at the above energy density were required to abolish skin resistance and selectively ablate stratum corneum without damage to adjacent dermal structures. Laser ablation of 12.6% of the surface area of stratum corneum produced a 2.8 and 2.1-times increase in permeability constant (kp) for 3H-hydrocortisone and 125I-λ-interferon, respectively. These studies demonstrate that a pulsed mid-infrared laser can reliably and precisely remove the stratum corneum, facilitating penetration of large molecules such as 125I-λ-interferon that cannot penetrate intact skin. This new technique may be useful for basic and clinical investigation of skin barrier properties

Surfing the spectrum - what is on the horizon?

Diagnostic imaging techniques have evolved with technological advancements - but how far? The objective of this article was to explore the electromagnetic spectrum to find imaging techniques which may deliver diagnostic information of equal, or improved, standing to conventional radiographs and to explore any developments within radiography which may yield improved diagnostic data. A comprehensive literature search was performed using Medline, Web of Knowledge, Science Direct and PubMed Databases. Boolean Operators were used and key-terms included (not exclusively): terahertz, X-ray, ultraviolet, visible, infra-red, magnetic resonance, dental, diagnostic, caries and periodontal. Radiographic techniques are primarily used for diagnostic imaging in dentistry, and continued developments in X-ray imaging include: phase contrast, darkfield and spectral imaging. Other modalities have potential application, for example, terahertz, laser doppler and optical techniques, but require further development. In particular, infra-red imaging has regenerated interest with caries detection in vitro, due to improved quality and accessibility of cameras. Non-ionising imaging techniques, for example, infra-red, are becoming more commensurate with traditional radiographic techniques for caries detection. Nevertheless, X-rays continue to be the leading diagnostic image for dentists, with improved diagnostic potential for lower radiation dose becoming a reality

WET PROCESSES FOR THE PREPARATION OF ISOMETRIC FERRITE PIGMENTS WITH SPINEL STRUCTURE AND DEFINED FINENESS

Au moyen d'un procédé humide de neutralisation et d'oxydation combinées, on parvient à régler la répartition granulométrique des ferrites à structure spinelle afin d'obtenir une distribution granulométrique étroite à l'intérieur d'une large gamme (10 - 100 m2/g de surface spécifique équivalente). Le procédé autorise la préparation de pigments magnétiques γ-CoxFe3-xO4,5-0,5x d'une finesse suffisante, isotropes, multiaxiaux et d'une haute coercivité ainsi que de γ-ZnxFe3-xO4,5-0,5x très fins pour les encres magnétiques colorées (Imprimerie et Toners).A wet neutralization/oxidation process allows ferrites with spinel structure to be produced in a wide range of defined, high degrees of fineness (10 - 100 m2/g) and a narrow particle size distribution. Finely divided, isometric, highly coercive and multiaxial γ-CoxFe3-xO4.5-0.5x magnetic pigments and very finely divided, highly magnetic γ-ZnxFe3-xO4.5-0.5x for coloured magnetic printing inks and toners can thus be obtained