2B Morphogenesis & Bioprinting II

Tissue Engineering Overview

  • Bioprinting at Johns Hopkins Whiting School of Engineering.

Need for Tissue Engineered Organs

  • Cost Analysis of Kidney Treatment:

    • Kidney transplant: ~$80,000

    • Bioprinting a kidney: ~$280,000 (possibly more)

    • Dialysis treatment costs: $55,000 - $75,000 per patient

  • Market Insights:

    • 3D Bioprinting market projected to be worth ~$1.82 Billion by 2022.

Current Bioprinting Challenges

  • Print Accuracy & Speed:

    • Need for biologically relevant bio-inks that maintain structure and viscosity during the process.

  • Cell Viability & Function:

    • Understanding how printing affects cell health.

  • Engineering Issues:

    • Challenges with 'overhangs' during printing.

  • Biological Issues:

A 3D Bioprinting System Overview

  • Referencing study: Kang et al. (2016) on producing human-scale tissue constructs with structural integrity.

Integrated Tissue Organ Printer (ITOP)

  • Components of ITOP:

    • XYZ axis controlled stage

    • Multi-cartridge dispensing module.

    • Closed acrylic chamber for temperature and humidity control.

  • Resolution:

    • 250 nm for XY, 500 nm for Z; Lulzbot achieving 50µm in Z and 100µm in XY.

Multi-cartridge Printing

  • Allows usage of various cell types, supporting materials, and sacrificial materials in tissue constructs.

Materials Used in Bioprinting

  • PCL (Polycaprolactone):

    • High molecular weight (43-50k).

    • Melting point: 92.5°C; operated with an 800kPa pressure.

  • Hydrogels:

    • Components: Gelatin, Fibrinogen, Hyaluronic Acid, Glycerol, etc.

    • Specific nozzle parameters for printing: 300 µm Teflon Nozzle.

  • Pluronic F-127:

    • Role as a sacrificial material enabling channel formation.

Cell Survival and Diffusion Considerations

  • Diffusion Limitations:

    • Cell survival is limited to ~100-200µm distance from blood vessels; requires controlled microchannel printing for nutrient and waste exchange.

Workflow in Bioprinting

  • Imaging data used to model printer nozzles for anatomical accuracy from clinical datasets.

Case Study: 3D-Printed Bone for Critical-sized Calvarial Defect

  • Highlights on scaffold design and effectiveness.

Printing Cells Overview

  • Human Amniotic Fluid-Derived Stem Cells:

    • Various protocols for osteopsup and construct stability.

  • Preparation Tables:

    • Information on composite hydrogels for different tissue types (bone, cartilage, muscle).

Alizarin Red Staining Technique

  • Used to analyze and confirm differentiation in tissue samples.

Critical-sized Cranial Defect Scaffolding

  • Discusses challenges of spontaneous healing and specifics of PCL-TCP scaffolds.

Histological and Immunohistological Findings

  • Analysis of tissue responses post-implantation, indicating success or challenges in bone formation.

3D-Printed Ear and Cartilage

  • Techniques involving specific cell types and differentiation media.

Testing the Functionality of 3D-Printed Ears

  • Assessing mechanical properties such as flexibility and elasticity.

Vascular Integration in Engineered Constructs

  • Reports on vascularization outcomes after the implantation of engineered ears.

Current Advancements in Skeletal Muscle Bioprinting

  • Discusses challenges in achieving ideal structure for muscle regeneration.

Future Directions in Cell-Based Treatments

  • Discusses the retention and engraftment of cells post-implantation and associated challenges.

Overview of Spheroids in Cardiac Engineering

  • Concept of spheroid ratios for optimal cell cooperation and tissue formation.

Key Benefits and Challenges in 3D Bioprinting

  • Summary of current methodologies and techniques, their pros and cons.

Research Contributions and Future Studies

  • Emphasizes the importance of vascularization and considerations for further research into cell-based treatments and bioprinting technologies.