Hongfeng Chen, Colin McFaul, Igor Titushkin, Michael Cho, Raphael Lee
Structural breakdown of the cell membrane is a primary mediator in trauma-induced tissue necrosis. When membrane disruption exceeds intrinsic membrane sealing processes, biocompatible multi-block amphiphilic copolymer surfactants such as Poloxamer 188 (P188) have been found to be effective in catalyze or augment sealing. Although in living cells copolymer-induced sealing of membrane defects has been detected by changes in membrane transport properties, it has not been directly imaged. In this project, we used Atomic force microscopy (AFM) to directly image saponin permeabilized and poloxamer-sealed plasma membranes of monolayer-cultured MDCK and 3T3 fibroblasts. AFM image analysis resulted in the density and diameter ranges for membrane indentations per 5 × 5 μm area. For control, saponin lysed, and P188 treatment of saponin-lysed membranes, the supra-threshold indentation density was 3.6 ± 2.8, 13.8 ± 6.7, and 4.9 ± 3.3/cell, respectively. These results indicated that P188 catalyzed reduction in size of AFM indentations which correlated with increase cell survival. This evidence confirms that biocompatible surfactant P188 augments natural cell membrane sealing capability when intrinsic processes are incapable alone.
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