title: Stable and fluid ethylphosphocholine membranes in a poly(dimethylsiloxane) microsensor for toxin detection in flooded waters.
abstract: Highly stable and fluid supported bilayer membranes were fabricated by fusion of positively charged ethylphosphocholine (DOPC+) vesicles into poly(dimethylsiloxane) (PDMS) microchannels for immunosensing of cholera toxin (CT) in flooded waters. Compared to phosphatidylcholine (PC) layers in the microchannels, DOPC+ membranes show exceptionally strong resistance to air-dry damage, as demonstrated by fluorescence recovery after photobleaching (FRAP) measurements and protein adsorption studies. In FRAP experiments, the mobile fraction of PC membranes was found to decrease by 10% upon drying/rehydration and the lateral diffusion coefficient decreased from 2.2 to 1.6 microm(2)/s, whereas the mobile fraction and diffusion coefficient for DOPC+ membranes remain virtually unchanged during this process. Characterization by confocal microscopy reveals that only 1% of the DOPC+ membrane in the microchannels was removed by the drying/rehydration process, as compared to 11% for PC. Protein adsorption trends indicate that the charge of DOPC+ membranes allows for tuning of solution conditions to enable the desired protein-membrane interaction to predominate at the interface. A flow-based immunoassay for bacterial toxin was developed with 5% GM1/DOPC+ membranes in PDMS channels, and a detection limit of 250 amol for CT was obtained from the calibration curves. The assay was successfully applied to detection of CT spiked in water samples from the Santa Ana River, with nearly identical response and sensitivity.
authors.affiliation: Department of Chemistry, University of California, Riverside, California 92521, USA.
authors.forename: K Scott
authors.initials: KS
authors.lastname: Phillips
authors.forename: Yi
authors.initials: Y
authors.lastname: Dong
authors.forename: David
authors.initials: D
authors.lastname: Carter
authors.forename: Quan
authors.initials: Q
authors.lastname: Cheng
mesh_terms: D015374:Biosensing Techniques; D002772:Cholera Toxin / Q000032:analysis*; D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D004190:Disasters; D005677:G(M1) Ganglioside / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008567:Membranes, Artificial; D044085:Microfluidics / Q000379:methods; D010713:Phosphatidylcholines / Q000737:chemistry*; D012828:Silicones / Q000737:chemistry*; D013499:Surface Properties; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D004129:Dimethylpolysiloxanes; D008051:Lipid Bilayers; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D012828:Silicones; D014874:Water Pollutants, Chemical; D005677:G(M1) Ganglioside; C013830:baysilon; D002772:Cholera Toxin; C017251:1,2-oleoylphosphatidylcholine