title: Characterization of pore structure of polymer blended films used for controlled drug release.
abstract: The characterization of the pore structure in pharmaceutical coatings is crucial for understanding and controlling mass transport properties and function in controlled drug release. Since the drug release rate can be associated with the film permeability, the effect of the pore structure on the permeability is important to study. In this paper, a new approach for characterizing the pore structure in polymer blended films was developed based on an image processing procedure for given two-dimensional scanning electron microscopy images of film cross-sections. The focus was on different measures for characterizing the complexity of the shape of a pore. The pore characterization developed was applied to ethyl cellulose (EC) and hydroxypropyl cellulose (HPC) blended films, often used as pharmaceutical coatings, where HPC acts as the pore former. It was studied how two different HPC viscosity grades influence the pore structure and, hence, mass transport through the respective films. The film with higher HPC viscosity grade had been observed to be more permeable than the other in a previous study; however, experiments had failed to show a difference between their pore structures. By instead characterizing the pore structures using tools from image analysis, statistically significant differences in pore area fraction and pore shape were identified. More specifically, it was found that the more permeable film with higher HPC viscosity grade seemed to have more extended and complex pore shapes than the film with lower HPC viscosity grade. This result indicates a greater degree of connectivity in the film with higher permeability and statistically confirms hypotheses on permeability from related experimental studies.
authors.affiliation: Chalmers University of Technology and University of Gothenburg, Department of Mathematical Sciences, SE-412 96 Gothenburg, Sweden; SuMo BIOMATERIALS, VINN Excellence Center, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden. Electronic address: henrike.habel@chalmers.se.
authors.forename: Henrike
authors.initials: H
authors.lastname: Häbel
authors.affiliation: SP Food and Bioscience, Structure and Material Design, Box 5401, SE-402 29 Gothenburg, Sweden; Chalmers University of Technology, Department of Materials and Manufacturing Technology, SE-412 96 Gothenburg, Sweden; SuMo BIOMATERIALS, VINN Excellence Center, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
authors.forename: Helene
authors.initials: H
authors.lastname: Andersson
authors.affiliation: Chalmers University of Technology, Department of Applied Physics, SE-412 96 Gothenburg, Sweden; SuMo BIOMATERIALS, VINN Excellence Center, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Olsson
authors.affiliation: Chalmers University of Technology, Department of Applied Physics, SE-412 96 Gothenburg, Sweden; SuMo BIOMATERIALS, VINN Excellence Center, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Olsson
authors.affiliation: Chalmers University of Technology, Department of Chemistry and Chemical Engineering, SE-412 96 Gothenburg, Sweden; SuMo BIOMATERIALS, VINN Excellence Center, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
authors.forename: Anette
authors.initials: A
authors.lastname: Larsson
authors.affiliation: Chalmers University of Technology and University of Gothenburg, Department of Mathematical Sciences, SE-412 96 Gothenburg, Sweden; SuMo BIOMATERIALS, VINN Excellence Center, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
authors.forename: Aila
authors.initials: A
authors.lastname: Särkkä
mesh_terms: D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D003692:Delayed-Action Preparations / Q000737:chemistry; D016503:Drug Delivery Systems; D010539:Permeability; D016062:Porosity; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D003692:Delayed-Action Preparations; D014867:Water; C013517:ethyl cellulose; D002482:Cellulose; C008079:hydroxypropylcellulose
keywords: Image processing; Permeability; Pore shape; Porous material; Scanning electron microscopy