Current Organ Transplant Crisis

• Hundreds of thousands on transplant waiting lists
• Need kidneys, hearts, livers to save lives
• Insufficient donor organs available to meet demand

Bioprinting Overview

• Branch of regenerative medicine under development
• Creates brand-new, customized organs from scratch
• Alternative to waiting for donor organs
• Currently can't print complex organs yet
• Simple tissues achievable: blood vessels, tubes for nutrient/waste exchange

Bioprinting Technology Mechanics

• Biological cousin of 3D printing
• Deposits layers of material to construct 3D objects slice by slice
• Uses bioink instead of metal/plastic/ceramic
  • Printable material containing living cells
  • Bulk: water-rich hydrogel molecules
  • Contains millions living cells + chemicals encouraging cell communication/growth
  • Single cell type or multiple types for complex structures

Meniscus Example Process

• Target: knee cartilage preventing shinbone/thighbone grinding
• Made of chondrocyte cells
• Cell sources:
  • Donor cell lines replicated in lab
  • Patient's own tissue (personalized, less rejection risk)

Extrusion-Based Bioprinting (Most Popular Technique)

• Bioink loaded into printing chamber
• Pushed through round nozzle attached to printhead
• Nozzle diameter: rarely wider than 400 microns
• Produces continuous filament thickness of human fingernail
• Computerized image/file guides strand placement
• Printed onto flat surface or liquid bath for stabilization
• Fast process: meniscus completed ~30 minutes

Post-Printing Stabilization

• Some bioinks stiffen immediately
• Others require UV light or additional chemical/physical processes
• Successful printing results in cells:
  • Signaling to each other
  • Exchanging nutrients
  • Multiplying

Current Achievements

• Simple structures: meniscus printable
• Bioprinted bladders successfully implanted
• Printed tissue promoted facial nerve regeneration (rats)
• Created: lung tissue, skin, cartilage
• Miniature semi-functional versions: kidneys, livers, hearts

Current Limitations & Challenges

• Complex biochemical environment replication difficult for major organs
• Extrusion-based printing destroys significant cell percentage if:
  • Nozzle too small
  • Printing pressure too high
• Major challenge: oxygen/nutrient supply to all cells in full-size organs
• Greatest successes limited to flat/hollow structures
• Researchers developing blood vessel incorporation methods

Future Potential & Questions

• Tremendous potential for saving lives
• Advance understanding of organ function
• Possible applications:
  • Tissues with embedded electronics
  • Organs exceeding current human capability
  • Features like unburnable skin
• Open questions:
  • Human life extension through organ printing/replacement
  • Access and availability of technology