title: Colorimetric assay for cellular activity in microcapsules.
abstract: Cellular activity in microcapsules was determined by a simple colorimetric assay, based on the cellular transformation of a tetrazolium salt, 3-(4,5-dimethyl-thiazol-2-yl)-2,5- diphenyl-tetrazolium bromide, into an insoluble formazan which was quantified in a spectrophotometer. The results showed that when encapsulated Chinese hamster ovary fibroblasts were exposed to the tetrazolium salt containing tissue culture medium, the formazan crystals were formed inside the poly(hydroxyethyl methacrylate-methyl methacrylate) microcapsules; capsules containing no cells or dead cells formed no formazan. A detectable amount of formazan was readily obtained even from single capsules. Formazan production was dependent on the incubation time, but not on the amount of added reagent. Capsules from a high cell-density encapsulation (4 X 10(6) cells/ml) formed more formazan than capsules from a low cell-density (4 X 10(5) cells/ml) encapsulation, suggesting a positive correlation between the cell density and tetrazolium transformation in microcapsules. The tetrazolium assay indicated the maintenance of cellular activity but slow, if any, proliferation in microcapsules over a 2 wk testing period.
authors.affiliation: Department of Chemical Engineering and Applied Chemistry, University of Toronto, Ontario, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Uludag
authors.forename: M V
authors.initials: MV
authors.lastname: Sefton
mesh_terms: D000818:Animals; D002214:Capsules; D002478:Cells, Cultured / Q000378:metabolism; D003124:Colorimetry / Q000379:methods*; D004396:Coloring Agents / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D005347:Fibroblasts / Q000378:metabolism*; D005562:Formazans / Q000032:analysis; D013778:Tetrazolium Salts / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism
chemical_list: D002214:Capsules; D004396:Coloring Agents; D005562:Formazans; D013778:Tetrazolium Salts; D013844:Thiazoles; C022616:thiazolyl blue