Center for Nanostructured Biomimetic Interfaces
Department of Chemical Engineering and Materials Science, Michigan State University
Arrays of lipid bilayer and liposomes on polyelectrolytes
Neeraj Kohli, Sachin Vaidya, Robert Ofoli, Mark Worden, Ilsoon Lee
Presented at 2004 Annual AIChE ConferenceNovember 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
MaterialsLipids 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
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
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
Center for Nanostructured Biomimetic Interfaces
Scheme 1
Center for Nanostructured Biomimetic Interfaces
Glass Slide
PDAC
(+ve)
WATER WATERSPS
(-ve)
Technique
Center for Nanostructured Biomimetic Interfaces
Stamp
PDAC (+ve) or PAH (+ve)
SPS(-ve)
Glass slide
PDAC or PAH
Technique
Center for Nanostructured Biomimetic Interfaces
Fluorescence
Center for Nanostructured Biomimetic Interfaces
TIRFM Shallow evanescent wave depth (80nm) allows for
selective surface illumination Monitor the adsorption of liposomes on PDAC, PAH
and m-dPEG acidprism
Glass slide coated with PEMs
spacer
bottom slide
syringepump
Center for Nanostructured Biomimetic Interfaces
Adsorption
0
20000
40000
60000
80000
100000
120000
140000
0 1000 2000 3000 4000
Time (seconds)
Flu
ore
sce
nce
(A
.U)
PDAC
SPS
PDAC
SPS
90% DOPC
10% DOPA
80 % DOPC20% DOPA
Center for Nanostructured Biomimetic Interfaces
Scheme 2
SPS
PDAC
m-dPEG acid
Center for Nanostructured Biomimetic Interfaces
Fluorescence
Center for Nanostructured Biomimetic Interfaces
Adsorption
Adsorption of DOPA-DOPC on m-dPEG acid and PDAC
0
50000
100000
150000
200000
250000
300000
0 500 1000 1500
Time (seconds)
Flu
ore
sce
nce
PDAC
PEG
Center for Nanostructured Biomimetic Interfaces
EPI-FRAPPLaser 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
Substrate Diffusion coefficient
Mobile fraction
PAH 2x10-9 cm2/s 0.9
PDAC 9x10-11cm2/s
3x10-9 cm2/s
0.24
0.31
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
Polyelectrolytes
Strong Polyelectrolytes
Weak Polyelectrolytes
Polycations
Polyanions
PDAC SPSpoly(diallyldimethylammonium chloride) sulfonated poly(styrene)
poly(acrylic acid)
poly(ethyleneimine)
DOPC
DOPA
NBD-PC