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Biomacromolecules 2008, 9, 748–751
Notes Measuring Macrodiffusion Coefficients in Microbicide Hydrogels via Postphotoactivation Scanning Anthony R. Geonnotti,*,† Matthew J. Furlow,† Tianshi Wu,† Michael G. DeSoto,† Marcus H. Henderson,† Patrick F. Kiser,‡ and David F. Katz†,§ Department of Biomedical Engineering, Duke University, Box 90281, Durham, North Carolina 27708, Department of Biomedical Engineering, University of Utah, BPRB Rm 108G, 20 South 2030 East, Salt Lake City, Utah 84112, and Department of Obstetrics and Gynecology, Duke University, Box 90281, Durham, North Carolina 27708 Received September 12, 2007 Revised Manuscript Received December 4, 2007
Introduction Hydrogels can function as biocompatible, engineered systems to provide controlled release of drugs in vivo. Whether they are employed as gel implants, tissue engineered scaffolds, or delivery systems for transdermal or mucosal delivery,1–4 hydrogels often function by controlling the diffusion of particles into or out of their polymer matrices. Biologically relevant predictions of hydrogel functionality in vivo (e.g., pharmacokinetic profiles) require accurate measurements of particle transport. However, determinations of diffusion coefficients in hydrogels are highly influenced by the length scales over which measurements are made.5–7 Because of heterogeneity within hydrogel macromolecular structures, local microdiffusion coefficients deviate from ones measured over longer length scales, especially as diffusing particle size increases.6,7 Therefore, in vitro measurement of diffusion coefficients should be performed on length scales similar to those of the in vivo transport processes of interest. Several techniques (e.g., FRAP, single particle tracking, scanning microphotolysis, multiple image photography) have been widely utilized to measure particle diffusion within hydrogels, but most provide measurements on molecular or cellular length scales (
