T. T. Shen 1

Tueng T. Shen, M.D., Ph.D.Shai Garty, PhD,

Shintaro Kanayama, MD, PhD,Bryan Y Kim, BA

Max Maginness, PhD, Buddy D. Ratner, PhD

World Cornea Congress VI World Cornea Congress VI

New sphere-templated polymeric scaffolds for artificial cornea

Financial Disclosure: The authors have no financial interest in the subject matter of this poster

T. T. Shen 2

BackgroundBackground

• Corneal blindness, affecting 12 million people, is the second leading cause of treatable blindness worldwide [1]. While corneal transplantation using high-quality human donor corneas has been successful in selected developed countries, majority of the people with corneal blindness today remain untreated because of the lack of donor cornea. Currently available artificial corneas for human use includes the Boston-Keratoprosthesis (Boston KPro) [2] and AlphaCor [3]. Both corneal substitutes have limited use worldwide because of the limited availability of donor cornea (Boston K-pro) and sub-optimal integration with host tissue (AlphaCor), leading to high risks for catastrophic infections and extrusions [4].

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Limitations of current artificial corneaLimitations of current artificial cornea

• Tolerated but not integrated

• Still needs donor tissue

• High cost: $5,000 - $10,000 per device

• High risk of infection

• Require long term medication

• Require long term follow-up

• Treatment of the last resort in the developed countries

• Limited application in the developing world

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PurposePurpose

• We have developed novel polymeric materials and unique engineered design as complete replacement for human cornea. Our artificial cornea is made as a one piece consist a transparent polymeric optic-core inter-connected with a flexible, well defined porous polymer periphery. The composite polymer fabrication is made using an injection molding technique. Our device is designed and engineered to enhance the essential functions of the human cornea (refractive function and strong barrier) and eliminate its weaknesses (astigmatism, vulnerable to infections). The design has the potential to be adapted in the developing nations where resources are limited.

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MethodsMethods

• Our design consists of a transparent polymeric optic core, fully integrated with a flexible, porous polymer periphery. The optic center is ensuring superb optic properties enable to restore vision and can be customized to refractive requirements of individual patients. The hybrid composite structure is made of collagen covalently attached to synthetic polymer. This rigid structure, is achieving improved biocompatibility. The well-defined porous periphery of the scaffold design based on the unique tissue integration properties of the spherically templated angiogenic regenerative (STAR) porous biomaterials. The STAR porous biomaterials are made by molding into a prefilled mold contains sintered uniform size PMMA beads. This engineered structure is maximizing the rapid tissue attachment and integration to the host. In addition, the surface properties of the device are readily customized for post-implantation healing when further facilitated by embedding bio-molecules to the porous peripheral scaffold.

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MethodsMethods

• Healing and biointegration of implanted scaffold was encouraged by optimizing the porous structure and embedding biomolecules in the polymeric scaffold. The polymeric system properties were examined both in vitro using different analytical tools including rheological and morphological analysis, microscopy and bioassays in addition to in vivo rabbit models. The ex vivo implants were further analyzed using histology, immuno-histochemistry and high resolution scanning electron microscopy (HR-SEM).

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Materials: Sphere-templated material Materials: Sphere-templated material

Effect of pore size on blood vessel density in sphere-templated polyHEMA implants

Marshall, A.J. and B.D. Ratner, Quantitative characterization of sphere-templated porous biomaterials. AIChE Journal, 2005. 51(4): p. 1221-1232

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Results (in vitro)Results (in vitro)

In vitro 3T3 Fibroblasts culture on surface of STAR material

HR-SEM of STAR Silicone material

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Results: In vivo integration model Results: In vivo integration model

suturing test

In vivo implant

SEM

Collagen staining

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ConclusionsConclusions

• Our preliminary findings suggest that the materials tested are well-tolerated in vitro using Fibroblast cells and corneal epithelial cells and in vivo as shown in the rabbits model. Those findings were supported by additional analyses including the immuno-histochemistry and morphological examinations. Those materials have the potential to be adapted as fully synthetic artificial cornea on a worldwide scale, especially in developing-nations with limited resources.

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ReferencesReferences

1. Whitcher JP, Srinivasan M, Upadhyay MP. Bull World Health Organ. 2001;79(3):214-21..

2. Duan, D, Klenkler BJ, Sheardown H, Expert Review of Medical Devices, 2006. 3(1): p. 59-72.

3. Chirila TV, Hicks CR, Dalton PD, Vijayasekaran S, Lou X, Hong Y, Clayton AB, Ziegelaar BW, Fitton JH, Platten S, Crawford GJ, Constable IJ, Progress in Polymer Science 1998; 23,3, 447-473.

4. Dudenhoefer EJ, Nouri M, Gipson IK, Baratz KH, Tisdale AS, Dryja TP, Abad JC, Dohlman CH. Cornea. 2003; 22(5):424-8.

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UW collaborators:• Professor Buddy Ratner, (BioE)• Professor James D. Bryers,

(BioE)• Professor Brian Otis, (EE)• Professor Karl Böhringer, (EE)• Professor Babak Parvis, (EE)Shen lab:• Shai Garty, PhD• Shintaro Kanayama, MD, PhD• Bryan Kim, BA

Funding:Coulter Foundation, NEI, NSF, RPB

AcknowledgementsAcknowledgements

Author:Tueng T. Shen, M.D., Ph.D.Associate ProfessorUniversity of Washington Eye InstituteAdjunct, BioengineeringUniversity of Washington School of Engineering