Scaffolds For Tissue Engineering Applications - Zeroth Review (16 Oct 2008)

Micro/Nanoporous Scaffolds for Tissue Engineering Applications Department of Chemical Engineering and Materials Science Amrita School of Engineering Coimbatore – 641 105 October 2008

Zeroth Review By Divya Haridas (CB105PE012) Karthikeyan G (CB105PE023) Krishna Priya C (CB105PE025) Premika G (CB105PE028) Guide Dr. Murali Rangarajan. Ph.D Co-Guide Dr. Nikhil K Kothurkar. Ph.D

Motivation of Tissue Engineering 

… Today around 80000 Indians are waiting for Organ / Tissue Transplantation

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Many children suffer from crippling diseases and deformities

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Current therapies like bone grafting has many limitations  additional cost of the harvesting procedure  pain and infection at the harvesting site

Concept of Tissue Engineering 

Life science and Engineering dealing with the development of biological substitutes that restore, maintain and improve tissue functions or a whole organ

Polymeric Scaffolds 

Three dimensional scaffolds play important roles as extracellular matrices onto which cells can attach, grow, and form new tissues

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Modeling, design and fabrication of scaffolds are always a difficult task in the regenerative tissue engineering

Scaffolds – Bone Formation

Scaffold Considerations 

Matrix Material Characteristics 

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Slow degradability  

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Bioactive and Biocompatible

For stable scaffold morphology For homogeneity of new tissues

High Porosity & interconnectivity  

To minimize the amount of implanted polymer To increase specific surface area for cell attachment & tissue in growth

Scaffold Considerations 

Pore Size 

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3D Pore architecture 

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150 – 500 µm for bones, < 50 µm for organs

Allows for cell attachment , proliferation and differentiation Provides pathways for bio-fluids Pore architecture influences mechanical strength

Tailoring possibilities  

Controllable pore size, porosity Control of matrix design

Fabrication Techniques 

Electrospinning - High voltage electrostatic field is

applied to polymer solution to form non-woven scaffold fibers 

Solid Freeform Fabrication - 3D scaffold is constructed from 2D layers (CAD/CAM methodologies) using 3D positioning system and extrusion head

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Fiber Bonding - Polymer fibers are immersed in polymer solution. On heating, the fibers weld together and polymer melts and fills the voids. Removal of polymer results in porous scaffold

Fabrication Techniques 

Phase Separation - A homogeneous multi-component

system phase separates (polymer rich - polymer lean phase) under certain conditions. Removal of solvent results in solidification of polymer rich phase which forms porous scaffold 

Solvent Casting and Particulate Leaching - Polymer solution is cast into the particle assembly (salt, paraffin). Vacuum is applied to evaporate the solvent. Particles are leached using solvent. Pore architecture resembles the particles

Technique

Advantages

Disadvantages

Electrospinning

Good mechanical strength, highly porous structure

Costly process, poor control over internal architecture

Solid Freeform Fabrication

Good mechanical strength, solvent free

High processing temperature

Fiber Bonding

Phase Separation

Solvent Casting/Particulate Leaching

High porosity

Limited range of polymer, Residual solvent, lack mechanical strength

Highly porous structure, permit incorporation of bioactive agents

Poor internal architecture, limited range of pore size

Large range of pore size, good control of porosity and pore size

Poor control over internal architecture

Focus of the Project 

Preparation of Scaffold from the feasible Fabrication Technique

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Incorporation of Hydroxyapatite for Bone Tissue Engineering Application

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Characterization of Fabricated Scaffolds

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Modeling and Simulation of HAp incorporated Scaffolds

Methodology Step 1 Identification of Fabrication Method 

The Particulate Leaching method is identified through Literature Survey during August – September 2008 by considering the constraints like do-ability in the Institution, with limited financial resources, in limited time

Methodology Step 2 Fabrication of Scaffolds by Particulate Leaching Technique

Preparation of Solid Paraffin Spheres Ma PX, Ji-Won Choi. Biodegradable Polymer Scaffolds with Well Defined Interconnected Spherical Pore Network. Tissue Engineering 2001;7(1):23-33.

Methodology Step 2 Fabrication of Scaffolds by Particulate Leaching Technique

Preparation of Polymer Foam Ma PX, Ji-Won Choi. Biodegradable Polymer Scaffolds with Well Defined Interconnected Spherical Pore Network. Tissue Engineering 2001;7(1):23-33.

Methodology Step 3 Incorporation of Hydroxyapatite and fabricating Scaffolds 

The major mineral phase in the bone is Hydroxyapatite. Incorporating them in Polymer Scaffolds offers bone regeneration potential

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Literature Survey on HAp incorporation in Polymeric Scaffolds and its fabrication

Methodology Step 4 Characterization    

Density Porosity Morphology to be studied using SEM Compressive Modulus using a Mechanical Tester

Methodology Step 5 Modeling and Simulation 

To study the kinetics of Hydroxyapatite (HAp) incorporation

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Physical /chemical absorption of HAp

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Resulting morphology changes in scaffold

Project Calendar Literature Survey Materials Purchase Experimental Process HAp Incorporation Characterization Modeling and Simulation Final Report

Au g

Sep Oct

No v

Dec Jan

Feb Ma r

Apr

Thank you