Nanobiotechnology of BiomimeticMembranes

Nanobiotechnologyof Biomimetic Membranes

DONALD K. MARTIN

Editor:Donald K. MartinAssociate ProfessorFaculty of ScienceUniversity of Technology, SydneyBroadway N.S.W. 2007Australiadonm@uts.edu.au

Library of Congress Control Number: 2006931774

ISBN-10: 0-387-37738-7ISBN-13: 978-0-387-37738-4

e-ISBN-10: 0-387-37740-9e-ISBN-13: 978-0-387-37740-7

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PREFACE

This book is focussed on the lipid membrane, since that structure is a keycomponent of the way that living cells are able to maintain and organise theirfunctions. Unlocking the secrets of those membranes provides important lessonsthat are valuable in guiding the construction of devices to be used for medicalapplications. That philosophy is a central theme for scientists and engineersworking in the field of biomimetics. Indeed, throughout this book we emphasisethat approach in order to define the discipline of nanobiotechnology.

We define nanobiotechnology to be an interdisciplinary field of research anddevelopment that integrates engineering, physical sciences, and biology throughthe development of very small physical and biological devices using biomimeti-cally inspired nano-fabrication techniques. In that sense, biomimetically-inspiredmeans that the fabrication processes are based on the way the naturalsystems are constructed, usually by self-assembly of molecules in an aqueousenvironment.

That approach is often termed bionanotechnology, rather than nanobiotech-nology. However, it is more appropriate to term the discipline that we support inthe pages of this book as being nanobiotechnology. We emphasise that a signif-icant research outcome is to exploit an understanding of biological processes inorder to guide and influence the creation of devices and processes for use inbiomedical applications, and this is usually defined as biotechnology. The nanoprefix is necessary to accurately describe the scale of the manipulations requiredof the proteins, lipids and other molecules in order to create those biomedicaldevices and processes.

We have not broadly included the myriad of aspects of nanobiotech-nology that are often included in other books that describe this discipline.We deliberately focus on the lipid membrane due to its importance in thefunction of the natural cells of the living organisms. Indeed, the targets ofthe majority of drugs and pharmaceuticals are membrane-incorporated proteins.That targeting is not by chance, since nature utilises the membrane andmembrane-incorporated proteins as key components in maintaining organi-sation and function in the body. The separation and compartmentalisation ofelectrolyte concentrations within the body is maintained by the lipid membranes

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and the membrane-incorporated proteins. Amongst other vital functions, thatseparation of electrolyte concentrations provides the electrochemical drivingforce for propagation of electrical “action potential” signalling in nerves andmuscles. Biomedical devices based around biomimetic lipid membranes willallow improved biocompatibility and connection of the devices with the naturalcells of living organisms. Perhaps the practical realisation of Drexler’s robotswill not be built from metal and plastic, but rather from biomimetic componentsutilising the principles of lipid membrane nanobiotechnology described in thisbook.

The book develops the principles of membrane nanobiotechnology bydiscussing methods to produce lipid membranes, methods of characterising lipidmembranes, and the application of membranes to produce biosensors. We haveaddressed those topics in some depth in order to produce a reference book thatis useful for researchers and senior undergraduates. The chapters have beenwritten by friends and colleagues who are expert in the disciplines of physics,engineering, chemistry, and biology. Nanobiotechnology is the interdisciplinaryglue that unites us, and I am indebted to those friends and colleagues who havegenerously and enthusiastically contributed the ideas and concepts describedwithin the pages of this book. On many occasions they have forgiven my indul-gences with time.

I must extend a special acknowledgement to the International Science Linkagesprogram under the Australian government’s innovation statement BackingAustralia’s Ability. That program had the foresight to fund the OzNano2Lifeprogram (www.ambafrance-au.org/oznano2life) which has provided the inter-national collegiality and “glue-funding” that has allowed nanobiotechnologyresearch programs to flourish between Australian and international laboratories.That program of research-without-borders has been assisted significantly by thesupport of the Embassy of France in Australia, and notably by successive ScienceAttachés, M. Alain Moulet, and Professor Robert Farhi.

Donald K. MartinSydney, Australia

August, 2006

CONTENTS

Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi

1. The Significance of Biomimetic Membrane Nanobiotechnologyto Biomedical Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Donald K. Martin

1.1. Introduction .......................................................................................... 11.2. Interaction of Lipid Membranes

with Transport Proteins........................................................................ 31.3. Reaction of Eukaryotic Cells

to the Physical Environment................................................................ 41.3.1. Example of the Influence of Membrane Ion Channels

on the Biology of Endothelial Cells ......................................... 51.3.2. Mechanical Transduction of Stress in Lipid Bilayers.............. 8

1.4. What is the Relevance of Lipid Bilayer Membranesto Nanotechnology? ............................................................................. 10

1.5. Can Biosensor Technology Benefit from BiomimeticMembrane Nanobiotechnology? .......................................................... 13

1.6. Does Biomimetic Membrane Nanobiotechnology Assistin Drug Delivery? ................................................................................ 15

1.7. Can Implants Benefit from Biomimetic MembraneNanobiotechnology?............................................................................. 16

1.8. Concluding Remarks............................................................................ 17

2. Langmuir-Blodgett Technique for Synthesis of Biomimetic LipidMembranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Agnès P. Girard-Egrot and Loïc J. Blum

2.1. Introduction .......................................................................................... 232.2. Langmuir Monolayer Formation ......................................................... 25

2.2.1. Surface Tension......................................................................... 262.2.2. Surfactants ................................................................................. 272.2.3. Surface Pressure........................................................................ 30

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2.2.4. Surface Pressure (�� – Area (A) Isotherms ............................. 332.2.5. Monolayer Stability................................................................... 37

2.3. Langmuir-Blodgett Technique............................................................. 392.3.1. Vertical Film Deposition Principles ......................................... 39

2.3.1.1. Transfer Process Energy.............................................. 412.3.1.2. Contact Angle Values ................................................. 422.3.1.3. Deposition Ratio.......................................................... 432.3.1.4. Advantages and Caution ............................................. 43

2.3.2. Elaboration of Organised Lipidic LB Films ............................ 442.3.3. Phospholipid LB Films ............................................................. 472.3.4. Free Supported Phospholipid LB Films ................................... 522.3.5. Asymmetric Phospholipid LB Bilayers.................................... 54

2.4. Functionalisation of Lipidic LB Films: Specific Features.................. 572.4.1. Protein Association with the Floating Monolayer before

LB Deposition ........................................................................... 572.4.2. Protein Association onto Preformed-Lipidic LB Films ........... 592.4.3. Oriented Protein Association in Lipidic LB Films .................. 60

2.5. Trends and Prospects ........................................................................... 62

3. Liposome Techniques for Synthesis of BiomimeticLipid Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75Stella M. Valenzuela

3.1. Introduction .......................................................................................... 753.2. Applications and Uses of Liposomes.................................................. 753.3. Liposome Structure is Influenced by its Phospholipid

Composition ......................................................................................... 763.4. Common Terminology Used in the Description of Liposome

Structure ............................................................................................... 773.5. Liposome Preparation .......................................................................... 77

3.5.1. Preparation of Multilamellar Vesicles...................................... 783.5.2. Preparation of Unilamellar Vesicles......................................... 79

3.5.2.1. Ultrasonication............................................................. 793.5.2.2. Extrusion through Polycarbonate Filters .................... 793.5.2.3. Freeze – Thawing........................................................ 793.5.2.4. Ethanol Injection ......................................................... 813.5.2.5. Detergent Method........................................................ 813.5.2.6. Preparation of Sterile Large Unilamellar Vesicles .... 81

3.5.3. Preparation of Giant Unilamellar Liposomes........................... 823.5.3.1. Electroformation .......................................................... 823.5.3.2. Rapid Preparation of Giant Liposomes....................... 823.5.3.3. Giant Unilamellar Liposomes Prepared in

Physiological Buffer .................................................... 833.5.4. Modified Liposomes ................................................................. 833.5.5. Purification of Liposomes......................................................... 85

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4. Characterization and Analysis of Biomimetic Membranes . . . . . . . . . . 89Adam I. Mechler

4.1. Important Properties of Biomimetic Membranes................................ 894.2. Methods of Characterization and Analysis ......................................... 91

4.2.1. A Few Thoughts........................................................................ 914.2.2. Atomic Force Microscopy ........................................................ 924.2.3. Quartz Crystal Microbalance .................................................... 964.2.4. Surface Force Apparatus........................................................... 964.2.5. Ellipsometry .............................................................................. 974.2.6. Surface Plasmon Resonance ..................................................... 98

4.3. Coverage and Mass.............................................................................. 994.4. Morphology and Mechanical Properties ............................................. 104

4.4.1. Imaging and a Few Common Artefacts ................................... 1044.4.2. Surface Forces and Continuum Mechanics;

AFM Simulation........................................................................1074.4.3. Mechanical Properties............................................................... 118

4.5. A Brief Outlook ................................................................................... 122

5. Biomimetic Membranes in Biosensor Applications . . . . . . . . . . . . . . . . . . 127Till Böcking and J. Justin Gooding

5.1. Introduction .......................................................................................... 1275.2. Biosensors ............................................................................................ 129

5.2.1. Classes of Biosensors................................................................ 1295.2.2. Why Biomimetic Membranes for Biosensing Applications? .. 130

5.3. Biomimetic Membranes for Biosensor Applications.......................... 1335.3.1. Hybrid Bilayer Lipid Membranes (Supported Lipid

Monolayers)...............................................................................1345.3.2. Solid Supported “Floating” Bilayer Lipid Membranes............ 1345.3.3. Tethered Bilayer Lipid Membranes.......................................... 137

5.3.3.1. Surface Attachment via Low Molecular WeightTethers..........................................................................137

5.3.3.2. Phytanyl Lipid Derivatives for HighlyInsulating Membranes .................................................138

5.3.3.3. Surface Attachment via Functionalised Polymers ...... 1405.3.4. Laterally Structured Bilayer Lipid Membranes........................ 140

5.4. Catalytic and Affinity Biosensors Fabricated using SupportedBilayer Lipid Membranes ....................................................................1415.4.1. Catalytic Biosensors based on Supported BLMs..................... 1415.4.2. Affinity Biosensors ................................................................... 143

5.4.2.1. Immunosensors based on Supported BLMs ............... 1435.4.2.2. DNA Modified BLMs ................................................. 1435.4.2.3. Detection of Toxins using Hybrid BLMs,

Supported BLMs and Vesicles....................................143

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5.4.3. General Remarks on Supported BLMs for BiosensingApplications...............................................................................147

5.5. Membrane Biosensors Based on Ion Channel Gating ........................ 1485.5.1. Signal Transduction via Ion Channels...................................... 148

5.5.1.1. Criteria for the Biomimetic Membrane ...................... 1485.5.1.2. Measurement of Membrane Conductance .................. 1495.5.1.3. Gating of Ion Channels Incorporated into

Tethered BLMs............................................................1495.5.1.4. Gating of Ion Channels Incorporated into

Membranes on a Sensor Chip .....................................1505.5.2. Taking Biosensors a Step Further: The AMBRI Ion

Channel Switch Biosensor ........................................................1505.6. Concluding Remarks............................................................................ 154

About the Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

CONTRIBUTORS

Loïc J. BlumLaboratoire de Génie Enzymatique

et BiomoléculaireEMB2/UMR 5013 - CNRS/UCBLUniversité Claude Bernard Lyon 1

43 Bd du 11 novembre 1918F-69622 Villeurbanne CedexFrance

Till BöckingSchool of Chemistry and School of

PhysicsThe University of New South WalesSydney, NSW 2052Australia

Agnès P. Girard-EgrotLaboratoire de Génie Enzymatique

et BiomoléculaireEMB2/UMR 5013 - CNRS/UCBLUniversité Claude Bernard Lyon 1

43 Bd du 11 novembre 1918F-69622 Villeurbanne CedexFrance

J. Justin GoodingSchool of ChemistryThe University of New South WalesSydney, NSW 2052Australia

Donald K. MartinFaculty of ScienceUniversity of Technology SydneyBroadway, N.S.W. 2007Australia

Adam I. MechlerMonash UniversitySchool of ChemistryClayton, VIC 3800Australia

Stella M. ValenzuelaFaculty of ScienceUniversity of Technology SydneyBroadway, N.S.W. 2007Australia

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