Tissue Engineering Flashcards
What are the five basic concepts of tissue engineering?
Tissue engineering is very bespoke and specific for one patient.
Step 1: Isolate the patients one cells via an appropraite sampling process: results in a mixed population of cells - don’t get lucky enough to get one cell type.
Step 2: Then we need to purify/enrich the desired cell types and expand them in cell culture.
Step 3: Seed them onto an appropriate scaffold.
Step 4: Mature them in a bioreactor that has the right growth conditions for the cell type desired.
Step 5: Implantation
What are the two different cell sources for tissue engineering?
Autogenic: Own body: MSCs, iPS cells, Satellite cells, Differentiated cells.
Allogenic: Someone else: often immune response: ES cells, iPS cells, MSCs, differentiated cells.
Biopsies and aspirates may contain numerous cell types, so the cell type of interest needs to be purified, removing unwanted cell types. What are 4 different techniques for this?
Differential adhesion: some cells will adhere to certain
surfaces.
Density centrifugation: sort by cell size.
FACS: sorts by size, granularity, surface markers.
MACS: sorts uses magnetic fields based on cell surface markers.
What is the importance of collagen/gelatin balls used in cell isolated and expansion?
They are needed so that the cells have a surface to adhere to and grow in suspension - they won’t otherwise.
What are the ideal properties of 3D scaffolds for cell growth? [7]
- Biocompatible with human body - no allergic reactions.
- Biodegradable - eventually degrade in the body to non-harmful constituents, leaving healthy tissue behind.
- Cytocompatible - compatible with cells.
- Porous - no porosity -> no nutrients to middle of scaffold and no waste out, dead cell mass.
- Mechanically appropriate - need to match the mechanic features of tissue going into.
- Architecturally appropriate.
- Growth promoting - controlled drug/GF release.
Scaffold materials include polypeptides and polysaccharides. What are examples of both?
PP: collagen, gelatin, fibronectin, fibrin, laminin, silk fibroin.
PS: Hyaluronic acid, Alginate, Chitosan
PP used as scaffolds [6]
Collagen, gelatin, fibronectin, fibrin, laminin, silk fibroin.
PS used as scaffolds: [3]
Hyaluronic acid,
Alginate, Chitosan
What is the rationale behind using synthetic polymers as scaffold materials? [4]
- Control of the degradation, strength, chemical functionality and biological signals.
- Reproducibility.
- Bulk production.
- Interesting properties: temperature responsive release of contents etc.
Examples: Poly(caprolactone), Poly(lactic acid), Poly(glycolic acid), Poly(lactic-co-glycolic acid) PLGA.
Poly(caprolactone), Poly(lactic acid), Poly(glycolic acid) and Poly(lactic-co-glycolic acid) are examples of what type of scaffold?
Polyesters
4 examples of polyesters used as scaffolds:
Poly(caprolactone), Poly(lactic acid), Poly(glycolic acid) and Poly(lactic-co-glycolic acid) are examples of what type of scaffold?
What are the 5 main different materials scaffolds for tissue engineering can be made from?
- polypeptides
- polysaccharides
- synthetic polymers
- Bioceramics and bioactive glasses.
- Decellularised tissues.
What is decellularisation and how does it relate to tissue engineering?
Decellularization is the process used in biomedical engineering to isolate the extracellular matrix (ECM) of a tissue from its inhabiting cells, leaving an ECM scaffold of the original tissue, which can be used in artificial organ and tissue regeneration.
Why was decellularisation developed?
This process creates a natural biomaterial to act as a scaffold for cell growth, differentiation and tissue development. By recellularizing an ECM scaffold with a patient’s own cells, the adverse immune response is eliminated.
Bioactive glasses are great scaffolds for the development of
Bone-like matrixes.
What are bioactive glasses composed of?
SiO2, Na2O, CaO and P2O5.
What are some of the methods of scaffold formation? (not hydrogels)
Compression Solvent casting Particle leaching Freeze drying Spinning - wet, dry and melt. Electrospinning 3D spinning.
The formation of hydrogels for scaffolds is driven by a number of different mechanisms, depending on the polymer, for example:
Thermal Ionic UV Enzymatic Covalent
What modifications typically need to be applied to scaffolds to enable them to be cell adhesive or growth promoting?
Scaffolds may require certain motifs to quide cell function and fate.
This may include the immobilisation of protein, enzyme, growth factors, drugs etc onto the functionalised surfaces of the scaffolds following plasma or wet chemical treatment.
________, in particular, can be readily modified using NaOH or primary amines.
Polyesters, in particular, can be readily modified using NaOH or primary amines
Subsequent reaction with coupling reagents can be used to attach bioactive motifs (or whole proteins)
Potential for scaffold patterning
Polyesters, in particular, can be readily modified using ____ or primary ______.
Subsequent reaction with coupling reagents can be used to attach bioactive motifs (or whole proteins)
Potential for scaffold patterning
Polyesters, in particular, can be readily modified using NaOH or primary amines
Subsequent reaction with coupling reagents can be used to attach bioactive motifs (or whole proteins)
Potential for scaffold patterning
What is RGD?
Arg-Gly-Asp - attached to fibronectin, laminin, collagen, vitronectin = increased cells. `
Nerve cells love to grow on what
Laminins
Why is scaffold morphology important in tissue engineering?
Cells do not live in the 2D environment provided by many scaffolds: the tissue environment is 3D.
