Slicing Algorithm

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Precision Extruding Deposition of 3-Dimensional
Scaffolds for Bone Tissue Engineering
Lauren Shor Advisor Dr. Selcuk Guceri Advisor
Dr. Wei Sun Department of Mechanical Engineering
Mechanics Drexel University Philadelphia, PA
19104, USA Acknowledgement NSF and ONR Koerner
Fellowship
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Introduction-Tissues Engineering
Scaffold (with cells)
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Introduction-Mechanical Properties of Human Tissue
YANG ET AL. Biomaterials, 23, 2119-2126, (2002).
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Scaffold Design

• The regeneration of specific tissues is dependent
  on the porosity and pore size of the supporting
  3D scaffold.
• A large surface area favors cell attachment and
  growth
• A large pore volume is to accommodate and
  deliver a sufficient number of cells
• High porosity is for the easy diffusion of
  nutrients, transport and for vascularization.
• Interconnectivity

100-350 microns for regeneration of bone, 500
microns for fibrovascular tissues for rapid
vascularization and survival of cells
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Introduction-Process of Scaffold Manufacturing
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Freeform Fabrication by Precision Extrusion
Deposition
Positioning controller
Mini-Extruder Controller
Mini Heaters
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System Control Software
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Introduction-Materials

• Hydroxyapatite
• Ceramic
• Biocompatible
• Osteoconductive
• Drawbacks
• Brittle
• Not easily processed
• Applications
• Used in dental and orthopedic surgery as fillers
  for bone defects
• Coatings on metallic implants to improve implant
  integration in host bone.

• Polycaprolactone
• Polymer
• Biocompatible
• Biodegradable
• Low melt temperature
• Drawbacks
• Long degradation rate
• Not bioactive

Ca10(PO4)6(OH)2
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Pattern Specification

• Basic process parameters
• Materials (melting point)
• Driven and speed
• Temperature
• Diameter of Nozzle
• Deposition speed

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SEM Images of Scaffold
0/120 layout pattern
0/90 layout pattern
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Interconnectivity
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Biological Characterization In Vivo
To determine if osteoblast-seeded PCL scaffolds
will induce osteogenesis in vivo.
5 million cells/implant
Implants removed after 4, 6 and 8 week time
periods
Scaffolds implanted subcutaneously in nude mice
Fetal bovine osteoblast cells harvested and
cultured
Fixation, sectioning and histological analysis of
explants
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In Vivo Study Results Histological
Dr. H. An, MUSC, 8 weeks
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Fabrication of Composite PCL/HA Scaffold

• PCL/HA Scaffolds
• Varying Parameters
• Pore size
• Porosity
• HA Concentration, 15, 33
• and 45

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HA/PCL Results Bulk Material
SEM imaging using Back Scatter Detector
PCL/HA 45
PCL/HA 45
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HA/PCL Results - Scaffold
SEM imaging using Back Scatter Detector
PCL/ HA Scaffold (33)
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Biological Characterization In Vitro
Dead at 4x
Live at 4x
Shows complete coverage of the entire scaffold
surface after only 4 days
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Biological Characterization In Vitro
Live At 10x
Dead At 10x
Live At 20x
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Complex Geometries
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Summary and Conclusion

• Construction of PCL and composite scaffolds using
  a novel deposition system, was achieved.
• The preliminary results show a promise of using
  the developed deposition system for fabrication
  of tissue scaffolds and constructs.
• SEM and Micro-CT analyses showed good correlation
  between designed construct and fabricated part
• Cellular biological studies and cell
  survivability studies were conducted and showed
  biocompatibility and promise for application in
  orthopeadic tissue engineering

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Questions?