Influence of microneedle shape on the transport of a fluorescent dye into human skin in vivo

• Published in: Journal of controlled release Vol. 147; no. 2; pp. 218 - 224
• Main Authors: Bal, Suzanne M., Kruithof, Annelieke C., Zwier, Raphaël, Dietz, Ekkehart, Bouwstra, Joke A., Lademann, Jürgen, Meinke, Martina C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.10.2010; Elsevier
• Subjects: Adult; Biological and medical sciences; Biological Transport; Confocal laser scanning microscopy; Confocal microscopy; Drug Delivery Systems - instrumentation; Equipment Design; Female; Fluorescent Dyes - pharmacokinetics; General pharmacology; Humans; In vivo visualisation; Male; Medical sciences; Microneedles; Microscopy, Confocal; Middle Aged; Needles; Pharmaceutical technology. Pharmaceutical industry; Pharmacology. Drug treatments; Skin - metabolism; Skin Absorption; Surface Properties; Transport; Vaccination - instrumentation; Young Adult; In vivo visualisation; Microneedles; Transport; Confocal laser scanning microscopy; Delivery system; Human; Dyes; Shape; Pharmaceutical technology; Confocal microscopy; In vivo; Skin; Microneedle
• ISSN: 0168-3659; 1873-4995
• DOI: 10.1016/j.jconrel.2010.07.104

Microneedles can enhance the penetration of vaccines into the skin for transcutaneous vaccination. In this study for the first time the influence of microneedle geometry on the transport through the formed conduits was visualised in human volunteers by confocal laser scanning microscopy. Three differently shaped 300 μm long microneedle arrays were selected and fluorescein was applied either before or after piercing. Based on the intensity a distinction was made between regions with high and low intensity fluorescence (HIF and LIF). The areas of both intensities were quantified over time. In most cases HIF areas were only present in the stratum corneum, while LIF areas were also present in the viable epidermis. The areas were larger if fluorescein was applied after piercing compared to before piercing. After 15 min almost no HIF was present anymore at the skin surface. The microneedle geometry, but not the manner of application affected the shape and depth of the conduits. In conclusion we showed that the different microneedle arrays are able to form conduits in the skin, but the geometry of the microneedles influences the penetration of the fluorescent dye. This is the first step towards a more rational design of microneedle arrays for transcutaneous vaccination. LSM images at different depths of the conduits formed by the three different microneedle arrays 5 min after application of the fluorescent dye. Dimensions of the images are 235 by 235 µm 2 [Display omitted]