Lecture 11 - Tissue/Organ Bioprinting

Question 1

Bioprinting

Answer 1

Computer-aided layer by layer additive biofabrication of functional living tissue/organ constructs

Question 2

3 Steps

Answer 2

• Preprocessing
• Processing
• Postprocessing

Question 3

Preprocessing

Answer 3

• Bioimaging
• CAD
• Clinical bioimaging and ultrasound for obtaining gross anatomical characteristics of tissue/organs

Question 4

Processing

Answer 4

• Actual printing

- Solidification

Question 5

Postprocessing

Answer 5

• After printing, printed tissue and organ constructs not yet fully mature, functional tissues and organs
• Must undergo rapid process of self-assembly, maturation and differentiation
• Require a special perfusion device (bioreactor) that allows these cells to survive
• To accelerate tissue maturation, chemical and mechanical conditioning of printed tissue and organ construct is needed. Each specific organ will needs a specifically designed perfusion media and condition
• To provide for non-invasive biomonitoring of maturation of printed tissue and organ constructs

Question 6

Cell Sources for Tissue/Organ Printing

Answer 6

• Induced pluripotent stem cells (iPSCs)
• Adipose derived stem cells
• Bone marrow derived stem cells

Question 7

Induced pluripotent stem cells (iPSCs)

Answer 7

• Type of pluripotent stem cell artificially derived from non-pluripotent cell
• Typically adult differentiated cells
• Induces specific genes (Oct-3/4, SOX2, c-Myc, Klf4) into cells
• Can theoretically differentiate into any cell type in body

Question 8

Adipose derived stem cells

Answer 8

• Isolated from adipose tissue

- Typically large quantities available

Question 9

Bone marrow derived stem cells

Answer 9

• Isolated from bone marrow
• Contains different types of stem cells, such as mesenchymal stem cells and hematopoietic stem cells
• Small quantities only
• Requires long-term culture

Question 10

Chemical Hydrogels for Tissue/Organ Printing

Answer 10

• Ideal (soft, low mechanical strength)
• Crosslinked poly(ethylene glycol) based hydrogel (degradable)
• Containing degradable hydrolytic bonds such as ester, anhydride, carbonate
• Containing degradable peptides

Question 11

Physical Hydrogels for Tissue/Organ Printing

Answer 11

• More convenient for printing as chemical crosslinking process not necessary
• Collagen
• Hyaluronan
• Alginate
• Chitosan
• PLGA-PEG-PLGA
• PEO-PPO-PEO

Question 12

Tissue Fusion

Answer 12

• Fluidity of printed drops (cells or hydrogel/cells) allows them to self-assemble into tissue ‘spheroids’
• Driven by cell-cell and cell-environment interactions