title: A microfluidic method to measure small molecule diffusion in hydrogels.
abstract: Drug release from a fluid-contacting biomaterial is simulated using a microfluidic device with a channel defined by solute-loaded hydrogel; as water is pumped through the channel, solute transfers from the hydrogel into the water. Optical analysis of in-situ hydrogels, characterization of the microfluidic device effluent, and NMR methods were used to find diffusion coefficients of several dyes (model drugs) in poly(ethylene glycol) diacrylate (PEG-DA) hydrogels. Diffusion coefficients for methylene blue and sulforhodamine 101 in PEG-DA calculated using the three methods are in good agreement; both dyes are mobile in the hydrogel and elute from the hydrogel at the aqueous channel interface. However, the dye acid blue 22 deviates from typical diffusion behavior and does not release as expected from the hydrogel. Importantly, only the microfluidic method is capable of detecting this behavior. Characterizing solute diffusion with a combination of NMR, optical and effluent methods offer greater insight into molecular diffusion in hydrogels than employing each technique individually. The NMR method made precise measurements for solute diffusion in all cases. The microfluidic optical method was effective for visualizing diffusion of the optically active solutes. The optical and effluent methods show potential to be used to screen solutes to determine if they elute from a hydrogel in contact with flowing fluid. Our data suggest that when designing a drug delivery device, analyzing the diffusion from the molecular level to the device level is important to establish a complete picture of drug elution, and microfluidic methods to study such diffusion can play a key role.
authors.affiliation: Department of Chemical Engineering, Bucknell University, Lewisburg, PA 17837, USA.
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Evans
authors.affiliation: Department of Chemical Engineering, Bucknell University, Lewisburg, PA 17837, USA.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Litzenberger
authors.affiliation: Department of Chemical Engineering, Bucknell University, Lewisburg, PA 17837, USA.
authors.forename: Anne E
authors.initials: AE
authors.lastname: Ellenberger
authors.affiliation: Department of Chemical Engineering, Bucknell University, Lewisburg, PA 17837, USA. Electronic address: james.maneval@bucknell.edu.
authors.forename: James E
authors.initials: JE
authors.lastname: Maneval
authors.affiliation: Department of Chemical Engineering, Bucknell University, Lewisburg, PA 17837, USA. Electronic address: erin.jablonski@bucknell.edu.
authors.forename: Erin L
authors.initials: EL
authors.lastname: Jablonski
authors.affiliation: Department of Chemical Engineering, Bucknell University, Lewisburg, PA 17837, USA. Electronic address: brandon.vogel@bucknell.edu.
authors.forename: Brandon M
authors.initials: BM
authors.lastname: Vogel
mesh_terms: D003692:Delayed-Action Preparations / Q000737:chemistry*; D004058:Diffusion; D004341:Drug Evaluation / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D020100:Hydrogels / Q000737:chemistry*; D008422:Materials Testing / Q000295:instrumentation*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D008970:Molecular Weight; D004364:Pharmaceutical Preparations / Q000737:chemistry*
chemical_list: D003692:Delayed-Action Preparations; D020100:Hydrogels; D004364:Pharmaceutical Preparations
keywords: Controlled drug delivery; Diffusion; Hydrogels; Microfluidics; NMR; PEG