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Arrays of lipid bilayer and liposomes on polyelectrolytes. Neeraj Kohli, Sachin Vaidya, Robert Ofoli, Mark Worden, Ilsoon Lee. Department of Chemical Engineering and Materials Science, Michigan State University. Presented at 2004 Annual AIChE Conference November 7 - 12, 2004, Austin, TX.
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Arrays of lipid bilayer and liposomes on polyelectrolytes Neeraj Kohli, Sachin Vaidya, Robert Ofoli, Mark Worden, Ilsoon Lee Department of Chemical Engineering and Materials Science, Michigan State University Presented at 2004 Annual AIChE Conference November 7 - 12, 2004, Austin, TX Center for Nanostructured Biomimetic Interfaces
Outline • Potential applications • Limitations of previous approaches • Our approach • Characterization techniques • Fluoresence microscopy • Total internal reflection fluorescence microscopy (TIRFM) • Fluoresence recovery after pattern photobleaching (EPI-FRAPP) Center for Nanostructured Biomimetic Interfaces
Potential applications • Biosensors • Biocatalysis • Cell-cell communication • Studying membrane mediated processes • Development of drug screening devices Center for Nanostructured Biomimetic Interfaces
Limitations of previous approaches • Applicable to limited number of substrates • No cushion between the lipid bilayer and the substrate • No ionic reservoir Approaches are needed to overcome these limitations Center for Nanostructured Biomimetic Interfaces
Materials Lipids • DOPC: 1,2-Dioleoyl-sn-Glycero-3-Phosphocholine (zwitterion) • DOPA: 1,2-Dioleoyl-sn-Glycero-3-Phosphate (Monosodium Salt) (negatively charged) • NBD PC: 1-Palmitoyl-2-[6-[(7-nitro-2-1,3-benzoxadiazol-4-yl)amino]hexanoyl]-sn-Glycero-3-Phosphocholine (zwitterion) Polyelectrolytes • PDAC: Poly(dimethyldiallylammonium chloride) (positively charged) • PAH: Poly(allylamine hydrochloride) (positively charged) • SPS: Sulfonated poly(styrene) ( negatively charged) m-dPEG acid Center for Nanostructured Biomimetic Interfaces
1 G. Decher , Science, 1997, 277, 1232. 2 A. Kumar and G. M. Whitesides, Appl. Phys. Lett., 1993, 63, 2002. 3 X. Jiang, H. Zheng, G. Shoshna, and P. T. Hammond, Langmuir, 2002, 18, 2607 Arrays of Lipid bilayers • Layer by layer assembly1, microcontact printing2 and polymer on polymer stamping3. • Two different schemes were used to make arrays of lipid bilayers • Scheme 1: either the PDAC or PAH patterned substrates were exposed to negatively charged liposomes • Scheme 2: m-dPEG acid patterns on PDAC were exposed to negatively charged liposomes Center for Nanostructured Biomimetic Interfaces
Scheme 1 Center for Nanostructured Biomimetic Interfaces
Technique Glass Slide PDAC (+ve) WATER SPS (-ve) WATER Center for Nanostructured Biomimetic Interfaces
SPS(-ve) PDAC or PAH Glass slide Stamp Technique PDAC (+ve) or PAH (+ve) Center for Nanostructured Biomimetic Interfaces
Fluorescence Center for Nanostructured Biomimetic Interfaces
syringe pump TIRFM • Shallow evanescent wave depth (80nm) allows for selective surface illumination • Monitor the adsorption of liposomes on PDAC, PAH and m-dPEG acid prism Glass slide coated with PEMs spacer bottom slide Center for Nanostructured Biomimetic Interfaces
Adsorption 140000 PDAC 120000 PDAC 90% DOPC 100000 10% DOPA 80000 Fluorescence (A.U) 60000 SPS 80 % DOPC 40000 20% DOPA 20000 SPS 0 0 1000 2000 3000 4000 Time (seconds) Center for Nanostructured Biomimetic Interfaces
Scheme 2 m-dPEG acid PDAC SPS Center for Nanostructured Biomimetic Interfaces
Fluorescence Center for Nanostructured Biomimetic Interfaces
Adsorption of DOPA-DOPC on m-dPEG acid and PDAC 300000 250000 200000 PDAC Fluorescence 150000 100000 PEG 50000 0 0 500 1000 1500 Time (seconds) Adsorption Center for Nanostructured Biomimetic Interfaces
EPI-FRAPP Laser beam passes through Ronchi ruling placed in the image plane Center for Nanostructured Biomimetic Interfaces
EPI –FRAPP recovery on PDAC Center for Nanostructured Biomimetic Interfaces
EPI-FRAPP recovery on PAH Center for Nanostructured Biomimetic Interfaces
Diffusion Coefficients Center for Nanostructured Biomimetic Interfaces
Conclusions • Fabricated arrays of lipid bilayers • Applicable to large number of substrates • Cushion below the lipid bilayer • Fluorescence microscopy, TIRFM and FRAPP were used. • PDAC showed only 50% recovery • PAH showed almost complete recovery • PAH had higher diffusion coefficients Center for Nanostructured Biomimetic Interfaces
Funding • Michigan Technology Tri-Corridor • Center for Fundamental Materials Research • MSU-Intramural Research Grant Program Center for Nanostructured Biomimetic Interfaces
Thank you Center for Nanostructured Biomimetic Interfaces
Polyelectrolytes sulfonated poly(styrene) poly(diallyldimethylammonium chloride) SPS PDAC Strong Polyelectrolytes Polycations Weak Polyelectrolytes Polyanions poly(acrylic acid) poly(ethyleneimine)
DOPC DOPA NBD-PC