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Investigation of amphiphilic star block copolymers as carriers for transdermal drug delivery

Figure 1: Molecular
model of amphiphilic
star block copolymer
The skin represents a formidable lipophilic barrier preventing the diffusion of most polar therapeutics directly into the bloodstream. However, the requisite exposure to acidic and enzymatically active gastro-intestine track makes the traditional oral route to drug delivery unsuitable for most peptides and acid-sensitive drug molecules. While liposomes and other self-assembled carriers have been applied successfully to act as a protective delivery vehicle, their large size and instability prevent their broad use in many specific applications such as transdermal drug delivery. In response, the Grayson research group has prepared a class of well-defined, amphiphilic block-copolymers (figure 1, left) which exhibit smaller, more hardy aggregates that can act as carrier molecules for transdermal delivery applications. The efficacy of these macromolecular carriers has been confirmed by measurement of their transport of a fluorescent dye through the porcine skin samples (figure 2, below).

Figure 2: Dye diffusion through porcine skin after 2 hours measured without carrier (left) where the dye remains on the surface of the skin, and with polymeric carriers (right) where fluorescence is observed throughout the stratum corneum and into the viable skin (viable cells stained blue)

Our recent publications in this area:
1) Poree, D. E.; Giles, M. D.; Lawson, L. B; He, J.; Grayson, S. M. Synthesis of Dendritic Star Block Copolymers and their Evaluation as Transdermal Carriers submitted, 2010.
2) Eugene, D. M.; Grayson, S. M.; Giles, Marco D. Characterization and evaluation of dendritic star block copolymer via ATRP for use as transdermal drug delivery agents. Polym. Prepr. 2010, 51, 99-100.
3) Willham, K. A.; Laurent B. A.; Grayson, S. M. The Synthesis of a pH-Independent Bifurcated Amphiphile. Tetrahedron Lett. 2008, 49, 2091-2094.

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