New Frontiers in Biomedical Systems: From Bioinspired Design to

BioMEMS and Nanotechnology

Wole SoboyejoPrinceton Institute of Science and Technology of

MaterialsAnd Department of Mechanical and Aerospace

EngineeringPrinceton University

Princeton, NJ

Acknowledgments

• Glaucio Paulino (UIUC)• Dulce Rufino• Ken Chong (NSF) • Jorn Larsen-Basse (NSF)• Carmen Huber (NSF)

Acknowledgments• Challa Kumar (LSU/CAMD)• Carolla Leuschner (Pennington Biomedical)• Warren Warren (Princeton)• Sylvia Centano (Princeton)• Dr. Jikou Zhou (Princeton)• Dr. Min Huang (Princeton)• Chris Milburn (Princeton)• Steve Mwenifumbo (Princeton/Cambridge)• Lauren Hayward (Princeton)• Lara Ionescu (Princeton)• Omar Bravo (University of Puerto Rico)• Robert Bond (West Windsor/Plainsboro)

Outline of Presentation

• Background and Introduction• Bioinspired Design of FGMs• BioMEMS

– Implantable BioMEMS Structures • Nano-Bio-Technology

– Functionalized Nanoparticles for Cancer Cell Detection

• Summary and Concluding Remarks

Background and Introduction

• Biomedical design is often done without adequate inputs from biology

• Examples – dental implants that fail after a few years- BioMEMS and nano-structures from non-biocompatible materials

• Objective is to introduce some basic ideas in biomedical design at different scales

MECHANICAL PROPERTIES OF DENTAL MATERIALS/MULTILAYERS

Tooth Structure

Dental ceramic E: 50~200 GPa

Dentin-like polymer E=20 GPa

Dental cement E=5 GPa

Enamel E=65 GPa

Dentin E=20 GPa

Dentin-Enamel Junction (DEJ): Graded

Dental restoration

ELASTIC MODULUS DISTRIBUTION IN DENTIN-ENAMEL JUNCTION (DEJ)

Marshall et al. J Biomed Mater Res 54, 87-95, 2001

MAXIMUM PRINCIPAL STRESS DISTRIBUTION

Dental Restoration

1 mm

E=65 GPa

E=20 GPa

Natural Tooth

1 mm

E=20 GPa

E=65 GPa

MAXIMUM PRINCIPAL STRESS

ceramic

Max

imum

Prin

cipa

l Stre

ss (M

Pa)

Graded ceramic/polymer

0

20

40

60

80

100

120

140

0 50 100 150 200 250

ZircorniaGlass

Mark II

Dicor MGC

DicorEmpress 2

Elastic modulus of ceramic (GPa)

FGM

polymer

cement

ceramic

polymer

DIFFERENT YOUNG’S MODULUS DISTRIBUTION

0

10

20

30

40

50

60

70

80

0 20 40 60 80 100

Cement thickness (µm)

You

ng’s

mod

ulus

(GPa

)

20

25

30

35

40

45

50

55

Max

prin

cipa

l stre

ss (M

Pa)

I

IIIII

IV

V

I II III IV V

Different Young’s modulus distribution

E=20 GPa

E=72 GPa

Introduction to BioMEMS Systems

Drug Delivery System Implantable Blood Pressure Sensor

BioMEMS structures are micron-scale devices that are used in biomedical or biological applicationsAt this scale, a wide range of devices are being made (e.g. pressure sensors, drug delivery systems, and cantilever detection systems)Explosive growth in emerging markets – civilian and military applications expected to reach multi-billion dollar levels

Biocompatibility of Silicon MEMS SystemS

500 nm

Coated BioMEMS Structure 500 nm Ti Layer on Si

Si is not the most biocompatible materialCan be made biocompatible through the use of polymeric or Ti coatings.Polymeric coatings used on Si drug release systems.Ti coating approaches are also being developed.

Si

Ti

Ti

Ti

Ti

SURFACE CHEMISTRY – CELL SPREADING

Si - 50 nm Titanium

Si

30 minutes 60 minutes 120 minutes

HOS Cells

PROTEINS INVOLVED IN ADHESION

Adhesion between cells/substrate surfaces -focal contacts or adhesion plaques.Consist of integrins, microfilaments, and proteins.Integrins bind to the extracellular matrix or cell surface.

Connected by proteins to the microfilaments (actin cytoskeleton).

Talin and vinculin -two main proteins responsible for this connection.

ADHESION - IMMUNO-FLUORESCENCE (IF) STAINING

Actin

Vinculin

IF staining - used to view focal adhesions (actin and vinculin).

Tagged anti-bodies bind to specific protein of a cell.

Focal adhesions of specific cells can be quantitatively measured.

Qualitative assessment of cell alignment and growth can be achieved on a multi-cell scale (contact guidance).

Schwarzbauer et. al, 2002

Cell Attachment on PS/Ti Surfaces

Cell Spreading on PS/Ti Surface 3D View of Attached Cell

SHEAR ASSAY MEASUREMENT OF CELL ADHESION

Shear Flow Schematic

Cell Detachment

Shear stress for detachment is given by

Where Q - flow rate & µ -dynamic viscosity

Considering initial onset of detachment to correspond to “adhesion” strength:

τ = 70 Pa Polystyrene (PS)

τ = 81 Pa Ti Coated PS

2wh6Qµτ =

Shear Assay Results

104Ti-Coated Silicon

82Silicon

81Ti-Coated Polystyrene

70PolystyreneAdhesion Strength (Pa)Adhesion Strength (Pa)MaterialMaterial

Shear Stress at detachment for 2 Day HOS cultures

26whQµτ =

Determined as wall shear stress given by:

Micro-Groove Geometry and Cell/Surface Interactions

• Cells can undergo contact guidance when in contact with micro-grooved geometries

• This depends on the size of the grooves relative to the size of the cells• Contact guidance has implications for wound healing and scar tissue

formation

100 µm

Cell

30 µm

Cell

12 µm Micro-Grooves2 µm Micro-Grooves

MEMS-Enhanced TrileafletValve

Our Approach to Early Cancer Detection and Treatment!

CAMD

LP conjugates

LP conjugates

LP conjugatesLP conjugates

LP conjugates

LP conjugates LP conjugates

LP conjugates

LHRH

LHRHLHRH

LHRH

LHRH

LHRH LHRH

LHRH

Magnetic core

Polymer shellwith lytic peptideconjugates

CAMD

Wet Chemical Synthesis of Nano-particles

Metallic, polymeric and metal-polymer Nano-particles using bottom-up approaches

Novel Micro reactor technology for scale-up and controlled synthesis

Synchrotron radiation based X-ray absorption Spectroscopic characterization

Capability to attach bio-molecules

Nanoparticles in tumor: Prussian blue Used to Stain Paraffin Embedded Histological Sections

Targeted Destruction of Prostate Cancer in Balb/c athymic nude mice

CAMD

PC-3.luc Xenograft bearing male nude mice were used

LHRH bound nanoparticles effectively bind to tumor

Use of Nano-LHRH results in accumulation68% of nanoparticles in tumor

Distribution of iron in other tissues is being mapped

TEM Imaging of CancerLHRH-SIOP in Tumor SIOP in Tumor

Fundamentals of Magnetic Resonance Imaging (MRI)

• Hydrogen atoms in water have a property called spin

• MRI generates a magnetic pulse that aligns all of the spins in a certain direction

• The magnetic resonances of the nuclei will cause differences in how they return to their normal spin state

• The MRI machine records the energy released as they realign at different times and generates an image

• A set of images are generated at certain small time intervals after the pulse sequence

Initial MRI Experiments: Cherry Tomato and Grape

• Injected grapes with saturated saline solution of nanoparticles

• Observed contrast at the location of the injection (nanoparticles)

The iron creates a magnetic field in the water, thus creating a blind spot (dark) for the MRI

MRI Imaging of Cancer

MRI Imaging of Cancer –multiCRACED Magnetic Anisotropy

Summary and Concluding Ramarks

• Overview of some recent work on bio-inspired design, bioMEMS and bionanotechnology

• Bioinspired FGM design proposed for crown/dentin interface (need to fabricate structures & test idea)

• Nano-scale titanium coatings designed for implantable biocompatible BioMEMS structures

• LHRH-coated magnetite particles provide opportunities for early detection of breast & prostate cancer

• Significant opportunities for mechanics and materials research – modeling, adhesion, detection of cancer

• We welcome your involvement in the ongoing Americas program (americas.princeton.edu – no www)