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)

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Potential applications Biosensors Biocatalysis Cell-cell communication Studying membrane mediated processes Development of drug screening devices

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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

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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

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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

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Scheme 1

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Glass Slide

PDAC

(+ve)

WATER WATERSPS

(-ve)

Technique

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Stamp

PDAC (+ve) or PAH (+ve)

SPS(-ve)

Glass slide

PDAC or PAH

Technique

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Fluorescence

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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

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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

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Scheme 2

SPS

PDAC

m-dPEG acid

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Fluorescence

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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

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EPI-FRAPPLaser beam passes through Ronchi ruling placed in the

image plane

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EPI –FRAPP recovery on PDAC

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EPI-FRAPP recovery on PAH

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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

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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

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Funding Michigan Technology Tri-Corridor Center for Fundamental Materials Research MSU-Intramural Research Grant Program

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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