Scaffolds Flashcards
What are the roles of the ECM?
Structural support Mechanical properties Bioactive cues Mechanical properties Bioactive cues Scaffold for forming new tissues Reservoir for growth factors
What must be considered when designing a scaffold?
Choice of material - architecture of scaffold, toxicity, scaffold/cell interactions
Tissue engineering - up-scaling, nutrient supply, can the tissue be made 3D?
Producing tissue from 3D scaffolds - what are the steps overall?
- Produce scaffold of biodegradable materials
- Cellularise –> seal scaffold with variety of cell types
- Functionalise if required - do surface properties need to be amended such as RGD domains added?
Note upon degradation that biproducts must not be toxic!
Types of materials used?
Natural / synthetic / semi-synthetic ACELLULAR TISSUE MATRICES
ACELLULAR TISSUE MATRICES
Ready-made matrices of decellularized organs and tissues.
These have their antigens and cellular componants removed so that there is no immune response induced
Methods of de-cellularisation of tissues?
Mechanical - physical scraping
Chemical - treat with acids or bases
Biological - treat with enzymes that digest cellular components
+ and - to ACELLULAR TISSUE MATRICES?
+ Can exploit 3D structure of ECM
+ Some are commercially available
- no control of accessibility - where will it come from?
- no control over source of tissue (dermis/bladder/tendon/pericardium/small intestine submucosa)
Architecture – how will scaffold adhere to this? Importance of microarchitecture?
- Scaffold will map out the shape of the new tissue construct and organs will assume this shape
- These are made to measure for a particular patient, the architecture is determined by the scaffold
- Microarchitecture is very important as they provide the tissue with certain properties eg bones are very POROUS
What is porosity and why is it important?
Pore is a space within a scaffold. Porosity = a collection of pores!!
Porosity means more vascularisation and interconnectivity within a tissue. Less connectivity between pores = less accessibility.
Too much porosity means less mechanical strength
What is the importance of proper decellularization and how can we ensure it has been done properly?
Will cause host response!!!
Can ensure proper decellularization by using staining techniques, PCR, and histological techniques
Outline process of porogen leaching ?
Why is this a good technique?
1) Polymer is dissolved in solvent and mixed with salt particles
2) Mixture poured into mould
3) Solvent is evaporated (with salt dispersed throughout)
4) Polymer is placed in water –> salt leaches out leaving a porous scaffold behind!
Technique easy and accessible
What are the main methods for scaffold fabrication?
- Porogen leaching
- Phase separation
- Additive manufacturing
- Electrospinning
Outline process of phase separation ?
- Polymer solution and solvent are mixed
- Thermally separated into polymer and solvent phases
- Freeze dried to form a solid object
- Solvent has produced pores in a honeycomb like structure
Outline process of electro spinning ?
- A polymer is ejected from a fine needle and a power supply generates an electromagnetic field
- EM field causes fibres to splay as they go through solvent phase
Method good as you can change parameters eg strength of voltage supply, conc of polymer, distance between needle and plate, fibres produced. Formation of extra fine fibres mimic the ECM well
Outline process of additive manufacturing ?
Process of joining materials to make objects from 3D data
- Liquid cartidges delivers polymer in layers in a repeating process, over and over
- Polymer is delivered by a roller in layers
- Design is transferred to virtual images
Precise morphologies can be created, combines medical imaging for anatomically shaped structures
