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Stanford Cornea Project. Laura Hartman, Dale Waters, Rachel Parke-Houben, Curtis W. Frank Stayce Beck, Luo Luo Zheng, Yuhua Hu Jennifer Cochran Resmi Charalel, Phil Huie, Vijay Vanchinathan Roopa Dalal, Michael Carrasco, Jaan Noolandi Christopher N. Ta. Who needs an artificial cornea?. - PowerPoint PPT Presentation
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Stanford Cornea Project
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Laura Hartman, Dale Waters, Rachel Parke-Houben,
Curtis W. Frank
Stayce Beck, Luo Luo Zheng, Yuhua Hu
Jennifer Cochran
Resmi Charalel, Phil Huie, Vijay VanchinathanRoopa Dalal, Michael Carrasco, Jaan Noolandi
Christopher N. Ta
Who needs an artificial cornea?
• In the United States, over 33,000 corneal transplants are performed each year
• Worldwide, 10 million people are blind due to corneal disease. Most of these people do not have access to corneal transplants and remain blind due to a lack of donor tissue supply and distribution.
trachoma
corneal ulcer
trachoma
corneal ulcer
Current available keratoprosthesis
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Boston keratoprosthesis (PMMA)
AlphaCor device (PHEMA)
≈1,200 devices implanted to date (still requires donor corneas)
≈ 300 devices implanted to date; limited use
Osteo-odonto keratoprosthesis
•224 devices implanted with surprisingly high success rates.
•requires complex surgery and is only performed by a select few surgeons throughout the world
Falcinelli, G., et al. Arch Ophthalmol, 2005. 123(10): p. 1319-29.
Properties of an Artificial Cornea
• Biocompatible• Optically clear centrally• Nutrient permeable• Mechanically strong• Surface epithelialization• Peripheral tissue integration
CAD model acknowledgement: L. Kourtis, Stanford Dept. of Mechanical Engineering
Epithelium
hydrogelStroma
hydrogelStroma
The Stanford Approach
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high diffusion + stable, optically clear hydrogel “invisible” material
1.protein modification(Collagen and EGF) Epithelium grows back
2.
Material
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Single Network Double Network
Single Network Double Network
1st network swollen in monomeric building blocks of
2nd network
polymerization of 2nd network
• no chemical linkage• two interpenetrating networks (IPNs)• highly improved mechanical properties
J.P. Gong, et al., Advanced Materials 2003
Mechanical Stability
80
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1PEG 3.4K PAA PEG 8.0K PEG 14K PAADN (PEG 3.4K-PAA)
DN (PEG 8.0K-PAA)
PAA DN (PEG 14K-PAA)
1st network: Poly(ethylene glycol) (PEG)
2nd network: Poly(acrylic acid) (PAA)IP
N
HO
OH
OHO
0
1
2
3
4
5
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Max
imum
Ten
sile
Str
ess
[MPa
]
PEG
(4.6
kDa)
PEG
(8kD
a)
PEG
(14k
Da)
PAA
PAA
PAA
IPN
IPN
water content: ~90%
tunable material
• mechanical stability(contact lens vs. inlay)
• pore size: diffusion(nutrient vs. drug delivery)
• longterm stability(implant vs. tissue scaffold)
Diffusion
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glucose
ascorbic acid
sodium bicarbonate
lactic acid
urea
amino acids
• A high rate of small molecule diffusion through the hydrogel is required to maintain a healthy epithelium
Hydrogel (~100 μm)
Flap edge
Epithelium
Stroma
Protein Tethering: Cell Re-Growth
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O OH O OH O O O OH
O O OHNH
R
hydrogel hydrogel
hydrogel
+NHS/EDC
phosphate buffer
NO O
R NH2+
R = protein, polypeptide, growth factor, amino acid, carbohydrate, phosphate-containing moiety, hormone, neurotransmitter or nucleic acid
• no de-swelling of the gel• washing in buffer possible• no denaturation of proteins
Protein Tethering: Qualitative
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• Using fluorescently-labeled collagen, we have shown that this tethering method supports a stable binding of ECM protein.
PEG Diacrylamide Hydrogel
Control (adsorption)
BINDING OF COLLAGEN
NHS/EDC (covalent linkage)
PEG Diacrylamide Hydrogel
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Phalloidin (red) and Nuclear (DAPI(blue)) staining of primary rabbit corneal fibroblast cells grown on PEGacrylate/PAA Hydrogel tethered with A)Control, B) Collagen,
C)Fibronectin, D)Laminin and E) 1:1 mixture of collagen and Fibronectin.
D
E
Protein Tethering: Cell Re-Growth
Corneal Fibroblast Cells Attach to ECM-Tethered Hydrogels
A) control
DC
B
In vivo experiments
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rabbit # 2 - post-op 50 days
Future Work
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MATERIAL• Determine diffusion coefficients for other proteins through human cornea• Apply principles to development of artificial cornea• Modify refractive index for inlay application (presbyopia)DEVICE
Protein tethering• Optimize the ECM content tethered to the hydrogel• Use time-lapse microscopy to study cell migration on the hydrogel• Addition of enhanced growth factor (EGF) to the protein layer
Tissue Integration• Fine-tuning is still needed to reduce the pore diameter to 50 – 100 μm• Confocal fluorescence microscopy will be used to demonstrate that the channels are interconnected• Tether proteins to the channel walls and test for fibroblast growth
IN VIVO EXPERIMENTS• Implant hydrogel-onlays/inlays • Implant artificial cornea
Funding
• National Institutes of Health / National Eye Institute– R01 EY016987– NIH Grant 5T90 DK070103-03.
• Singapore Eye Research Institute (SERI)• BioX• Stanford Office of Technology Licensing• Stanford MedScholar Program• Fight for Sight• Visx
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